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

Hard to believe that the whole conundrum about contagious equine metritis (CEM) that is still affecting the Canadian equine industry started a little bit more than a year ago, when a Quarter Horse stud in Kentucky tested positive for the causative agent, Taylorella equigenitalis. Tracing the contacts of that stud lead to the quarantine and testing of 990 horses in 40 states, as well as 19 mares in Canada, including 9 in Ontario. Out of 274 exposed stallions, 22 were ultimately found to be positive, none of which had any detectable clinical signs that they were infected, meaning if they hadn’t been tested, they may have kept on going about their business breeding – and possibly infecting – mares for years to come. The rest of the exposed horses were mares, five of which turned out to be infected. One particularly interesting fact was that four of these mares had been bred by artificial insemination - previous to this it was thought that CEM was only readily transmissible by live cover from an infected stud, not via semen shipped in a straw.

Thankfully all of the Canadian mares were negative, but unfortunately the Canadian equine industry is still suffering the consequences of what has happened to our close southern neighbour. Fourteen countries have increased import requirements for Canadian (and obviously US) horses in terms of CEM testing, and another major blow was the loss of Canada’s low-risk status with the UK's Horserace Betting Levy Board (HBLB).

Canada must maintain strict import requirements for horses to prevent CEM from getting into the country. Most of the horses imported into Canada come from CEM-positive countries, and it’s getting more difficult to argue not including the US on that list as well. The risk is constantly present, and remaining diligent about quarantine and testing – and rules like ensuring horses are not on antibiotics for some other reason when they’re cultured – is key. Semen import restrictions for semen coming from the US to Canada will stand for 2010. While this certainly causes a headache for breeders, requiring an import permit and a health certificate for the stud stating that it has not stood on a CEM-quarantined farm, is it enough to protect Canadian horses? The next step would be to require all studs to be tested for CEM before their semen can be imported to Canada. That is no small request. Testing a stud involves culturing the stud himself, and then having him test-breed two mares which then also need to be culture-negative. Anecdotally the entire process can cost in the neighbourhood of $5-7K per horse, which at the moment all needs to be borne by the horse owner. That gives you some idea of what an enormous undertaking it was to quarantine and test 274 exposed stallions during last year’s outbreak.

In the US, 87% of exposed horses have now been cleared, and there have been no new positives in the last 8 months. However, there are still 17 states where there are quarantined farms. There is talk of voluntary testing of over 2000 studs in the US in 2010, as well as targeted surveillance of stallions imported in the last 10 years and those standing at large AI centers. Only time will tell if these extra efforts will serve to calm the fears of countries that are now hesitant to import horses and semen from the US, or whether they will reveal more cases of CEM and confirm the fears that CEM may have unknowingly become endemic in the US in the past decade.

More information on CEM is available in our archives.

This blog is based on a presentation by Dr. Tracey Chenier, a theriogenologist and faculty member at the Ontario Veterinary Collge, given at the recent 2010 Ontario Veterinary Medical Association Conference.

Photo credit: David Campbell (click for source)

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A three-year-old Standardbred gelding was presented to the hospital for evaluation and treatment of diarrhea (colitis). The previous week the horse had developed a mild hind-limb lameness which seemed to come and go, and it was decided to treat the horse with antibiotics “just in case” it had something to do with an infection. The horse was treated with ceftiofur (an antibiotic, often sold under the brand name Excenel or Naxcel) for five days. On the fifth day, the gelding developed moderate to severe diarrhea. The next morning the horse also had a fever. He was treated with anti-inflammatories and quickly referred to the hospital for intensive care.

On presentation, the gelding was very quiet. He had a very high heart rate, reddish gums and he was significantly dehydrated. Intestinal sounds could not be heard over the abdomen, indicating that the horse’s intestines were not moving normally, and there was a “ping” on the right side of the abdomen, indicating that there was gas accumulating in the cecum (part of the large intestine). Treatment with intravenous (IV) fluids was started right away to try to correct the dehydration and keep up with the amount of fluid the horse was losing in its diarrhea.

