ECOLOGIC STUDIES OF ARBOVIRUS IN GUNMA PREFECTURE, JAPAN

Abstract

During 1959 to 1965, continuous surveys for arbovirus from mosquitoes were carried out in Gunma Prefecture. Mosquitoes were collected at study sites by aspirators, sweeping nets, bait traps, and/or dry ice traps from May to October every year. Pools of female mosquitoes identified by species were tested for arboviruses by intracerebral inoculation of suckling mice, and following results were obtained : 1) 12 species of mosquitoes were collected in study sites. However, Japanese encephalitis (JE) virus was recovered from only Culex tritaeniorhynchus and Culex pipiens, and arboviruses other than JE virus were obtained from Culex tritaeniorhynchus and Aedes vexana. No virus was isolated from other species.2) About half of the isolates other than JE virus were identified as group A, Simbu or Bunyamwera groups. The remaining virues are still on the way of identification study, but they were assumed to be immunologically related neither Getah (group A) nor Akabane (Simbu group) viruses.3) Mosquito infection with JE virus was regularly limited to the period from July to September in this area, but some of the Non-JE viruses were isolated in early season before JE virus appeared in mosquitoes.4) It was clear that JE and Getah viruses were the prevalent viruses in Japan, because they had been recovered every summer. On the other hand, Akabane and Bunyamwera viruses might be incidentally introduced in the area recently.5) Details of the methods employed for virus isolation were described.