Detection of St. Louis encephalitis and western equine encephalomyelitis RNA in mosquitoes tested without maintenance of a cold chain.

Western equine encephalomyelitis and St. Louis encephalitis viral RNA can be detected 20 days after death of infected Culex tarsalis in the absence of a cold chain. Viral RNA was detected with the reverse transcription-polymerase chain reaction in mosquitoes infected either parenterally or perorally in the laboratory and then killed and held for up to 20 days at 27 degrees C. Cell culture assay and in situ enzyme immunoassay did not detect infectious virus in the same mosquitoes.