By the next morning the horse’s attitude was improved, but his gums were still an abnormal colour (“toxic mucous membranes”, see picture), indicating that there were inflammatory cytokines (substances released by cells when they’re in distress) and likely bacterial toxins in horse’s bloodstream. Also, despite the IV fluids, the gelding was still dehydrated, likely because he was pooling fluid from his body tissues in his intestine, as well as the more obvious loss of fluid in his ongoing diarrhea. This went on for another two days, despite intensive treatment in the hospital. On the fourth day, the gelding developed severe signs of colic. His large colon became progressively more distended with gas, and the contents of his small intestine started to back-up into his stomach. His heart rate became extremely high, and his pain could not be controlled with sedatives or anti-inflammatories. A belly-tap yielded a red-tinged fluid (normally belly fluid is light yellow), and the concern at that point was that the intestines had become twisted (which can happen in horses with diarrhea as a result of their abnormal intestinal motility). Despite the risks, it was decided to take the horse to surgery - but there was no twist in the bowel. The cause of the colic was that the large colon was severely distended with gas and fluid, and it was barely moving at all. The appearance of the large colon was consistent with extreme inflammation, and the tip of the cecum looked so bad that the surgeons decided to remove it because it was likely dead or dying.

The horse recovered from anesthesia, and IV fluid therapy was continued. Later that day, when the horse was offered some pellets, some intestinal sounds were detectable. The horse soon started to pass diarrhea again, but overall his attitude was much brighter, and his hydration status and (remarkably) blood protein levels remained stable.

Unfortunately the day after surgery the gelding became reluctant to move around the stall. Increased digital pulses were detected on the front feet, and the horse was sensitive to hoof testers – the gelding was developing laminitis. Despite additional treatment, the signs of laminitis became worse and worse. In the end the horse was euthanized, less than a week after being admitted to the hospital.

On necropsy, the entire large colon was severely thickened, filled with green-yellow fluid, and the mucosa (inside surface of the intestine) was ulcerated. Signs of severe acute laminitis were present in all four feet. A specific causative agent of the colitis could not be identified – tests for Salmonella and clostridial toxins were all negative. This is not too surprising as no agent is identified in over half of all adult horse colitis/diarrhea cases. But there is no doubt what set this terrible chain of events in motion – treatment with antibiotics, for a condition that may or may not have ever required antibiotic treatment in the first place.

We talk a lot about antibiotic-induced colitis/diarrhea in horses, but until you’ve seen it for yourself, it can be hard to believe that drugs used every day in both people and animals can have such a devastating effect on a horse. Antibiotics certainly do save lives, but unfortunately there are no “miracle cures” that are entirely without drawbacks. This case clearly demonstrates one of the most important reasons why we so strongly advocate prudent use of antibiotics in horses – their use should never be employed lightly. Although this is a “worst case scenario” that overall occurs uncommonly, the potential is there and should always be taken into consideration.

Photo credit: M. Anderson 2007

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An eight-year-old Quarter Horse gelding was presented for examination due to chronic weight loss over several months. Lately he’d also been lying down frequently and exhibiting increased breathing effort, so he was treated for what was suspected to be mild signs of colic, but failed to improve. He’d also collapsed once during mild exercise.

On examination, the gelding was quiet, alert and otherwise physically normal except for his poor body condition. However, on rectal palpation there was a large, firm, non-painful mass within the caudo-dorsal (i.e. upper rear) abdomen. revealed a large (42 centimeter) firm mass in the caudo-dorsal abdomen. The mass was further evaluated using ultrasound via the rectum. the mass was multi-lobulated (i.e. made up of many pockets on the inside) and had a large blood supply. It did not appear that the mass was directly attached to or growing in any abdominal organs (e.g. kidneys, intestine). Blood work showed a high white blood cell count (mature neutrophilia), moderate anemia, and high protein levels due to an abnormal increase in globulins (hyperglobulinemia).

