Equid Blog : Horse Health & Diseases : University of Guelph : Ontario Veterinary College : Equine Infectious Diseases

TheHorse.com has just published a readers' poll that asked the question "What is your most important parasite concern?"

Here are the results, with my commentary:

Small strongyles (cyathostomes): 26.08% (103)

• A narrow victory over large strongyles but a worthy winner. Cyathostomiasis is definitely a problem and it can cause serious disease. It seems to be increasingly common, or at least increasingly diagnosed. Resistance to dewormers among this group of parasites is also becoming a concerning problem.  Cyathostomes are probably the most important overall parasite issue, in terms of real impact on horse health, in most areas.

 Large strongyles (bloodworms): 23.04% (91)

• Large strongyles, particularly Strongylus vulgaris, used to be a major problem, before the advent and widespread use of ivermectin. These worms migrate through blood vessels in the abdomen and can cause blood clots to form, compromising the blood supply to the colon. This used to be a leading (if not main) cause of surgical colics and killed a lot of horses. They are a very rare problem now because of their susceptibility to drugs in the ivermectin family and fenbendazole.

Tapeworms: 15.70% (62)

• It's hard to determine the importance of tapeworms. There have been conflicting studies about their relevance, with some studies indicating they play a role in certain types of colic (e.g. gas colic, ileocecal intussusceptions) and others saying they are not involved in disease. The risks probably vary by region and type of colic, and tapeworms probably play a role in some colics, but it is difficult to quantify just how big a role.

Bots: 11.90% (47)

• It's not surprising that this was a popular choice since people are (hyper)aware of the tiny bot eggs that can be deposited on the horse's haircoat, especially on the lower legs. However, while bot eggs are visible and the sight of adult bot worms attached to the stomach during a gastroscopy can freak people out, bots are pretty innocuous. Adult bots can cause small superficial errosions in the stomach wall where they attach, but this isn't of much relevance to the horse. The main issue with bots is how much the adult flies annoy horses when buzzing around and laying their eggs.

Other 10.13% (40)

• I'm not really sure what people meant when they chose "other." I can't think of any other parasites that would be contenders for "most important."

Ascarids (roundworms): 9.37% (37)

• I'm surprised this isn't higher. Ascarids are controllable but can and do cause disease, particularly in foals. The main issue is when foals are not dewormed properly early in life, and accumulate a large burden of worms. When these foals are eventually dewormed, the worms  die all at once and can cause an intestinal obstruction.

Pinworms: 3.80% (15)

• It's good to see that there's not much concern, but no one should be most concerned about pinworms. Pinworms are, at best, a minor annoyance that can cause tail rubbing.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

Strangles (Streptococcus equi infection) is suspected to be the cause of death of at least six horses in an Australian outbreak.  At least 30 suspected cases has been identified and affected stables are under some form of quarantine. Local horse and pony club events have been canceled to help limit the spread.

Little information about the clinical signs is available, but usually it's pretty easy to establish a high index of suspicion based on the typical signs of strangles, particularly during an outbreak. Confirmation of strangles in an outbreak is also usually pretty easy, since isolation of the bacterium is quite straightforward. Results are expected soon.

Strangles outbreaks are not uncommon and this disease is constantly circulating in most horse populations at some level. Some references say that approximately 10% of affected horses die, a number that I think is excessive, but the key point is that strangles can be fatal to a small but not inconsequential percentage of affected horses. The potential severity of disease plus the high infectivity are big reasons why good control measures are needed.

One common problem with strangles control is described by horse trainer Joe Byrne, who said "the most damaging thing with strangles is the attitude of "ignorance and secrecy". Owners with infected stables "straight away clam up, don't tell anyone" and remain operating like nothing has happened and that is very problematic."  Indeed it is.

Photo: A horse with strangles (S. equi infection) showing the characteristic severe swelling of the submandibular lymph nodes (click image for source).

• Email This
• Print
• Comments
• Trackbacks
• Share Link

While it seems straightforward, disinfection is pretty easy to screw up. It's not uncommon for me to find illogical or completely ineffective "disinfection" practices when I do farm investigations. In general, people don't really understand much about disinfectants and disinfection. That's not too surprising because it's not exactly a common or enthralling topic (and I didn't really know much about it until I became focused on infection control).

Good routine cleaning and disinfection practices are important for all barns, but the specific needs vary greatly between facilities. Proper disinfection practices are particularly important in certain situations, such as in foaling stalls, stalls housing sick horses and isolation areas. Because problems are so common, everyone should think about their disinfection program and the disinfectant(s) they use. When in comes to the disinfectant, here are some questions everyone should ask themselves:

Is it actually a disinfectant?

• Some people mistakenly use cleaners as disinfectants. Cleaners help remove debris and make the surface look good (i.e. clean), while disinfectants kill microorganisms through their chemical activity. You need a clean site for disinfectants to work, but using a cleaner in place of a disinfectant won't get rid of the microorganisms that remain after the visible dirt has been removed.

What kind of disinfectant is it?

• Disinfectants are a little like antibiotics. They have a "spectrum of activity" which tells you what types of microorganisms that they kill. Some disinfectants kill a wide range of microorganisms while the activity of others is more limited. Some work well in the presence of some dirt and debris, while others are readily inactivated and essentially won't work at all unless the surface is very clean first. Some are quite toxic and some are pretty innocuous.

What concentration should be used?

• There should be specific instructions on the product. Some are "ready-to-use" and don't need dilution. Most come as concentrates that need to be properly diluted. Excessive dilution will reduce the chance of of the disinfectant working. Inadequately diluting the concentrate ends up costing a lot more because you waste the product, and high concentrations of some disinfectants can be harmful. "Add two splashes to a bucket" is not proper dilution. You need to measure.

What contact time is needed?

• Disinfectants don't work instantly. They need time. Usually, it's anywhere from five to thirty minutes, depending on the disinfectant.

Common disinfection errors or misconceptions

A nice smell means it's clean.

• Clean actually has no smell at all. Products that leave a residual smell do so for aesthetic purposes, not for any real effect.

All disinfectants are created alike.

• Disinfectants are quite variable, in terms of the different organisms they can kill, how well they work in the presence of dirt and debris, how quickly they work, how toxic they are, and other factors.

The label says it kills 99.99% of microorganisms so it must be great.

• This type of advertising is misleading. Killing 99.99% of selected organisms in a lab environment is different than killing the entire range of possible microorganisms encountered in a barn, and in the presence of debris and difficult-to-disinfect surfaces.

If the area is dirty, just use more disinfectant

• Cleaning removes 80-95% of microorganisms, and is the most important step of the disinfection process. If the area isn't cleaned properly and has a lot of dirt and debris, the disinfectant will not be very effective, regardless of how much is used.  There's no substitute for good old fashioned "elbow grease" when it comes to getting a barn clean.

One disinfectant is good, so two must be better

• A single disinfectant with a good disinfection protocol is adequate. There should be no need for multiple products, unless you want to have a higher level disinfectant available for certain situations (e.g. a stall for a horse with diarrhea). However, you should never mix disinfectants, because highly toxic by-products can be produced.

I'm not having any infectious disease problems, so I don't need to worry about my disinfection practices.

• Everyone that has an outbreak can say, right before the outbreak, that they had no infectious disease problems. Just because things are going well today doesn't mean that things will be fine tomorrow. It's a common perception, however, and often we don't find out about peoples' inadequate disinfection (or other infection control) practices until we are dealing with an outbreak. There's no guarantee that a better disinfection program would have prevented the outbreak, but it certainly wouldn't have hurt and may have helped reduce the problem.  It's much easier to review things and make improvements before there are problems.
  

• Email This
• Print
• Comments (1)
• Trackbacks (1)
• Share Link

Hopefully, everyone that breeds horses knows the importance of colostrum. Unlike human babies, foals don't get antibodies from their dam before they're born. They need to drink colostrum, the antibody-laden first-milk, to get these antibodies which help fight off early infections. Failure to get adequate antibodies from the mare, known as failure of passive transfer (FPT) of maternal antibodies, is a life-threatening problem that needs to be treated quickly. Like most things, prevention is better than treatment, so efforts aimed at reducing failure of passive transfer are critical.

In the vast majority of foalings, things go well: the foal comes out on its own, gets up in a normal period of time, starts nursing and ingests an adequate volume of good quality colostrum.

Sometimes, an adequate volume of good quality colostrum is not available. This can be because the mare leaked colostrum before foaling, the mare didn't produce colostrum, the mare rejected the foal or the mare died during foaling. Whatever the reason, lack of colostrum is an emergency and needs to be addressed promptly to reduce the risk of serious infections. There are a few possible ways to do this:

• Get colostrum from another mare that has just foaled: Great idea, but difficult in practice unless you have a large farm or a network of other local breeders that might have a mare who  just foaled and has colostrum to spare.
• Commercial colostrum replacers: Not a great option. They're very convenient, and likely better than nothing if all other options are exhausted, but they just don't do the job like the real thing.
• Plasma: Plasma can be given orally in the first 18-24 hours of life or intravenously after that, to provide antibodies. It doesn't replace all the goodies found in colostrum, and it's expensive, but it's often the best option available to most people.
• Stored colostrum: Banking colostrum by collecting and freezing extra colostrum from mares (or all the colostrum from mares whose foals died during birth) is a cheap and relatively easy approach. It's easiest for large farms with lots of mares, but anyone can do it. (Remember, however, not to deprive a live foal of any of the colostrum it needs so you can build up a store.  Some mares may only produce enough colostrum for their own foals.)  For stored colostrum to be useful, however, it must retain its beneficial properties during storage.

A recent paper in the Journal of the American Veterinary Medical Association (Nath et al 2010) looked at this aspect. They checked colostrum quality in mares at the time of foaling, and if poor quality colostrum was identified, foals were supplemented with stored, frozen colostrum within six hours of birth. Blood antibody levels were checked 24 hours after treatment. Overall, 5.8% of foals had suboptimal antibody levels, but only one foal (0.4%) had true failure of passive transfer of maternal antibodies, with antibody levels <400 mg/dL. The rest of the "low" group had partial failure of passive transfer, meaning they had lower than ideal (400-800 mg/dl) antibody levels, but these levels are not necessarily a problem, particularly in an otherwise healthy foal on a well-managed farm.

It's not exactly an earth-shattering study, and only limited conclusions can be made because of some aspects of study design (e.g. not proving that supplementation was the reason that foals had adequate antibody levels, no statistical comparison of the incidence of failure of passive transfer between foals that were or were not supplemented, treating some foals that didn't fit the study criteria and not treated a couple that did), however this study showed that this type of approach - checking colostrum of mares at birth and supplementing foals whose mares produce poor colostrum - is a practical approach and resulted in a very low percentage of foals with inadequate antibody levels.

The take home message, perhaps, is that you need to pay attention to colostrum quality. If you check colostrum quality of mares that have just foaled and intervene in situations when poor quality colostrum is present, or when the foal can't/won't ingest an adequate amount of colostrum, you can make sure that failure of passive transfer of maternal antibiotics is a rare event.

More information about colostrum management is available on the equIDblog Resources page and in our archives.

(click image for source)

• Email This
• Print
• Comments
• Trackbacks
• Share Link

The rather large, long-lasting and remarkable outbreak of piroplasmosis continues in the US. A report from the OIE on June 10 describes 23 new cases in 3 states (Colorado, Texas, Oklahoma). None of these are linked to the large outbreak in Texas that has been previously reported, which is not good news.

The origin of infection and route of transmission are unclear. The report states "Preliminary results of these investigations indicate that the transmission of the organism may have resulted from management practices (use of shared needles or substances between horses) rather than by a tick vector." That's what's been said for many of the cases in the US. Piroplasmosis is naturally transmitted by certain tick species. Finding cases in areas where those ticks are not found indicates one of a few possibilities:

• Horses were infected in other regions where infected ticks are present: This is relatively easy to rule out based on travel history, and there's no indication that these are travel-associated infections.
• The cause of piroplasmosis, Theileria equi, is being transmitted by human activity: Specifically, this blood-borne parasite can be transmitted by things like reusing needles and syringes between horses.
• The ticks are actually there, they just haven't been identified.
• Other types of ticks are able to transmit the infection, we just don't know it yet.

Typically, these reports have blamed management practices (e.g. re-using needles) for transmission of T. equi. One problem I have with that is it doesn't tell me where the infection came from. Needle sharing can certainly result in T. equi transmission, but that doesn't account for how the pathogen came to be in the horse population in the first place. Without a clear link to an endemic area or earlier outbreak, there's got to be concern that this organism is more widely disseminated than we realize, and/or that there are other natural sources of transmission that aren't know.

Regardless of how T. equi got to these regions, poor management practices need to be addressed. It's just common sense. Anything that could result in transmission of blood between horses must be avoided. The small amount of money and/or time saved by re-using needles or other instruments isn't worth the risk associated with disease transmission.

