ON THE INCIDENCE OF JAPANES ENCEPHALITIS AND THE MOSQUITOES COLLECTED BY LIGHT TRAP AT OKAYAMA

Abstract

Observations made on the mosquitoes collected by light trap in the Okayama University Medical School campus during a period of six years (1950-55) showed that the endemic of Japanese encephalitis usually breaks out in this area about two weeks to one month after the peak population of Culex tritaeniorhynchus in August, though a few sporadic cases have been reported from within Okayama Prefecture in May through June and September through October. This unusual occurrence of encephalitis suggests that some other vectors like Culex pipiens may take place of Culex tritaeniorhynchus. On an epidemiological basis Culex pipiens has been suggested as a vector. But an attempt to isolate the virus either from Culex tritaeniorhynchus or from Culex pipiens by intracranial inoculation of filtered emulsion of all the mospuitoes collected during the past two years (1954-55) has failed.