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

Equine infectious anemia (EIA) virus, a chronic and potentially devastating bloodborne virus, was identified in two horses in Britain. The two affected horses were from a group of horses imported from Romania via Belgium. They were tested as part of standard import testing regulations designed to do exactly what happened here - diagnose this important infectious disease at the time of importation so that the infected horses cannot spread the disease in the country. The two positive horses will be euthanized, the unfortunate but standard response to this virus, because infected horses can pose a risk of infection to other horses for their entire lives. Other horses on the premises are under quarantine and are likely being tested further. The risk of transmission to other horses during the presumably short period of time they've been on the farm is probably low because, as an insect borne disease, biting fly activity has probably been pretty low during the cold British winter weather. (Transmission by sharing needles or other human-associated ways of cross-contamination of blood is also a concern, and has been a problem in other outbreaks.)

Chief veterinary officer Nigel Gibbens stated that these are the first imported cases of EIA identified since 1976. This is a good example of why we need to continue routine infection control measures such as import testing, even when nothing is found for years. Some people try to argue that since certain problems don't seem to be present, or at least are not identified, that infection control testing or activities should be decreased. This situation illustrates why that's bad thinking. Despite only picking up one incident in the past 34 years, this is a very important finding - failure to detect the positive horses could have lead to widespread infection in the country, which would ultimately make it very difficult and expensive to try to control. You never know when the next outbreak is lurking around the corner, and complacency is a big enemy of infection control.

Image source: www.collectgbstamps.co.uk

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After a rather lengthy process, Hoosier Park (Anderson, Indiana) has lifted its strangles quarantine. A quarantine was implemented on September 12th after a horse on the premises began exhibiting signs of strangles. Fifty-four horses were placed under quarantine. When S. equi, the bacterium that causes strangles, was identified in a quarantined horses, officials decided to move all quarantined horses out of the track facility. Presumably, once it was clear that the quarantine was not just a matter of waiting for confirmation that all horses were actually negative, they decided that the risk of having potentially infectious horses living at the track was unacceptable (pretty logical thought process). Now that those horses have been removed and no other cases have been found in the approximately 1000 other horses housed in the other track barns, they are back to business as usual. The quarantined barn is being disinfected and will not be used for the rest of the 2009 racing season.

This incident demonstrated a very aggressive but apparently effective response to strangles. They have presumably ended this latest outbreak and hopefully won't have to deal with it again. However, infectious diseases and outbreaks are inherent risks in the racing industry (as well as other competitive horse industries). The way we manage race horses, moving them around, mixing them, having various (and sometimes minimal) preventive medicine programs, having minimal measures to keep sick horses off the track, and a financial disincentive (i.e. people lose money) to keep horses away, means that infectious disease risks are not going to go away. It's not a question of whether there will be another strangles outbreak on a racetrack. It's a question of when and where.

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The Kentucky state veterinarian has banned horses kept at Hoosier Park racetrack (Anderson, Illinois) from barn areas of any Kentucky racing facility because of concerns about strangles. Two Hoosier Park horses were diagnosed with this highly infectious disease caused by the bacterium Streptococcus equi, and 57 horses have been quarantined. Horses from Hoosier Park that have been isolated and monitored for 21 days may enter Kentucky facilities.

The idea behind the 21 day quarantine is that within 21 days, most horses that have been exposed to strangles will develop signs of disease within that time period. However, the problem is that horses that have been infected with strangles can get over the infection and look great for 21 days (or much, much longer) but still carry S. equi in their throats or guttural pouches. So, while this is a reasonable approach, it by no means guarantees that S. equi will be kept out of Kentucky. However, in reality there are never any guarantees when it comes to infectious diseases like this. While some cases of strangles get a lot of attention, it's an endemic disease that is circulating in the horse population, and certainly is present in some horses in Kentucky already. Responding to outbreaks and limiting the risk of outbreak-associated transmission is very important, but it's equally important to make sure that routine infection control practices are in place on tracks (and elsewhere) to reduce the risk of disease transmission every day.

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

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Earlier this summer, the Canadian Food Inspection Agency imposed quarantine restrictions on certain US states because of vesicular stomatitis. Texas is now (again) considered vesicular stomatitis free, since the previous cases have resolved and no new cases have been identified. Accordingly, import restrictions on horses coming from or through Texas have been lifted. 

Restrictions have been reduced for horses from New Mexico. Horses from non-infected counties can get import permits if they:

• Have been inspected and had no signs of vesicular stomatitis within 10 days of export.
• Have not been to or through an infected county within 21 days.
• They are from a farm at least 25 km from any quarantined farm.
• The have a negative ELISA test within 10 days of export.

(Image source: www.signs-up.com)

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Because quarantine and testing are not 100%, good general infection control practices are also required. The presence of a quarantine must not create a false sense of security and thereby be used as an excuse to relax basic infection control practices. These include things like restricting direct and indirect contact (e.g. sharing buckets) between horses, good hand hygiene by people working with the horses, and close monitoring for signs of disease, among other things. The intense preparations that are involved here show the importance of infectious disease in the equine industry and an excellent awareness of the problem.

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