What can I do to protect my animals from West Nile virus?



West Nile virus was introduced to Utah last year, and because it now exists in our resident population (especially in birds), there will likely be an outbreak again this year.


West Nile virus is transmitted by infectious mosquitoes that become infected when they feed on birds with the virus. The virus stays in the mosquito’s salivary glands, and during blood feeding, it is injected into the animal. The virus then multiplies and may cause illness in the animal. However, there is no reason to destroy an animal that has been infected with West Nile virus. Full recovery from the infection is likely after treatment. There is no documented evidence of person-to-person, animal-to-animal or animal-to-person transmission of West Nile virus.


Consider this information to protect your animals from the disease.

  • Horses and mules can be seriously affected with West Nile virus; therefore, vaccination of equine animals is encouraged. There are currently two vaccines that can be used to provide protection. Both are sold through veterinarians only. The vaccine should be given prior to mosquito season. The first year, two doses are necessary with three to four weeks between doses. The animal will not have protective immunity until two weeks after the second dose. After the first year, only one dose is necessary. Equines can also receive a booster dose during peak season (August and September) to provide extra protection if an area is experiencing a heavy outbreak of West Nile virus. Owners should consult with their veterinarian about timing, use in pregnant mares or use in foals.
  • Cats, dogs and most traditional house pets are not likely to have problems with West Nile virus. They can be carriers of the virus, but they cannot transmit it to humans or other animals. Veterinarians and pet owners should take normal infection control precautions when caring for an animal suspected of having this or any other viral infection.
  • If you find a dead crow or raptor, contact your local health department or the regional office of the Division of Wildlife Resources. They may then sample other birds to determine if West Nile virus is present in the area. The Utah Department of Health will also conduct testing of selected birds for West Nile virus. Testing is conducted by collecting oral swabs and sending them to a testing lab. For further information on dead birds, visit: http://www.wildlife.utah.gov/wnv/dead_bird.html or go to the West Nile virus page at: http://www.wildlife.utah.gov/wnv/

For further information on West Nile virus, visit: http://extension.usu.edu/files/agpubs/WestNileWeb.pdf

The Utah Department of Health has information at: http://health.utah.gov/wnv/

The Utah Dept of Agriculture and Food keeps an updated site on the current status in horses and animals at: http://ag.utah.gov/wnv/wnv_home.html The site also has questions and answers and other informational links.

Posted on 18 Jul 2006

Clell Bagley
Extension vetrinarian

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