These findings were highly suggestive of a large abdominal abscess, but a cancerous mass could not yet be ruled out. It was decided to take the horse to surgery the next day in order to better evaluate the mass, collect samples and remove it if possible. In surgery, the mass was found to be right at the root of the intestinal mesentery (the large membrane that carries the blood supply to the intestines), and there were a large number of adhesions between the mass and the base of the cecum, as well as to some loops of the small intestine. A needle and syringe were used to remove a sample of the mass’s contents in a sterile manner. The fluid retrieved had the appearance of thick pus, which further supported the tentative diagnosis of an abscess. Unfortunately, due to the location and size of the mass, as well as the number and size of adhesions, it could not be safely removed. The horse was therefore euthanized while still under anesthesia.

Necropsy examination confirmed that the mass was an abscess. The capsule of the abscess was extremely thick and tough, indicating that it had been developing over a very long period of time. A long-standing abscess such as this explained all of the gelding’s clinical signs – weight loss and moderate anemia due to chronic disease, high globulin levels due to constant stimulation of immune cells by the infectious focus, and recumbency and collapse due to discomfort caused by entanglement of the intestines in the adhesions associated with the abscess.

Culture of the fluid sample retrieved at surgery yielded a heavy, pure culture of Streptococcus equi subsp. equi – the bacterium that causes strangles. This horse had what’s known as “bastard strangles,” which is a recognized complication that occurs occasionally in horses that have had the classic upper respiratory infection. In these cases the S. equi invade beyond the respiratory tract and can end up anywhere in the body. Then, just as the bacterium does in the lymph nodes around the head and throat in classic cases, the S. equi can form abscesses. The abscesses may form in internal lymph nodes (which is likely what happened with this gelding) or in organs like the kidneys or even the brain. These abscesses tend to develop slowly and insidiously. Even if they can be identified, they are typically extremely difficult to treat effectively, and unfortunately euthanasia is often the end result. Other bacteria that can cause similar abscesses include Rhodococcus equi, Corynebacterium spp. and Arcanobacterium pyogenes.

Strangles is endemic in the horse population – whenever horses are mixed or brought together in large groups there is a risk of strangles transmission. We cannot eliminate the risk, but we can try to reduce it as much as possible using basic infectious disease control measures. More information about strangles is available on the equIDblog Resources page and in our archives.

Image: A Standardbred in poor body condition due to chronic debilitation as a result of large abdominal abscess, similar to the case described here (photo credit: M. Anderson).

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equIDblog has now been active for one year, and look how far it’s come! Just this week we surpassed 75 000 unique hits since our launch. We now regularly have over 700 unique hits on the site per day during the week, and the numbers are still growing. It's great that we're able to provide a reliable source of information about equine infectious diseases to such a wide and diverse audience.

Everyone involved in equIDblog would like to take this opportunity to thank all the visitors who come to our site, and especially those who keep coming back for more! Please continue to help us spread the word about equine infectious disease control so everyone can do their part to help protect our equine companions, on a local, national and even global scale!  Questions, comments and suggestions are always welcome!  -Scott & Maureen

(Image credit: Tatiana Sapaterio)

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European Antibiotic Awareness Day is an initiative of the European Centre for Disease Prevention and Control.  This year it falls on November 18.  The aim of the Day is to provide an annual opportunity for raising awareness about the threat to public health of antibiotic resistance and how to use antibiotics responsibly.

Responsible use of antibiotics can help stop resistant bacteria from developing and help keep antibiotics effective for the use of future generations.  Successful national public awareness campaigns are already resulting in more rational use of antibiotics and a reduction in levels of antibiotic resistance in Europe.

Responsible use of antibiotics includes use in people and in animals.  Here are some of the things you can do to help with regard to antibiotic use in your horses:

• Only give your horse antibiotics if directed to do so by your veterinarian.
• Make sure your horse gets the full dose of medication at the correct time(s) of day.  If you are having problems injecting medication or getting your horse to swallow pills, contact your veterinarian as soon as possible.  Your veterinarian may be able to give you advice on some "tricks" for getting your horse to take the medication, or sometimes the medication can be provided in a different form (e.g. a liquid instead of a pill, oral versus injectable).
• Always ensure your horse finishes the entire prescription.  There should be no leftover pills or medication.  Do not stop giving your horse the antibiotics just because it looks/acts like its feeling better.  This is a common mistake that can have disasterous consequences!  You should NEVER "save a few pills for the next time."
• Never give your horse antibiotics that were prescribed for you, another person or any other animal, whether they are expired or not.

