In 1973, 11 night heron were caught on an island known as a breeding site of sea gulls. No.Japanese encephalitis virus was isolated from spleen, liver, or kidney of any bird. An infection experiment was carried out on 8 young heron with the virus. At the end of an observation period of 35 days hemagglutination-inhibition antibody against the virus was found to range from 1: 10 to 1: 160 in titer. Besides, the virus was recovered from the liver of 2 birds. This antibody was held by 83 night heron and two of 62 sea gulls examined.
