Sensitivity of the VecTest antigen assay for eastern equine encephalitis and western equine encephalitis viruses

VecTest assays for detecting eastern equine encephalitis virus (EEE) and western equine encephalitis virus (WEE) antigen in mosquito pools were evaluated to determine their sensitivity and specificity by using a range of EEE, WEE, St. Louis encephalitis virus (SLE), and West Nile virus (WN) dilutions as well as individual and pooled mosquitoes containing EEE or WEE. The EEE test produced reliable positive results with samples containing > or = 5.3 log10 plaque-forming units (PFU) of EEE/ml, and the WEE test produced reliable positive results with samples containing > or = 4.7 log10 PFU WEE/ml. Both assays detected the respective viral antigens in single virus-positive mosquitoes and in pools containing a single positive mosquito and 49 negative specimens. The SLE and WN assays also contained on the dipsticks accurately detected their respective viruses. No evidence was found of cross reaction or false positives in any of the tests. The VecTest assays were less sensitive than the EEE- and WEE-specific TaqMan reverse transcriptase polymerase chain reaction and Vero cell plaque assay, but appear to be useful for detecting arboviruses in mosquito-based arbovirus surveillance programs.