At some point, they may have to stop calling this an outbreak, and recognize that piroplasmosis is an endemic disease in the US. There's evidence that this outbreak has been underway for years and the presence of cases unrelated to the large Texas outbreak that was reported earlier suggests that there are multiple foci of infection in the US.

(Picture source: http://icanhascheezburger.com)

• Email This
• Print
• Comments
• Trackbacks
• Share Link

Methicillin-resistant Staphylococcus aureus (MRSA) is a huge problem in people and is an emerging pathogen in horses. Most earlier reports of MRSA in horses involved one strain, called CMRSA-5 in Canada, USA500 in the US, and sequence type 8 (ST8) as a more general term. This human-origin strain seems to be adapted for survival in horses, and in North America, this strain has accounted for most MRSA infections in horses and MRSA infections in people linked to horse contact.

Another MRSA strain, ST398, has recently emerged as a big problem associated with livestock (particularly pigs). This strain is very common in pigs internationally, and is a major cause of infections in people in some European countries. There are also a few reports of ST398 in horses. Most are from Europe, although we have found this strain in one horse in North America. At last week's ASM Conference on Antimicrobial Resistance in Zoonotic and Foodborne Pathogens in Toronto, Dr. Engeline van Duijkeren from the Netherlands presented a case of human ST398 infection linked to a horse.

In the reported case, a 16-year-old girl had a lesion on her foot that was initial diagnosed as a spider bite infection (a common misdiagnosis of early MRSA skin infections). It didn't respond to initial treatment and MRSA was isolated on culture. The girl didn't have any history of contact with pigs or cattle, but had close contact with a foal. That foal had previously been in an equine hospital because of a wound infection, but the wound was not cultured. The same MRSA strain that caused the infection in the girl, however, was found in the foal's nose (the prime site for MRSA carriage by healthy horses). Fortunately, the girl's infection responded to treatment once treatment was adjusted for MRSA.

In some ways, this case is not too surprising, since we know ST398 MRSA can cause disease in people, and since it is found in horses, transmission from horses to people was likely inevitable. However, it's the first report of human infection with this strain associated with horse contact. MRSA exposure is a potential risk for anyone working with horses, since we know that this organism can be found in a small percentage of healthy horses. We don't have great information about how to prevent horse-human transmission, but simple things like only using antibiotics when needed and attention to hygiene (especially hand washing) when working with horses are presumably important factors.

More information about MRSA in horses can be found on the equIDblog Resources page.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

I was giving an Infection Control talk today at Canada's Outdoor Equine Expo, and someone asked about what horse owners should expect their veterinarian to do for infection control. It stemmed, I think, from some points I was making about how things are different between different types of farms, and how a lot of what we do with horses is completely different than the strict biosecurity that applies to certain animals like pigs and poultry. In those types of operations, upon arrival, veterinarians usually change into clean coveralls and boots, and often even need to shower at the farm before they go in. They'll then remove their coveralls (and possibly shower-out), disinfect their footwear and anything they brought in before leaving, and as an additional precaution they may not even go to another farm that day. This is completely different from what we do on horse farms. It's not practical to use such an extreme degree of biosecurity on horse farms, nor is it necessarily indicated.  However, some thought about "best practices" for infection control is certainly warranted in every situation.

The short answer to the question is "there is no standard for infection control and hygiene for veterinarians visiting horse farms." That being said, there are a few general comments I'd make:

• At a minimum, your veterinarian should arrive looking clean.  It's reasonable to expect veterinarians to clean their footwear and ensure that their clothing is clean before coming to your farm. If there is manure, pus, blood or anything else on their footwear or clothing, they're not clean. Are they a risk? Who knows, but if there is visible dirt and debris present then they are much more likely to be carrying something infectious than if their clothing is clean.
• As veterinarians get ready to leave your farm, they should be cleaning/disinfecting their equipment, cleaning their footwear, checking their clothing and washing or disinfecting their hands. Watching this can give you an idea of what your veterinarian probably did on the farm before yours. If your veterinarian is careful and pays attention to hygiene, that's a great sign.
• The more strict the infection control measures on your farm, the more strict you and your veterinarian should be about these types of measures. A farm with a revolving door of horses going to shows and sales, with a minimal infection control program, is very different from an essentially closed broodmare farm, where the only thing that comes onto the farm is semen. In the latter instance, the facility is close to a pig or poultry farm where true biosecurity is a possibility. In the former, there's little containment and basic infection control (or simply damage control) is what's really being done. That doesn't mean it's okay to be lax in any situation, but a veterinarian going onto a highly contained farm should be expected to go the extra mile with regard to personal hygiene and infection control measures.
• I've heard some horse owners comment about veterinarians in coveralls looking like "cow vets," with the implication that cow vets are not who they want treating their horses. They want to see their vet dressed like they're going out on the town, or at least in nice street clothes. However, I'd much rather see a vet in coveralls or a lab coat that can be easily changed between farms or when soiled. It's much easier to take off a pair of coveralls (and have a good supply of them in your truck) than to change your street clothes. Even though someone in street clothes might look nicer, it doesn't mean they're any better. This is a mindset issue and people need to be considering infection control when they're making such judgements.

In human medicine, patients are being educated to ask questions and demand that their healthcare providers practice good hygiene. People are being encouraged to ask nurses and physicians if they've washed their hands, and ask them to do so if they haven't when they walk into a patient's room. We need to get the same mindset in veterinary medicine. Veterinarians need to realize that they are being watched, and that paying attention to infection control and hygiene indicates good practice. While it's a touchy area at times, horse owners need to realize that they can (hopefully diplomatically) express any concerns about their veterinarian's hygiene, to try to improve any deficiencies. There is no easy solution and there are few clear answers, but general hygiene practices are a key aspect of infection control that are often overlooked.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

A large British equine charitable facility has closed temporarily because of a large influenza outbreak. Approximately 80% of horses at the Bransby Home of Rest for Horses have become infected. In a large facility like this, once you have 80% of the horses infected, there's very little chance of controlling the outbreak within the facility, although it's still very important to take precautions (such as closing the facility) to prevent the disease from spreading to other farms. Unless there is a discrete group of horses that is well removed from everyone else on the property, you have to assume that all the horses have been exposed. At that point, you basically just have to let the outbreak burn itself out, and try to manage any complications that develop in individual animals.

In some ways, if you're going to have a major disease outbreak, influenza's a good one to have. It doesn't often cause serious illness, it rarely causes death, it's not transmissible to people and it doesn't have a "silent" carrier state. The lack of a carrier state is very important since, unlike strangles (Streptococcus equi), once horses recover from influenza, they only shed the virus for a short period of time. With strangles, some recovered horses appear healthy but will continue to shed the bacterium for long periods of time, and may continue to infect other susceptible horses.

Facility manager Sally Howard is quoted as saying "Staff are always extremely careful to ensure all animals that are received by the charity are put into quarantine for at least four weeks and then thoroughly tested before being allowed to mix with the herd."

• This is a great quarantine plan. Unfortunately, something went wrong here. If there was a true 4 week quarantine and if good protocols were used, influenza would not have made it into the herd. An investigation should look into why influenza was able to break through this quarantine. Some possible explanations are neglecting to quarantine a horse, not quarantining a horse for the proper length of time, mixing quarantined horses (i.e. a horse could be quarantined for 4 weeks, but if it gets exposed to a newly quarantined horse near the end of this time period, it could become infected and be introduced to the herd before it shows clinical signs of disease), and people spreading the virus from quarantined horses to resident horses on clothing or other items. 

"The source of this infection is not yet known but we will try to discover and eliminate it."

• I understand the sentiment but it's not practical. The initial source is no longer an issue, at least in terms of managing this outbreak. There are no long-term influenza shedders, so the horse that brought influenza onto the farm is likely influenza-free now. What they need to do now is ride out the outbreak and figure out why it happened.

"Vaccines are available but the ongoing cost of protecting 271 horses would add significantly to the already high costs of maintaining the herd."

• That's a tough situation and one that is a constant challenge for centres such as this. If resources are limited, what stays and what goes? Proper herd health for that many horses is certainly expensive, and good infection control practices are very important when you have a lot of horses. This outbreak has shown what can happen when you don't vaccinate, and the costs and disruption of the outbreak certainly would have paid for a lot of vaccine, but hind sight is always 20/20.  Deciding how to spend limited resources is a difficult decision.

Fortunately, this outbreak should be controlled soon, in part because it has spread so widely on the farm. There are few susceptible horses left, and when the influenza virus cannot find any more horses it can infect, it will disappear.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

The glanders outbreak in Bahrain does not appear to be under control or slowing down. Official data are limited, but anecdotal reports that I've received directly and from various internet and news reports paint a concerning picture. A Facebook page has been started, and contains some interesting first-hand information about the outbreak and local efforts to stimulate a more aggressive outbreak response. The latest data from the OIE, which was submitted May 10, reports six infected horses, all of which were euthanized. It also states that the first two positive horses came from Syria and Kuwait six months ago, and that other horses in the same stable then became infected. It will be interesting to see whether any more information is forthcoming, and to find out:

• How many animals have been diagnosed now?
• If there is a history of glanders on the farms from which the index horses originated? (Did it really come from another country, or might there be an unknown local source?)
• What control measures are actually in place? Some people in Bahrain describe a very lax approach to control in some areas.
• How many horses are being tested? You can only identify the scope of the problem with widespread testing.

Image source: Stop-Glanders-in-Bahrain Facebook page

• Email This
• Print
• Comments
• Trackbacks
• Share Link

Around here, there's been a huge outcry about a ringworm outbreak in dogs and cats in an animal shelter.  Since I've spent the better part of the day talking about about ringworm control in small animals, I thought I might as well write about some horse ringworm issues as well.

Ringworm basics:

• Ringworm is a fungal disease caused by dermatophytes. The most common dermatophyte fungus that causes ringworm in horses is Trichophyton equinum.
• This fungus is spread through direct contact with infected horses, as well as contact with items contaminated by hair and skin cells from infected horses (e.g. tack, blankets, grooming supplies). People can move the fungus between horses, as can insects, but direct contact between horses and shared use of contaminated items account for the vast majority of infections.
• Not all horses that are infected have signs of disease. That's good for the individual horse but it also means that there can be "silent" carriers that are sources of infection for other people and animals.
• Young horses are more likely to develop infection than older horses.

Ringworm infection in horses:

• Ringworm typically causes fairly mild skin disease, characterized by patchy areas of hair loss, redness and scaling. Sometimes the lesions are itchy and the horse may cause more damage to the skin by scratching/rubbing, but most often ringworm doesn't seem to bother horses.
• Lesions are more common in the girth and shoulder areas, often because contaminated equipment was the source of infection, and because the warm, moist environment under the tack is perfect for ringworm to invade the skin and grow..

Diagnosis of ringworm in horses:

• The appearance of the skin lesions (when present) is quite suggestive, but other problems like dermatophilosis (rain scald) and staphylococcal skin infections can produce similar signs.
• A Wood's lamp (UV light) is sometimes used to detect the fungus because some dermatophytes will glow when exposed to UV light. However, most strains found in horses don't glow, so the test is not very useful.
• Culture is the best method of diagnosis, but it can take a few days to a few weeks to grow dermatophytes.

Treatment of ringworm in horses:

• Ringworm should go away on its own, given time.
• Topical treatment with substances like povidone iodine, lime sulfur, enilconazole or other antiseptics and antifungals can be used to try to speed up the process. All of them have good and bad points, and there is no consensus about which is best and whether it is even needed.

Infection control for ringworm:

• Affected horses should be isolated to prevent spreading ringworm to other horses and people. This is a zoonotic disease that can be easily spread to people in contact with the horse or items the horse has contaminated.
• Tack should be cleaned and disinfected after every use. Tack is difficult to properly disinfect. A dilute (1:50) bleach solution should be used whenever possible. There is an eniconazole preparation that is intended for environmental use, and that might be a good option for more sensitive items. Cheap items that cannot be properly cleaned and disinfected should be discarded.
• Remember that dermatophytes can survive in the environment for many months, so even equipment that has not been used for a long time may still be contaminated with infectious fungus if it was not properly cleaned before being put away.

(click image for source)

• Email This
• Print
• Comments
• Trackbacks
• Share Link

The current glanders outbreak in Bahrain has led to questions about how to control this disease. When determining an outbreak response plan, you need to know some basic information about the bug and how it is transmitted. Here are some relevant pieces of information about this disease:

Burkholderia mallei, the cause of glanders, is a bacterium that is highly contagious and highly fatal.

• Highly contagious and highly fatal are a bad combination, so the need for a prompt and thorough investigation is clear.

It is transmitted by direct contact. The bacterium is shed mainly through oral and nasal secretions and skin ulcers.

