Equine Piroplasmosis

Introduction

In the fall of 2010, the United States will host the World Equestrian Games (WEG) at the
Kentucky Horse Park in Lexington, Kentucky. Because horses that are positive to equine
piroplasmosis (EP) will be able to participate in all disciplines including endurance, we expect an
increased interest in the disease. We have prepared this document to answer questions about EP
and the measures the United States will take to allow EP-positive horses to participate in the
WEG. If you have additional questions, we have provided references and contact information
for obtaining information below. Finally, we expect to update this document as additional
information becomes available before the WEG.

What is equine piroplasmosis (EP)?

EP is a tick-borne disease caused by two parasites, Babesia caballi and B. equi. Certain ticks are
biological vectors in which the parasite amplifies and then is transmitted to horses under certain
conditions. If horses become affected, fever, anemia, jaundice, hemoglobinuria, central nervous
system disturbances, and sometimes death may result. In the acute phase, some infected horses
are less severely affected and may show little or no symptoms with no decrease in performance.
Those that survive infection in the acute phase may carry the parasites for prolonged periods
during which they are potential sources of infection to other horses via tick-borne transmission or
mechanical transfer by biting ticks, needles, or surgical instruments.