Here are the foreign animal diseases North American horse owners need to keep an eye on and why.

Many Americans still vividly remember the turmoil both in the horse industry and the nation at large after West Nile virus (WNV) first surfaced here in 1999. The sudden death of local crows and exotic birds in a New York City zoo, increased numbers of encephalitis cases in horses, and the same among elderly people, led doctors to recognize the first WNV cases in the Western Hemisphere.

Fifteen years later, WNV is considered endemic (native) in this country, and widespread vaccination against the mosquito-borne disease, along with vector control measures, is commonplace (and recommended). In a perfect world we’d keep such foreign animal diseases at bay in the first place, so veterinarians in a number of sectors work to safeguard our country’s horses. But what is a foreign animal disease (FAD) in the first place? In this article we will define these pathogens and describe some of the concerns associated with introducing new, or transboundary, diseases to the U.S. horse population. We will also summarize the initial steps to take if faced with a potentially foreign disease.

What Exactly is an FAD?

“From our point of view, a foreign animal disease is one that does not exist in the United States,” says Rory Carolan, DVM, equine specialist with the USDA-Animal and Plant Health Inspection Services (APHIS) Veterinary Services’ National Equine Programs, in Riverdale, Maryland.

An FAD’s emergence could have multiple repercussions, including equine il