SECTION Training
Conrad Schumacher
Celebrate the Ordinary

SECTION Juniors

SECTION Shows

The West Nile virus (WNV) is a virus that affects a horse's neurological system.  This virus was first isolated in the United States in New York in the late summer of 1999.  currently, the virus has been found in almost all states and Ontario.

"Within a couple of years, the WNV will be nationwide, so we should treat this virus as if it's here to stay," said Dr. Judy Marteniuk, MSU Extension veterinarian and large-animal clinician at Michigan State University's College of Veterinary Medicine.

Transmission of WNV is by mosquitoes. Birds serve as the reservoir host after having been bitten by an infected mosquito.

People, horses, and other mammals (bats, cats, chipmunks, skunks, squirrels, and some domestic rabbits) are incidental hosts and do not spread the disease.

"We call horses dead-end hosts because they cannot pass this virus to other horses, humans, or mosquitoes," said Dr. John Berends, equine reproductive specialist and MSU Extension veterinarian.

The virus can be passed from bird to bird only by mosquito bites. WNV can be transmitted to other parts of the country through the movement of infected migratory birds or inadvertent transport of infected mosquitoes in horse trailers and/or tack and supplies.

Only a small percentage of infected horses or people actually become sick.  Clinical signs of a horse sick from WNV are: ataxia (in coordination, stumbling, limb weakness), somnolence (sleepiness), dullness, listlessness, facial paralysis (droopy eyelids, lower lip) and inability to rise.  Other signs may include: a mild fever, blindness, muscle trembling, excitability and seizures.

Unlike EEE and WEE which have a very low survival rate, clinically affected horses appear to have a 65 percent chance of recovery and return to normal function when treated.

Once a horse has been infected with the WNV and survied, it is protected from development of clinical disease for an extended period of time.

There is no specific treatment, according to Berends and Marteniuk.  Horses that are clinically infected are treated by supportive measures, such as IV fluids, control of fever, safe quiet housing.  "Prevention remains the best practice to follow", Marteniuk said.  

Briar Fox Farm recommends that you call your vet. and get the inoculations for your horses.

Was this article helpful to you?  Please let us know by voting.

Mosquitoes
Transmission of WNV is by mosquitoes.

Birds
Birds serve as the reservoir host after having been bitten by an infected mosquito.

Migratory Birds
Virus passed from bird to bird only by mosquito bites. WNV can be transmitted ot other parts of the country through the movement of infected migratory birds.