World Equestrian Games Piroplasmosis Control
International equine athletic events can create a lot of hassles from an infectious disease standpoint. Mixing animals from different areas creates a prime opportunity for transmitting infectious diseases between horses. An additional concern is when some horses might carrying infections that are considered "foreign" to horses from other areas.
During the 1996 Olympics in Atlanta, concerns about the potential for introduction of piroplasmosis (to the US) led to much angst, and restrictions such as only allowing horses carrying the disease to compete in indoor events. Piroplasmosis concerns have also played a role in planning the World Equestrian Games in Kentucky.
Piroplasmosis is caused by the bloodborne parasites Babesia caballi and Theileria equi, and is spread by ticks (as well as re-using needles and other modes of blood transmission). While it can be a fatal disease, some infected horses appear healthy, and these silent carriers can spread the disease to the ticks, which then spread it to other horses.
What to do regarding piroplasmosis was an important consideration for the World Equestrian Games. To even be awarded the games, a clear and fair plan was required to get approval from both the FEI and US Department of Agriculture. Balancing infectious disease risks with limited disruption of activities isn't easy, and it's not an exact science. Significant efforts have been taken to reduce the potential for piroplasmosis transmission. These include:
- Surveys of the park taken prior to the bid that showed minimal tick activity.
- Planning the event for late September and October because ticks are typically dormant by that time of the year (in Kentucky).
- Trapping small mammals at the park from 2006-2008 to study tick levels and types.
During the games:
- Known piroplasmosis carriers will be housed together in a separate barn that will be treated to eliminate ticks.
- Carriers will be inspected for ticks when they enter or leave the stable area.
- In advance of the event, all horses currently at the park have been inspected and treated for ticks.
You can never guarantee that an infectious disease won't slip through even the most strict measures, but that's the nature of infection control. This seems like a nice evidence-based, logical plan to reduce the risk of piroplasmosis dissemination during the Games.
Photo by Ronald Yochum, 2006 (click for source)
Following a repeating trend that has been ongoing over the past couple of years, piroplasmosis has been identified in more US horses with no clear source. 
The rather 
Cushing's disease (more correctly called pituitary pars intermedia dysfunction (PPID) in horses) is a relatively common problem in older horses. It is caused by a pituitary adenoma (a benign tumour in the pituitary gland located at the base of the brain) that results in excessive production of various hormones. Horses with Cushing's (PPID) tend to have a long curly haircoat, excessive sweating, muscle loss and a pot-bellied appearance. They are also at increased risk of various infections, in part because the disease compromises their immune system. They are also at risk of certain infections because of things like the long hair coat and the increased risk of laminitis that are specifically associated with PPID. 
It's common for people to wipe injection sites in horses with alcohol before inserting the needle. It's so ingrained into some peoples' minds that they may complain if their veterinarian doesn't use an alcohol wipe before injecting. But what does that little swab really do, and is it needed?
I assume that people wouldn't voluntarily and regularly walk around barefoot on dog feces (or feces of any type), yet it's perplexing that some people regularly clean out horse stalls in bare feet (I've seen it done!). While horse manure may not be as inherently gross as dog poop, it's still feces, and like all feces contains a huge population of various bacteria, some of which can be harmful. The risks of barefoot mucking may also extend to bare feet inside boots, although I don't think sock-averse people need to panic.
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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.
The UK's 
Rotavirus is an important cause of diarrhea in young horses. (It's also a major cause of diarrhea in infants, but a .jpg)
Following on the heels of a few outbreaks of piroplasmosis in the US over the past year is 
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Equine Piroplasmosis Disease Investigation Continues
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 .jpg)
The ongoing large 
For a country that is "piroplasmosis-free," the US sure has a lot of piroplasmosis. The Texas Animal Health Commission has reported that this bloodborne disease, caused by Theileria equi, has been confirmed on a ranch in south Texas. The farm is quarantined and testing is under way to determine the scope of the problem. They are presumably also looking at ticks in the area to see if the types of ticks that are able to transmit the infection are present, and trying to figure out where the infection came from.
