大阪府における日本脳炎の生態学的研究 : 3. 豚へのワクチン接種によるコガタアカイエカの感染と患者の発生に対する効果

Abstract

The effects of swine immunization during 1967-1973 as one of the precautionary measures against Japanese encephalitis (JE) were examined on the basis of the results of natural infection of Culex tritaeniorhynchus with JE virus and of incidence of human JE cases. The swine were immunized with live attenuated JE virus vaccine during this period except in 1967 when inactivated vaccine was used. From the point of view that JE viral infection rates vary depending upon mosquito abundance, it can be said that the infection rate of mosquitoes was lower in vaccinated areas than in unvaccinated areas in 1968-1970. However, in 1967 and 1969,8 and 2 human JE cases, respectively, were confirmed from vaccinated areas. This suggests that swine vaccination was not effective enough for control of JE among humans. Infection rate, the earliest date of isolation of JE virus from mosquitoes and the level of mosquito population tended to vary with the environmental condition of the collection sites. Therefore, comparison of the results of natural infection of mosquitoes with JE virus between the vaccinated years and unvaccinated years in areas which are favourable for the production of Cx. tritaeniorhynchus and infected mosquitoes, will reveal the effectiveness of swine vaccination.