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

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.

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Proliferative enteropathy, caused by the bacterium Lawsonia intracellularis, is an important disease of older foals, particularly in certain regions and on specific farms. Infection by this bacterium results an abnormal small intestine, which ultimately causes severe loss of blood protein. One major problem with this disease is that it is not often spotted until it's very advanced. Like many diseases, the earlier you can diagnose it, the better you can treat it. Unfortunately, sometimes foals are so sick by the time anyone notices, it's very hard for them to recover, even with intensive care. There are a couple of different ways to diagnose Lawsonia infection, but I'm not going to get into specific testing (more information on that can be found in our archives and on the equIDblog Resources page). The point I want to emphasize is finding this disease early.

On farms that have had problems with Lawsonia in the past, specific testing may be part of a routine diagnosis and control program. However, that's not going to be the case for most farms. While specific testing for Lawsonia is hard to justify in those circumstances, close attention to early signs of diseases is critical.

This disease usually hits foals that are a few months of age (and is most commonly diagnosed in 5-6 month old foals). Foals this age are not always watched and handled closely, compared to younger foals and older animals. With Lawsonia, foals can look good from a distance, despite being quite sick. It's even more of a problem in the fall in cooler climates where a longer haircoat can more easily mask weight loss and poor body condition.

So, what can you do to help find the problem early?

• Get your hands on the foals. Handling them regularly will give you a better assessment of their strength, body condition and overall health. Actually touching them will let you feel muscle mass and tone, and detect foals that are not growing well or not in as good body condition as they should be. Such foals should be examined by a veterinarian promptly, with Lawsonia being one of the considerations for a cause.

Having good, regular contact with foals is a free and (relatively) easy way to help protect their health (and as a bonus, it also gets them used to people and used to being handled from an early age).

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As foaling season approaches, it's a good idea for people to review proper umbilical care. The umbilicus is an important route of infection in foals, and can be associated with problems including local umbilical abscesses, large abdominal abscesses extending to the liver, and overwhelming body-wide infection (sepsis). The reason the umbilicus is such a critical structure is that it contains three major blood vessels (two arteries and one large vein) and the urachus (which connects the umbilical cord to the foal's bladder) . When the umbilicus ruptures shortly after birth, these structures are exposed to the bacteria-laden environment of the outside world and can be a route of entry for local and deep infections. Care of the umbilicus during the initial high-risk period is a key part of raising a healthy foal.

Do all foal's need specific umbilical care? Not really. Most foals, especially those born normally in a clean environment to a healthy mare and who received adequate colostrum, don't need anything done. However, it's not always easy to differentiate these low-risk foals from others, and it is possible for the healthiest foal born in the cleanest environment with ingestion of an adequate volume of good quality colostrum to develop complications, so most people perform some form of post-birth umbilical care (and that's a good thing). The key is making sure that it's the right umbilical care.

The goals of umbilical care are pretty basic:

• Prevent bacteria from entering the umbilicus.
• Avoid damaging the umbilicus and other body tissues, and avoid delaying normal drying of the umbilicus.

What to use?

• Research has indicated that a 0.5% chlorhexidine solution is the optimal umbilical dip. Other disinfectants can also kill local bacteria on the umbilicus but may not be as effective, may not work as well in the presence of debris (dirt, manure...), or may be irritating to body tissues.

Read the label:

• Make sure you are actually using 0.5% chlorhexidine and that it's a solution (diluted in water), not a tincture (diluted in alcohol). If you don't have 0.5% chlorhexidine solution and are unsure about how to dilute it properly, ask your veterinarian.

More is not better!

• Don't think that since 0.5% is good, 5% must be 10 times better. The stronger the concentration, the greater the chance of damage to local tissues, which can increase the risk of complications. Stick with 0.5%.

More is not better! Part 2

• The umbilicus should be dipped in disinfectant, not marinaded in it! The goal is to cover the umbilicus and not other tissues (e.g. the abdominal wall). You don't need to soak the umbilicus or hold the disinfectant in place over it. Short term contact (dip) is adequate. Dip it and walk away. The umbilicus needs to dry up - repeated soaking isn't helpful.

More is not better! Part 3

• The umbilicus should be disinfected shortly after birth, then every 6-8 hours for the first 24 hours of life. That's usually enough. If the umbilicus still appears wet at that time, it can be dipped again. Continued dipping "just is case" is not needed.
  

Don't tie off the umbilicus:

• Tying off the umbilicus can actually increase the risk of complications such as infection and patent urachus (urination through the umbilicus).

Hands off!

• Don't touch, poke or otherwise make contact with the umbilicus with your hands. It's not needed and it's a great way of transferring bacteria to the umbilicus.

If in doubt, call your veterinarian:

• A proactive call to your veterinarian is much better and cheaper than an umbilical infection, umbilical abscess, septic foal or patent urachus. These are all expensive complications and  often difficult to treat successfully. Foals can change very quickly, and waiting to "see what happens" for a day or two can be the difference between a minor complication and a life-threatening problem.

