Regular testing to determine disease status and limiting contact with infected or untested horses remain the cornerstones of defending horses against equine infectious anemia (EIA). But how often are owners having horses tested to ensure they’re not harboring a disease? Results from a recent Canadian study suggest it depends on several factors, including geographic location.

Last year, veterinary officials reported 37 EIA cases on 19 premises across Canada. As of Jan. 31, 2018, there were two positive test results in Alberta. Based on Canadian Food Inspection Agency (CFIA) data, the number of reported cases continues to fluctuate.

It’s important to remember that most EIA testing is done on a voluntary basis, making it very difficult to know the disease’s true prevalence, said Katharina Lohmann, DVM, PhD, Dipl. ACVIM, a professor at the University of Saskatchewan’s Western College of Veterinary Medicine, in Saskatoon.

“At an extreme, if nobody tested their horses, there’d be no EIA detected, but that wouldn’t mean that the disease has disappeared,” she said. “Over the past five years, one could interpret the CFIA data to mean that there have been less cases, but there is a lot of fluctuation, especially when you look at individual provinces.”

Researchers don’t know why the fluctuation happens, she added. It could be that disease incidence truly varies, or testing intensity varies and, therefore, the disease goes undetected for a period before it “shows up” again.

To better understand the rate at which Canadian horse owners request testing and the outcomes of those tests, Lohmann and a team of researchers studied results of testing conducted from 2009 to 2012.

“In our study, more cases of EIA were detected in Western provinces,” she said. “But there was more owner-initiated voluntary testing for EIA done in the Eastern provinces. It was surprising to me how big the difference in testing intensity was between the East and West.

“It is interesting to note that more cases were detected in areas where there was less voluntary testing, but we do not provide evidence that these two observations are causally related,” she added. “We do not prove that there are more cases because there is less voluntary testing.”

Additionally, the researchers could not determine how many horses the tests represent and did not account for repeated testing of the same horses within a given year. It is possible that the numbers are in part explained by horses in the East simply being tested more frequently (within a year) than in the West, Lohmann added.

She said it’s important for horse owners to understand that reducing EIA cases is about reducing risk rather than eliminating the disease completely. To achieve this, Lohmann recommends:

  • Testing horses yearly;
  • Only adding new horses to a herd or group after they have tested negative;
  • Requesting a test as part of the purchase process for new horses; and
  • Using one needle per horse for vaccinations and administration medications.

The study, “A retrospective study of owner-requested testing as surveillance for EIA in Canada 2009-2012,” was published in the Canadian Veterinary Journal.