Abstract
Antibodies against swine (H1N1) and Hong Kong (H3N2) types of influenza virus were surveyed in 5, 022 pigs raised in Shimane Prefecture in Japan during the seven years period. from 1978 to 1985. Hemagglutination inhibition (HI) antibody titers of 40 or higher measured by micro-titer technique were considered as positive antibody against the virus.
Positive rates of antibody against A/SW/Shimane/1/78 (H1N1) were 36.7-69.6% in each year observed. There was no significant difference in antibodypositive rates measured at various seasons throughout the year. However, a marked difference in antibodypositive rates could be revealed among the farms observed. The number of pigs bearing antibody against the Hong Kong type of virus (A/Shimane/1/80 (H3N2)) increased after 1980 and gradually decreased after reaching a high level of 54.4% in 1983. There was no correlation between incidence of swine and Hong Kong types of influenza virus infection; however, dual infection with the two types of the virus in pigs was suggested by serological surveillance.