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Rotavirus is an important cause of diarrhea in young horses. (It's also a major cause of diarrhea in infants, but a different rotavirus is involved). Exposure to rotavirus is very common - most, if not all, horses are exposed to it early in life. Disease only occurs in foals, but not every foal that gets exposed becomes sick. Most often, rotavirus causes diarrhea if foals between 1 and 6 months of age, with most cases occurring between 1 and 3 months of age. Foals less than 1 month of age can be affected, but it's less common.

Foals become infected by swallowing the virus, which they usually pick up from the feces of other horses (including their mares) in their environment. The exact source of infection is rarely identified. It is likely that some healthy adult horses are the reservoirs and shed the virus in their manure.

Like other types of diarrhea, rotaviral diarrhea in foals can range from mild diarrhea alone to severe diarrhea with weakness, loss of appetite and dehydration. Colic can occur because of intestinal cramping associated with diarrhea. You cannot differentiate diarrhea due to rotavirus from other types of diarrhea by appearance alone. The diarrhea must be tested to identify the cause.

There is no specific treatment for rotavirus infection, but "supportive care" is often provided. One of the primary components of supportive care is fluid therapy, which may be needed for foals that start to become weak and dehydrated. Aggressive intravenous fluid therapy may be needed in some cases, depending on the severity.

Rotavirus vaccines are available in some regions, although there is limited evidence that they have much of an effect. Few people recommend vaccination. Rather, good attention to foal management practices, hygiene and early diagnosis of infected foals is the key. Foaling mares outside on pasture has been an effective practice in some outbreaks, presumably because there is less rotavirus contamination on pasture.

Image: Colourized TEM of rotavirus particles (source: CDC PHIL 173)

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A new study was recently published in the Journal of Veterinary Internal Medicine (Frederick et al. 2009) which looked at infectious agents found in the feces of foals with diarrhea. Specifically, they looked for rotavirus, Clostridium perfringens, C. difficile, Salmonella, parasite eggs and Cryptosporidium oocysts.

They found at least one infectious agent in the feces of 122 (55%) of the 233 foals in the study. That means, despite testing for a wide range of pathogens, they could not identify an infectious agent in 45% of the diarrheic foals. This is very similar to the situation typically found in adult horses with diarrhea. This could have happened for a number of reasons:

1. No test is perfect. It’s possible that in some of the cases one of the test results was a “false negative,” meaning it did not detect the infectious agent even though it was there.
2. A few cases may have been caused by other infectious agents that were not included in the diagnostic panel.  For example, Rhodococcus equi is a common cause of respiratory disease in foals, but it has also been associated with diarrhea in some cases.
3. The diarrhea was caused by an agent of which we are unaware, and for which we have no test. Researchers are constantly looking for other bacteria, viruses or parasites that may be capable of causing or contributing to diarrhea in foals and adult horses.
4. The diarrhea was not caused by an infectious agent. For example, the authors failed to discuss foal heat diarrhea as a cause of clinical diarrhea in very young foals. This is a well recognized cause of foal diarrhea, but no infectious agents are involved.

The most commonly identified pathogens were rotavirus (20% of cases), Clostridium perfringens (18%), Salmonella (12%) and C. difficile (5%). Overall 191 (87%%) of the foals survived, and survival was not associated with any pathogen identified in the feces (i.e. in this study, foals were not more likely to die if they had one particular pathogen in their feces than another). This must be interpreted very cautiously, however, because the study does not account for other kinds of illness in these foals, or even whether diarrhea was the primary problem for which they were referred to the hospital. Diarrhea, especially in very young foals, can be very serious because they can dehydrate very quickly and are very susceptible to shock of various kinds.

There were a few other issues with this study that are important to keep in mind as well:

1. The group of foals they looked at ranged in age from newborns to 10-months old. The digestive tract of a foal undergoes drastic changes in the first year of life, and it is well known that certain infectious agents only cause disease in foals of particular ages. For example, different parasites may take weeks to months to develop within the intestine of a foal, so even if a foal is infected as soon as it’s born, these parasites cannot cause disease for quite some time. For this reason, it would have perhaps been more useful to look at the data separately for different age groups.
2. There was no control group in this study. Most of the time, if an animal has diarrhea and the test you perform tells you there is a known diarrhea-causing pathogen in the feces , you assume the diarrhea is due to that agent. This is not necessarily always the case. Some pathogens are carried around by totally normal animals, who may get diarrhea for a completely different reason. So what we really need to know now is: if the authors tested 233 foals with normal feces (and the same ages), how common would each of these pathogens be?

While the data may be interesting to look at, this paper doesn't really tell us anything new that will change the way we treat or manage foals with diarrhea in general.  Nonetheless, the information may still be useful for helping to design and interpret future research studies about these pathogens and diarrheal disease in foals.

