Transmission of Northway and St. Louis encephalitis viruses by arctic mosquitoes.

Transmission of a Canadian arctic isolate of Northway virus has been demonstrated after incubation of arctic Aedes communis mosquitoes at 13 degrees C for 27 days after intrathoracic injection of 300 plaque forming units of virus. Replication has also been demonstrated after intrathoracic injection of domestic A. aegypti mosquitoes of this virus. Virions of Northway virus, 84--92 nm diameter were morphologically typical of a bunyavirus after propagation in salivary glands of A. communis or in tissue cultures of baby hamster kidney (BHK-21) cells. An Ontario isolate of St. Louis encephalitis was transmitted by bites of A. communis after 27 days incubation at 13 degrees C after oral ingestion of 3 or 30 mouse LD50 virus. This mosquito species transmitted virus after 13 to 76 days incubation at 13 degrees C following intrathoracic injection of 3 mouse LD50 or higher virus doses.