Peak mosquito activity in the United States occurs July through October, which places horses at the highest risk of contracting West Nile virus (WNV).1 Much of the United States has experienced increased rainfall this spring, and the first cases of West Nile have already been documented this year. With the right vaccine and preventive measures, it’s not too late for owners to help protect their horses against this life-threatening disease.
West Nile is transmitted by mosquitoes--which feed on infected birds--to horses, humans and other mammals. In 2014, the United States recorded 19,623 cases of West Nile disease or infection, according to the Centers for Disease Control and Prevention as of January 2015. 2 Cases include mosquitoes, birds, humans and horses. California topped the charts with 7,008 cases, followed by Texas with 2,484 cases. The case numbers are reflected in this U.S. map.
Vaccination remains the most effective way to help protect horses against West Nile virus and other mosquito-borne diseases, such as Eastern equine encephalitis (EEE) and Western equine encephalitis (WEE). Veterinarians and horse owners continue to trust WEST NILE-INNOVATOR, the first vaccine on the market when West Nile struck, to help protect their horses.3
Researchers recently tested horses’ responses to six West Nile virus vaccination regimens and found some substantial differences in their immune responses.4 While all of the vaccinated horses demonstrated an initial immune response, by Day 28, the antibody titer response of the horses vaccinated with WEST NILE-INNOVATOR was four times higher than those vaccinated with the one-dose, big combination WNV-containing vaccines.
“We thought WEST-NILE INNOVATOR would produce a higher immune response than the large one-dose combination West Nile vaccines, but we did not think it would be nearly four times higher,” said Kevin G. Hankins, DVM, senior veterinarian, Equine Veterinary Operations, Zoetis.
West Nile is a core vaccination requirement, along with vaccinations for EEE, WEE, tetanus and rabies, according to the American Association of Equine Practitioners (AAEP) guidelines.5
For horses that have not been vaccinated or are overdue for vaccination, it’s not too late to help protect them against this life-threatening disease. WEST NILE-INNOVATOR and a combination of other booster vaccines can help provide added protection horses need to stay healthy.
“We have a disease that is here to stay with an effective vaccine but no treatment in the case of infection,” Hankins said. “That makes vaccination a cheap insurance policy.”
In conjunction with vaccination, good management techniques can help prevent West Nile cases. Techniques include:
- 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 basis6
- Applying insect repellents or bringing horses inside during peak mosquito feeding hours between dusk and dawn
Remember, West Nile does not always lead to signs of illness. In 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.7 If horse owners notice signs of WNV infection in their horses, they should contact a veterinarian immediately, especially if horses are exhibiting neurological signs. The case fatality rate for horses exhibiting clinical signs of West Nile infection is approximately 1 in 3 horses.5
By providing proper vaccination and mosquito population management, horse owners can do their part to help prevent West Nile infections.
Visit a resource center from Zoetis to download tools to help remind horse owners of peak mosquito season and the risk of West Nile virus that comes with it. For more information on WEST NILE-INNOVATOR, visit westnileinnovator.com. WEST NILE-INNOVATOR is also backed by the Zoetis Equine Immunization Support Guarantee. To learn more, visit zoetisUS.com/isg.
Zoetis (zō-EH-tis) is the leading animal health company, dedicated to supporting its customers and their businesses. Building on more than 60 years of experience in animal health, Zoetis discovers, develops, manufactures and markets veterinary vaccines and medicines, complemented by diagnostic products and genetic tests and supported by a range of services. In 2014, the company generated annual revenue of $4.8 billion. With approximately 10,000 employees worldwide at the beginning of 2015, Zoetis serves veterinarians, livestock producers and people who raise and care for farm and companion animals with sales of its products in 120 countries. For more information, visit www.zoetisUS.com.
1. Reed, S.M., Bayly, W.M., Sellon, D.C. Equine Internal Medicine, 3rd ed. WB Saunders Co., Philadelphia, PA; 2010:630.
2. Centers for Disease Control and Prevention. West Nile Virus Activity by State – United States, 2014. Available at: http://www.cdc.gov/westnile/statsMaps/preliminaryMapsData/activitystatedate.html. Accessed April 23, 2015.
3. West Nile-Innovator and Fluvac Innovator MDI Sales Data as of 12/31/14. Zoetis. Dec. 2014.
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. Core Vaccination Guidelines. American Association of Equine Practitioners website. Available at: http://www.aaep.org/-i-165.html. Accessed April 23, 2015.
6. West Nile Virus. Florida Department of Agriculture and Consumer Services, Division of Animal Industry website. Available at: http://www.freshfromflorida.com/Divisions-Offices/Animal-Industry/Education/For-the-Community/Animal-Disease-Information/West-Nile-Virus. Accessed April 23, 2015.
7. What Horse Owners Should Know About West Nile Virus. Pennsylvania’s West Nile Virus Control Program website. Available at: http://www.westnile.state.pa.us/animals/horses.htm. Accessed April 23, 2015.