Image source: www.bbc.co.uk (credit: George Ring)

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We've survived the summer, and with cool(er) weather soon on its way we are now into what I like to call "weanling season" (which follows naturally after "foal season").  One of the common things veterinarians get called about at this time of year is 5-6 month-old foals that just "aren't right."  They may not be growing well, they may be skinny, they may not have the same healthy haircoat as other foals in the same group, and they may generally just be "dragging their heels" a bit - not very energetic, and maybe sometimes a little depressed.  Of course this is particularly problematic in the fall when some farms are trying to get their foals ready for sale, and they want them looking their best!

Bloodwork on these scraggy foals often shows low - sometimes extremely low - protein levels in their blood.  Blood protein is very important for normal body function and controlling tissue fluid levels, and the body (especially the liver) works very hard to maintain normal levels.  Low blood protein (also called hypoproteinemia) in these animals usually indicates that the protein is being lost from the body, and the most common route for this to happen is through the intestine. (It can also be lost through the kidneys, but renal disease in young animals is generally uncommon.)  Some of these foals have diarrhea as well, or may go on to develop diarrhea if left untreated.

What is it that turns a foal's intestine into a protein sieve?  One possibility, and a hot research topic at the moment, is the bacterium Lawsonia intracellularis, which causes the condition known as proliferative enteropathy.  But any severe infection of the intestine has the potential to affect the barrier that normally keeps blood protein fluids in the bloodstream, so other causes of enteritis and colitis such as Salmonella and Clostridium also need to be considered.  Heavy burdens of intestinal parasites can cause similar problems - some of these may be difficult to test for because the larval stages do not produce eggs that can be found on a fecal test, and developing resistance issues mean that routine deworming cannot guarantee that parasites are not present.  There are no doubt other causes as well that haven't been identified - in half of all diarrhea cases in (adult) horses, a causative agent cannot be identified, even with a complete diagnostic work-up. 

In horses, if only the small intestine is affected (enteritis) - even in severe cases - the animal usually will not have diarrhea.  However, if the infection spreads to the colon, or if the bacterial populations in the colon are affected badly by the foal's poor health status and abnormal "flow" of feed material due to the infected intestine "upstream", then colitis will develop as well, resulting in diarrhea.  Anytime the normal intestinal bacteria of a horse are disrupted, the animal also becomes more susceptible to other bacterial pathogens such as Salmonella and Clostridium as well.

What should be done with these "scraggy" weanlings?

1. Have them examined by your veterinarian as soon as possible.  Don't wait for them to start looking really sick.  These weanlings can be frustrating to diagnose and treat at the best of times, but the farther they're allowed to slip, the harder it is (and the longer it takes) to bring them back.

2. Look for other foals that might be affected.  Especially in larger groups of foals, one particularly sick animal may stand out, but there could be several others flying just under the radar that you may not notice unless you really take the time to look at each foal individually.

3. Separate healthy weanlings from those that aren't 100%.  It may be difficult or impossible to individually isolate all the "scraggy" animals depending on numbers and the facilities available, particularly more severely hypoproteinemic foals that may take weeks to months to recover.  At a minimum, the foals that appear healthy should be separated from and always handled before the ones that may be affected by an intestinal infection.  Any animal with diarrhea should be isolated.  The duration of isolation required will depend on the specific diagnosis (if one can be made).

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

Image source: www.virginiawildhorserescue.com

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Tyzzer's disease is a rare but devastating disease caused by the bacterium Clostridium piliforme. This bacterium causes severe liver disease and sudden illness in young, otherwise healthy foals between the ages of 1 and 6 weeks. Usually on any particular farm only one foal is affected at a time, but small outbreaks can occur.

There is still a great deal we don't know about C. piliforme and Tyzzer's disease. It is presumed that foals become infected by ingesting the bacterium from the manure of other horses or from the environment. No one knows how often foals are exposed to the bacterium in this way - it may happen to a lot of foals, but only a few of them get sick, or it may happen very uncommonly, but make most of the exposed foals sick.  Tyzzer's disease occurs very suddenly and progresses incredibly fast.  Affected foals are often simply found dead, even though they looked completely normal only hours earlier.  If they are found alive, foals may be slightly to extremely weak and lethargic, and they may have a fever, diarrhea, and increased heart and respiratory rates. The gums and whites of the eyes may be yellowish (i.e. jaundice), which is sign of liver failure. Even if foals with Tyzzer's disease are found alive, their condition usually worsens very quickly and they often start having seizures before they die.

A diagnosis of Tyzzer's disease is usually made by post mortem (necropsy) examination. Clostridum piliforme cannot be grown on regular culture plates in the lab like most of the disease-causing bacteria with which we deal (this also makes it very difficult to study). Special stains of liver tissue (silver stain) can help identify C. piliforme under the microscope. Real-time PCR, a molecular method that detects the DNA of C. piliforme, is also available.