• Horses can transmit the disease by close contact with other horses. Transmission through items that are likely to be contaminated, such as feed and water buckets, is also possible. Transmission through other contaminated items like tack or anything else that has had direct or indirect contact with secretions from the horse could also occur.
• This means that a careful investigation must be performed to ensure that all horses that have potentially been exposed (directly or indirectly) are identified. People working with infected horses (e.g. veterinarians, farriers) can spread the bacterium between farms on their clothing or instruments. All these potential sources need to be investigated, which takes time and effort.

It primarily infects horses, mules and donkeys, but can occasionally infect other species like dogs, cats, camels, goats and people.

• This means that the focus of the investigation and the control meausres cannot focus on horses alone. All animals in contact with infected horses should be tested.

Infected horses may show a range of clinical signs. There are three main forms of glanders: nasal, pulmonary and skin. Nasal discharge is common, as are nasal ulcers. Fever is usually present and can be very high. Other signs that may be present include enlarged lymph nodes and bumps on the skin. Skin ulcers can develop (see image). Affected horses may cough, sometimes severely. Severe disease can develop and death can occur within a few days. Untreated, about 95% of horses will die.

• Signs of glanders, especially early in the course of infection, aren't necessarily dramatic, and could be mistakenly dismissed as routine viral upper respiratory tract infection. During an outbreak, any animal with respiratory disease must be promptly evaluated as a potential glanders case.

Infected animals that survive can shed the bacterium for years.

• This means that the outbreak won't naturally "burn itself out" like some other diseases. If all infected horses are not identified, a reservoir of infected horses may remain to continue to infect other horses.

Glanders can be diagnosed using various tests.

• The availability of tests, some of which are fairly rapid, facilitates control. The key is getting samples for testing and ensuring that the right animals get tested.

Glanders has been eradicated in many areas of the world.

• This means a couple of things: 1) The disease is potentially controllable. 2) Based on the government's response, it seems glanders is not normally seen in Bahrain, therefore significant efforts should be expended to get this outbreak under control at a national level if the coutry is to return to its previous state with regard to this disease.
• A critical question that needs to be answered is from where did the disease come in the first place? It appears glanders is considered a foreign disease in Bahrain, even though it is endemic in other countries in the region. Unless a clear source of infection identified, you have to wonder whether the bacterium is present in some small percentage of the horse population already.

Animals that recover from infection do not develop protective immunity.

• With many infectious diseases, individuals that have been infected are no longer susceptible for a certain period. This helps control the disease because the number of susceptible individuals decreases over time. The fact that the disease is highly fatal reduces the impact of this factor, but any horse that recovers has to be considered susceptible again.

B. mallei is susceptible to most disinfectants, if used properly. It can survive in the environment for prolonged periods of time, but is better able to survive in humid environments.

• Prolonged environmental survival is a concern. Unlike some organisms (e.g. influenza), you can't assume that this bacterium will die quickly on surfaces contaminated by infected horses. You need to identify potentially contaminated sites and disinfect them. Disinfection must be done properly, which is often a problem. One potentially helpful characteristic of this pathogen may be its preference for humid or wet conditions. I don't know much about the Bahraini climate but, based on its location on the Persian Gulf, hopefully at this time of year hot and dry weather predominates.

These are just some of the points to consider when developing an outbreak investigation and intervention plan. A key to any outbreak response is to take the time to think about what is going on, what might happen, and what needs to be done. Sometimes, people start acting without thinking everything through, which may lead to missing important aspects, and wasting time and money on irrelevant areas. Let's hope this investigation is being done in a thorough and thoughtful manner. Hopefully more details about the response will become available.

Image: Artist's rendition of a horse with glanders, showing characteristic purulent skin ulcers on the medial aspect of the hind leg. (click image for source)

• Email This
• Print
• Comments
• Trackbacks
• Share Link

A strangles outbreak has been identified in Northern Queensland, Australia.  The number of affected horses, the number of at-risk horses and the scope of the outbreak aren't clear, but Queensland authorities have made recommendations to the horse-owning public.

Veterinary officer Charlotte Williamson states "The best form of protection is an annual vaccination."

• Unfortunately, it's not. Strangles vaccination is moderately effective at best and should not be the primary component of a strangles prevention program. It can be potentially useful in high risk situations, but it's far from a cure-all. If you use vaccination as your main preventive measure, you may have a lower likelihood of your horse getting sick. If you have a good general infection control program that prevents S. equi from getting on the farm, the immune status of your horses doesn't matter.

Fortunately, other good infection control practices were highlighted by Dr. Williamson, including:

• Keeping horse gear and equipment clean and disinfecting equipment between use.
  
• Washing hands before and after handling different horses.
• Monitoring visitor movements on your property and avoiding visitor contact with your horses unless they have clean hands, clothing and boots.
  
• Keeping records of horse movements on and off your property. (Actually, keeping records doesn't help prevent introduction of an infectious disease, it helps identify how it got there when an outbreak occurs. More important is having proper protocols for moving horses.)
  
• Quarantining new horses to your property for at least two weeks before introducing with others. (This is better than no quarantine, but it doesn't pick up healthy strangles carriers, an important source of infection. If you really want to prevent introduction of S. equi, you need to test new horses. This isn't practical in all situations, unfortunately.)
  
• Isolating sick horses from other horses on your property. (This also requires good protocols for handling infectious cases so that S. equi isn't inadvertently spread from an isolated horse)
• Feeding and tending to sick horses after dealing with other horses

• Email This
• Print
• Comments
• Trackbacks
• Share Link

We've taken the plunge into (the time- and money-sucking abyss of) pony ownership for our 3 daughters. Foxie Casie, a 4-yr-old Welsh cross, arrived yesterday, much to the delight of the girls and mixed delight and trepidation to their parents. I figured I might as well discuss some of the infectious disease-related issues dealing with acquisition of a new pony.

Vaccinations

• She came vaccinated against rabies and tetanus, with the last round having been done this spring. I'll re-do rabies and tetanus next spring. She'll get a rabies vaccination every year, but I will probably stretch out the tetanus vaccine since yearly vaccination is likely not necessary (especially considering tetanus vaccination is labeled for every 5 years in Australia).
• I always debate about the necessity of West Nile virus (WNV) vaccination, since it's very rare now in Ontario and I'm not aware of any mammalian cases in the general vicinity. I'll probably err on the side of caution and vaccinate her, but will do so in late summer, in advance of the true high risk period here. Typically, any WNV cases that occur here develop late August through October, so vaccinating the pony in late July, to get peak immunity during the main risk period, makes sense.
• I will probably not vaccinate her against eastern equine encephalitis (EEE) since it's so rare and hasn't been found around here.
• She lives with no other horses and won't be traveling off the farm in the near future, so there's no need to vaccinate against things like influenza, equine herpesvirus or strangles.

Deworming

• She was dewormed about one month ago. I'll check a fecal egg count soon and go from there. Since she's the only horse on the farm (the sheep are low risk for passing parasites to her), if we get started right and keep her from contaminating the pasture, a pretty conservative parasite control program with periodic fecal egg counts and deworming as needed should suffice.

New horse infectious disease issues

• She didn't have much of a trailer ride and appeared healthy when I saw her the day before, so shipping associated diseases like pleuropneumonia ("shipping fever") are pretty unlikely.
• Diarrhea's always a concern. Risk factors for diarrhea include shipping, stress, diet change and antibiotic use. Well, she's been shipped, presumably stressed, had her diet changed and been introduced to pasture, so she has some risk factors. She's not exposed to other horses, which helps, and she has no need for antibiotics (at least at the moment). So, basically, I'll give her a good diet (good hay and not-very-lush pasture) and keep an eye on her. My diarrhea research background probably makes me look at her feces more than the average person, but so far, so good.

I'm sure there'll be more to come... hopefully not much from the actual infectious disease standpoint. 

• Email This
• Print
• Comments
• Trackbacks
• Share Link

Strangles outbreaks are a pain. They can result in infection of a large number of horses and major hassles. Unfortunately, while many people behave properly during outbreaks, there are also people out there who either don't think, don't listen or don't care (or don't do any of these). 

I've had a few strangles outbreak calls this week and problems with people not listening to the veterinarian's or farm manager's recommendations have been a common theme. I realize that keeping horses on the farm while an outbreak is being addressed can be inconvenient, particularly for some people who have trained hard for specific shows, but taking your horse off the farm while a strangles outbreak is underway and exposing other horses to yours is completely unethical. People that take their horse off the farm in the midst of a strangles outbreak are a major cause of new outbreaks, and a big part of the reason this disease continues to be common.

If you have a horse that has been exposed to strangles, act ethically.

• Keep the horse at home while the status of the farm and the horse are being determined.
• Don't expose it to other horses until you know it's negative, ideally through testing it and getting three negative nasopharyngeal (throat) cultures.
• Don't kid yourself into believing that you can prevent infection of other horses at a show or another event. You can do things to reduce the risk, but if your horse is shedding S. equi (the bacterium that causes strangles) you cannot completely prevent the risk of exposure.
• Get good advice regarding how to address the problem (e.g. from your veterinarian), and listen to the advice.

You should also think about this:

• If you knowingly take an exposed horse somewhere and other horses get sick, could you get sued for any resulting problems? I don't know of this happening (yet), but it's certainly a possibility and you don't want to be the test case.
• Do you really want to be known as the strangles vector, and the person that caused an outbreak?
• Ignoring a strangles outbreak won't make it go away. In fact, trying to ignore it usually just leads to it being a more prolonged outbreak. It's really a matter of "short term pain for long term gain."

More information about strangles can be found in on the equIDblog Resources page.

Image source: www.regardinghorses.com

• Email This
• Print
• Comments
• Trackbacks
• Share Link

Strangles continues to be a hot topic in southwestern Ontario. Whether it's really because of increased numbers of cases this year or just more talk (especially on the internet) isn't clear, but there are many questions, concerns and misconceptions regarding this disease and Streptococcus equi, the bacterium that causes it.

One question that often gets asked is: "How long does S. equi survive in the environment?"

There is no simple answer to this question, despite many people trying to give one. Survival of bacteria outside of the host (i.e. a horse) depends on many different factors, including temperature, humidity, the presence of other bacteria, exposure to sunlight (UV light), and whether the surface the bacteria are on can be properly cleaned and disinfected. These factors vary tremendously between different potentially contaminated areas of a barn or farm.

Consider these two different locations:

• S. equi deposited on a smooth fence rail or other outside surface doesn't survive for long. It's exposed to tough environmental conditions, particularly sunlight. A recent study (Weese et al. Can Vet J 2009) looking at wood, metal and rubber surfaces artificially contaminated with S. equi and left outside showed that S. equi died very quickly, often within 24 hours.
• Contamination of an indoor surface, like a stall wall, is different. It's a more sheltered environment, with no sunlight and probably a more moderate (or at least less variable) temperature. We don't know how long the bacterium could survive indoors. A couple of weeks is probably not unreasonable, in the absence of cleaning and disinfection.

The bottom line is the potential for environmental survival of S. equi is quite variable and largely unknown. Anyone giving definitive answers doesn't understand the situation. At best, we can give some general guidance, but we can never say for certain when a surface will be S. equi-free. We can have the most confidence saying that an outdoor surface that has good exposure to direct sunlight will probably not harbour S. equi for long, but beyond that, we have to hedge our recommendations a great deal to be on the safe side.

Is the environment a significant source of infection anyway? It's hard to say. Certainly, horses are a much more important source. The hands and clothing of people in contact with infected horses may be as (or more) important than the environment. We should still pay attention to environmental surfaces, but recognize the limitations in what we know.

• Good general infection control practices are needed to reduce environmental contamination. Quarantine of new horses and keeping different groups of horses in discrete areas of the farm help reduce widespread contamination.
• Stall surfaces should be amenable to cleaning and disinfection. Stall walls should be a solid, sealed surface, to prevent bacteria from hiding in cracks and crevices.
• Items in contact with horses' faces and mouths (e.g. buckets, hay nets, tack) should not be shared between horses if at all possible. Each horse should have its own water and feed buckets.

