Evaluation of a reverse transcriptase-polymerase chain reaction assay for detecting St. Louis encephalitis virus using field-collected mosquitoes (Diptera: Culicidae)

A reverse transcriptase-polymerase chain reaction assay (RT-PCR) was compared with a tissue culture assay (TC) and an enzyme immunoassay (EIA) to detect St. Louis encephalitis virus (SLEV) in mosquito pools. Overall, 1,725 mosquito pools with a low viral prevalence (3.3%-5.0%) were tested. The comparison of the EIA to TC showed that the EIA was 0.947 sensitive, 0.988 specific, and 0.987 accurate. Comparison of RT-PCR to TC showed that the RT-PCR was 0.947 sensitive, 0.980 specific, and 0.979 accurate. Comparison of the RT-PCR to EIA showed that the RT-PCR was 0.878 sensitive, 0.987 specific, and 0.982 accurate. Because of speed, accuracy, and cost, either the RT-PCR or the EIA is recommended as the primary screen. RT-PCR has an advantage over EIA, because the amplified product contains sequence information which can confirm its identity. TC, EIA, or both can be applied as a 2nd assay for the confirmation of samples suspected as positives by the RT-PCR.