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Testing for exclusion of West Nile virus in horses

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Roles and Responsibilities for WNV exclusion testing requests
Sample collection and submission
Further information on testing
Further information


Defra, Scottish Government, Welsh Government and APHA have agreed to offer testing for exclusion of West Nile virus (WNV) to horse keepers and their veterinary surgeons.

A private veterinary surgeon (PVS) may ask APHA to attend a consultation case where WNV is very low on the differential diagnosis list. APHA would then either rule out suspicion of notifiable disease on clinical grounds, or begin an official investigation and impose restrictions if disease is suspected.

This page explains how a PVS should proceed if they wish to carry out testing for this disease without an APHA investigation taking place.

The PVS pays APHA to test samples for WNV where the APHA duty vet agrees that notifiable disease is not suspected. No official restrictions will usually be applied, although the holding should consider, with their PVS, any voluntary restrictions.

APHA will charge the full cost for the testing at the laboratory.

In addition to testing to exclude APHA also offer commercial WNV diagnostic tests.

Roles and responsibilities for WNV exclusion testing requests

Role of submitting PVS

1. The PVS must contact the APHA Field Services office responsible for the premises where the horse is located to discuss the incident with the APHA duty vet prior to the submission of samples. Contact numbers are available on GOV.UK.

2. If after the discussion WNV is not suspected, but PVS wishes to exclude WNV from differential diagnosis they can proceed with the submission.

3. The PVS must agree to meet all costs associated with the collection and submission/carriage of samples to APHA Weybridge and all of the laboratory test costs.

4. The PVS must submit the samples to APHA Weybridge accompanied with the fully completed West Nile Virus Serology Submission form (WNV02), being sure to include the case authorisation reference number issued by the APHA duty vet. This number should be in the format: WNV/APHA region/Year/Sequential number. The APHA region should be in word format e.g.'Midlands', as this will be used by the laboratory when reporting results.

5. During normal working hours the PVS must inform APHA Weybridge of the expected time of arrival for the samples by phoning the Virology office on 0208 225 7671 and send an email to:

This email from the PVS must include the following:

  • Case authorisation reference number supplied by the APHA duty vet.
  • Owner and holding name.
  • Number of samples submitted.
  • Expected date and time of arrival of the submission.

Outside normal working hours the APHA duty vet is responsible for contacting APHA Weybridge.

6. The PVS must ensure that all samples are packaged in an approved manner and arrange carriage/despatch to APHA Weybridge.

7. If there is any change in the clinical picture that could suggest a notifiable disease the submitting PVS must report this immediately to the APHA duty vet.

Role of APHA duty veterinarian

1. Discuss incident with submitting PVS.

2. If WNV is suspected proceed with standard report case procedures.

3. If agree that WNV is not suspected proceed with exclusion testing process.

4. Issue unique case authorisation reference number to submitting PVS.

5. Advise PVS if necessary that relevant information about the Exclusion Testing for WNV process is available on the Vet Gateway, including the required submission form.

6. Advise PVS that the laboratory at APHA Weybridge should be contacted by telephone and email to provide submission information – as described in paragraph 5 of role of submitting PV) above.

Sample collection and submission

1. The PVS is responsible for collecting and submitting the samples for testing.

2. The PVS must clearly label all samples and fully complete the West Nile Virus Serology Submission form (WNV02).

Sample Reception
APHA Weybridge
New Haw
KT15 3NB

3. Samples must be received at the APHA Weybridge laboratory by 09:00 on Friday (or on the working day before a public holiday) to be eligible for the in-hours testing charge rate.

Further information on testing

1.The PVS must ensure that their requirements relating to testing and reporting are clearly completed on the submission form.

2. For further advice on WNV sample submission please see our guidance documents.

3. Test prices are available on GOV.UK.

4. Normal working hours for the testing laboratory are:

a. Monday – Thursday: 09:00 – 17:00.

b. Friday: 09:00 – 16:00.

c. The testing laboratory cannot be contacted outside of these hours, or on Bank Holidays.

Please do not contact the laboratory by telephone or email asking for test results. All testing and reporting will be performed within the stated test turnaround times wherever possible. Contacting the lab may delay the testing/reporting process.

Further information

Information on WNV is available on GOV.UK.

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