Unfortunately, most foals with Tyzzer's disease die before, or shortly after, they are found to be ill.  In most cases there is hardly enough time to even start treatment because the disease is so severe and progresses so rapidly. There are only three foals ever reported to have survived Tyzzer's disease, or what was strongly suspected to be Tyzzer's disease.  Very aggressive therapy (i.e. in a referral hospital) is needed immediately to try to save affected foals, but the prognosis is very grave.

There are no known measures that can be taken to help prevent Tyzzer's disease in foals.  Fortunately, the condition is rare, and there is no evidence that it is transmissible to humans.

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As previously discussed, diarrhea in young foals can range from a messy inconvenience to a rapidly life-threatening condition. A very common but fortunately relatively harmless cause is a syndrome called foal heat diarrhea, so named because it usually occurs around the time of the mare's first heat after foaling, when the foal is about 7-10 days old. Foals with foal heat diarrhea have diarrhea but no other problems like weakness, decreased appetite, colic or fever. If any of these other signs are present, then the foal has something other than (or in addition to) foal heat diarrhea.

The cause of foal heat diarrhea is not known. It doesn't actually have anything to do with the mare's heat, or the mare at all in fact - it even occurs in foals that are bottle raised and have no contact with a mare. It's likely the result of normal changes in the bacterial microflora in the intestinal tract of the foal that just happens to occur at this age.

Foals are usually diagnosed with foal heat diarrhea when they are the right age and have mild diarrhea but no other problems. Testing for (and ruling out) other causes of diarrhea like salmonellosis helps to support this diagnosis.

Any foal with diarrhea must be monitored closely for developing signs of illness.  Don't fall into the trap of simply chalking up a diarrhea episode to foal heat diarrhea and forgetting about it.  If you're wrong, a foal with diarrhea due to an infectious cause can go from looking "okay" to too weak to stand and nurse (or worse) within a matter of hours.

Foal heat diarrhea does not require any treatment in almost all cases. Occasionally, foals can get weak or dehydrated if they don't drink enough to make up for the fluid lost in the diarrhea, but this is quite rare. Foals almost always get better on their own. If they don't, there is probably something else going on and diagnostic testing is needed to determine what that is.

The fact that foal heat diarrhea gets better on its own may be one reason there are so many "proven" foal diarrhea treatments by which people swear. Some people are convinced that certain treatments are highly effective because when they treat foals, they get better. However, with foal heat diarrhea, which is probably the most common cause of diarrhea in foals, the animals get better regardless of (or despite) what you do. That's why well-designed research trials that include untreated control groups are needed to determine if treatments actually work.

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Rhodococcus equi is a very well recognized pathogen in horses – it is a common cause of pneumonia in foals between the ages of 1-6 months, and infection is also sometimes associated with other problems such as diarrhea, swollen joints and abscesses in other parts of the body. The infection can be very difficult to treat because the bacteria are able to live inside white blood cells, which helps protect them from the body’s immune system, and because they often cause abscesses to form, which are difficult for antibiotics to penetrate. Rhodococcus equi infection in foals has been studied extensively, but there’s still a lot we don’t know how the body defends itself against this organism.  These are a few things we do know:

• Almost all foals are exposed to R. equi as neonates, but most of them never develop signs of infection.
• Giving newborn foals hyperimmune plasma (plasma with extra antibodies against R. equi) may have some beneficial effects on farms where the infection is a recurrent problem, but this practice is still controversial.
• Adult horses are essentially immune to the infection.
• In almost all cases if clinical disease in foals, the R. equi strain involved carries a special gene called vapA.
• Mortality rates in foals vary considerably from 0% to 30%.
• So far, efforts to develop a vaccine to help protect foals have been unsuccessful, but research in this area is ongoing.

People can also be infected with R. equi, and as in foals, pyogranulomatous pneumonia (infection of the lungs which results in the formation of many abscesses) is one of the most common conditions caused by this organism. However, there are a few important differences between infection in people and infection in horses:

• 85% to 90% of people with R. equi infection are immunocompromised, meaning their immune system is weakened or suppressed for some reason, e.g. HIV infection, or immunosuppressive drugs taken by organ transplant or cancer patients.
• Among people infected with R. equi who have normal immune systems (i.e. immunocompetent), about half of the infections are localized, meaning they only affect one small part of the body. Many of these are associated with wound infections.
• Only 20% to 25% of the R. equi isolates in people carry the vapA gene.
• Infection in immunocompetent people can be fatal in approximately 11% of cases, but among HIV-infected patients the mortality rate from R. equi infection can be as high as 50% to 55%.

Rhodococcus equi is actually a soil organism, and this is likely the most common source of the organism for both horses and people. Only approximately 1/3 of humans infected with R. equi report that they have had contact with horses or pigs (pigs can also carry the bacterium). So we don't know how much of a risk an infected foal is to a person.  However, it is prudent for people, particularly those with weakened immune systems, to take precautions to avoid potential transmission of R. equi from horses.

