Of the world’s horse population, only about 10% live in countries deemed free of equine piroplasmosis (EP); the United States is one of those regions. However recent disease outbreaks have prompted further investigation into the re-emergence and control of EP in America.

At the 9th International Conference on Equine Infectious Diseases, held Oct. 21-26 in Lexington, Ky., Robert Mealey, DVM, PhD, Dipl. ACVIM, associate professor of immunology and infectious diseases in Department of Veterinary Microbiology and Pathology at the Washington State University College of Veterinary Medicine, discussed the current EP situation in the United States and recent research on the topic.

Naturally, the pathogens that cause EP–Theileria equi or Babesia caballi–are transmitted via certain species of ticks, Mealey said. Many of the cases seen in recent years in America, however, have been spread via the reuse of needles, syringes, and other blood-contaminated equipment that has not been sanitized between uses.

"We haven’t seen a lot of severe clinical disease in the United States," he added, noting that subclinical infections are much more common.

Disease Re-emergence in America

Changing gears, Mealey discussed several recent U.S. outbreaks and the suspected or confirmed modes of disease transmission.

Florida, 2008–In 2008, a Florida racehorse with clinical disease tested positive for EP, and an investigation into the source of the disease found that several horses recently imported from Mexico likely carried the disease agent into the country. Investigators later