Ecological studies on Japanese encephalitis (JE) in Osaka Prefecture : 4. Relations of summer meteorological conditions to the number of human JE cases and to the size of vector populations, especially with regard to recent low epidemics of JE

Abstract

In two areas under different environmental conditions for the breed − ing of Culex tritaeniorhynchus ， the vector mosquito of Japanese encephalitis (JE) virus ， the relation between the mosquito abundance and yearly data Qf meteorologi ・ cal conditions was analyzed statistically ， especially in relation to the urbanization for the period 1968 − 1990 in Osaka Prefecture ． Correlation coef 行cients of the devia ． tion from regression between the mean number of mosquitoes caught during July and that caught during August， to the cummulative temperatures Qr total amount of precipitation during five different periQds were calculated ． In the barn near pad ・ dy field there were correlation between the two meteorological factors and the devia − tion from regression with a maximum deviation， However ， recently there were little correlation between them with a minimum deviation for any barn during the years 1968 − 1990 ， as environmental conditions in the areas around the barns in which mosquitoes were collected became less appropriate for the mosquito breeding year by year． Therefore ， the more the appropriateness of environmental conditions for the mosquito breeding lowers ， the more the effectiveness of meteorological condi − tions on the level of mosquito population lowers． This may be a reason for recent fewer JE cases in spite of the favorable meteorological conditions for the breeding of Cx． tn ' taeniorhynchus． The effect of summer temperature on the epidemic size was observed only for the period 1968 − 1972 ． No trend was discerned after that period， N 工 工 一 Eleotronio Library