• Try to reduce dust levels on the farm. Because R. equi most often lives in the soil, it can get stirred up into the air in dusty areas, which can then lead to inhalation by animals and people. Doing things like planting grass or other vegetation, installing windbreaks in high-traffic areas, or wetting down dusty stalls or paddocks can help reduce dust levels in the air.
• Keep open wounds and other broken skin covered when working around animals.
• Always wash your hands after handling a foal (or any horse)
• If you have a foal that develops signs of R. equi infection, make sure you have your veterinarian examine it as soon as possible so the diagnosis can be determined and the foal can be treated properly as soon as possible. Some foals with R. equi may develop severe pneumonia very quickly, so it’s important that they are examined right away.

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

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Rhodococcus equi is a common pathogen in foals between the ages of 1 and 6 months of age that is most infamous for its ability to cause pneumonia. Classic R. equi infection results in the formation of large abscesses throughout the lungs of young foals (see picture left), which can be especially difficult to treat because the bacteria are able to hide from the body’s immune system by living within white blood cells. However, this organism’s bag of tricks doesn’t end with lung abscesses – it can also travel to other parts of the body and cause all sorts of trouble. These kinds of infections may occur with or without the classic lung infection, and are referred to as extrapulmonary disorders (EPDs).

At the 2008 Forum of the American Association of Equine Practitioners (AAEP), researchers at Texas A&M presented the results of a study they recently completed looking at EPDs in 150 foals with R. equi infection over a 20 year period. Here are some of the highlights:

• 74% of the foals had an EPD associated with their R. equi infection. On average foals had two EPDs each and up to as many as nine EPDs in a single animal.
• Many of the EPDs did not cause separate, detectable clinical signs. These were therefore most often found on necropsy in foals that died.
• The most common EPD was diarrhea, which occurred in 50 foals (33%).
• Immune-mediated polysynovitis (inflammation and swelling of the joints without infection of the joints themselves) was the second most common EPD
• 31 foals (21%) had ulcers and inflammation somewhere in their intestine (ulcerative enterotyphlocolitis), all of which were diagnosed at necropsy
• 25 foals (17%) had abscesses in the abdomen, 71% of which could be detected by ultrasonography

Thirty-nine different EPDs were identified in the group.  Other EPDs included uveitis (inflammation of the eye), hepatitis (inflammation of the liver), septic arthritis (joint infection), lymphadenopathy (enlarged lymph nodes), peritonitis (inflammation of the lining of the abdomen) and septicaemia (bloodstream infection).

• Among the foals with EPDs, 43% survived hospitalization, whereas 82% of foals without EPDs survived.  However it is very important to remember that many EPDs were only detected at necropsy, therefore they were more often found in foals that died, but it is unknown if they actually occurred more commonly in one group or the other.
• Risk factors for foals developing EPDs included longer time from onset of clinical illness to referral (e.g. foals that were sick at home for longer before being sent to the hospital were more likely to have an EPD), higher heart rate on admission and a higher white blood cell count.

It’s important to remember that even though an infectious pathogen may usually affect an animal in a certain way, “the bugs don’t read the textbooks” (as we often say), and they can cause problems in other ways. That’s just one of the reasons it’s so important to have your veterinarian perform a full physical exam of your animal if it is sick - even if it looks similar to something you’ve seen before - in case the pathogen causing the problem starts to affect other parts of the body, which may require more or different kinds of treatment.

Photo credit: M. Anderson

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Diarrhea is a relatively common problem in foals. It can range from very mild to fatal, and sick foals can get worse (i.e. "crash")  very fast. Outbreaks of diarrhea in foals can also occur.  So while most cases of foal diarrhea are mild, the implications of this condition for both the foal and the farm can be huge.

There are a variety of potential causes of diarrhea in foals. One is Clostridium difficile, a bacterium which can be found in the intestinal tract of a small percentage of healthy adult horses and foals, but which can also cause disease under certain conditions. Clostridium is a type of spore-forming bacterium - it produces spores that are able to survive for a very long time (i.e. years) in the environment, and that are resistant to most disinfectants. Most cases of C. difficile infection in foals are single, sporadic cases, but outbreaks on breeding farms can occur and can be very difficult to control. Typically such outbreaks start out with a few individual (sporadic) cases of foal diarrhea early in the foaling season, with a gradual increase in the number of cases over the following weeks to months. Often it gets to the point that  all foals born later in the season develop diarrhea. You cannot tell the difference between diarrhea caused by C. difficile and that caused by other infectious agents just by examining the foal - diagnostic tests are needed to make the diagnosis (watch for an upcoming post for more information about this kind of testing).

