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10 Facts About Equine West Nile Virus

Horses are at the highest risk for contracting WNV during peak mosquito season, July through October. Ensure your horse is protected.

Heavy rainfall and floodwaters threaten the country's Heartland with heightened mosquito and West Nile virus (WNV) risk. With rising numbers of reported WNV cases, ensure you are aware of these 10 important WNV facts.

  1. Africa, Eastern Europe and West Asia have long experienced the impact of WNV; however, the disease is fairly recent to North America with the first case diagnosed in 1999.
  2. West Nile virus is transmitted by mosquitoes, which feed on infected birds, to horses, humans and other mammals.
  3. Horses represent 97 percent of all reported non-human mammalian cases of WNV disease.
  4. Infected horses begin to show signs of disease as early as three to 15 days.
  5. More than 25,000 cases of WNV have been reported in U.S. horses.
  6. The disease presents a 33 percent fatality rate to horses.
  7. Disease risk increased in 2018, with 384 cases of equine WNV reported, nearly 80 cases more than in 2017.
  8. Horses are at the highest risk for contracting WNV during peak mosquito season, July through October.
  9. When properly vaccinated, horses have shown to be 30 times less likely to contract WNV.
  10. Vaccination provides horses with nearly 100 percent protection against WNV.

Incorporate mosquito management techniques to help keep horses, people and animals of all kinds safe from this dangerous disease.

One acre of land can house 1 million mosquito eggs. Help eliminate the mosquito population by removing mosquito-breeding habitats, such as anything that can hold water. If your yard or barn area has any low-lying areas that collect water after rainfall, be sure to fill these in. Hang fans throughout your barn. Mosquitoes typically avoid moving air. Additionally, deploy proven mosquito prevention products, such as the Mosquito Eradicator, to control 95 percent of mosquitoes for 90 days.

Learn more about Valley Vet Supply, and the new and proven Mosquito Eradicator, at

About Valley Vet Supply

Valley Vet Supply was founded in 1985 by veterinarians to provide customers with the very best animal health solutions. Building on nearly 50 years’ experience in veterinary medicine, Valley Vet Supply serves pet and livestock owners with more than 23,000 products and medications hand-selected by Valley Vet Supply veterinarians and founders. With an in-house pharmacy that is licensed in all 50 states, and verified through the National Association of Boards of Pharmacy (NABP), Valley Vet Supply is the dedicated source for all things horse, livestock and pet. For more information, please visit

Find other interesting information about Horse Health in our section on Health & Education.

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