More information about strangles is available in our archives and on the equIDblog Resources page.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

Infectious disease outbreaks in barns get a lot of attention, and none of it's good. Unfortunately, the same degree of attention is rarely given to measures used to reduce the risk of infectious diseases. Infectious diseases are an inherent risk of horse ownership, but there are a lot of things that we can do better to help reduce the risks. Developing a good infection control plan is one thing. Enforcing it is another. The best laid infection control plans are often rendered useless because people don't comply with them. This is a particular problem in some boarding stables that have multiple different horse owners with different ideas, perceptions, veterinarians and willingness to cooperate. One way to help improve infection control in these situations is a good boarding contract. Why? Because a boarding contact can lay out exactly what is expected from everyone up front, and the repercussions that can occur if someone (barn owner or horse owner) doesn't do what is expected. Infection control responsibilities should be built into every boarding contract. This helps improve infection control by laying the foundation for application of good infection control practices. There are several infection control topics that should be addressed in boarding contracts. Some things to consider include:

• When does a veterinarian have to be called? You don't want to mandate unnecessary veterinary visits, but prompt examination of horses that might have infectious diseases is very important. For example, horses that have strangles are not able to infect other horses for the first couple of days after their initial fever spike. Identifying these horses early lets you get them isolated and reduce the risk of infection. Waiting a couple of days can put the whole barn at risk.
• What information has to be shared? Veterinarians are bound by confidentiality rules and can't share information about their patients with other people unless they have permission. That means a veterinarian may tell an owner they have an infectious horse, but if that person doesn't do anything or tell anyone, the veterinarian can't inform the barn owner that a risky situation is present. Mandating reporting of certain things to the barn could help with this.
• What happens when a horse with an infectious disease is identified? It's best to spell this out in advance so that everyone knows that there may be restrictions on horse movement or other activities to reduce the risk of transmission.
• Will testing be required in certain situations? In some cases, testing of horses is very important to determine if there is a problem and what it is. It needs to be determined up front if the barn can mandate such testing in specific situations, and who pays for it. If one person refuses to test as part of a program to determine if a farm is free of strangles after an exposure or outbreak, all of the other efforts might be jeopardized.

Will all these ideas be popular? No. Infection control practices are often somewhat cumbersome, but they are important. Yes, some people will fight them. Yes, some people may threaten to leave.  But:

If you are a barn owner, wouldn't you rather have a barn full of people that are reasonable, have respect for the health of all horses in the barn, and are willing to commit to doing things right?

If you are a horse owner, wouldn't you want your horse is a barn where you know that people are committed to reducing the risk of infections?

For me, the answers are clear.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

Few things get the horse rumour mill going like strangles. This infectious disease carries such a stigma that the simple act of having a sick horse (or even the suggestion that someone has a sick horse) can lead to rumours that spread like wildfire, along with complaints, accusations and other generally antisocial behaviour. Currently, depending on what rumours you listen to, there are either major strangles outbreaks going on in multiple large facilities across Ontario, or everyone is fine and there are no sick horses of any type in the province. (Like most things, the truth probably lies somewhere in between.)

Strangles, caused by the bacterium Streptococcus equi, is an important equine infectious disease. It's present in horses internationally and there are always cases and small outbreaks underway in Canada (as in other countries). It's also potentially controllable using good infection control practices, but the stigma, rumours, denials and other associated problems hamper such efforts.

Because of the stigma associated with strangles, some peoples' approach is to deny the possibility that their horse may have the disease, or to avoid getting proper testing done. I've heard people deny that they have strangles on their premises, but in the same sentence say that they aren't letting any people on the farm for a couple of weeks with no explanation as to why. I've also seen situations where strangles is clearly present but people refuse to have culture samples taken - because if no cultures are taken and found to be positive, they can still say that they haven't had any horses diagnosed with strangles (even with stall after stall of horses with fever, nasal discharge and draining abscesses). Fortunately, most horse owners and farm managers don't take this approach, but the fact that some do gives strength to the rumours that often circulate.

Denying that an infectious disease problem exists is never a good idea, because it usually hampers implementation of the required control measures. It's also unethical if these denials and improper practices lead to more infections. If strangles is on a farm, people need to own up to the fact and act accordingly. Yes, the proper control measures are a hassle and can interfere with showing, racing or other uses. But closing your eyes and hoping it goes away does not work. At the same time, people need to take a balanced approach when they hear about strangles. Having a horse with strangles does not necessarily mean that there is bad management on the farm. Yes, many infections could be prevented with good infection control precautions, but we can't prevent all infections at this point. The more people point fingers about strangles cases, the greater the pressure for people to hide the problem.

• If you have strangles on your farm, admit it. There's no use hiding it because the truth will  come out eventually, and the rumours may be worse than the truth, anyway. Let people know what's going on and what you are doing to control it. It's often the absence of information that causes most of the fear and complaints.
• If your horse is on a particular farm when a case of strangles is diagnosed, be part of the solution, not a hindrance. Help out by supporting the barn owner and other horse owners. Do what is being asked of you. Don't immediately take your horse off the property (and possibly spread the outbreak to another facility). And cut them some slack - it may not be their fault, and it could just as easily have been your horse that was infected.
• If you've had strangles in your horse or on your farm, take the time to figure out what happened and why. This shouldn't be done to assign blame. It should be done to figure out how to prevent it the next time.

Strangles isn't Ebola. It's a problem, but one that can and should be handled with a reasonable and logical approach. More information about strangles can be found on the equIDblog Resources page.

Image: Draining abscesses of the submandibular lymph nodes of a horse with a classic case of strangles (credit: Dr. Nancy Loving, thehorse.com)

• Email This
• Print
• Comments
• Trackbacks
• Share Link

TheHorse.com has a good article about deworming, which includes six good parasite-fighting tips from Dr. Craig Reinemeyer. Check out the full article for all the details. Here are the key points and some comments:

1. Stop focusing on the wrong things

It's easy for people to get hung up on a few concepts or topics and not see the big picture or the real problems. We need to think in terms of the horse(s), not the parasites. We're trying to optimize horse health. That doesn't necessarily mean killing all parasites, nor does it mean relying soley on drugs to control them. Conceptually, we need to think about parasite control, not just deworming.

2. Plan parasite control around parasite biology, not a calendar

There is no "standard" deworming program. Every program needs to be tailored to the geographic region, farm and horse. What happens here is Ontario is very different from what happens in Florida in terms of parasites.  For example, the risk of transmission in horses turned out on pasture in Florida in February is certainly different from those turned out in snowy fields in Ontario at the same time of year. Even in the same region, what happens on one farm may be very different than what happens on another. When designing a parasite control program, you need to consider what is going on with worms in the horses and in the environment to determine the optimal approach.

3. Don't encourage resistant parasites

Most people know antibiotic-resistant bacteria are a bad thing, but often concerns about anti-parasitic resistance are ignored. We only have a limited number of antiparasitic drugs, and there aren't many more coming in the near future. Heavy use or misuse creates an environment where resistance may emerge. It's being seen with certain bugs and certain drugs, and needs to be taken seriously - now.

4. Don't treat all horses the same

As I mentioned above, you need to tailor parasite control to something that is relevant for the region, farm and horse. Different horses are at different risks of exposure. Some horses are naturally more resistant to parasites, so these animals don't need to be (and indeed shouldn't be) treated the same as more susceptible horses. Deworming should be tailored to the needs of the individual horse. Yes, it takes more effort and some thought, but it's worth it.

5. Practice evidence-based parasite control

That means use all available information to make decisions. It includes knowing what parasites are a concern on the farm (which requires testing), what antiparasitic drugs have been effective on the farm (which requires testing to determine treatment success), an understanding of farm management practices, and information from research about deworming strategies and drugs. Performing fecal egg counts is a critical component of this, and something that is not done nearly enough.

6. Be prepared to change

Something that works today may not work in the future. You can't get stuck in your ways and assume that since something worked in the past, it will always work.

Image source: www.ponytalesblog.com

• Email This
• Print
• Comments
• Trackbacks
• Share Link

Often, when someone calls and asks about management of strangles, one of the first questions is "What disinfectant should I use?"

There are basically two answers that I give:

1) Streptococcus equi, the cause of strangles, is susceptible to most disinfectants, provided they are used properly. That means using them at the proper concentration, providing the recommended contact time (5-30 minutes, depending on the disinfectant) and ensuring that there is minimal organic debris (e.g. dirt, manure, pus) present on the surface to be disinfected. The latter is a key point, as disinfectants do not work well in the presence of debris, so it's therefore understandably very difficult to really disinfect a stable. Some stable surfaces (e.g. sealed solid walls and floors, buckets) are able to be disinfected if it is done properly, while other surfaces (e.g. dirt floors, unsealed wood walls, leather) are essentially impossible to disinfect.

2) Disinfection is a very minor component of strangles control. It is something to pay attention to and it should be done properly, but too often people to focus on disinfection as the key infection control measure. Just disinfecting surfaces, but ignoring aspects like cohorting exposed and unexposed horses, restricting horse movement, testing for carriers, regular temperature checks of all horses to detect early cases, using good personal hygiene and using protective outerwear, is bound to fail in terms of controlling an outbreak.

So, don't ignore cleaning and disinfection, but don't' rely on it as the main component of strangles control.

More information about strangles can be found on the equIDblog Resources page.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

Rhodococcus equi is a bacterium that is an important cause of respiratory disease in foals. It typically causes numerous abscesses in the lungs, and it is an important cause of illness and death in foals from a few weeks to about six months of age. Infections of other parts of the body can occur, and these can cause serious problems because they can be hard to diagnose and hard to treat.

A recent study in the Journal of the American Veterinary Medical Association (Reuss et al 2009) described extra-pulmonary disorders (EPDs, disorders in parts of the body besides the respiratory tract). They studied 150 foals, and 74% had a least on EPD. These included:

• Immune-mediated synovitis (25%): This is a well-recognized problem where R. equi-infected foals get enlarged joints because of accumulation of excess joint (synovial) fluid. Fluid-distended joints can occur with joint infections, but with immune-mediated synovitis it's caused by the immune system alone. This typically does not result in long-term joint problems, although it's important to determine whether the foal has an infection which needs aggressive care, or just inflammation which is best left alone.
• Abdominal abscesses (17%): This is a very serious problem and abscesses in the abdomen can be very difficult to treat. These foals often die.
• Uveitis (11%): Inflammation of the eye, which can occur as a result of the immune response or infection. 
• Septic synovitis (9%): As opposed to immune-mediated synovitis, this is an infection in the joint. This is very serious and can cause permanent joint damage.
• Pyogranulomatous hepatitis (11%): This is inflammation of the liver with abscesses and pus.
• Pleural effusion (3%): Accumulation of fluid between the lungs and body wall. This can be the result of severe lung disease.
• Meningitis (3%): Infection of the layer covering the brain, which is never a good thing.

Foals that had EPDs were more likely to die than foals with infections only involving the lungs, which isn't particularly surprising. In particular, the presence of uveitis, bloodstream infection, joint infection (not immune-mediated synovitis) and abdominal abscessation were associated with failure to survive.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

Herd immunity is an important infectious disease concept. Basically, it involves trying to ensure that a high enough percentage of a population is resistant to an infectious disease so that the disease cannot be spread easily through the group. Ensuring that a large percentage of the population is vaccinated helps protect individuals that cannot be vaccinated (because of allergy, disease or other reasons) or that did not properly respond to vaccination (not all vaccines protect all vaccinated individuals).

"Herd immunity" usually refers to this concept when applied to herds of animals (such as horses or cows), but the "herd" can be a a small local population, a regional population, or broader, and it can be people or animals. For some human infectious diseases, it's been shown that vaccination of 75-95% of the population is required to prevent outbreaks. If vaccination rates start to slip, the chance of an outbreak increases. This is best seen in some areas where vaccination rates decline in certain groups of kids because parents are reluctant to have their children vaccinated (for one reason or another), and subsequently outbreaks of disease start occurring (or increasing).

Vaccination is an important (but not the only!) infection control tool. For diseases that are transmissible between horses (or dogs, or people, or whatever other "herd" is being considered), vaccination of a single horse helps protect that individual from disease, and also helps protect the rest of the population.

During a public health infectious disease course that I teach, a student showed a link to this interesting and amusing demonstration of herd immunity from the UK. Make sure you have your sound turned on. It's an entertaining description of the concept of herd immunity.

When you're deciding on your vaccination program, for both individual horses or a farm, be conscious of the herd immunity concept.

This equIDblog entry was originally posted on the Worms & Germs blog on 05-Oct-09.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

During a strangles outbreak, people often ask how (and when) they can say their farm is "strangles-free." They usually don't like the answer. Declaring a facility to be free of strangles, a highly contagious disease caused by the bacterium Streptococcus equi, is not cheap, easy or quick. It is, however, important.

A major source of the strangles bacterium is horses that have been infected but either didn't get sick or have recovered, yet are still shedding S. equi in their nasal secretions. In some horses, S. equi can persist for long periods of time (i.e. months) in their nasopharynx (throat area) or guttural pouches. Identification of these carriers is crucial for strangles control and must be done to have confidence that strangles has really been eradicated from a farm.

Identification of carriers involves taking samples from the nasopharynx to test for the bacterium. Nasopharyngeal washes are preferred but nasopharyngeal swabs (note: this is different from a nasal swab) are also acceptable. These should be collected by a veterinarian. They can be tested for S. equi by culture or PCR (a molecular test), or both. Any positive horses need to be investigated further, including endoscopy and culture of the guttural pouches.

