Getah Virus Isolations from Mosquitoes in an Enzootic Area in Japan

Abstract

Adult female mosquitoes were collected weekly over the period from June 18 to November 5, 1979, in livestock pens in an enzootic area of equine Getah virus infection. a total of 55 virus strains was isolated in cell cultures or suckling mice from 27, 550 mosquitoes. Of the 55 isolates, 18 were identified as Getah virus and the remaining 37 strains as Japanese encephalitis virus. Of the 18 Getah virus isolates, 15 were recovered from 11, 471 mosquitoes of Aedes vexans nipponii in 280 pools, the field infection rate being 1:765 and the remaining three strains were isolated from 10, 693 mosquitoes of Culex tritaeniorhynchus in 254 pools, the field infection rate being 1:3, 564. Thirteen of the 15 Getah virus isolates from A. vexans nipponii were recovered from the mosquitoes in a pig pen and the remaining two strains from those in a horse baited stable. The field infection rate of A. vexans nipponii in the pig pen was 1:451. All the Getah virus isolations were made in September and October, when the emergence of A. vexans nipponii had a peak. These observations suggest that A. vexans nipponii may be a principal vector for equine Getah virus infection in the Kanto district and C. tritaeniorhynchus may also serve as a vector.