Isolation of western encephalitis virus from mosquitoes in Alberta.

Abstract

Mosquitoes were collected in Alberta during the spring, summer, and early fall of 1965. Western encephalitis (WE) virus was isolated from pools collected between August 11 and August 25.Two positive pools, one of Aedes vexans (Meigen) and one of Culiseta inornata (Williston) were collected by sweep nets in irrigated areas of southern Alberta near places where horses were reported sick with WE virus. Seven other positive pools, three of C. inornata and four of Culex tarsalis Coquillett, were collected in southern Alberta from mammalian burrows, which are hibernating habitats for C. inornata, C. tarsalis, and Anopheles earlei Vargas. This indicates that C. tarsalis and C. inornata can enter hibernation infected with WE virus. None of the A. earlei pools tested were positive for WE virus.About 50% of the C. inornata and 9% of the C. tarsalis collected from mammalian burrows were blood-engorged at the time of collection. None of the A. earlei collected from mammalian burrows were blood-fed.