CONTROL OF THEILERIA-SERGENTI INFECTION BY VACCINATION

Bovine piroplasmosis caused by Theileria sergenti is a major cause of economic loss in grazing cattle in Japan. Infected calves show chronic anaemia with intraery-throcytic piroplasms and occasionally die in se vere cases. We found that parasite stacks and isolates consist of gene tically and antigenically mixed populations. To differentiate parasite populations bearing 3 allelic forms of p32/34, an immunodominant piro plasm surface protein, 3 sets of oligonucleotide primers were designed to amplify either of 3 alleles by polymerase chain reaction (PCR). By using this allele-specific PCR,,ve found that the majority of T. serg enti-infected calves in Japan hat-bored mixed parasite populations bea ring C and I type parasites. To control Theileria infection, we produc ed 2 vaccine candidates: recombinant baculovirus p32 and synthetic pep tide containing Lys-Glu-Lys (KEK) motif. Immunization with either reco mbinant p32 or synthetic peptide containing KEK sequences with Freund' s complete adjuvant resulted in low parasitemia and reduced the clinic al symptoms compared to control calves. Interestingly, the parasite wi th the p32 allelic form corresponding to the one used as the immunogen was suppressed.