Three negative samples from the nasopharynx and/or guttural pouches, collected weekly, are required to declare a horse free of strangles. If a positive horse is identified during the process, the clock starts again on its testing, plus all other horses with which it has had contact. Even though a horse may have had three negative samples, if it has been in contact with a positive horse, you have to assume there's a chance it was infected after testing started, so you need three more samples after its last contact with any positive horse.

While this process is not cheap, easy or quick, it is strongly recommended.

At the same time, it's also a good idea to review why the strangles outbreak occurred and how it can be prevented in the future. This is a step that's often overlooked.

More information about strangles can be found on the equIDblog Resources page and in our archives.

Image: A horse with draining tracts from classic strangles abscesses between the lower jaw bones

• Email This
• Print
• Comments
• Trackbacks
• Share Link

An Australian horse group, the Queensland Horse Council, is calling for the equine industry to change its culture in terms of biosecurity. I agree completely, however, as I've said before, I think the term "infection control" is really what we are talking about here. Biosecurity involves keeping pathogens off a farm, as is done with tight controls on pig farms. Infection control also tries to do this, but realizes it's not completely possible with how we manage horses, and therefore also focuses on controlling the impact and spread of infectious diseases on the farm.

This is obviously in response to the recent Hendra virus outbreak in Australia. It usually takes a remarkable (and sometimes tragic) event to get people talking about infection control. It becomes a hot topic, people call for improved efforts and resources, and everyone gets on board... for a few weeks. After a short period of time without problems, people tend to revert to their usual behaviour, and infection control often gets marginalized again. The key, therefore, is establishing a sustained effort. That's the hardest part of infection control, be it in a hospital or on a farm.

Queensland Horse Council (QHC) president Debbie Dekker is quoted in the Sydney Morning Herald as saying "We are a pretty gung-ho lot and biosecurity is treated like some sort of wussy thing. Everyone needs to tighten up their biosecurity practices."

Well said.

"We still have a lot of people who don't know about Hendra virus so we need to get the information out to horse owners."

Communication and education are key. Just telling people they need to do something is not going to be very effective. Infection control practices usually involve some degree of effort or change in normal practices. If people don't understand why they should change, they are less likely to do so.

Sporadic infectious diseases and outbreaks will continue to happen (in horses, people and others). We can never completely eliminate the risk. We can, however, reduce some of the risks. While nothing can change what has happened with the most recent Hendra virus outbreak, we should at least make sure some good comes out of it, and that it leads to improved infection control awareness in Queensland and beyond.

Thanks to Dr. Doug Powell of Barfblog for the headline.

Image source: www.qldhorsecouncil.com

• Email This
• Print
• Comments
• Trackbacks
• Share Link

It's a good general practice to isolate and monitor any horse that has been off the farm, especially one that has been to an equine hospital. This is often a touchy area for equine hospitals - telling people to isolate and monitor their horses might suggest to owners that the hospital has an infectious disease problem, and lead to negative perceptions of the facility or having people take their business elsewhere. However, it's been proven time and again that the "head in the sand" approach does not work for infectious diseases. Discussions of infectious disease risks in horses that have been hospitalized should be taken as an indication that the facility has an open and proactive infection control program. Therefore, places that talk about disease rates may very well be the safest facilities, because they are monitoring infectious disease, taking precautions and showing that they care about infection control.

Horses coming home from equine hospitals are always going to be at some increased risk of shedding infectious agents. Here's why:

• Some healthy horses carry various infectious agents at any given time. Stress, shipping, diet change, antibiotic treatment and other factors that occur during hospitalization can result in increased shedding of these organisms that the horse was already carrying. For example, equine herpesvirus lives dormantly in a reasonable percentage of healthy horses. They don't usually shed the virus, but may start shedding when they are stressed. So, a horse that was not shedding herpesvirus could start shedding as a result of hospitalization, and thereby expose other horses on the farm. Similarly, stress, shipping, diet change, antibiotics and anesthesia can cause horses that were already carrying low levels of Salmonella to start shedding high levels of the bacterium, potentially resulting in disease in the affected horses or transmission to others.
• Horses can acquire infectious agents in hospitals. An inherent risk of visiting any hospital (like any fair or other event) is exposure to infectious agents. Horses that go to hospitals are at higher risk of picking up things because of the reasons described above. The more horses present and the poorer the infection control program, the greater the risk. Regardless of the quality of infection control at the equine hospital, some risk always remains, but a good infection control program can greatly reduce the risk.
• Horses that return from hospitals are often at higher risk of becoming infected with (i.e. more susceptible to) various bacteria and viruses for a short time after they return home. Therefore, they might be at greater risk of picking up something that is circulating on the farm already but not causing major problems to the otherwise healthy horses.

Routine isolation and monitoring of horses returning from equine hospitals is a good management practice. The likelihood of a problem developing is low, but it's much better to have problems occur when the horse is isolated so they can be contained. A short isolation period lets horses get rid of infectious agents they have picked up or started shedding as a result of hospitalization, so they don't expose other horses. It also lets you identify problems that develop (e.g. diarrhea, cough, fever) as a result of being off the farm, before the horse is expose to other animals on the farm.

The ability to properly quarantine horses on a farm is variable, depending on the facility, but effort should be taken to provide the greatest degree of isolation/quarantine that is feasible and practical. Every farm should have an infection control program that includes a plan on how to handle horses that have returned from equine hospitals.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

TheHorse.com reports that a third horse that tested positive for the reportable, foreign disease equine piroplasmosis (Theileri equi infection) was illegally removed from quarantine in Kansas... in June. Two other horses were broken out of quarantine shortly after they were diagnosed in June, and have yet to be found. These horses could be anywhere spreading this disease, and may result in the US losing its piroplasmosis-free status. The latest OIE report indicates that the third horse was reported missing the day after the other two horses. That's one more potentially infectious horse on the loose, and one more threat.

This appears to be a good example of what can happen when you combine recklessness, carelessness and stupidity (perhaps with a little bit of laziness on the side). Any effective quarantine needs to be properly implemented and monitored. Any breaches of quarantine need to be immediately identified, reported, investigated and communicated. I haven't seen any previous information about the missing Kansas horse; I can't find anything in earlier press releases or other statements. If this information was withheld, it shows pretty blatant disregard for effective communications. People need to know when there are disease threats. Knowing that a horse with piroplasmosis is on the loose is important because this horse has to have gone somewhere - possibly a public stable or other facility with other horses. If people knew a horse was broken out of quarantine one night and someone showed up at the barn with a horse the next day, they could ask some questions or call the authorities to help protect their farm and their animals. Without this information, they're helpless.

(Image source: www.funnyphotos.net.au)

• Email This
• Print
• Comments
• Trackbacks
• Share Link

There is apparently still no evidence regarding the location of two horses with piroplasmosis that were stolen out of quarantine in Missouri. I've been trying to find out more information, to no avail. TheHorse.com quotes a senior USDA veterinarian who states that, as of June 30, the location of the horses was still not known.

This is a pretty concerning situation. While piroplasmosis is not highly transmissible, these two missing horses could be putting many other horses at risk, as well as the piroplasmosis-free status of other regions of the US (if they have been moved to other states or infected other horses that have subsequently traveled to other states).

Piroplasmosis, which is caused by the bloodborne parasite Theileria equi, is transmitted by ticks and through contaminated needles.  If these horses are in an area where there are tick species that are capable transmitting this parasite, piroplasmosis could be silently spreading. Whoever took these horses, and anyone associated with this situation, are incredibly irresponsible and are putting many other horses at risk. This is another good reminder of why you need to be careful and ensure you know as much as possible about all horses (and their owners) that you allow on your property.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

The horse population is perpetually at risk for major disease outbreaks. Sometimes we get lucky and nothing happens, sometimes we get regional outbreaks of disease, and rarely we see large national outbreaks (e.g. influenza in Australia). There are many reasons for this risk, and most involve how we manage our horses. Unlike other domestic animals that rarely travel and are not commonly exposed to large numbers of "new" animals on a routine basis, some sectors of the horse population are highly mobile and there are regular chances for disease exposure. Some of these risks are inevitable (e.g. traveling for competition, emergency visits to an equine hospital).

Ideally, every horse that leaves the property for any reason, be it a show or a stay at an equine hospital, should be isolated upon return. Keeping a horse isolated for 1-2 weeks provides time for transmissible infections to be identified, and for elimination of certain infectious diseases that are only shed for a short period of time (e.g. equine influenza). This is most important when there are high-risk horses on the property (e.g. pregnant mares) or when horses are traveling to places with a high risk of exposure to an infectious disease.

Obviously, isolation of all horses upon return is not practical in all situations, such as when horses are leaving for events on a regular basis or when appropriate facilities do not exist. In these situations, you have to accept that you are putting yourself (and the other horses in the barn) at increased risk for infectious diseases. Therefore, other components of a good infection control program are even more critical, such as rapid identification of horses that might have an infection,  a sound infection control plan when such horses are detected, a solid preventive medicine program and good general hygiene measures. Good management practices will reduce (but not eliminate) the risk of disease transmission when an unknown carrier gets on the farm.

If isolation of all returning horses is not possible, you should take particular precautions around:

• Horses that have been to events where sick horses are present.
• Horses that have been in contact with horses from sales.
• Horses that have been at an equine hospital (especially one without an infection control program).

Even if you can't (or won't) isolate new arrivals, you can do other things, such as:

• Make sure that new horses are checked carefully on a daily basis (or more often) for signs like fever, loss of appetite, cough, nasal discharge, enlarged lymph nodes and diarrhea. Also, make sure something happens with that information! It's not helpful if someone is checking temperatures but doesn't know what to do if they identify a horse with a fever.
• Keep new horses as far away as possible from resident horses. For example, keep them at the least-used end of the barn, maybe with an empty stall in between them and any other horses. It doesn't replace true isolation but it's better than nothing.  In particular, keep new horses away from the highest risk horses, like broodmares.
• If you have to turn out new arrivals, turn them out by themselves or at least always turn them out with the same group horses, so that if they are infectious, a limited number of horses are exposed.
• If you have any doubts about the health of a new horse, get it examined by a veterinarian. Some diseases have narrow windows of time when horses may show signs of infection but not yet be able spread the disease (e.g. horses with strangles will spike a fever before they start to shed the bacterium). Therefore, prompt action is critical. Calling a veterinarian out earlier can help determine the appropriate measures to take and make the difference between one sick horse and one sick farm.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

The American College of Veterinary Internal Medicine (ACVIM) has released a consensus statement on equine herpesvirus type 1 (EHV-1). The ACVIM is the specialty organization for veterinary internal medicine in North America, and every year it produces consensus statements on selected large and small animal topics. These are developed by a group of experts in the field, who review current knowledge (and knowledge gaps) and come up with a comprehensive overview of the subject. This consensus statement has detailed information on various aspects of EHV-1, including diagnosis, vaccination and infection control. It can be accessed through the ACVIM website, on the equIDblog Resources page, or by clicking here.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

Disinfection of stalls is an important infection control tool, especially stalls that have housed horses with potentially infectious diseases and stalls used for foaling. Unfortunately, proper disinfection of stalls is difficult even at the best of times, and is rarely achieved on most farms.

Three things are required to successfully disinfect a surface:

• A surface that is amenable to disinfection
• The right disinfectant
• Proper use of the selected disinfectant

Surface amenable to disinfection can be difficult to come by in a barn. Surfaces must be cleaned prior to disinfection. You cannot disinfect dirt, bedding, manure or similar substances. You also cannot thoroughly disinfect porous surfaces because bacteria can live in the pores and cracks, and thereby avoid contact with the disinfectant.   Another issue is biofilms - accumulations of debris produced by bacteria on surfaces that protect the bacteria from disinfectants. Good physical cleaning helps reduce biofilm accumalation. A common problem with disinfection in barns is failure to remove organic debris (e.g. bedding, manure, dirt) prior to applying a disinfectant.

Using the right disinfectant is critical. I’ve done many infection control investigations on farms where I've found that the "disinfectant" being used is actually just a cleaning agent with no disinfectant properties. Even among disinfectants, not all products are created alike. There are differences in range of activity against microorganisms, activity in the presence of organic debris, how quickly they kill, toxicity to animals and people, and how hard they are on surfaces.

Even an excellent disinfectant will be ineffective if it’s not used properly. Common errors include not diluting the disinfectant properly and not providing adequate contact time with the surface in question. Disinfectants do not typically kill instantly - they need time to take effect. Often, 10-30 minutes of contact time is recommended.

