- West Nile Virus (WNV) is a mosquito-borne virus that affects humans and other animals, particularly horses. The mosquito vectors primarily involved are the Culex species which are known to occur in some parts of the UK.
- West Nile Virus Infection is a non-contagious form of viral encephalitis spread by mosquitoes. Migrating birds are the most likely mechanism by which WNV could be introduced into the UK because birds are the main carriers. WNV can be transmitted to both humans and
- The effects of WNV infection in horses can range from mild to potentially fatal inflammation of the brain.
- Clinical signs of WNV infection may include fever, incoordination, stumbling, falling, weakness, muscle twitching, seizures, drooping lips, lip smacking, head drooping, grinding teeth, and abnormal sensitivity to touch or sound. Serious cases may be unable to rise (recumbent).
- Humans, horses and other mammalian species are considered ‘dead-end hosts’, which means they do not normally spread the disease to other people or animals.
- Clinical Signs
- In most cases horses show no obvious signs of disease but become seropositive (i.e. positive to the blood test for antibodies to the virus).
- Affected animals develop a fever and often encephalitis (inflammation of the brain).
- Rates of mortality can be significant in affected horses.
- Protection
- The risk of infection can be reduced by protection from vectors.
- In January 2009 West Nile Virus vaccine was authorised for use throughout the EU.
- **DDx:**These symptoms may also be seen with other diseases such as eastern encephalitis, equine protozoal myeloencephalitis (EPM) and rabies.