West Nile virus can affect humans, horses, and many types of birds. It is carried by mosquitoes, which become carriers by feeding on infected birds. The first case in Oregon was reported in Malheur County in August 2004. In 2007, 17 Oregon horses tested positive for the virus and there were 27 human cases.
Since the virus is now endemic in Oregon, the Oregon Veterinary Medical Association and its member veterinarians remind you that it is important to vaccinate your horses, as well as to give annual boosters. The vaccine requires two doses given three to six weeks apart. Immunity may not be achieved until up to six weeks after the second dose, and some horses may require a third vaccination. An annual booster should be given prior to the start of the mosquito season in your area; typically, this booster would be given around this time of year. Consult your veterinarian for more information on immunizing your horses against West Nile Virus.
The virus causes inflammation of the brain. Equines who contract the
virus can experience lack of coordination, stumbling, confusion, fever,
stiffness, muscle twitching, depression, and weakness in the legs.
About one-third of infected horses die.
If You Suspect Your Horse is
Infected with West Nile Virus, contact your veterinarian for an
examination. Veterinarians are required to report horses with the
appropriate clinical signs. Contact the Oregon Dept. of Agriculture at
(503) 986-4760 before submitting any samples for testing.
only get the virus from the bite of an infected mosquito; the disease
does not spread from other animals to humans, or from person to person.
The illness causes no symptoms in 80 percent of those who are infected.
Of those who develop an infection, most are mild, with fever and
flu-like symptoms. About one in 150 develops severe illness, including
coma, convulsions, paralysis and vision loss. The most severe cases, as
well as most deaths, occur in those over 55 who have conditions such as
diabetes or hypertension or chronic illness.
Minimize the Threat of Exposure to West Nile Virus :
addition to vaccinating your horses, the best way to minimize the
threat of West Nile for your and your horses is to control mosquito
populations and prevent exposure to them.
sources of standing water that can serve as a breeding ground for
mosquitoes, including children’s wading pools, old tires, buckets, and
water in bird baths weekly. Consider avoiding outdoor activities from
dusk until dawn or take extra care to use repellent and protective
clothing during evening and early morning. When possible, wear long
sleeves, long pants and socks when outdoors. Treating clothes with
repellents containing permethrin or DEET will provide extra protection,
since mosquitoes may bite through thin clothing. Do not apply
repellents containing permethrin or DEET directly to skin.
For more information or to make a report:
DHS Information Line: (866) 703-4636 To report the suspicious illness
or death of equines or livestock: Oregon Department of Agriculture,
(503) 986-4760To report a dead or ill bird:.