Here are some tips for disinfecting stalls:

• Make the stall as disinfection-friendly as possible. Wood surfaces should be sealed with two coats of marine-quality varnish or paint, and repainted whenever defects in the surface are found. Concrete is very porous - any concrete that needs to be disinfected should also be painted to seal it.
• If you use removable rubber floor mats, remove them and disinfect them separately. Sunlight is a great "disinfectant" - leaving mats in the sun for a day or two is a great supplemental disinfection tool. If you leave mats in the stall during cleaning and disinfection, bacteria will live in the nice moist area under the mats that you don't reach with the disinfectant.
• Thoroughly clean the stall before trying to disinfect it. Disinfection cannot be achieved without proper pre-cleaning. Remove all bedding and other debris. Scrub surfaces so they are clean prior to disinfection. However, avoid power washers as these can damage surfaces, creating nooks and crannies in which bacteria can hide, and can spread bacteria into the air.
• Choose a disinfectant that works relatively well in the presence of some organic debris.
• Read the label of the disinfectant carefully to ensure that you are using the proper concentration and contact time.
• Don't forget to also disinfect buckets, hay nets and other items that are in the stall.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

Canadian horse breeders are calling for efforts to streamline semen importation requirements that have been implemented by the Canadian Food Inspection Agency in response to the "outbreak" of contagious equine metritis (CEM) in the US. The new regulations and increased paperwork are causing tremendous problems for breeders trying to import semen in a timely manner. Any delays in clearing semen shipments at customs can result in decreased viability of the semen as well as problems scheduling personnel to perform insemination of the recipient mares. Sometimes, samples can't get through at all. Breeders shipping semen from the US must get health papers (sometimes from someone a few hours away) to send with shipments. Many of the challenges are simply logistical and bureaucratic problems that should be able to be addressed with some common sense and willingness to help. Regulatory and industry personnel need to figure out ways to address these problems without compromising the health of Canadian horses. 

While important regulations should be reviewed to see if they can be more practical and efficient, it is critical that biosafety not be sacrificed for convenience. The impact of a single case of CEM in Canada would be tremendous. It's increasingly clear the the CEM situation in the US is not completely understood.  It is not a readily definable outbreak with a clear source that can be tracked. Rather, this disease appears to be have been present in the US for a few years (at least), and that efforts to get the situation back under control will be very complicated. A "loose" effort in Canada could have disasterous effects.

Many equine veterinarians are concerned that the regulations currently in place are not adequate to prevent CEM from entering Canada. One major concern is the failure to evaluate horses moving across the border. The current regulations only deal with horses from farms where CEM has been diagnosed - it's far from certain that US authorities know where all the CEM-infected animals are. Since transmission of CEM is more likely during live breeding than artificial insemination, horses from these farms are a big concern. This is also potentially a situation where well-intentioned rules could have the wrong effect. Some people are shipping their horses to the US for breeding, because sending them down and bringing them back up doesn't require any extra precautions for CEM if the farm is not a "known" CEM farm. If there are some breeding farms that are infected but not identified, which is definitely possible, then the unregulated movement of these breeding animals could create a very hazardous scenario.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging problem in horses. Owners often ask if they should have their horses tested to see if they are MRSA carriers. There's no simple answer that applies to all farms, but basic points that need to be considered include:

• MRSA is endemic in the horse population. A small percentage (<5%) of healthy horses carry MRSA at any given time, and it likely circulates regularly between groups of horses.
• MRSA infection only occurs in a small percentage of the horses that are exposed to the bacterium - most horses never develop signs of illness.
• MRSA can be transmitted to between horses and people.

So you can see why people might want to test their horses and there are few situations where screening really makes sense. Remember, though, that screening is only useful if you plan to do something about the results. If your horse is MRSA positive, what will you do? If the answer is nothing, or you'll just make sure you wash your hands well after handling your horse, I'd tell you that you should be doing that anyway and not bother with the test. However, there are a few scenarios when screening horses for MRSA is a good idea:

• Screening is a key component to any plan to eliminate MRSA from the farm. Eradication of MRSA can usually be accomplished quite effectively using screening and good infection control practices (and, if there are no clinically infected horses, not one dose of antibiotics!).
• Some farms routinely screen incoming horses for strangles before they are allowed to have contact with resident horses. This can be done for MRSA as well, to reduce the risk of MRSA getting onto the farm and silently spreading from horse to horse. It's not as straightforward for MRSA as it is for strangles, because we know less about the best  screening methods and, probably more importantly, people (not just horses) can bring MRSA onto the farm.
• When an MRSA outbreak is underway, or when efforts are being made to determine why a particular horse developed an MRSA infection, screening can be useful - but again, only if there's a plan to use the results.
• Our equine hospital screens horses for MRSA on admission, so that we can isolate carriers and reduce the risk of transmission to our highly susceptible hospitalized patients. It also helps us identify farms with MRSA problems that might benefit from implementing an eradication program. We also screen horses at the time of discharge to make sure MRSA has not been transmitted to them while they were in hospital.

Screening your average horse on your average farm is harder to justify. A single negative result might give you a false sense of security, because a horse that is negative today might be positive tomorrow, or it might positive already but the current testing methods couldn't detect it.  The use of good infection control practices is much more important than testing for day-to-day MRSA control.  Screening for MRSA is something that is usually only considered in specific circumstances.

More information about MRSA can be found on the equIDblog Resources page.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

The other day, I wrote about a few different types of surveillance that can be used in equine hospitals - active, passive and syndromic. Infectious disease surveillance, however, is not just for hospitals. Every horse farm should have some form of infection control program. In most situations, it doesn't need to be complicated, fancy or time consuming, but it means organizing some basic infection control policies and procedures. Syndromic surveillance is great for use on horse farms.

Syndromic surveillance involves looking for specific syndromes (e.g. particular clinical signs (not specific diseases per se) such as fever, cough, diarrhea, or off feed) that might indicate an infectious disease. These basic, easy-to-identify syndromes can be the early warning that something might be amiss, then closer examination can be used to determine if there is actually is a problem.

An important key to disease surveillance is it is only effective if something is done with the information collected. There has to be a plan based on the results of the syndromic surveillance, with regard to what needs to be done for the affected horse and on the entire farm.   For the horse, it usually means a visit from a veterinarian to determine what's wrong, and if it might be due to an infectious pathogen.  For the farm, it means making sure that horse doesn't have a chance to infect other horses (in case it is an infectious disease), and ensuring that the information is recorded so bigger problems (e.g. outbreaks) can be identified as early as possible. The plan for what to do when one of these syndromes is detected needs to be written down so it's very clear for everyone, and easy to find if someone's not sure what to do. One of the most important steps is making sure someone (i.e. someone "in charge") is notified.

Here's a scenario: A horse develops a mild fever overnight and doesn't eat all its grain.

Response 1 (what should happen): The fever and decreased appetite are identified and the person in the barn in charge of the surveillance program is notified. They record that a horse has a fever and talk about what to do with the horse so everyone knows. The horse is restricted to its stall until the cause of the fever is identified. An hour later, the same person in charge of surveillance gets reports from two other people about horses with fever. This obviously raises concern and they try to determine what is happening. They know that a new horse arrived a while ago and that the horses with fever were turned out with it. They immediately call the veterinarian, who suspects strangles may be the cause. All horses with a fever are isolated and tested. Other horses in the barn are closely monitored for signs of illness. Because horses with strangles spike a fever a couple days before they are able to transmit the disease, these horses do not spread the disease any further.

Response 2 (what usually does happen): The first fever and decreased appetite may or may not be identified. Since the horse doesn't really look sick, they decide to wait and see how it looks over the next day or two. A couple days later, someone notices the horse has enlarged lymph nodes. Then they call the vet, who diagnoses strangles. As the vet looks around the barn and talks to people, he/she finds out that a few other horses have big lymph nodes, and realizes that an outbreak of strangles is already well underway. Most horses may have been exposed at this point and a large outbreak is probably inevitable.

Which scenario would you want? Which response would be most likely in your barn?

Surveillance scares off many people just because of the name and the thought that it is expensive, complicated or requires special training. It doesn't. All it needs is people in a barn who communicate and some basic written policies on how to handle horses and potential diseases.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

I seem to be on a run of strangles posts at the moment. There was a recent article in the Brown Daily Herald about the school’s equestrian team, in which was mentioned a recent strangles outbreak in the team’s horses. Two horses were affected according to the article, and the encounter with this highly infectious disease was described as a "hiccup". I’ve written about different approaches to infectious diseases and outbreaks (the good and the bad) and commented on the need for a logical, proactive and open response to diseases like strangles. This report includes some glaring deficiencies.

With 2 horses affected, there has presumably been transmission of the disease on the farm. That means that every horse was potentially exposed, and many horses could be incubating infection or be carriers. The proper response would be to consider everyone infected until proven otherwise, ideally by culturing all the horses for the bacterium that causes strangles, Streptococcus equi.

The description of the response to the outbreak was pretty brief, so I’ll go with the assumption (hope) that the writer didn’t describe the entire response. One of the precautions that was described was “dipping their boots into bleach before mounting any horses.” Boots are a minor to irrelevant source of infection, and this alone is not going to do much to prevent the spread of strangles.

"It was easy to tell that something was wrong in the barn on Friday, March 13. The sides of Bristol's stall were boarded with fresh wood and the entrance was blocked off by a rope. Bristol stood in the stall with a green warmer wrapped around him, facing the outside of the barn, and his slow, warm breaths were visible in the cold barn air. But the team had to continue. They had a competition the next day.”

Here’s where I get more concerned. It's good that they took measures to isolate the affected horse, but there was a strangles outbreak in the barn that was (as of yet from the description) uncontrolled, yet the riders were going to a competition the next day, and no additional precautions were mentioned. That’s a great recipe for turning a minor single-farm cluster into a regional outbreak.

“With the strangles infection in the barn last Friday, Coach Michaela Scanlon wanted to make sure that her riders took extra precautions, such as not wearing any equipment that they had worn at earlier practices, so as not to spread the infection.”

This is a more useful measure, to help reduce transmission of S. equi from contaminated gear. However, changing clothes still doesn’t help much in the absence of a concerted infection control response.

Hopefully Brown’s equestrian team didn’t spread strangles to other horses at the show. I understand the desire to go to a competition anyway, when you have infected horses in the barn but many horses that appear healthy. A lot of effort and money can go into preparation for shows. However, people should take infection control seriously and realize their ethical obligation to do their best to protect their and other peoples’ horses. Infectious diseases are always a risk at shows and we can’t eliminate them altogether. Every infectious disease that a horse acquires at a show is not necessarily an indication that someone did something wrong, but a lot of illness could be prevented if people use common sense and have some consideration for the impact their actions may have on other people and their animals.

More information on strangles can be found in on the equIDblog Resources page.

• Email This
• Print
• Comments (1)
• Trackbacks
• Share Link

I usually hesitate to write posts about strangles cases or outbreaks. I don't want to give the impression that these are unusual events, because strangles is not a rare disease, in terms of either single cases or outbreaks. When I post about an outbreak, it's usually because there's something particularly interesting about the outbreak or the report about it. Such is the case with the recent identification of strangles in a horse in a Newmarket (UK) racing stable. At last report, only a single horse was infected, the horse has been isolated, and infection control measures have been implemented (although it would be nice to have some details about exactly what those infection control measures are).

What is noteworthy is the rapid and open response. Mark Tompkins, chairman of the Newmarket Trainers' Federation, said the following about Mr. William Jarvis, the trainer in charge of the stable where the infected horse was found:

"He has done everything right by letting everyone know about it as early as possible. He has been absolutely brilliant... His string of horses are being tested and swabbed constantly and he will exercise his horses in the afternoon when no-one else is on the heath."

This is what needs to happen when strangles is identified: a rapid, no-nonsense response with open communication between all parties involved. Too often, people try to hide cases or don't tell the whole story. Horse owners and trainers that think hiding the disease is the best way to handle things ought to take note of the statement by Tim Morris, the British Horseracing Authority equine science and welfare director, who said no restrictions were being imposed on Mr Jarvis's horses because he had shown a responsible attitude by reporting the sickness.

Strangles is an endemic disease. It's not going away. Having a horse with strangles shouldn't be considered something that needs to be hidden. There's nothing illegal or unethical about having a sick horse, but trying to hide the fact that you have a horse with a disease than can infect other horses... that's another story altogether.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

A mandatory influenza vaccination policy at the Crawford City Fairgrounds (Pennsylvania), implemented this year following an outbreak of influenza at the facility in 2008 is being met with disdain.

Among the complaints:

"A two-day horse show is different than an eight-day fair exhibition.'" Two days is lots of time to transmit infectious diseases.

"If a horse is sick and can’t perform, people won’t bring them to a show." Unfortunately, that's not the case. Also, not all horses that are shedding infectious diseases look sick.

"All these requirements will not guarantee healthy horses." Absolutely true. But, with infection control, we are trying to reduce the risk and incidence of diseases. We know we'll never eliminate the risk.