There is little information about control measures for C. difficile infection that have been proven to work. However, our understanding of the organism and what it does in horses and other species lets us make some general recommendations:

• Only use antibiotics when it's really necessary. "Routine" use of antibiotics in foals (which some people use to try to compensate for poor management practices) is not needed, and may increase the risk of C. difficile.
• Use good general hygiene practices, particularly around the time of foaling and in areas where neonatal foals live or often are. Clostridium difficile is spread by the fecal-oral route, meaning foals swallow the C. difficile from manure contamination in their immediate environment.
• Isolate all horses (foals and adults) with diarrhea so that they are less likely to spread it to other horses.
• Do not try to treat healthy horses or foals to try to get rid of C. difficile. There's no evidence that it works and it could actually make it more likely that the horse/foal will get sick.
• Let your veterinarian run the appropriate diagnostic tests to identify the cause of diarrhea in any adult horses or foals, particularly on farms where more foals are expected to arrive. It's better to find out early with what you are dealing, in case specific preventive or early treatment measures can be used to help stop an outbreak from occuring.
• Make sure you have a good infection control program for your farm.

No vaccine for C. difficile is currently available, nor will one be available in the near future. Other techniques for preventing this disease are being evaluated but none are yet proven.

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

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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.

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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.

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With foals, as with so many other things, one bad thing tends to lead to another.  This is compounded by the fact that when neonatal animals start to "crash", they tend to crash fast.  So in order to stop the vicious downward spiral before it's too late, it's important to recognize the early signs of things gone wrong and take appropriate action as soon as possible.

Septicemia is one of the most serious conditions in foals, and unfortunately a relatively common occurence in neonates.  It is caused by infection of the bloodstream that causes inflammation all over the body, so there are a lot of different clinical signs that can be associated with septicemia.  Most affetced foals will have several of these signs, but not necessarily all of them.  Some of these signs can also be caused by other problems, but remember that a newborn foal with problems of virtually any kind is at higher risk for developing septicemia.  Signs of septicemia may include:

• Depression
• Lack of suckle reflex (normal foals should try to suck on a person's fingers or a bottle nipple if placed in the foal's mouth)
• Fever (too high a temperature), or hypothermia (too low a temperature)
• High heart rate (most new born foals have a heart rate between 80-120 beats per minute)
• High respiratory rate or trouble breathing
• Gums and lips an abnormal colour (e.g. dark red or purplish)
• Swollen, painful joint(s)
• Cloudy eyes (i.e. anterior uveitis)

In septic foals (i.e. foals with septicemia) other signs may develop depending on what organs are most severely affected.  For example, inflammation in the brain may lead to seizure activity, and inflammation of the kidneys can lead to renal failure and lack of urine production.

In most cases, the appropriate action to take if you have a foal with any combination of these signs is to call your veterinarian as soon as possible.  A sick neonatal foal is an emergency.  Even a few hours can make a huge difference in the outcome of some cases, and the difference of a day can sometimes be the difference between life and death.  It is better to be safe than sorry, so have the foal examined by a veterinarian as soon as possible so it can be given the treatment it needs.

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It's incredible how the vast majority of neonatal foals, perhaps especially those born in the cold mid-winter, are able to survive all the challenges they face the moment they hit the ground - clearing their lungs to take their first breath, learning to stand and suckle so they can get milk from the mare before their body reserves run out, suddenly being exposed to the elements and having to regulate their own body temperature, and a world of bacteria, viruses and other pathogens just waiting to take advantage of their unprepared immune system.

Mother nature has found ways to protect these unsuspecting newborns from many of these threats.  Horses are precocial animals, meaning their young are born relatively mature, so normal foals are able to stand and even walk within hours of birth.  This is in contrast to altricial species, like dogs, cats and people, whose young are born essentially helpless.  The umbilicus is meant to close off as it breaks off the placenta and soon dries out in foals that are able to stand, which helps prevent bacteria from invading through this portal.  The most important protection from infection for foals comes from the mare's colostrum, which provides antibodies that the foal absorbs into the bloodstream within hours.  The foal also receives special antibodies from the mare that stay in the intestine, coating the intestinal lining to help prevent invasion from bacteria the foal swallows while exploring its new world.  When everything goes according to plan, foals are happy and healthy and actually require very little human intervention to get there.

Unfortunately, when things go wrong with foals there is often a domino effect, with one bad thing leading to another.  If a foal can't stand, it can't get its colostrum, its umbilicus doesn't dry properly, and it soon becomes weak as its very limited energy reserves run out, making it even less likely to be able to stand.  If the umbilicus doesn't break properly or dry out as it should, bacteria may invade the foal's body, leading to infection of the bloodstream, liver or bladder, or a patent urachus which causes the foal to urinate through its umbilicus.  Without colostrum, even the normal bacteria from the foal's own mare and stall can be harmful.  One of the most serious consequences of any complication with a neonatal foal is called septicemia - the presence of bacteria and bacterial toxins in the bloodstream, which causes inflammation throughout the body, and can result in infection in almost any organ or body system.  The mortality rate for foals with septicemia varies widely between studies, anywhere from 33-75%.

