A total of 1452 sera of sows, more than 12-month-old of age, were collected from 70 farms over 4 geographical regions in Taiwan. Hemagglu-tinating-lnhibition (HI) test for detection of antibody were carried out on microtitre system by using hemagglutinating encephalomyelitis virus (HEY) as antigen at dose of 4 hemagglutination (HA) units. Result of the tests revealed that sera from 6S out of 70 farms were shown positive reaction against HEY antigen, the average positive rate was 28.6S% (416/1452).
The distribution of the positive reaction revealed that the southern region was the highest (40.75%); and that in easten region was the lowest (14.17%); nothem and middle regions were 27 and 22.4% respectively.
Antibodies against HEY were proved from sera collected in Taiwan in 1979 and every subseqent year. Sera from 1979, 45.32% (155/342) of sera collected over 6 counties in southern region of Taiwan were antibody posi-tive, therefore, it is concluded that HEY infection may be widespread in Taiwan at least since 1979.