滋賀県下における日本脳炎の疫学的研究(1965～1973年)

第IV編総括並びに結論

抄録

This final paper summarizes the results of epidemiological studies of Japanese encephalitis in Shiga Prefecture between 1965 and 1973, described in the preceding three papers. Based on the results obtained in these study series, certain possibilities regarding epidemic outbreaks of Japanese encephalitis in the future was suggested.
Throughout the period of the investigation, a gradual decrease in human incidence was observed. This correlated well with the decrease of vector mosquitoes (Culex tritaeniorhynchus). Changes in meteorological conditions and the amounts of two insecticides sprayed were discussed as explanatory reason for the decrease of vector mosquitoes.
In spite of the parallel decline of human infection and mosquito number, JEV infection rate in swine born in a nonepidemic season reached 100% the next summer season, sooner or later. There must be certain animals which originally supply JEV to swine. Some of them are hibernating animals in which Japanese encephalitis virus (JEV) passes the winter, and others are migratory birds by which JEV is transported from endemic areas to Japan.
Consequently, it can be said that the possibility of epidemic outbreak of Japanese encephalitis still remains in Japan. Care must be therefore taken to exclude the epidemic factors by extermination of vector mosquitoes and maintaining social immunity by vaccination of both man and domestic animals.