Larvae of Aedes aegypti were exposed to mouse brain suspensions of St. Louis encephalitis virus (SLE). The virus was shown to be infective to larvae of these mosquitoes and was found in subsequent pupae and in adult male and female mosquitoes.
The minimal infection rate in the mosquitoes was between 1 and 2 per cent. The exposure of larvae to a higher titered SLE virus bath resulted in an increased number of pupal pools positive for the virus.
Transmission of SLE virus to baby chicks by mosquitoes exposed to the virus as larvae has been demonstrated.