Saskatchewan and other regions of Western Canada are in the midst of the largest equine infectious anemia (EIA) outbreak the area has seen in years, involving more than 70 horses and 22 different properties thus far in 2012. In response, two veterinarians discussed the importance of disease surveillance in controlling–and possibly even eradicating–the deadly disease from North American horse populations.
EIA is an incurable infectious disease of horses that is spread by biting insects such as flies. Like the human immunodeficiency virus (HIV), there is neither cure nor vaccine for EIA. All positive horses are either humanely euthanized or placed under lifelong quarantine.
First recognized in North America in Wisconsin in the late 1800s, EIA outbreaks were increasingly identified across the continent, causing alarm throughout the industry. The Coggins test, which reliably identifies affected horses, was introduced in the 1970s and plays a key role in stopping virus spread from infected horses, to the insect vectors, to more horses.
According to the latest statistics, less than 1% of the horses residing in Saskatchewan are voluntarily tested for the EIA virus. Similarly, an estimated 75-80% of horses in the United States are not currently tested for EIA, despite some states requiring annual testing of every horse residing within those borders.
“In many ways EIA is a disease that would be very easy to contain, if not eradicate, because we have a good test and horses are the only animals that are infected,” said Scott Weese, DVM, DVSc, Dipl. ACVIM, a professor in the Department of Pathobiology at the University of Guelph’s Ontario Veterinary College in Canada.
That said, Weese explained, “it would take time, commitment, and money, to ensure all horses are tested, and the willingness of the industry to accept the resulting need to euthanize an undetermined number of horses.”
Currently, in both Canada and the United States, testing is voluntary and owners are required to foot the bill.
“Many horses are tested regularly; however, there’s actually more of a need to test horses that have never been tested before rather than horses that have been tested and been negative multiple times,” added Weese.
Angela M. Pelzel, DVM, a Western regional epidemiologist with the USDA Animal and Plant Health Inspection Service Veterinary Services, concurs and added, “State and federal regulatory officials have long lamented that if we were able to test every horse in the U.S. we could eradicate this disease in our country.”
Pelzel explained that large numbers of horses are being tested over and over that reside in or travel to states that haven’t had an EIA case in many years.
“Rather than using targeted surveillance, which we do in most of our other regulatory programs, we seem to only use convenient sample streams in which to test [for EIA],” she said. “Convenient sampling will only get you so far, as you can see.”