West Nile Virus Can Infect Humans As Well As Horses

West nile transmission Westnile.ca.govIf you’re a horse owner, you’ve probably been aware of the West Nile Virus potential for your horse for several years and, hopefully, have given your horse the proper vaccinations. However, there have recently been news stories about  cases of human West Nile cases.  You may be hearing the following – we’ve investigated to see what’s true. 

FACT: People and animals can become infected from the bite of certain kinds of mosquitoes that are infected with the virus. Mosquitoes may pick up the virus when they bite, or take a blood meal, from wild birds that are infected with West Nile Virus.


FACT: Mosquitoes transmit the virus when biting to take a blood meal.


FACT: Infection occurs primarily in the late summer or early fall in the northeast and Mid Atlantic regions.


FACT: Only humans and horses can get West Nile.

FALSE. In addition to humans and horses, dogs and cats have been found to be susceptible to the disease.

FACT: Humans and horses can get the virus from other infected mammals.

FALSE FOR BOTH. Once a mammal is infected, it is considered a “dead end” infection and mosquitoes cannot ingest the virus.

FACT: There are symptoms to watch for if you think you have West Nile.

FALSE FOR HUMANS In approximately 80 percent of West Nile virus infections in humans cause no symptoms (also known as “asymptomatic”). Click HERE for more information on symptoms of West Nile in humans.

TRUE FOR HORSES Symptoms in horses may include a general loss of appetite and depression, in addition to any combination of the following signs:

  • fever
  • weakness of hind limbs
  • paralysis of hind limbs
  • impaired vision
  • ataxia (weakness)
  • head pressing
  • aimless wandering
  • convulsions (seizures)
  • inability to swallow
  • walking in circles
  • hyperexcitability
  • coma

FACT: There is a vaccine to prevent West Nile.

FALSE FOR HUMANS. Also false for dogs and cats.

TRUE FOR HORSES. Click HERE for recommendations by the American Association of Equine Practitioners on how, when and how often to vaccinate for West Nile.

FACT: There are steps you can take to eliminate the possibility of mosquitoes, and therefore West Nile.

TRUE FOR BOTH  Mosquitoes by far are the biggest carrier of West Nile. Mosquitoes breed in standing water – eliminate the standing water and you’ll start eliminating mosquito breeding grounds. Be sure to:

  • Empty and refill outdoor water troughs or buckets every few days.
  • Turn over plastic wading pools when not in use.
  • Turn over wheelbarrows and don’t let water stagnate in birdbaths.
  • Aerate ornamental pools or stock them with fish. Water gardens can become major mosquito producers if they are allowed to stagnate.
  • Clean and chlorinated swimming pools when not in use. Mosquitoes may even breed in the water that collects on pool covers.
  • Use landscaping to eliminate standing water that collects on your property, especially near manure storage areas. Mosquitoes may breed in any puddle that lasts for more than four days.
  • Clean clogged roof gutters every year. Millions of mosquitoes can breed in roof gutters each season.
  • Most barns have their population of birds and some birds can be beneficial to insect control. However, if your area is infected with West Nile, consider reducing the number of birds in and around the stable area. Also, periodically look around the property for dead birds, such as crows. Use gloves to handle dead birds and place the birds in plastic bags for disposal.
  • In addition, use mosquito spray or topical on yourself and your horses, especially at night. For more information on best mosquito repellents, click HERE.  Consider fly sheets that stop “no see ems” for horses and long sleeves and pants for humans.

For help in assessing mosquito exposure risks on your property and for suggested control practices, contact your county extension office, county Department of Environmental Protection, county Department of Health, or mosquito and pest control company.

Photo credit:  westnile.ca.gov

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