Abstract
Seasonal changes in Trypanosoma theileri infection in grazing cattle (Japanese Black) were investigated by means of buffy-coat culture and indirect fluorescent antibody tests (IFT). Blood samples were collected from 24 cows every month from April to September. T. theileri was detected in 3 out of 24 (12.5%) of the samples collected before grazing in April. After the animals were put out to graze in a pasture, the detection rate of T. theileri increased toward the summer; and in September 14 out of 24 (58.3%) animals were positive. Throughout the investigation, the overall antibody titer was distributed in the range between 1: 40 and 1: 2, 560. The antibody titer in infected cows, however, ranged from 1: 80 to 1: 1, 280. Geometrical antibody-titer means increased toward summer, to reach a maximum of 1: 640.0 in September.
