West nile virus screening

Screening
Commercial kits for human serologic diagnosis of WNV infection are currently in development. Until these kits are available, the CDC-defined IgM and IgG ELISA should be the front-line tests for serum and CSF.46-48 These ELISA tests are the most sensitive screening assays available. The HI and indirect immunofluorescent antibody (IFA) test may also be used to screen samples for flavivirus antibodies. 

Surveillance methods
West Nile virus can be sampled from the environment by the pooling of trapped mosquitoes, testing avian blood samples drawn from wild birds and sentinel monkeys, as well as testing brains of dead birds found by various animal control agencies and the public. Testing of the mosquito samples requires the use of RT-PCR to directly amplify and show the presence of virus in the submitted samples. When using the blood sera of wild bird and sentinel chickens, samples must be tested for the presence of West Nile virus antibodies by use of immunohistochemistry (IHC) or Enzyme-Linked Immunosorbent Assay (ELISA).

Dead birds, after necropsy, have their various tissues tested for virus by either RT-PCR or immunohistochemistry, where virus shows up as brown stained tissue because of a substrate-enzyme reaction.