What is West Nile Virus (WNV)?

Horse with Droopy Face NeuroWNV is a virus transmitted by mosquitoes and, therefore, cases typically occur when mosquito activity is high. A horse infected with WNV can show a variety of symptoms which could include:

  • low grade fever
  • colic
  • lameness
  • decreased appetite
  • dull demeanor.

Horses more severely affected may show signs of:

  • ataxia (wobbly gait)
  • weakness
  • trouble standing
  • muscle twitching
  • abnormal behavior
  • facial paralysis
  • other neurologic signs

The disease can be life-threatening in horses and humane euthanasia is often recommended for horses who are most severely affected.

Can my horse transmit WNV to other horses or to humans?

Horses can NOT transmit the virus to other horses or humans. So isolation of these horses is not necessary. It is, however, important to recognize that if one horse on the property is affected then the other horses are also at high risk considering they are in the same mosquito environment.

How can I protect my horse from WNV?

Vaccination is the BEST way to prevent disease. We recommend horses are vaccinated for WNV every year before the start of mosquito season. Here in the Roaring Fork Valley, we typically vaccinate March thru May. Horses that are in endemic areas with extended mosquito seasons (i.e. Texas, Florida) may benefit from revaccination every 6 months. Ideally, vaccination is done by a veterinarian using an FDA approved product. Not every vaccine is created equal.

Beyond vaccination, horse owners can implement mosquito control via fly sprays, fly sheets, and reducing standing water in pastures and turn outs. These methods are not as effective as vaccination.

How can my horse be tested for WNV?

Horses showing symptoms of WNV can be tested for the disease from a blood sample. In certain scenarios, it may also be recommended to submit cerebrospinal fluid (CSF) for testing. Collection of CSF can be relatively difficult and may not be appropriate for all horses. We do not recommend testing of horses who are not showing clinical signs.

WNV is a reportable disease which means that any horse that is tested has to be reported to the USDA government officials. This reporting does not get you in trouble, but allows for disease documentation to help in reducing the spread of disease and awareness of its occurence. 

Is WNV treatable?

Horse Neuro in Sling with HelmetThere is no specific treatment for WNV but supportive care can be provided in the form of anti-inflammatories, antioxidants, fluid therapy, and placing a horse in a sling if they are unable to stand or at risk of becoming recumbent. Not all facilities have the ability to sling a horse as it requires specific equipment and stalling. Roaring Fork Equine Medical Center does not have the capabilities of slinging horses at this time.