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West Nile Virus (WNV)

West Nile Virus Update

October 1, 2012

The Oregon Department of Agriculture (ODA) confirmed one additional case of equine West Nile Virus (WNV) on September 24, 2012. The horse is a four year old gelding Quarter Horse located in Klamath County. Its owner newly acquired the horse and its vaccination status was unknown.

West Nile Virus has been confirmed in two Oregon horses in 2012. Both cases were located in Klamath County. The first horse is deceased and the second horse appears to be improving.

Clinical signs for WNV can range from very mild to life threatening. Affected animals may become depressed; lose their appetite; display hypersensitivity to touch and muscle twitching; become drowsy, develop incoordination and other nervous system related signs. Mortality in horses that become sick can be as high as 30-40%.

Horse owners should consult with their veterinarian about a WNV vaccination program to ensure maximum protection for their horses.
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Protecting against WNV

Vaccinate horses
Horse owners in Oregon are being advised to help protect against West Nile Virus by vaccinating their animals and taking steps to control mosquitoes this summer. For those who have already vaccinated their horses in the past, a booster shot will strengthen immunity.
The vaccine for horses is available through local veterinarians.
A low percentage of mosquitoes carry the virus and a low percentage of horses bitten by infected mosquitoes become ill. But a horse showing signs is a serious situation. The disease causes inflammation of the brain and about one-third of affected horses die. Symptoms include stumbling, lack of coordination, weakness in the legs, depression, muscle twitching, and death.
For questions on equine testing contact the Oregon Department of Agriculture, 503-986-4680.  

Control mosquito breeding sites
Help reduce the number of mosquitoes in areas outdoors where you work or play, by draining sources of standing water. In this way, you reduce the number of places mosquitoes can lay their eggs and breed.
  • At least once or twice a week, empty water from flower pots, pet food and water dishes, birdbaths, swimming pool covers, buckets, barrels, and cans.
  • Check for clogged rain gutters and clean them out.
  • Remove discarded tires, and other items that could collect water.
  • Be sure to check for containers or trash in places that may be hard to see, such as under bushes or under your home.

Protect yourself
  • The hours at dusk and dawn are peak mosquito biting times. Consider avoiding outdoor activities during these times or take extra care to use repellent and protective clothing during evening and early morning. Mosquito activity usually starts by April 15th and decreases significantly by September 15th.
  • When possible, wear long-sleeves, long pants and socks when outdoors.
  • Treating clothes with repellents containing permethrin or DEET will give extra protection, since mosquitoes may bite through thin clothing. Do not apply repellents containing permethrin directly to skin. Do not spray repellent containing DEET on the skin under your clothing.
  • Mosquitoes lay their eggs in standing water. Limit the number of places around your home for mosquitoes to breed by getting rid of items that hold water.
Individuals and businesses who offer pesticide application services for the control of mosquitoes in Oregon are required to be licensed by the Oregon Department of Agriculture.

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To report a dead or ill bird, contact your county health department or vector control agency , or Oregon Fish and Wildlife (phone 503-947-6322, fax 503-947-6330).
To report suspicious illness or death of livestock, contact the Oregon Department of Agriculture, 503-986-4760.
Health care providers and clinical laboratories are required to report cases and suspect cases of diseases of unusual public health significance immediately upon identification. On weekends and holidays, call 503/731-4030 to reach the state health department doctor on call.

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West Nile Virus hotline

Call 503-988-NILE (6453) for more information.

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WNV serum samples for DHS

The Center for Disease Control and Prevention and the Oregon Department of Human Services are interested in obtaining serum samples from equine cases that may have an encephalitis-like-illness to test for West Nile virus.

There is no cost for testing. Collect serum samples from suspect WNV cases and send to Oregon State University, Veterinary Diagnostic Laboratory. We have used this is the same format for sample collection for the last few years. We have attached a copy of the Equine Submission Form. Please fill it out and send it along with samples. We have also attached other information about sample collection and biosecurity guidelines for WNV.

Please fill out the attached form and send with the sample to OSU-VDL.

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