Fighting equine diseases: Medicine improving, but movement increases risk

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Dec 01, 2009


6 steps to a healthier world for the nations horses
National Report — When it comes to contagious equine diseases, there is good news and bad news.

The good news is that medical research is improving vaccines and treatments. The downside is that horses are so mobile that the risk of contagious disease is unparalleled, according to Dr. Roberta Dwyer, infectious disease spokesperson for the American Association of Equine Practitioners.

"In the past 10 years, we've improved diagnostic techniques to detect infectious diseases and developed new vaccines," Dwyer explains. At the same time, more prestigious equestrian events and races around the world are bringing equine athletes together from both hemispheres. Not only does that increase the disease-transmission risk, but new threats are emerging from the use of sperm and eggs across borders, threats that take advantage of two breeding cycles.

It's all about stallion breeding revenue, says Dr. Peter Timoney, who's spent more than 30 years studying horse disease and is now a faculty member at the Gluck Equine Research Center, University of Kentucky. "If owners have horses with potential, they want to be able to compete with their animals in financially lucrative and prestigious events, sometimes around the world," he says.

"The increased value in international movement of horses runs counter to the risk of spread of infectious diseases," he says. "Enhanced trade in horses and equine germplasm increases the risk of a global spread in disease. Facilitation of trade comes at a price."

Still, the spread of equine diseases in the United States can't be blamed entirely on other countries, Timoney says. Variations in climate and animal populations from state to state and region to region facilitate outbreaks.

Keys to surveillance

Beyond the development of better medicine, Timoney hopes to see better international reporting of diseases. "It behooves us to develop a system that enables the sharing of information," he says. "We need to emphasize surveillance and reporting."

Equine veterinarians are critical to identifying and reporting new diseases or new outbreaks of old ones. "The first line of defense in safeguarding the domestic equine industry is the equine practitioner," he says. "They're the people who can most frequently report these occurrences. And if they're suspicious, they'll take the appropriate steps and report findings to their state veterinarian."

As diseases spread beyond typical breeding grounds with mutations and climate change, Dwyer hopes veterinarians will keep urging clients to stick to the core list of vaccines developed by the AAEP. What wasn't a problem in an area this year may not stay that way forever, she says.

"People may not be vaccinating because of economic constraints," Dwyer says. "That's why the AAEP came up with the list of core vaccines. We want owners to take these diseases — Eastern equine encephalomyelitis (EEE), Western equine encephalomyelitis (WEE), rabies, WNV and tetanus — very seriously."

Diseases carried to horses by mosquitoes and other blood-sucking arthropods are of even more concern. "No vaccine is 100 percent," Dwyer says. More expensive than vaccines may be the time, money and labor in cleaning up water pools to get rid of mosquito breeding areas. "You can't have old tires around accumulating water," she says. (See "6 steps to a healthier world for the nation's horses.")

Ultimately, the future of disease management may lie in better reporting. Timoney, whose research focuses on the sexually transmitted equine sarteritis virus, hopes disease management by anecdote will give way to more accurate reporting. "We need to get away from anecdotally derived data," he says. "We want to know that there were X number of occurrences in states A, B, and C."