This equIDblog entry was originally posted on the Worms & Germs blog on 18-Nov-09.

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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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From Guest Author Dr. Angelika Schoster, Department of Clinical Studies, University of Guelph.

Equine hoof canker (pododermatitis chronica verrucosa) is described as a chronic, proliferative dermatitis, beginning in the caudal part of the cleft of the frog and gradually expanding to the sole and wall. Equine canker is not lethal in and of itself, but because of where it occurs on the foot, and because it can be so difficult to treat and it recurs so often, it can severely compromise a horse’s ability to do its job (even if that job is just walking around in a field sometimes). The etiology of equine canker has been a topic of discussion for over 50 years, but so far no specific cause for the disease has been found.

Canker is usually diagnosed based on the appearance of the affected horny tissue and a distinctly fetid odour. The definitive diagnosis has to be confirmed by microscopic examination (histopathology) of biopsies collected from the affected tissue.

Treatment of canker has always been a dilemma for veterinarians and farriers because it is so difficult. Treatments used today can range from surgical intervention (removal of the affected tissue) to conservative medical management using topical medications of many different kinds.

The proliferative but non-metastatic nature of canker is similar to that of equine sarcoids. Like canker, sarcoids also tend to be difficult to treat and often recur. Both canker and sarcoids often include a mixture of proliferative and erosive changes in the skin secondary to overgrowth and thickening of the tissues. Due to these similarities, it has been speculated that bovine papillomavirus (BPV) might also be involved in causing canker. A large study in Europe (which will hopefully be published soon) has found evidence to suggest that a variant of BPV-1 plays a role in the development and/or maintenance of canker lesions in horses. Much more study is still needed, but this is another interesting example of how an infectious pathogen may ultimately play a role in a disease that’s origin has remained a mystery for decades.

More information about papillomaviruses is available in our archives.

Image: Severe canker in the frog of a horse's hoof (source: www.answers.com)

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At the recent symposium of the American College of Veterinary Surgeons, there was an interesting abstract presented about liposome technology.  Liposomes are basically teeny-tiny "bubbles" made up of the same basic components as cell membranes.  They are sometimes call nanoparticles because they are so small, but they are still much bigger than even large molecules, which gives them some interesting biological abilities.  When liposomes are injected into the bloodstream, they go all over the body, but they tend to accumulate where there is tissue inflammation, because blood vessels become "leaky" in inflamed tissue, allowing these nanoparticles to escape the bloodstream.  What's great about liposomes is you can put different things inside them (such as drugs), and they help deliver their contents to inflamed sites in greater concentration and over a longer period of time, while reducing the exposure of the other body tissues to whatever they're carrying.  This can ultimately help improve the efficacy and safety of the drugs they carry.  Liposomes also tend to accumulate in tumors, so they are sometimes used to deliver anti-neoplastic chemotherapy drugs to these sites.

Liposomes have actually been around for a long time.  They were first described by Dr. Alec Bangham in 1961, and since then have become valuable tools in biology, biochemistry and medicine.  The technology still has its share of problems that need to be worked out.  Some people may have acute adverse reactions when liposomes are injected intravenously.  Sometimes the body's immune system will "attack" the liposomes, taking them out of circulation prematurely.  Much work is still being done to find better ways to help liposomes target particular tissues.

In terms of treating infectious diseases, liposomes can be used to deliver antibiotics to infected tissues.  Because of the targeted delivery system, the toxic/side effects of drugs on the rest of the body can be reduced while still achieving the same (or higher) concentrations of drug at the site of infection.  An example of this is the drug Abelcet (Enzon Pharmaceuticals), which is a liposomal preparation of the very toxic antifungal drug amphotericin B.  Abelcet has been licensed for use in the US and Europe since 1995.