Equine sarcoids are skin tumours that affect horses, donkeys, mules and zebras. They are the most common type of tumour found in horses, and account for 35-90% of all equine skin tumours. Sarcoids are generally not life-threatening – unlike some other tumours, they do not metastasize (i.e. spread to other organs or tissues). However, they can be locally aggressive growths, meaning they may invade deep into the tissues immediately surrounding the primary tumour. They are also very difficult to treat, and therefore can affect a horse’s welfare or quality of life, depending on the size and location of the sarcoid. There is some evidence of a genetic predisposition to sarcoids in some horses as well. Involvement of bovine papillomavirus in the development of sarcoids was first suggested by Olson and Cook in 1951, who were able to reproduce sarcoid-like lesions in horses by inoculating them with tissue from bovine warts. Since then, researchers have used PCR to show that the vast majority of sarcoids contain BPV DNA, whereas normal horses and non-sarcoid skin tumours do not. Although BPV DNA has been found in healthy horses living in close contact with sarcoid-bearing animals, there is currently no evidence that BPV or sarcoids are transmissible horse-to-horse.
The recent 
An Australian horse group, the .jpg)
In the wake of the 
Unfortunately, Dr. Alister Rodgers, who had been hospitalized with Hendra virus infection acquired from a sick horse, 
What's the link between chickens, Campylobacter, anti-ulcer drugs and horses? Well, nothing direct but .jpg)
I received the following question the other day: "I have a friend who had chemo embolization on tumor on liver in late June. She is in hospital now, and an abscess was discovered on liver. Pathology results said "equine strep". Her brother visited immediately after procedure, and he works with horse full time."
A veterinarian, 
To steal a line from Winston Churchill, equine protozoal myeloencephalitis (EPM) is a riddle, wrapped in a mystery, inside an enigma. It's a frustrating disease from many standpoints, and myths abound. 
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A recent post about mandatory vaccination in show horses sparked a discussion about concerns regarding adverse reactions to vaccines. Dr. Carolyn Cooper of the 
Hendra virus, a virus that can kill horses and people, has resurfaced in Queensland, Australia. This bat-borne disease has caused 
Dr. Bob Wright of the 
Earlier this summer, the 
There is apparently still no evidence regarding the location of .jpg)
International events like the 
It was only a matter of time, but eastern equine encephalitis (EEE) has been found in more US states this year. EEE is an seasonally important disease in some areas, including Louisiana. More cases in more states, and perhaps even some regions of Canada, are likely over the course of the summer and fall.
Not long after the 
The 
Clostridial myonecrosis (also called clostridial myositis or gas gangrene) is a very serious infection caused by growth of Clostridium bacteria in muscle. Clostridia are anaerobic spore-forming bacteria, meaning they only grow in environments without oxygen and they can stay dormant in the form of very tough (e.g. difficult to kill) spores. Clostridal spores can be found in healthy muscle. Presumably they enter the bloodstream periodically from the intestinal tract, but aren't able to grow because of the presence of oxygen in healthy muscle. They lie dormant, waiting for the right conditions to start growing - which in most horses never occurs. Clostridial spores can also be introduced into muscle during injections (e.g. vaccines, medications), surgery or trauma..jpg)
Two horses from different farms in the 
No, not dental plaque like you get on your teeth - in this case we’re talking about aural plaques, which are a type of skin lesion that some horses develop on the inside surface of their ears. These plaques are usually depigmented, meaning the skin cells of which they are made do not have the same pigment in them as the cells of the surrounding skin, making the lesions appear pale grey or off-white. Other than being considered unsightly in some cases, aural plaques usually don’t cause problems for the horse – they’re not itchy, sensitive or painful. They can occur in any horse, no matter the age, breed or sex. Occasionally some horses may develop similar plaques on the udder or around the anus or vulva (under the tail). The diagnosis of an aural plaque is typically made based on the horse’s clinical signs alone (i.e. a raised, depigmented skin lesion inside the ear that is not associated with any inflammation or discomfort).
