Equine West Nile Threat Increases During Peak Mosquito Season

Equine vaccination and proper management help offer protection.

From AQHA Corporate Partner Zoetis

Horses are at highest risk of contracting West Nile virus during peak mosquito activity, which occurs July through October in the United States.1 However, there’s still an opportunity to help protect horses against this life-threatening disease. Veterinarians and horse owners continue to trust WEST NILE-INNOVATOR®, the first vaccine on the market when West Nile struck the United States, to help protect their horses.2

“Although West Nile is not a new concern for the equine community, horse owners and veterinarians must remember how critical it is to vaccinate horses annually against this deadly disease,” said Kevin Hankins, DVM, senior veterinarian, Zoetis Equine Technical Services. “A horse that is not vaccinated annually is still very much at risk, which is why we continue to see a great number of West Nile cases in unvaccinated horses.”

Learn why it is critical to vaccinate your horse against West Nile virus in AQHA’s Common Horse Health Issues ebook. Help protect your horse with WEST NILE-INNOVATOR® from Zoetis.

Protect your horse from West Nile Virus with ZoetisWest Nile virus is transmitted by mosquitoes — which feed on infected birds — to horses, humans and other mammals. Vaccination remains the most effective way to help protect horses against West Nile and other mosquito-borne diseases, such as Eastern equine encephalitis and Western equine encephalitis. If vaccinated, horses have shown to be 30 times less likely to contract West Nile.3

For horses that have not been vaccinated or are overdue for vaccination, WEST NILE-INNOVATOR can help provide the added protection horses need to stay healthy. A study showed that separate administration of WEST NILE-INNOVATOR and FLUVAC INNOVATOR® generated four times the immune response to West Nile virus than was produced by a big one-shot combination vaccine.4

In conjunction with vaccination, proper horse management techniques can help prevent West Nile cases, such as:

  • Destroying any mosquito-breeding habitats by removing all potential sources of stagnant water;
  • Cleaning and emptying any water-holding containers, such as water buckets, water troughs and plastic containers, on a weekly basis; 5
  • Applying insect repellent or bringing horses inside during the peak mosquito feeding hours of dusk to dawn.

West Nile does not always lead to signs of illness in horses. For horses that do become clinically ill, the virus infects the central nervous system and may cause symptoms such as loss of appetite and depression. Other clinical signs may include fever, weakness or paralysis of hind limbs, impaired vision, ataxia, aimless wandering, walking in circles, hyperexcitability or coma.6 If horse owners notice signs or symptoms of West Nile infection in their horses, they should contact a veterinarian immediately. West Nile virus is fatal in 33 percent of horses that exhibit clinical signs of disease.7

To learn more about proper vaccination and WEST NILE-INNOVATOR, visit

Did you know that if vaccinated, horses are 30 times less likely to contract West Nile virus? Download AQHA’s Common Horse Health Issues ebook and learn how you can help protect your horse’s health during peak mosquito season.

1 Reed SM, Bayly WM, Sellon DC. Equine Internal Medicine, 3rd ed. Philadelphia: WB Saunders Co. 2010;630.

2 Data on file, MDI sales data for WEST NILE-INNOVATOR as of 12/31/15, Zoetis LLC.

3 Epp T, Waldner C, West K. Efficacy of vaccination for West Nile virus in Saskatchewan horses, in Proceedings. 51st   
Annual Convention of the AAEP 2005;180-182.

4 Cortese V, Hankins K, Holland R, Syvrud K. Serologic Responses of West Nile Virus Seronegative Mature Horses to West Nile Virus Vaccines. J Equine Vet Sci. 2013;33:1101-1105.

5 West Nile Virus. Florida Department of Agriculture and Consumer Services, Division of Animal Industry website. Accessed May 11, 2016.

6 What Horse Owners Should Know About West Nile Virus. Pennsylvania’s West Nile Virus Control Program website. Accessed May 11, 2016.

7 Core Vaccination Guidelines. American Association of Equine Practitioners website. Accessed May 11, 2016.

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Protect your horse from West Nile Virus with Zoetis