The abstract presented at the ACVS (C. Underwood et al.) described the use of liposomes containing a radioactive marker (99-m Technetium) in horses.  They injected 10 healthy horses with a dose of liposomes, monitored them for adverse effects (of which there were none detected), and then used the radioactive marker to determine where the liposomes accumulate in a horse under normal conditions.  Their ultimate objective is to determine if liposomes can be used to better deliver antimicrobials to areas of infected bone (osteomyelitis), which are typically very difficult to treat.  Liposome technology still has a long way to go before it's being used widely in horses, but this was an important first look at how liposomes can possibly be applied to equine medicine in the future.

Image credit: Kosi Gramatikoff (1999)

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A five-year-old Quarter Horse mare was found down in the field in the mid-afternoon.  The horse was seen moving around the field normally less than eight hours earlier.  She was found near a fence, but there were no external signs of trauma on the mare's body.  Some green feed material was present at the nostrils.  With encouragement the mare was able to stand, but she was very unsteady and uncoordinated, particularly in the hind limbs. Upon examination by the veterinarian in the field, it was also noted that the horse could not open her mouth normally (lockjaw - which is often a sign of tetanus in horses), and the mare seemed "dazed".  There were three other horses kept in the same field, all of which appeared completely normal.  All the horses were fed the same round-bale hay (a new bale was just put out the previous day).  The mare was vaccinated for rabies in 2008 and West Nile in 2009 (spring).  There was no movement of horses on or off the farm (i.e. the horses were not taken to shows/competitions or off-site rides).

When the horse arrived at the hospital, she was down on the trailer.  By that time she had a fever, high heart and respiratory rates, and she was dehydrated.  Although she was still aware of things going on around her, she was very depressed.  She was still able to see, and she could move all four legs and her tail.  However, it was even difficult for her to lie on her chest (e.g. sternal recumbency), so she would roll to one side instead (e.g. lateral recumbency).  Her jaw remained rigid, but she could still move her tongue a little.

With a lot of encouragement and help the mare was able to stand up and stumble off the trailer, but she was so weak and uncoordinated in all four legs that she fell down again before she could even walk the 10 metres to her stall.  Eventually she made it to her stall, and she was able to stand for about an hour before she lied down (or fell down) again.  A urinary catheter had to be used to drain the mare's bladder because she did not seem to be able to urinate on her own.

The mare was treated with intravenous fluids (supportive therapy), and anti-inflammatories and steroids to try to reduce the inflammation that was suspected to be going on in her brain and spinal cord.  Despite all this, her condition continued to worsen, and by the next morning the mare could not even sit up and was becoming less aware of her surroundings.  The mare was therefore humanely euthanized.

Post-mortem tests in this mare confirmed there was inflammation in the brain based on a high number of inflammatory cells in her cerebral spinal fluid (CSF).  Because of the clinical presentation, some of the brain tissue also had to be sent away for rabies testing, which was (thankfully) negative.  Once that result was back, samples were also tested for evidence of infection with equine herpes virus (EHV-1), West Nile virus and Sarcocystis neurona (the cause of equine protozoal myeloencphalitis), all of which were also negative.  Botulism was also considered, but this disease is very difficult to test for in horses.  In the end, the final diagnosis, and the cause of the mare's neurological signs, was infection with eastern equine encephalitis (EEE) virus .

This case of EEE was diagnosed in September 2009 in Southwestern Ontario.  The description of the presentation, and how rapidly this mare deteriorated, demonstrates just how devastating and severe this disease can be.    This case also tells us that there are mosquitos in the area that are carrying EEE.  Vaccination of the other horses in the region will not provide protection before the end of this mosquito season, but owners of horses in the same area should seriously consider (and discuss with their veterinarian) vaccination of their horses against EEE in the spring, prior to the next mosquito season.  No one can say for certain if vaccination of this mare would have prevented the infection, or decreased the severity of the infection, but it likely would have helped.  In the meantime, as always, decreasing exposure to mosquitos as much as possible (if there are any left) should be the priority.

