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West Nile Virus and Horses
Horses are affected by West Nile virus (WNV) much more often than any other domestic animals. Many horses infected with WNV do not develop any illness, but of horses that become ill, about 30 percent die or need to be euthanized. Other livestock and poultry do not commonly show any illness if infected with WNV.

A WNV vaccine is available for horses. Please contact your veterinarian for more information. Additionally, because mosquitoes are linked with WNV transmission, you can prevent or control future WNV outbreaks among horses by controlling mosquito populations and preventing horses from being exposed to mosquitoes.

For more information on WNV prevention and control in equine and other livestock, visit the United States Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) West Nile Virus website at

For information on submitting horse samples for testing in Wyoming, visit the Wyoming State Veterinary Laboratory website at

Agriculture and Livestock
Cattle, sheep, and pigs rarely develop serious illnesses from West Nile virus (WNV) infection, and mortality in chickens has not been documented. Additional information is available at United States Department of Agriculture’s (USDA)  West Nile Virus in farm animals.

Other Resources
For information on West Nile virus and agricultural issues, visit the United States Department of Agriculture’s (USDA) Equine West Nile Virus website at