Suspect WNV cases in Great Britain can be tested by APHA under the ‘testing to exclude’ process, provided the case has been discussed with an APHA duty vet before any samples are submitted. If after these discussions it is decided that the clinical signs are suggestive of WNV, APHA will initiate a field investigation. If the case is not suspected to be WNV, a sample can be submitted to APHA to exclude WNV under the ‘testing to exclude’ process.
There are three different serological tests available that are able to detect antibodies against WNV and these are currently only available in UK at the government’s APHA laboratory. The plaque reduction neutralisation test (PRNT) is the most specific test available and is often only applied after positive ELISA tests. The mELISA detection test is for the presence of IgM WNV antibodies raised shortly after infection and is advised to be used in conjunction with WNV total antibody detection ELISA (cELISA), which alone cannot differentiate recent IgM from longer lasting or post-vaccination IgG responses.
Highly sensitive virus detection using PCR can be carried out on infected tissues recovered at post mortem examination.