"There’s no sense giving a shot that will do more damage than the disease." Influenza vaccination is very safe. While adverse effects can occur with any vaccine, influenza vaccines are quite low risk.

"Potentially, requiring a 30-day vaccination for each show will cost horse exhibitors and 4-H members in horse clubs too much money." The cost of vaccination is dwarfed by other costs of participating in such events. People spend a lot of money on board, feed, tack, supplements (many of which are useless), trailering and many other items. In the grand scheme of things, vaccines don't add much to the total yearly cost.

No one knows whether mandatory vaccination against influenza ought to required for all horse shows as an infection control precaution. However, given the fact that outbreaks can occur, that all events involving mixing of large numbers of horses pose a high disease risk, and that vaccination is relatively cheap and effective, it seems like a logical requirement to me.

• Email This
• Print
• Comments (2)
• Trackbacks
• Share Link

Infectious diseases are a major problem in young foals. Diseases, including diarrhea, pneumonia, meningitis, umbilical infections and joint infections can range from mild to rapidly fatal.  Even in foals that survive the initial infection, these conditions can sometimes result in permanent problems. A study published in a recent edition of the Equine Veterinary Journal (Wohlfender et al, 2009) looked at infectious diseases in the first 30 days of life in 1031 foals on 36 breeding farms in the Newmarket, UK area. This very large study provided some interesting information:

• The overall incidence of infectious diseases was 8.3%, meaning around 1 in 12 foals developed some type of infectious disease during the first 30 days of life.
• The most common infectious problem was diarrhea, which occurred in 5.9% of foals. Foals with diarrhea that didn't have other signs of illness were not included.  This is because most young foals with diarrhea and no other abnormalities likely have foal heat diarrhea, which is not an infectious disease.
• Umbilical infections developed in 0.7% of foals.
• Joint infections occurred in 0.4% of foals.
• Bone infections occurred in 0.2% of foals.
• Respiratory infections were uncommon, occurring in only 0.6% of foals.
• There was no difference in the incidence of infections in foals that were treated routinely with antibiotics to "prevent" infections. Whether or not this practice is effective has been a controversial issue for a long time.  The best way to answer the question would be to have a study that randomly assigned foals to receive antibiotics or no antibiotics, and then monitored both groups for infections.  This study didn't do that, so there could be some "bias" to this particular finding, but the results are still useful. I don't find the results surprising - there has never been good evidence that antibiotics are routinely needed in newborn foals. This study may help control routine (and in my opinion unnecessary) antibiotic treatment in healthy newborn foals.

This study provided more information confirming that infectious diseases are a significant problem in foals, and that measures are needed to reduce the incidence of infections. It also provided evidence that routine antibiotic use is NOT an effective means of doing this. While there is a lack of good, objective evidence, routine hygiene, sound management and every-day infection control practices are probably critical factors for infectious disease prevention in these young animals.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

As part of the 2008 Conference of the American Association of Equine Practitioners, equIDblog's own Dr. Maureen Anderson gave a presentation about MRSA in horses and people. While there, she gave in an interview for the The Horse, which can be found here. This short video gives some good general information about MRSA in horses and people that work with horses.

More information about MRSA can also be found in our MRSA archives and on the equIDblog Resources page.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

Diarrhea is a potentially life-threatening condition in horses. It's also frustrating from a diagnostic standpoint because, even with the most complete/comprehensive testing, a cause is only identified in a minority of cases. This is true for other species too, including people, and is a reflection of the complex nature of the intestinal tract and the numerous possible causes of intestinal disease. Diagnostic testing obviously costs money, so if it gives us an answer less than half the time anyway, it begs the question - why bother? Well, here are some points to consider:

• In some situations, you may find a cause that requires a different treatment, so diagnosis has a direct impact on patient care and probably the outcome.
• Many causes of diarrhea are infectious and it's important to know if other horses may have been exposed to a transmissible pathogen.
• Some causes of diarrhea, especially Salmonella, can also infect people, and it's important to know to what people have been exposed.
• It's also important to know whether a horse might still be shedding a transmissible pathogen after its diarrhea resolves. For example, horses with salmonellosis can shed Salmonella for a while (often a few weeks, sometimes longer) after they have recovered from their diarrhea. This could be a source of infection for other horses and people.
• Outbreaks of diarrhea can occur. It's much better to know early on what you are dealing with, rather than waiting until mulitple horses have been infected.

I consider diagnostic testing money well spent in cases of diarrhea. Some people don't want to test because they don't want to know, particularly about Salmonella. However, it's been proven again and again that the "head-in-the-sand" approach will backfire when it comes to infectious diseases.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

I don't know whether Truro Raceway (in Nova Scotia, Canada) has bad luck, bad infection control or is just really open about any problems. Following an outbreak of strangles in December (see here for details), strangles has again been identified in a horse at the track. One horse has tested positive and two barns have been quarantined until 3 negative cultures are obtained from the horses. Racing, fortunately, has not been affected.

This isn't a surprising situation because strangles (caused by the bacterium Streptococcus equi) is an endemic disease in the horse population, meaning it is always present in a small percentage of horses at any time. It circulates regularly through the population - mixing of horses contributes to its spread. Racetracks are a great place for infectious diseases to spread and early control is the key. Truro seems to be on the right track based on their aggressive but balanced response. They've identified a problem, taken a logical course of action, but have not overreacted. Presumably, they feel that the two quarantined barns are the only ones likely to have been exposed to the pathogen, so there is no need to take broader action. Sometimes, people panic and take excessive actions in an outbreak. This can lead to people being hesitant to report problems (for fear of a draconian response), which can end up making things worse in the end. I wonder whether any increased infection control practices were implemented following the December outbreak, and/or whether any are being considered now.

The risk of strangles can be reduced, but not eliminated, through use of good infection control practices. More information on this disease can be found in our strangles archives and on the equIDblog Resources page.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

While it's a little early in the foaling season, it never hurts to think about vaccination plans for foals. Vaccination is an important part of the disease prevention program - but it's only one part... general infection control practices are as, or often even more, important. Vaccination of foals is not the same as vaccination of adult horses. Foals may be more or less susceptible to certain infections. They may have greater or lower risks of exposure, and they may respond differently to vaccines.

There is no standard vaccination program for foals. Specific vaccination programs need to be designed for each horse on each farm based on risk of exposure and infection, cost and many other factors. Your veterinarian can help you determine what your animals should be vaccinated against. When it comes to foals, here are some important things to considered:

• Foals typically need to be vaccinated several times to get the desired immune response. There are at least a couple of reasons for this. First, if a foal has high antibody levels from colostrum, it may not respond properly to the vaccine until those antibodies are used up. These antibody levels drop over time, but the rate and timing of the drop is different for each foal. Vaccinating the foal several times (at appropriate intervals) helps reduce the risk of vaccine failure from colostral antibodies. Second, foals are born with a fully functional immune system, but the immune response to an infectious agent or vaccine is slow and low the first time an individual encounters it. The first dose of vaccine may produce some response, but a much higher response is generated with boosters.  This is actually true of adult horses as well.
• Over-vaccination can be a problem. Vaccination too early and/or too frequently could actually result in a decreased immune response or complete vaccine failure, a phenomenon known as immune tolerance. So, giving many doses of vaccine starting at a very young age may actually be counter-productive. This is probably a bigger concern with influenza vaccination compared to other vaccines.

Talk to your veterinarian about vaccination. Over-, under- and improper vaccination can lead to increased disease risks, plus wasted time and money.

Guidelines for vaccination of foals have been developed by the American Association of Equine Practitioners. These are also available from the link on the equIDblog Resources page.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

This post originally appeared (in modified form) on www.wormsandgermsblog.com on January 1, 2009.

An important step in diagnosing infectious diseases and determining the optimum approach to treatment and management is rapid and accurate diagnostic testing. Many different testing methods are used, particularly bacterial culture (at least for bacterial diseases). Molecular testing has revolutionized the field of microbiology, and is making inroads into the field of diagnostic testing. Polymerase chain reaction (PCR) testing is a very powerful tool that can be used to detect DNA or RNA from specific microorganisms.  This technique can be very useful, but it can also be easily misused or misinterpreted.

The potential PROS of molecular diagnostic testing include:

• Rapid turnaround time: Testing can take as little as a few hours versus a few days for other tests like bacterial culture.
• Sensitivity: Organisms that are difficult or impossible to grow in a lab can be detected, and they can often be detected at lower levels than with other diagnostic methods.

The potential CONS of molecular diagnostic testing include:

• Sample contamination: This is a common concern with highly sensitive molecular tests - even a minute amount of contamination in the sample can cause a false positive result.
• Test inhibition: Samples from complex biological sites (e.g. stool) can contain substances that interfere with the many complex molecular reactions upon which the tests rely. Without good (and proven) methods to prepare the sample, this can result in a false negative result.
• Biologically irrelevant results: Some bacteria that cause disease are also commonly found as part of the normal microflora in healthy animals - simply finding it does not tell you that it is necessarily relevant to the problem. For example, Clostridium difficile can be found in the intestine of normal, healthy horses, but the diagnosis of C. difficile diarrhea requires detection of the bacterial toxins in stool samples, not just the bacterium itself.  A molecular test that simply identifies the presence of C. difficile, even if it identifies strains that possess the genes to produce toxins, tells you nothing about whether the bacterium was actually producing toxins in the animal.
• Lack of validation: This is a common problem with many (if not most) molecular tests. Some companies, especially those that just run molecular tests, offer a huge array of completely unvalidated and sometimes illogical tests.  It is also important to remember that tests must be validated for each species in which they are used - a test that works well in people will not necessarily work on a sample from a horse or a dog.

Molecular testing can be useful in some situations. If you are unsure, here are some things to ask the lab:

• Do they have a validated test that provides relevant results?  If they don't have good data (ideally published data) that their test is useful, accurate and reproducible, I'd avoid it.
• Do they have a quality control program, which includes running positive and negative control samples with each test batch?

Finally, as with any test that we use in veterinary (or human) medicine, it's important to evaluate all  results in the context of what is happening with the animal - treat the patient, not the test result.

• Email This
• Print
• Comments
• Trackbacks (1)
• Share Link

Recently, Truro Raceway (the original home of Standardbred champion racehorse "Somebeachsomewhere"), was quarantined because of two suspected cases of strangles, a highly infectious equine disease caused by the bacterium Streptococcus equi subspecies equi (more information about strangles can be found on the equIDblog Resources page and in the  strangles archives). The first round of tests from December 7 came back negative on December 18, and the quarantine has now been lifted (apart from the barn with affected horses).

That's all good news. In the bigger picture, though, was anything learned, and were any measures taken to reduce the risk of this happening again?  A lot of this comes back to the debate about accepted versus acceptable disease risks, which we've covered before on equIDblog.

I've never been to Truro, but I assume they are no better and no worse than the vast majority of tracks, meaning they are in a perpetual state of waiting for an outbreak to happen. Let's hope they have performed (or will perform) a good review of what happened, and consider how to reduce the risk of future problems, including the following measures:

• A mandatory reporting system for signs potentially associated with infectious diseases of concern: This would allow for prompt investigation and implementation of any needed control measures. A balanced approach to diseases control is necessary so that horsemen don't feel the pressure to withhold such information for fear of being ostracized or having their livelihood compromised by excessive or unnecessary quarantines. Education is key to convincing people that this is important.
• An improved (or establishment of) a 'culture of infection control': People need to be thinking about infection control on a daily basis, not just when there is an outbreak.
• Performance of an infection control review and development of a formal written infection control program for the facility: This should involve experts in veterinary infection control, but also track managers and horsemen so that all relevant parties have input. This type of review needs to consider the facilities (e.g. barn layout, quarantine areas, sinks for handwashing in barns) as well as protocols (e.g. ship-in protocols, reporting and managing potentially infectious horses, infection control education).

• Email This
• Print
• Comments
• Trackbacks
• Share Link

Lawsonia intracellularis is a bacterium that causes an intestinal disease called proliferative enteropathy in young horses. One of the reasons we still don't know a lot about this disease is that this bacterium can't be grown in a lab. One of the areas in which researchers are working to find more information is from where horses that become sick initially get Lawsonia...  Is it from healthy horses that are carriers? Does it circulate in the horse population, or is there an outside source? Does it come from pigs (pigs can also be affected by disease due to Lawsonia infection)?  Do other animal species such as wildlife carry it?

A recent study by researchers at the University of California (Davis), published in the Journal of Wildlife Diseases (2008 44:992-998), looked at the presence of Lawsonia in wildlife on horse farms. They found DNA from the bacterium in feces from jackrabbits, striped skunks, Virginian opossums, and coyotes, but not from feral cats, Brewer's Blackbirds, raccoons, or ground squirrels.

