RESEARCH ON THE SCHIZONT CELL-CULTURE VACCINE AGAINST THEILERIA-ANNULATA INFECTION IN XINJIANG, CHINA

Theileria annulata infection (TAI) is one of the most serious diseases of cattle in Xinjiang Autonomous Region of Uigur Minority Nationality . It has been recorded in 14 prefectures, except the Tulufan Prefectur e, but the enzootic areas are mainly distributed around the Zhunger Ba sin and Talim Basin. According to the records collected in the ten yea rs before vaccination with the schizont cell culture vaccine was carri ed out, the average incidence rate of TAI in enzootic areas was 7.22% and the mortality rate was 24%. The milk production of cattle sufferin g from TAI was sharply decreased, and there were usually abortions in pregnant cows. The incidence rate and mortality rate were greater in h igh grade cattle, so TaI was a constraint to improving cattle breeds. To control this disease effectively in Xinjiang, researchers at the Xi njiang Academy of Animal Science began to study the schizont cell cult ure vaccine in 1972. In 1977 an immortalised cell line was achieved fr om a primary cell culture starting with white blood cells from cattle suffering from acute TAI caused by art artifical tick bite. The cell c ulture medium mainly consisted of calf serum lactalbumin-hydrolysate, Eagles' medium DMEM and three antibiotics. As a vaccine, the above cel ls were mixed with preserving medium containing gelatin. This paper de scribes the experiments on the immunological properties of the vaccine carried out in subsequent years. Up to 1996, vaccine doses for 1,186, 150 cattle have been produced and sold. This vaccine has had a critica l effect on the control of TAI in Xinjiang. Owing to the sharp decreas e in the incidence rate and mortality rate of TAI after cattle were va ccinated, the annual economic benefit of the vaccine is at least 1,620 ,000 yuan.