Review Of CEM and Implications For Canada
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)
Often, when someone calls and asks about management of strangles, one of the first questions is 



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Following on the heels of a few outbreaks of piroplasmosis in the US over the past year is
Equine Piroplasmosis Disease Investigation Continues
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.
At the ongoing 

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

There is apparently still no evidence regarding the location of
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At least 21 ponies belonging to a Venezuelan polo team died shortly before a competition yesterday in Florida. Not much information about what happened has been released. It was reported that the ponies exhibited
The other day, I wrote about a few .jpg)
I usually hesitate to write posts about strangles cases or outbreaks. I don't want to give the impression that these are unusual events, because strangles is not a rare disease, in terms of either single cases or outbreaks. When I post about an outbreak, it's usually because there's something particularly interesting about the outbreak or the report about it. Such is the case with
"A two-day horse show is different than an eight-day fair exhibition.'" Two days is lots of time to transmit infectious diseases.
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.
I don't know whether Truro Raceway (in Nova Scotia, Canada) has bad luck, bad infection control or is just really open about any problems. Following an outbreak of strangles in December (
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.
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.
The outbreak occurred at a racetrack in Zagreb. Not surprisingly, an H3N8 strain was responsible. Investigation of the cases determined that vaccine status had no influence on disease - both vaccinated and unvaccinated horses became equally sick. The vaccine used in Croatia at that time contained three influenza strains, including two different H3N8 strains, but the strains that were used were from 1963 and 1979. When they compared the strain that caused the outbreak and the vaccine strains, there were multiple genetic differences, which is not surprising given influenza's capacity to evolve over time. There were far fewer differences with the more recent strains used in vaccines in most other countries.
An outbreak of salmonellosis has killed at least 22 horses in Kjalarnes, Iceland
That's all good news. In the bigger picture, though, was anything learned, and were any measures taken to reduce the risk of this happening again? A lot of this comes back to the debate about
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
One horse owner stated "If I had known it was out there, I would have done things differently." While I understand where she's coming from, it's important for all horse owners to remember than exposure to infectious diseases is an ever-present risk. Streptococcus equi, and various other infectious agents, are widespread in the horse population, and there is never a "no-risk" situation. For that reason, we should be taking practical measures to reduce the risk of disease transmission at all times, not just when we know there is an infectious disease in the area.
A few years ago, I investigated an equine herpesvirus (EHV) outbreak associated with a yearling sale. We found a lot of sick horses, both from the sale and horses that were infected when purchased horses were brought home. A lot of actively racing horses got sick and missed races, which cost people even more money. Part of the investigation was asking people what percentage of horses from sales they expected to get sick right after the sale. The average answer was 80%, and many people said 100%. When you think about it, it's absolutely astounding that people will spend what is often a great deal of money to buy a horse that they expect will get sick, and then (more often than not) put it in the same barn as their other horses, thereby putting all the animals at risk of infection.
As of this morning, no new cases of equine herpesvirus (EHV) infection have been identified at Laurel Park in Maryland. (
Equine herpesvirus type 1 (EHV-1) infection was confirmed in a filly at Laurel Park in Maryland (
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).
