Ecology of Japanese Encephalitis Virus in Okinawa, Japan 3. Supplementary note on the attempt of the isolation of Japanese encephalitis virus from hibernated female mosquitoes of Culex tritaeniorhynchus in Okinawa island in 1977

In the previous paper (Ura, 1977), it was pointed out that Japanese encephalitis (JE) viruses associated with hibernated female mosquitoes of Culex tritaeniorhynchus were isolated in February, 1976, at the northern district of the main island of Okinawa. Following this findings, JE virus dissemination at the survey area was demonstrated through the year in 1976. The serial survey was carried out at the same survey station, particularly, in the interepidemic season, from January 20 through March 1 in 1977. The virus isolation from 42 pools of 1,935 hibernated vector mosquitoes was unsuccessful. However, on May 12/13 and 20/21, 1977, JE virus was isolated from mosquitoes of Culex tritaeniorhynchus caught in the field and pig-sheds. These findings suggested that the persistence of the virus in vector mosquitoes was interrupted in winter season in 1977, and the virus might be carried again in the survey area in the epidemic season.