Equine Piroplasmosis

Background
Equine Piroplasmosis (EP) is classified as a foreign animal disease not present in the U.S. Regulations requiring the testing of all horses entering the U.S. to determine their EP status have been in place for many years. EP occurs in Africa, Europe, Asia, South and Central America. The tick vectors that spread the disease exist in the United States.

EP is a protozoal infection of horses spread by ticks. The dis¬ease may be fatal in up to 20 percent of previously unexposed animals. After having the clinical disease, horses can be carriers for long periods of time. There is no vaccine for the disease and treatment options are not fail-proof. It appears that the major threat to the U.S. is the non-clinical seropositive lifetime carriers.

For many years the Complement Fixation (CF) test was used as the import test to determine the EP status of imported horses. However, research as far back as 1971 has shown that the CF test is not an appropriate test for EP because equine immunoglobulin IgG(T) does not fix complement. This yielded an unknown small percentage of “false negative” test results. Consequently, an unknown number of EP seropositive horses legally entered the U.S. In August 2005, the C-ELISA test was declared the official diagnostic test at import to replace the CF test.

Current Status
Because of the number of EP positive horses that may have legally entered the U.S. over many years when the CF test was in use, positive horses may be detected from time to time. Horses that are being exported with the intention of being returned to the U.S. will likely be tested for EP prior to export to help ensure their return. In such cases, the U.S. needs to have a plan of action on how any positive results will be handled. Some possible solutions being considered include lifetime quarantine or euthanasia. The current focuses are to maintain existing import restrictions, to develop cohesive state and federal policy, and to fund research for an effective treatment.

AHC Position
The AHC supports the continued discussion and evaluation of how to address U.S. resident equines that test positive for Equine Piroplasmosis and supports the funding of research for an effective treatment.