Not long ago, we didn’t know that some now-common equine diseases even existed. Potomac horse fever, hendra virus infection, and contagious equine metritis, among others, were all once considered emergent diseases. And while we no longer think of them as new conditions, there are likely many more just waiting to make their first appearance or spread across an international border into a previously unaffected country.

At the recent 2015 University of Kentucky Equine Showcase, held in Lexington, Peter J. Timoney, FRCVS, PhD, shared some important insight into emerging equine diseases. Timoney is a professor and former department chair and director of the University of Kentucky Gluck Equine Research Center, also in Lexington.

What is an emergent disease?

Emergent diseases are those that are recorded for the first time in a population (such as Potomac horse fever or hendra virus) or those that might have been around for a period of time, but had not been diagnosed (like mare reproductive loss syndrome or contagious equine metritis), Timoney said.

Factors contributing to disease emergence include:

  • Microbial change and adaptation;
  • Host susceptibility to infection;
  • Climate change;
  • Altered ecosystems;
  • Changing population demographics,
  • International movement and trade; and 
  • Land use and economic development.

And, of course, Timoney said, "horses are not exempt when it comes to emergent diseases."

Emergent Infectious Diseases in Horses

Since 1969, numerous diseases—most of which are commonpl