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WEST NILE DISEASE
West Nile disease arrived in the Rogue Valley in the fall of 2004 and through the year 2005 and beyond is considered endemic. The Rogue Valley was one of the last areas in the continental United States to be affected by the virus, which is carried by infected migrating birds. Since its appearance in New York in 1999, West Nile virus has become the fastest-growing health threat to horses in the United States. Of interest however is the fact that reported cases of WNV infection in horses has declined much due in fact to vaccination.
Horses become infected with West Nile virus when they are bitten by mosquitoes that have recently bitten infected birds. Horses and humans become infected in this way, but cannot transmit the disease directly to other individuals by contact, or by mosquito vector. Only birds develop enough of the virus in their blood stream to allow mosquitoes to transmit the disease after a blood meal. Horses and humans are termed 'dead end hosts' because of this.
Some horses show no symptoms after becoming infected, others, especially the very young and very old, become clinically ill. Symptoms of West Nile infection usually appear within 5 to 15 days and include: stumbling or tripping, muscle weakness or twitching, partial paralysis, loss of appetite, depression, head pressing or head tilt, impaired vision, wandering or circling, inability to swallow, inability to stand up, fever, convulsions, and coma. These signs are caused by the viruses effect on the brain and spinal cord.
Treatment for West Nile infection primarily involves supportive care, since no specific therapy currently exists. With supportive care, most clinically affected horses survive infection, but approximately 35% die of the disease or have to be euthanized.
Vaccination is effective in preventing the disease, and is strongly recommended in this area. All horses should receive an initial series of vaccinations, followed by yearly boosters. Please consult our West Nile Vaccination Update page to get the latest recommendations on vaccination. Our current recommendation is to vaccinate annually in April. If you vaccinate your horse earlier or later than April, twice yearly vaccination is recommended.
To further protect your horse, and yourself, practice mosquito control around your property. Eliminate common mosquito breeding areas by draining shallow ponds or placing special chemicals in them to suppress larvae development (these are environmentally safe and available through farm supply stores and Jackson County Vector Control). Look for and eliminate any places water can collect and become stagnant. Clean water troughs once a week.. Keep your horses stabled in screened stalls at dawn and dusk when mosquitoes are most active. Turn off lights that attract mosquitoes at night or use fluorescent lights which do not attract mosquitoes. Use mosquito repellant.
Please follow the links below for more information, including a map of confirmed and pending cases in United States..
Maps (USGS):
http://cindi.usgs.gov/hazard/event/west_nile/west_nile.html
Emergency Management Warnings (USDA):
http://www.aphis.usda.gov/lpa/issues/wnv/wnv.html
Jackson County Vector Control:
http://www.jacksoncountyvectorcontrol.org/