Papillomaviruses (PVs) are small DNA-based viruses that are recognized causes of disease in many animal species and humans. More than 100 different human papillomavirus types (HPV) have been identified, which can cause a range of problems from annoying (but benign) warts to malignant cervical cancer. The ability of papillomaviruses to cause cancer was first recognized in animals, specifically with cottontail rabbit papillomavirus (CRPV), bovine papillomavirus (BPV) and canine oral papillomavirus (COPV). In general, PV infection causes benign disease in the vast majority of individuals, but the viruses have the potential to cause malignant disease in a small proportion of the mammals they infect as well.
The latest edition of 
Coincidentally, just after writing my post on the concerns about 
Climate change is a pressing topic these days. There are many potential ramifications of climate change, including shifts in disease patterns. The climate affects the populations of insects that can transmit infections. This can result in expanding ranges of certain diseases, or movement of diseases into totally new regions.
In equine hospitals, intravenous (IV) catheters are often placed in the large jugular vein in the neck of horses to make it easier for everyone (the horse included) to give the animal fluids and/or medication. However. any time the body's normal barriers (e.g. the skin) are broken (e.g. by placing a catheter through the skin into a vein), there is an increased risk of infection. Catheter site complications can range from mild inflammation of the skin around the catheter, to serious infection causing thrombosis (blockage) of the vein and abscesses.
Lawsonia intracellularis is an important cause of disease in weanling foals, causing a disease called proliferative enteropathy. Antibiotics, mainly erythromycin,are usually used as part of the treatment for this condition. However, little is known about the true antibiotic susceptibility of this bacterium. The problem is that Lawsonia does not grow in culture plates in a lab like most other bacteria with which we deal - it can only grow in cells, which makes it very difficult to test for antibiotic resistance. Antibiotic therapy for this disease is therefore chosen based on basic knowledge about the bacterium and anecdotal information about how animals respond to treatment. Obviously, this is not the ideal situation.
Unlike dogs, which commonly have urinary tract disease, urinary tract infections (UTIs) are very uncommon in horses, but they can occur.
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 
An abscess is an accumulation of pus. Pus is basically dead bacteria, partly broken-down cellular debris, and white blood cells. Sometimes there can be a thick capsule of tough, fibrous tissue surrounding an abscess, particularly if it has been there for a long time (see picture left). Most abscesses occur as the result of a local infection that the body was able to contain (at least partly), but could not eliminate altogether, and that didn't "drain" naturally to an open space (e.g. outside the body). Over time, some abscesses may continue to grow and become quite large, which can cause many different problems depending on where the abscess is. "Sterile" abscesses can also occur, but are much less common - these lesions are not associated with a bacterial infection, but may occur following a severe trauma or in association with certain tumours.
Equine piroplasmosis is a blood-borne disease that is caused by the parasites Babesia equi and Babesia caballi. Infected horses may develop mild disease characterized by weakness and loss of appetite. In more serious cases, horses may develop fever, anemia, jaundice (yellow gums and eyes), a swollen belly and respiratory problems. Other signs that are sometimes present include neurological abnormalities, red urine (secondary to destruction of red blood cells) and death. In contrast, many infected horses may no signs of illness whatsoever. Horses that recover may carry the parasite for a long period of time, and these horses can be a source of infection for other horses if there are ticks in the area capable of transmitting the parasite (not all species of ticks can transmit the disease). This can lead to the need for long quarantines. Horses that become persistent carriers of piroplasmosis need to be quarantined for life, euthanized or sent to a country where the disease is endemic.
