Ecologic Studies of Japanese Encephalitis Virus in Japan

SummaryInfection with JE virus was a regular late-summer phenomenon among nestlings at two ardeid colonies near Tokyo. Avian infection demonstrable by recovery of virus or appearance of antibody was first found in late July and early August of each year during 1952–1956 and was, for practical purposes, coincident with the demonstration of JE virus in mosquitoes. Frequencies of avian infection during virus dissemination (as measured by HI antibody) ranged from .01 to .47, being consistently greater in Black-crowned Night Herons than in Plumed or Little Egrets. Ardeid infection in two colonies near Nagoya in 1955 was similar in incidence and timing to that near Tokyo. Except for cormorants, no clear-cut evidence for infection of other bird species was obtained, and while serologic survey of Japanese wild birds suggests widespread involvement, the relative efficiency of other bird species for dissemination of JE virus is unknown.