West Nile Virus

West Nile Virus (WNV) causes encephalitis in birds, horses and humans.  The virus is transmitted from infected birds by mosquitoes.  Humans and horses appear to be especially susceptible.  Studies done by the U.S. Department of Agriculture show that infected horses will not transmit WNV to other horses or to people.  However care should be taken when handling blood from suspect animals.

Symptoms of disease caused by WNV may include the following:

• Flu-like signs (fever and depression)
• Skin twitching, especially around the muzzle.
• Hypersensitivity to touch and sound
• Driving or pushing forward without control
• Incoordination

Because permanent neurological problems and death can occur, early recognition and initiation of treatment is important.  No specific treatment protocol exists however most cases will resolve with supportive therapy and anti-inflammatories.

Efforts to prevent disease in horses caused by WNV is through the use of the West Nile Vaccine from Fort Dodge Pharmaceuticals and through actions that will reduce exposure to mosquitoes.  The vaccine is safe and appears to be effective. AAEP vaccination guidelines recommend vaccinating twice a year.

The most effective way to limit the mosquito population is to destroy the mosquito larval habitat.  This is done by reducing the amount of standing water.  Water troughs should be cleaned at least once a week.  Keeping weeds trimmed and lawn mowed help eliminate areas where mosquitoes rest.  Directly protecting horses from mosquito bites is more difficult.  Fly and mosquito repellents may be helpful.  Products containing pyrethroids are considered safe for horses.   Spray stalls, aisle walls and other areas such as under shade trees where horses congregate.  Fans can also be used to discourage mosquitoes from residing in your barn.