This study provides some interesting insights about Lawsonia in horses, and raises the possibility that wildlife could be a source of infection. However, it does not tell us how to prevent the disease or whether wildlife really are a relevant issue when it comes to infecting horses. We certainly do NOT recommend trying to eradicate wildlife in the vicinity of horse farms as a Lawsonia prevention tool. However, making horse barns (especially feed storage areas) less inviting to wildlife is a good idea - this is a sound standard infection control measure that everyone should consider, as it may reduce the risk of several infectious diseases (e.g. equine protozoal myeloencephalitis (EPM)).

More information on Lawsonia can be found on the equIDblog Resources page, and in our earlier post entitled "Lawsonia intracellularis - New Horizons".

• Email This
• Print
• Comments
• Trackbacks
• Share Link

A few years ago, I investigated an equine herpesvirus (EHV) outbreak associated with a yearling sale. We found a lot of sick horses, both from the sale and horses that were infected when purchased horses were brought home. A lot of actively racing horses got sick and missed races, which cost people even more money.  Part of the investigation was asking people what percentage of horses from sales they expected to get sick right after the sale. The average answer was 80%, and many people said 100%. When you think about it, it's absolutely astounding that people will spend what is often a great deal of money to buy a horse that they expect will get sick, and then (more often than not) put it in the same barn as their other horses, thereby putting all the animals at risk of infection.

Why do we put up with a system where we accept this degree of illness? Is this expected and accepted rate of disease really acceptable? More specifically, are there practical (and really just common sense) measures that can be used to reduce the risk of horses getting infected at sales and/or transmitting disease to other horses once they reach the home farm?

Specific thoughts and facts about how to reduce disease transmission on farms, tracks, sales and everywhere else horses gather will come in other posts, but infection control is not rocket science. Basic measures can greatly reduce the risk of disease transmission. However, the first step is to change people's attitudes - it should never be considered "normal" for such a high percentage of animals to be sick.  If 80% of the horses get sick, we're doing something wrong.

• Email This
• Print
• Comments
• Trackbacks (1)
• Share Link

Respiratory tract disease is a very common problem in horses that has a wide range of causes, including bacterial and viral infections, as well as non-infectious conditions. Nasal discharge (i.e. a "snotty nose") is often one of the first signs of respiratory disease noticed by owners. Unfortunately, the nasal discharge itself cannot tell you what the problem is, nor how to deal with it.  If your horse develops nasal discharge, you should contact your veterinarian to determine the best approach to diagnose the cause and the best way to treat the animal.  Here are just a few of the factors that need to be considered:

• Does the nasal discharge come from one or both nostrils? Discharge that predominantly comes from just one nostril is more likely due to a problem in a sinus, or possibly one of the guttural pouches (but guttural pouch infection can also cause discharge from both nostrils, even if only one side is affected).
• Does the horse have a fever? Bacterial or viral infections usually (but not always) also cause a fever.
• Are there any other signs of illness, such as decreased appetite or decreased energy. If so, an infection is more likely.
• Is there more than one horse affected? This may indicate that a transmissible pathogen (virus or bacterium) is involved.
• Have new horses been introduced to the barn, or has the horse encountered other horses while off the farm? If so, this increases the likelihood of a viral infection.
• What does the discharge look like? Thick, yellow discharge is more often (but not always) caused by bacterial infection.  Clear, watery discharge may be caused by viral infection, or sometimes non-infectious causes such as heaves. Bloody discharge can indicate serious problems.
• Does the horse cough, and if so, when?  Is coughing more common during exercise, when the horse is inside, or while the horse is eating hay?  These signs may be associated with a non-infectious condition such as heaves.

Nasal discharge is a sign that something abnormal is going on. Some causes of nasal discharge are very minor, but others are very serious. Some are not infectious, but others can be easily transmitted to other horses. Good communication with your veterinarian is important.  Do NOT give your horse antibiotics unless your veterinarian prescribes them.  Nonetheless, if there are any signs that suggest an infection (viral or bacterial) might be present, you should isolate your horse right away, at least until it has been examined by a veterinarian, in order to prevent possible infection of other horses.

• Email This
• Print
• Comments
• Trackbacks (1)
• Share Link

Infectious disease risks increase whenever you mix large numbers of horses together, especially horses from many different farms. The risk is further increased if horses are allowed to have direct contact with each other, and indirect contact through people that touch many different horses. Add a little stress from shipping and you have a prime situation for infectious disease transmission.  Unfortunately, this very same situation is something that happens countless times every week, at horse shows and other events. Diseases associated with horses being at shows are very common. Some people think that horses getting sick is an unavoidable aspect of competing. While it is true that you can never completely eliminate the risk of infection, I think that our traditionally "accepted" degree of illness in show horses should not be considered "acceptable," and that we should be working harder to decrease the risks of disease transmission in these animals.

Here are some general recommendations to help do just that:

• Avoid direct contact between your horse and other horse - don’t let horses touch each other. 
• Make an extra effort to avoid going near any horses that appear to be sick, such as those that are coughing, or have nasal discharge or diarrhea.
• Don’t share items like water buckets, feed bins and hay nets between horses.
• Wash your hands or use an alcohol-based hand sanitizer after touching another horse.
• Don’t take a sick horse, or a horse that might have been exposed to a horse with an infection, to an event. You don’t want your horse to get sick at a show, and you also shouldn't put other peoples’ horses at risk of infection.
• Make sure your horse is appropriately vaccinated. Horses that go to shows or other events are at higher risk of exposure to certain infectious diseases. Your veterinarian should design a vaccination program that is appropriate for your horse.
• Make sure events that you attend have strict rules for keeping sick horses off the property. If they don’t, or if those rules aren’t being followed, let them know that you think it is unacceptable.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

Streptococcus equi is the bacterium that causes of strangles, and important and highly infectious disease of horses. This bacterium is widespread in the horse population and outbreaks of strangles are not uncommon. Outbreaks are manageable if adequate time and resources are available, but some aspects of strangles control are complicated by a lack of good information.

One area that people often ask questions about is the ability of S. equi to survive outside of a horse, and how to handle the general environment (e.g. barn, paddocks) during an outbreak of strangles. Two older studies reported that S. equi can survive on environmental surfaces for up to 60 days. This has led some people to recommend prolonged quarantine of pastures that have been used by infected horses. However, these studies were conducted in the controlled and relatively hospitable environment of a laboratory, without exposure to sunlight, temperature changes and competing bacteria that are found in the "real world".

A recent study, presented the 2008 Forum of the American College of Veterinary Internal Medicine (ACVIM), evaluated S. equi survival in a more "real world" situation: outdoors, on objects like fence rails, feed bins and water buckets. These items were experimentally contaminated with S. equi, and the length of time that the bacteria survived was studied. Surprisingly, S. equi only lived for a short period of time under these conditions, typically a day or less.

Does this mean that we should allow horses into potentially contaminated areas after only a couple days? Probably not. The results of this study only apply to the conditions that were studied, that is outside with exposure to sunlight, and during the summer. It is safe to assume that survival is short term on farms under these conditions, but it could be longer during cloudy periods and in shady areas. We don’t know the optimal time for which to quarantine stalls and paddocks, but it is reasonable to assume that long-term quarantine, as has been recommended in the past, is not needed in most situations. If it is sunny and there is exposure to sunlight, 1 to 2 weeks is probably well beyond the survival period of S. equi.

More information about strangles will soon be available on the equIDblog Resources page.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

You may notice a recurring theme on equIDblog anytime we talk about infectious disease control, particularly when it comes to zoonotic diseases (those that can be transmitted between animals and people): an emphasis on handwashing. There is increasing emphasis on hand hygiene (i.e. hand washing and use of alcohol hand sanitizers) education in hospitals because the hands of healthcare workers are a major (if not the most important) means of disease transmission between patients. Despite hand hygiene being easy, cheap and effective, people rarely wash their hands as often as they should, and they often don't do it properly.

Most of the research about hand hygiene that has been published has focused on its use and impact in human hospitals, but this area is now also being studied more with regard to animals and veterinary medicine. A study published earlier this year in Veterinary Microbiology provided more evidence that hand hygiene is a critical infection control measure when dealing with animals. The study looked at MRSA carriage rate in veterinarians who work with horses. In addition to finding a high rate of MRSA carriage among these veterinarians (which was consistent with other reports indicating that equine vets are at higher than average risk for exposure to MRSA), the study looked at factors associated with MRSA carriage. Vets that reported routinely washing their hands between farms and those that reported washing their hands after contact with potentially infectious cases had a significantly less likely to be carrying MRSA. That should come as absolutely no surprise, but it's one more piece of evidence that we need to pay more attention to this routine infection control measure, in human hospitals, in veterinary environments, out in the barn, and even in households.

Remember, the 10 most important sources of infection are the fingers on your hands!

Click here for instructions on how to wash your hands properly.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

Many people in the horse world have heard the hype about methicillin-resistant Staphylococcus aureus (MRSA) in horses. MRSA can cause infection in horses, just like it can in people, dogs, cats and many other animals. It’s usually what we call an “opportunistic” pathogen, meaning it usually takes advantage of a person or an animal that is already sick or injured, like someone who’s in the hospital and has just had surgery. And because MRSA is resistant to many different antibiotics, the infection can be difficult to treat. The big concern with MRSA in recent years is that infections are now sometimes occurring in people who aren’t sick, and who don’t have wounds or incisions, which is where MRSA usually likes to move in. It’s very important to find out from the start if an infection is being caused by MRSA, so that it can be prevented from spreading to other people and animals, and so that it can (if necessary) be treated with the right kind of antibiotic.

Horses are a bit of a special case when it comes to animals and MRSA. When researchers look at the DNA of MRSA from a dog or a cat, it usually turns out to be one of the common human MRSA strains (usually called a “clone”) from the same area. This means that the dog or cat probably picked up the MRSA from a person somewhere.  When researchers look at the DNA of MRSA from horses, however, they often find a different clone, which seems to be more common in horses and people who work with horses than in people in general. A very similar situation has also been discovered in pigs. The worry is that this “horse MRSA clone” can survive in and be transmitted between horses better than the human MRSA clones. That means that in order to control MRSA, just controlling it in the people won't do the trick - we need to take steps to stop the spread of MRSA in horses specifically as well.

Here are some key points to help reduce the risk of your horse (and you!) getting MRSA:

• Always wash your hands with soap and water (or use an alcohol-based hand sanitizer) after handling a horse, and before handling another horse.
  • This is especially important if you have touched a horse’s nose, or any cuts or wounds that the horse may have.
  • Don’t go down the row of stalls in the barn and pet every horse on the nose! They love the attention, but this is a great way to spread MRSA if it’s there!
• New horses coming into the barn, or animals coming back from a hospital, should be kept separate from all the other animals and only dealt with after all the other horses, for 3-4 weeks.
  • This is an important measure for controlling many infectious diseases, not just MRSA.
• If your horse has a cut that looks infected, cover it with a bandage of some kind and contact your veterinarian. Your veterinarian can culture the wound to determine if it is an MRSA infection.

This equIDblog entry was originally posted on the Worms & Germs blog on 06-May-08.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

When people talk about prevention of infectious diseases on horse farms, they often use the term "biosecurity." I don’t.  I prefer to use the term "infection control." Here’s why:

• Biosecurity is a term often used in association with rearing of food animals, particularly chickens and pigs. In these types of facilities, new animals are rarely or never introduced to an established group, control of personnel access is very strict, and significant efforts are made to prevent exposure of animals to new infectious agents.
• In my opinion, we do not (and cannot) practice true biosecurity on horse farms because of the way horses are managed - the movement of horses on and off farms, movement of people that work with horses, and diseases that are always circulating in the horse population. The simplest daily, weekly or monthly activities - going to a show, buying a new horse, going off-site on a ride, bringing in visitors/farriers and other people that have had contact with horses - in combination with the fact that even healthy horses can carry  potentially harmful bacteria and viruses, means that there is always an risk of exposure to infectious agents on horse farms.
• We are not able to completely exclude infectious agents like bacteria and viruses from entering horse farms (i.e. making them "biologically secure"). However, what we need to strive for is to limit the problems that develop when these agents do enter the farm. For example, we know that the majority of horses carry equine herpesvirus in a dormant state in their bodies. We can’t eliminate it, but we try to reduce the risk of problems like herpesvirus abortion in mares by vaccinating mares while they're pregnant.

While it may be somewhat an issue of semantics, I think it’s important that horse owners have a realistic mindset. There is always, and will always be, infectious disease risks when dealing with horses in any situation. Some risks are avoidable while others are not.  The key is to implement measures to reduce the inevitable impact of infectious disease exposure on our horses.

• Email This
• Print
• Comments
• Trackbacks
• Share Link

• Email This
• Print
• Comments
• Trackbacks
• Share Link