There are a few things people can do to help prevent neonatal sepsis without interfering with mother nature, who already does far more than we ever could:

• Keep things clean: Barns are not sterile environments, but making sure your mare foals in a nice clean stall on clean dry bedding can significantly decrease the amount and number of pathogens (particularly bacteria) that a foal first encounters when it hits the ground.
• Keep mom clean: The very first creature a foal will encounter is its own mare, specifically her hind end.  As the mare approaches her foaling date, it's important to keep her hind end, tail and udder especially as clean as possible. (Most mares will foal when there's no one around, so you may not have a chance to clean her up right before she foals!).
• Warm and dry: A cold, wet environment represents an additional challenge to a newborn's system, which can interfere with its ability to stand, suckle and fight off infection.  Try to ensure that the foal is born in a warm, dry place.
• Colostrum:  Make sure the foal drinks enough colostrum.  If anything else goes awry, this is one of the most important things you can do to help protect the foal against additional complications.  If the foal doesn't nurse from the mare, bottle feeding and tube feeding colostrum are other options.
• Umbilical care: The foal's umbilicus should close and dry out on its own, but in this case a little prophylactic treatment is warranted.  Dipping the umbilicus (without constantly soaking it) can help prevent bacterial invasion until it has dried out completely.

More information on colostrum and umbilical care are available in our archives and on the equIDblog Resources page.

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I was reading a fact sheet on foal care today that was available online. It was one of those sources that gives a mixture of good, mediocre and bad information. One thing that I didn't like was a reference to tetanus antitoxin administration being a common practice in newborn foals. That might have been the case a couple of decades ago, but it is certainly not recommended now.

Tetanus is certainly a serious problem in horses, and foals are at risk for exposure because the bacterium that causes the disease, Clostridium tetani, is widespread in the environment. Good measures need to be in place to reduce the risk of foals developing tetanus. The most important steps are:

• Ensure the mare is properly vaccinated for tetanus prior to foaling. This includes a booster that should be given approximately 30 days before foaling.
• Ensure that the foal gets enough good quality colostrum (see the information sheet on the Resources page for more details about colostrum for foals).
• Treat the umbilicus properly after birth (for more information, see our previous post entitled "Starting Out Right - Foal Umbilical Care").

If these things are done, there is no need to give tetanus antitoxin to a newborn foal. In fact, it's not only unnecessary, it's a potential health risk. Tetanus antitoxin neutralizes tetanus toxins that are in bloodstream. It used to be widely used in horses of all ages if they were wounded. However, administration of tetanus antitoxin has been associated with a disease called Theiler's Disease or serum hepatitis. While rare, this is a severe and almost always fatal liver disease.

Tetanus antitoxin is only potentially indicated in foals whose mares were not vaccinated against tetanus (or their vaccination status is unknown) and possibly in foals that did not receive adequate colostrum.

More information on tetanus, colostrum and vaccination recommendations can be found on the  equIDblog Resources page.

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The umbilical cord is the foal's lifeline in the uterus. Unfortunately, it can also be a great way for bacteria to enter the foal's body after birth. Infection of a neonatal foal's umbilicus can result in local infection at the site, a patent urachus (an open communication between the umbilicus and the bladder, resulting in urination through the umbilicus), abscessation of the umbilicus (which can extend all the way to the liver or back to the bladder) or sepsis (bloodstream infection). Fatal disease from an umbilical infection is not uncommon. Therefore, it's obvious that we need to try to reduce the risk of bacteria entering the umbilicus and causing infection.

Everyone that has foals should know about proper umbilical care. If umbilical care is neglected altogether or done improperly, the foal may be at serious (and unnecessary) risk of infection. Improper umbilical care, especially the use of irritating substances, can damage the delicate tissues, and may in fact do more harm than good.  Here are some important points about proper care of the umbilicus for foals:

• Ideally, the umbilicus should be inspected and treated within 30 minutes of foaling (see picture right: normal umbilicus 20 minutes post-foaling).
• The umbilicus should be dipped with a 0.5% chlorhexidine solution (NOT a tincture, which contains alcohol). This is preferred to iodine-based products. If iodine is used, milder forms (i.e. povidone iodine) should always be used, and they should be diluted properly prior to use. Stronger is not better - high concentrations of iodine can be very irritating and cause severe skin damage.
• The entire umbilicus should be treated, but care should taken to prevent soaking areas around the umbilicus.
• Umbilical treatment should be repeated every 6-8 hours for the first 24 hours of life, but do not over-treat the umbilicus - it is crucial that the tissues ultimately dry out.  The umbilicus should not be kept moist all the time, as this makes it easier for bacteria to invade the tissues.
• Avoid touching the umbilicus directly with your hands. If this is necessary, hands should be washed thoroughly first or gloves should be worn.  Always wash your hands thoroughly after.
• Any problems with the umbilicus (e.g. bleeding, urine coming out, large size, hot and painful, chronically moist) should be reported promptly to your veterinarian.
• Suturing, tying or other forms of closing off the umbilicus should be avoided if at all possible.

