West Nile Virus Testing

Antigen Testing

A simple rapid screening antigen test for the detection of West Nile Virus and/or St. Louis Encephalitis Virus (SLE) in mosquitoes is used in-house by the County. The dipstick test used is recognized by the Center for Disease Control (CDC) as an effective test for these purposes.

To run the test, mosquitoes are ground up in a special solution and a dipstick is then placed in the solution. The antigen for WNV/SLE, if present, binds to specific antibodies on the test strip producing a reddish color change indicating the presence of viral antigen in the sample. The assay doesn't measure the quantity of viral antigen in a sample only the presence of it.

The same antigen test can be applied to oral swabs from dead birds to detect West Nile virus.

RT-PCR Testing
Reverse transcriptase - polymerase chain reaction (RT-PCR) is a technique commonly employed in molecular genetics to screen for RNA, which is the genetic material of West Nile virus, rapidly. This technique allows for very small amounts of the virus to be detected in pools of mosquitoes.

This technique is also used to detect WNV in oral swabs from birds as well as in samples from humans.