Horses that most often become infected and sick from A. equuli are foals. This bacterium can cause a wide range of infections in these young animals, including septicemia (bloodstream infection), meningitis, pneumonia, omphalophlebitis (umbilical infection) and septic arthritis (joint infection). Foals can get infected from contact with other horses or even their own mares because the bacterium is so common. However, it typically only becomes a problem in foals that do not receive .jpg)
Mastitis (inflammation of the udder) is a relatively uncommon problem in mares. Some of the likely reasons that mares develop mastitis much less commonly than other animals (such as cows) is that they have comparatively small teats, and the udder, even when engorged, remains well tucked up between the hind legs. This decreases the risk that the teats will be traumatized or soiled compared to the large, low-hanging teats of a cow. Also, frequent nursing by foals (normally several times an hour) keeps the udder relatively empty and helps prevent build up of bacteria in and around the teat. The fact that people don’t frequently touch a mare’s teats and udder also helps prevent contamination with bacteria from our hands or from other sources that may be transmitted indirectly on dirty hands.
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 
Equine dysautonomia, or "grass sickness", is a very important disease in some areas of the world, particularly the United Kingdom and some parts of South America (where it's called mal seco). The cause of the disease is still unclear, but there is increasing evidence implicating the bacterium Clostridium botulinum, which produces the toxin that causes 
Streptococcus zooepidemicus (technically Streptococcus equi subspecies zooepidemicus), commonly called Strep zoo, is an important bacterium in equine medicine. It is one of the most common bacteria isolated from infections in horses. Like other streptococci, S. zooepidemicus is a Gram positive coccus, meaning that it stains purple with Gram stain and has a ball shape (coccus). Streptococci tend to stick together in chains (see picture right) which are often described as "string of pearls."
I just got back from the 
There's something ironic about traveling to a conference to speak about infectious diseases and coming down with food poisoning. As I lay in bed in Orlando in a relatively non-functional state Friday, I had lots of time to contemplate the good and bad points of vomiting. As much as it is unpleasant, the ability to vomit is useful, and it is something horses lack. As one of the many anatomical quirks that horses possess, horses are essentially unable to vomit, regardless of what in happening farther down the intestinal tract. This is serious problem, because unlike people who can relieve the pressure of a distended stomach by vomiting, the only thing a horse's stomach can do is get bigger and bigger until it finally bursts. Stomach rupture is fatal and kills numerous horses every year - it causes massive infection in the abdomen (peritonitis) due to the spillage of the bacteria-laden intestinal contents.
The investigation of the 
Until the outbreak investigation in the USA is complete and the disease is contained, use extreme caution or simply refrain from importing breeding animals, semen, embryos etc. from the USA.
Potomac Horse Fever (PHF), a disease named for the 
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.
In December 2008, an outbreak of contagious equine metritis (CEM) was reported in Kentucky. The index case was a healthy stallion that underwent routine testing for exportation of semen and the causative agent, Taylorella equigenitalis, was isolated by cutlure on December 15. By the end of the month, three more stallions on the same farm were also identified as infected. At the moment, it is estimated that there are 28 horses in Kentucky and another 156 horses outside Kentucky that have been exposed. Another 250 horses are being traced across 27 states. The last outbreak of CEM in the USA was in 1979 in Missouri, although a few sporadic cases have been identified in the country in the last three decades. It is a reportable disease in both the USA and Canada, and there are strict import (and export) regulations for horses entering the USA and Canada from CEM-positive countries.
This post originally appeared on the 
EPM was first identified in horses in the 1970s, but it took more than twenty years before the causative agent, the protozoal species Sarcocystis neurona, was identified. Shortly thereafter, the definitive host of S. neurona was identified as the opossum (specifically the Virgina opossum (Didelphis virginiana) in North America). In the opossum, the parasite lives and reproduces in the animal’s intestine without causing much damage, and oocysts are passed in the feces. Horses, on the other hand, are aberrant or “dead end” hosts – if they ingest the parasite from the opossum feces, they cannot spread it to other animals of any species. However, in a horse, the parasite can leave the intestine and migrate through the animal’s tissues, ultimately reaches the brain and/or spinal cord. Damage to the nervous system caused by migration of the parasite. Although EPM has been identified in horses outside of the Americas, the vast majority of these cases are horses that were imported from or at one point traveled to the New World.