Image: TEM of the salivary gland of a mosquito infected with eastern equine encephalitis (EEE) virus (source: CDC Public Health Image Library #7057).

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If you have a horse, sooner or later you have a horse with a gash somewhere on its body.  Horses seem to have an uncanny ability to find the one sharp branch or protruding splinter of wood or nail in any paddock, pen or stall that no one else can ever find, no matter how hard you look.  But in the end, horses, just like people, sometimes get cuts.  Some cuts probably never even get noticed.  Thankfully, a lot of them heal by themselves with no interference from us.  In other cases, though, the cuts can get infected, and that's when you and your veterinarian need to step in and help that horse out.

Unfortunately, the "knee-jerk" reaction in many of these cases seems to be to put the horse on antibiotics.  Under some circumstances I don't disagree that this may be necessary, especially if the wound may involve tendons or a joint or deeper tissues.  In a lot of cases, however, this type of treatment may not be the best thing for the animal.  Use of local therapy for wounds, instead of systemic (e.g. oral or injected) antibiotics, should always be carefully considered.

Local therapy for wounds can include a variety of different types of treatments, such as drainage of discharge, removal of dead tissue (debridement), flushing of the wound (lavage), topical antibiotics, antiseptics, and sometimes newer (or older) compounds like honey.

Let's compare some of the potential pros and cons of local versus systemic therapy:

• Treating what counts: Local therapy is targeted at the site of infection - the wound itself.  Some antibiotics that are too toxic to be given systemically, or can't be given safely at a high enough dose to be effective, can be applied directly to the wound at a higher concentration, delivering a more effective blow to the infecting organism.
• Not treating what doesn't count: Avoiding the use of systemic antibiotics decreases exposure of the bacteria that are part of the horse's normal bacterial flora, particularly those in the intestinal tract.  This helps to decrease the risk of disrupting the flora, which can otherwise result in antibiotic-associated diarrhea.  It also helps decrease the risk of other bacteria in the horse's body developing resistance to the antibiotic being used.
• "Taking out the trash": Drainage, debridement and lavage help remove all the "junk" in a wound by getting rid of dirt, pus and dead tissue.  Often times, these are the most important components of treatment, and likely have more of an effect on the outcome than any of the drugs that may be used.  Whatever can be physically removed from the wound decreases the amount of junk and bacteria with which the horse's body needs to deal, and also eliminates material in which bacteria can hide from the immune system.
• Cost savings: Often times local therapy involves more time for cleaning and bandaging, but less drugs, because you're only treating the infected site, not the entire horse.

• It's not easy: As difficult as it sometimes can be to give a horse needles or make it swallow medication, these methods are often chosen because they are perceived as the "easy way out." Local therapy for a wound can be a lot of work - it takes time, it sometimes means getting yourself a little dirty, and some owners don't like the "ick" factor of having to deal directly with the wound itself.  However, systemic antibiotics should not be used as a substitute for proper wound care.
• Every wound (and every horse) is different: Not every infected wound is amenable to local treatment.  Deep wounds can be especially difficult to treat this way, because the deepest parts of the wound simply aren't accessible.  Also, depending on the temperament of the horse and/or the location of the wound, the animal may not tolerate local therapy of the site without sedation, in which case it is best left to your veterinarian.  It is always very important to ensure that you can safely treat your horse.

Even for wounds that do require systemic antibiotic treatment for one reason or another, local therapy should not be neglected, and can be critical to achieving a successful outcome.  It's important to try to resolve infections (of any kind) as quickly and efficiently as possible in order to avoid complications associated with chronic infection, and minimize the risk of antibiotic resistance developing (if antibiotics are used).  That means using all the available tools at our disposal, including simple wound care and local therapy, to treat them. But remember:

• Always wear disposable gloves if you need to clean, treat, bandage or otherwise touch a wound, and wash your hands well with soap and water afterward.  This will help prevent bacteria from the wound from being transmitted to you, and bacteria from your hands from infecting the wound.
• Do not give your horse antibiotics of any kind before consulting your veterinarian.

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