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On December 9, the Infectious Diseases session was held at the 2008 AAEP Conference in San Diego, CA. Topics presented covered several conditions, including MRSA, Clostridium difficile, equine infectious anemia (EIA), parasite resistance and deworming protocols, and Lawsonia intracellularis.

Lawsonia intracellularis is a bacterium that causes a disease called (among other things) proliferative enteropathy in foals and weanlings. More information about this disease is also available on the equIDblog Resources page. This disease is relatively new in the horse world, being first identified in the 1990s. It has traditionally been considered a disease of pigs, where it causes several syndromes of clinical disease, including one similar to that seen in foals. In pigs that carry the bacteria in their intestine, clinical disease is brought on by stressful events, and the same may be true in foals. The infection causes severe thickening of parts of the small intestine, and the inflammation causes loss of large amounts of protein from the bloodstream. Affected foals are usually very “unthrifty” and quiet/depressed, and many often develop edema (non-painful, cool swelling) along their abdomens or under their jaws.

In pigs, prevention of disease due to Lawsonia infection involves decreasing stressful events and vaccination with an oral vaccine. Dr. Nicola Pusterla of the University of California (Davis) presented the results of a study that was done recently looking at the effects of vaccination of foals against Lawsonia in three different ways – giving the vaccine orally, giving the vaccine orally after treating the foals for three days with a gastroprotectant (omeprazole), and giving the vaccine rectally. The reason for the last two groups was to decrease the risk of the vaccine being destroyed by the acidic environment of the normal stomach. Indeed, they found the antibody response to the vaccine in the bloodstream was better in these groups than in the untreated foals that were given the vaccine orally. Of the 12 foals that received the vaccine, all of them stayed healthy throughout the study period (42 days).

Although seeing some work on developing a vaccine for this disease is great, we are still a long way from being able to use vaccination to prevent disease in foals. While the animals in the study produced antibodies in the bloodstream, Lawsonia actually lives inside cells, where antibodies usually cannot get to them. Immunity against intracellular pathogens like this requires cell-mediated immunity, which is much harder to measure. It’s also important to remember that even with a vaccine, control of this disease (as with any infectious disease) depends on a lot of other factors, like reducing stress on animals and preventing transmission and spread of the bacteria. Unfortunately, no one is even sure exactly what the source of the Lawsonia is in most foals (although there’s a good chance that they ingest it, possibly with fecal contamination from foals that are shedding Lawsonia).

As more and more cases of Lawsonia are seen, both in North America and now in Europe, researchers will continue to learn more about how this disease is spread, and hopefully one day develop a vaccine to help us prevent it.

Keep watching this site for more of the latest and greatest from the 2008 AAEP Conference!

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As every horse breeder should know, colostrum is one of the keys to any foal's survival. This antibody-rich first milk is critical for preventing early, often fatal infections in foals. Foals that don't get an adequate volume of good quality colostrum within the first 18-24 hours of life (while they can still absorb antibodies through their intestine) are at high risk of dying from any of a number of different infections.

Sometimes colostrum from a newborn's mare may not be available.  This is an emergency situation, so every breeder (whether they have one mare or 100 mares) should have a contingency plan for treating the foal or obtaining colostrum from another source, just in case.  This may be necessary if:

• The mare does not produce any milk (i.e. she doesn't "bag up") prior to foaling.
• The mare leaks colostrum/milk from her udder prior to foaling.
• The mare dies during delivery.

Finding an alternate source of colostrum after a foal is born, within those critical first 18-24 of life, can be very difficult.  Like most things, planning ahead can make finding such a source much easier, and a little proactive effort may save your foal's life. A few potential options are:

• Save extra colostrum from other mares on your farm.  Most mares produce more colostrum than their own foal will need.  Any extra colostrum can be milked out and frozen for use later in the year, or even in future years (although the quality of the colostrum does decrease somewhat when it is stored for a very long time).  Always make sure each mare's own foal gets enough colostrum first.
• Get colostrum from a colostrum bank, if there is one in the area.
• Get together with local breeders and start your own colostrum bank, with different people saving colostrum and/or being on call to collect colostrum from newly foaled mares, if anyone needs some.

Foals can also get the antibodies they need from plasma, which can be given intravenously (as a transfusion) or even orally (within the first 18-24-hours).  However, commercial plasma is usually quite expensive, and it doesn't replace many of the other components of colostrum from which newborn foals benefit.  Feeding the foal equine colostrum, from one source or another, is still the best recommendation.

More information on colostrum is available on the equIDblog Resources page.  More information about colostrum banking is available in this article from the California Thoroughbred magazine.

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