EPM commonly gets blamed for a lot of minor abnormalities in horses (mostly gait abnormalities), often without being properly diagnosed. Part of the problem is that exposure to the parasite in the New World is very common (>50% of horses in many areas), but definitive diagnosis of disease due to EPM can be very difficult. The classic sign of EPM is pronounced asymmetrical muscle wasting (note the profound muscle wasting of the left gluteal muscle in the picture) in different parts of the body. There are very few other diseases that result in this kind of condition, so a fairly confident diagnosis can be made in these cases. Horses with more subtle or less classic signs are more problematic.
Lawsonia intracellularis is a bacterium that causes an intestinal disease called proliferative enteropathy in young horses. One of the reasons we still don't know a lot about this disease is that this bacterium can't be grown in a lab. One of the areas in which researchers are working to find more information is from where horses that become sick initially get Lawsonia... Is it from healthy horses that are carriers? Does it circulate in the horse population, or is there an outside source? Does it come from pigs (pigs can also be affected by disease due to Lawsonia infection)? Do other animal species such as wildlife carry it?
Equine infectious anemia (EIA) (aka "swamp fever") is a very important disease in horses, and can also affect donkeys and mules. This is the disease for which horses are given a Coggins test, which is required every six months for horses attending most shows and competitions, and for horses traveling internationally. EIA is caused by a retrovirus, more specifically a 
On December 9, the Infectious Diseases session was held at the 2008 
The December 2008 newsletter from the University of Guelph's 
One (of many) unique anatomical aspects of horses is their guttural pouches. These pouches open into the throat area and are essentially large openings in what is the equivalent of a horse's 
The fungal infection can weaken the wall of the artery, ultimately causing it to rupture. This results in massive blood loss (which comes out of the horse's nose) and it is a potentially life-threatening event.
Sporotrichosis is a fungal infection of the skin and superficial lymph vessels caused by Spororthrix schenckii. This organism is often found on decaying plant material, although it can also infest living plants like sphagnum moss and rose bushes. Sporotrichosis is an uncommon condition in horses, but it occurs all over the world. It is most common in tropical and subtropical regions and is rare in northern climates.
One, several, or many firm round nodules may be found. Typically they are not itchy or painful to the horse, but as they get bigger the nodules burst and ooze a pus-like discharge. When the infection tracks up a lymphatic, the nodules may occur in a row along the vessel, appearing like "beads on a necklace". The lesions may heal and recur numerous times over months or years. These clinical signs are very suggestive of sporotrichosis, but bacterial lymphangitis should also be considered. Sometimes the yeast organisms can be seen in the discharge using a microscope, but the definitive diagnosis is made by culturing the fungus. The treatment of choice is a form of iodine that can be given orally, although more conventional antifungal drugs may also be effective (but also much more expensive). The prognosis for recovery is good.
The discovery of antibiotics was one of the most important medical advances in history, and these drugs have had an immense impact on human and animal health. While antibiotics have saved countless lives, their use can also be associated with some very serious side effects and complications. For example, in horses, antibiotic-associated diarrhea (colitis) is a major issue.
Recently, I wrote about a 
The described clinical signs in affected horses are very non-specific, so it's hard to speculate about the causative pathogen. There are a variety of potential culprits, including equine influenza virus (EIV), but so far testing has not detected EIV or any other known pathogens. This "mystery" disease does not appear to affect other animals or people (but without knowing what is causing it, this is difficult to say for certain). It is possible that this is a "new" disease, but the vast majority of infectious disease outbreaks are caused by pathogens that we already know about. Specialists from Britain have been called in to help with the investigation. Hopefully more information will be available soon.
Eastern equine encephalitis (EEE) was recently identified as the 
In adult horses, botulism is caused by ingesting a toxin produced by the bacterium Clostridium botulinum. This bacterium will not grow in the presence of oxygen, however in can grow in conditions that are sometimes present in improperly fermented haylage and silage. As the bacterium grows, it produces botulinum toxin, one of the most potent toxins on the planet. Ingestion of botulinum toxin leads to progressive paralysis (i.e. severe weakness and flacid muslces).
Over 
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