What’s the current protocol for West Nile Virus?

Ask the Equine Vet: West Nile

Q: What’s the current protocol for West Nile Virus? I’ve heard once per year and twice per year. I’ve also heard that experts predict a high mosquito population this year. Should I be concerned?

A: Given the strong seasonality of mosquitoes in our region, annual vaccination for West Nile Virus (WNV) is adequate. In some parts of the country where mosquitoes can be present year-round (like Florida), more frequent vaccination is often done.

We do recommend trying to give your horse’s annual WNV booster in the late spring/summer to have maximal immunity during the highest risk season. If we do have a high number of mosquitoes this season, that could increase the risk of your horse acquiring WNV – it depends upon whether or not the mosquitoes are infected with the virus. To date, WNV in horses has been more common on the east side of the state, but they have found positive birds and mosquitoes on the west side as well.

Generally the vaccine is well-tolerated and has good efficacy against preventing, or at least reducing, the severity of clinical disease.

Answered by Wendy Harless Mollat, DVM, Diplomate ACVIM, Pilchuck Veterinary Hospital


Originally appeared in the Washington State Quarter Horse Association’s monthly newsletter, May 2012 edition: www.wsqha.com