SEROPREVALENCE SURVEY OF AINO VIRUS-INFECTION IN DAIRY-CATTLE OF FUKUOKA, JAPAN IN 1990

The seroprevalence and seroconversion to Aino virus infection were epi demiologically analyzed in Fukuoka Prefecture, by a cohort study, in 1 990. Serum samples (872) were taken from 436 cattle of 128 farms in fi ve different districts at twice sampling with four month-intervals and were tested by a serum neutralizing test with Aino virus. In the firs t sampling (May-July), 38.3% of sera and 40.6% of farms tested were po sitive and 33.3% of cattle and 40.6% of farms were sere-converted duri ng the period of September-November in 1990. Significant differences w ere found in seroprevalence of farms and seroconversion of cattle/farm s among five districts; there was, however, a highly significant corre lation between seroprevalence and seroconversion of farm. Consequently , five districts of Fukuoka Prefecture were classified into four epide mic areas according to seroprevalence and seroconversion factors of a principal component analysis.