Outbreaks of equine viral arteritis (EVA) are infrequent in the United States but, because a large percentage of the equine
population is susceptible, several leading experts continue to push for improved awareness and protective measures.
An extensive outbreak affected the Thoroughbred breeding industry in Kentucky in 1984. Another affected the Quarter Horse
industry in several states in 2006. But other breeds that weren't exposed face a bigger risk of infection.
In April 2004, the U.S. Department of Agriculture (USDA) released an EVA guide (Uniform Methods & Rules, or UMR), setting
out "minimum standards for detecting, controlling and preventing EVA, and minimum requirements for the intrastate and interstate
movement of (potentially infected) equines."
The guide was endorsed by APHIS (Animal and Plant Health Inspection Service), USDA Veterinary Services, the U.S. Animal Health
Association (USAHA), the American Horse Council and the American Association of Equine Practitioners (AAEP).
Is it enough? Many experts don't think so.
The guide provided a template for states to develop their own EVA-control programs, but many have not done so.
Requirements to report EVA outbreaks to state veterinarians vary widely from state to state, as do requirements for vaccination
and EVA testing, some states being more stringent than others. In Kentucky and New York, for example, all Thoroughbred stallions
are required to be vaccinated (and serologically tested) against EVA, though there are no such requirements for other breeds
in those states.
One of the first concerns experts cite is a need for testing horse semen shipped into the United States for EVA.
Dr. Peter Timoney, MVB, PhD, FRCVS, chairman of the Department of Veterinary Science at the Gluck Equine Research Center,
University of Kentucky, has urged USDA to require such testing for years.
"Though he's harped on that continuously," says Peter Sheerin, DVM, Dipl. ACT, of Lexington's Rood and Riddle Equine Hospital,
"I don't know why the USDA remains reluctant to place regulations on incoming foreign semen, unless people have not complained
The 2006 EVA outbreak among Quarter Horses raised questions about EVA testing and how to deal with breeding mares to EVA-positive
stallions that were shedding virus. "Timoney's recommendation to those breeders was to encourage use of vaccination and quarantine,"
says Sheerin. "If you're aware that you're going to be using EVA-positive semen, that can be dealt with. But during the Quarter-Horse
outbreak, people didn't know they were dealing with infective semen and that certain stallions were shedding virus. Infective
semen was shipped to many states and to Canada, so EVA spread very quickly to a significant number of those states." The virus
causes mild upper-respiratory disease in adult horses, abortion in mares and illness and death in young foals.
"For breeds in which EVA is endemic, a majority of the animals have been exposed, so they've been 'self-vaccinated,' so to
speak, and accordingly don't have a problem," Sheerin says. "The virus is not endemic in Quarter Horses, so when it spread
in 2006 the vast majority of that population was fully susceptible. That's how we ran into the mess that we had."
Besides the lack of EVA awareness among Quarter-Horse owners and breeders in 2006, "there is a huge lack of regulation in
the AI (artificial insemination) industry in equines," says Reed Holyoak, DVM, PhD, Dipl. ACT, at the Oklahoma State University
College of Veterinary Medicine. "There are no regulations, and so we just open ourselves up to this threat (from EVA) all