Suspensions of field collected and artificially infected pools of Culex tarsalis and blood samples from chickens exposed to vector attack in the field were tested for WEE and SLE viruses in hamster kidney and chick embryo tissue cultures and in mice. Both tissue culture systems were equally or more sensitive hosts for recovery of WEE virus than the mouse, and virus was isolated and identified more rapidly in the tissue culture systems. Chick embryo tissue culture was not satisfactory for isolation of SLE virus, but hamster kidney tissue culture was more satisfactory than the mouse for isolation and identification of this virus.
Toxicity of blood samples or mosquito suspensions in the tissue culture systems was minimal and slight changes in technique eliminated this problem. Inclusion of large numbers of freshly blood-engorged mosquitoes in pools could interfere with isolations of WEE virus in tissue cultures.