Theileria parasite infection in East Asia and control of the disease.

Bovine piroplasmosis caused by Theileria sergenti is a major cause of economic loss in grazing cattle in Japan. We found that parasite stocks and isolates consist of genetically and antigenically mixed populations. To differentiate among parasite populations bearing 3 allelic forms of p32/34, an immunodominant piroplasmin surface protein, 3 sets of oligonucleotide primers were designed to amplify either of 3 alleles of T. sergenti/T. buffeli/T. orientalis by polymerase chain reaction (PCR). By using this allele-specific PCR, we found that in East Asia the majority of bovines infected with benign Theileria parasites harbored mixed parasite population. As a possible means of controlling Theileria sergenti infection, we produced 2 candidate vaccines; a bactilovirus expressed recombinant p32 and a synthetic peptide containing of Lys-Glu Lys (KEK) motif. Immunization with either of two candidates resulted in lower parasitemia and reduced the severity of clinical symptoms as compared to control calves.