Agency: Agricultural Research Service Issued: July 1, 1997 Abstract: Equine babesiosis, caused by Babesia equi or Babesia caballi, is a tick-borne hemoprotozoan disease of horses. Clinical disease is characterized by fever, anemia, and icterus. Mortality rate is high during initial infection of horses introduced into enzootic regions, and horses which survive initial infection are protected from clinical disease upon subsequent challenge. Horses with antibody to either parasite are restricted from importation into the United States. The complementation fixation test (CFT) is presently used for detecting antibody to B. equi or B. caballi in the serum of potentially infected horses. However, this test is not wholly accurate, and false-negative results are possible. The invention provides a novel, cloned protein isolated from the merozoite of B. equi. The protein contains a conserved region found in all strains of B. equi. The protein has been proven to be a sensitive and specific indication of the presence of antibodies to B. equi in the serum of potentially infected horses in various tests, including a test wherein the serum of 154 potentially infected horses were evaluated using the invention's protein in a competitive inhibition enzyme-linked immunosorbent assay (CI ELISA). The protein can also be used to raise antibodies specific to B. equi. Inventors: Donald P. Knowles Lance E. Perryman Animal Disease Research Unit (Same as first inventor) 337 Bustad Hall (509) 335-3193 Washington State Universotu Pullman, WA 99164 509-335-6029; 509-335-8328 (fax) Industry Keywords: veterinary diagnostics, animal import, anamal transport industry