What is West Nile virus?
West Nile is a virus that can cause inflammation of the brain or the lining of the brain and spinal cord.
How is West Nile virus spread?
The virus is spread by the bite of an infected mosquito and can affect people, horses and many types of birds. Among humans, most cases result from mosquito bites, but the virus can also be transmitted through blood transfusion, organ transplants and breast milk. Mosquitoes get infected when they feed on an infected bird.
What animals are susceptible to West Nile virus?
West Nile virus affects horses, mules, donkeys, and other equines much more often than other animals. Other livestock and poultry do not commonly show any illness if
exposed to West Nile virus.
Has West Nile virus been found in Washington?
Yes. The virus was detected for the first time in 2002 in a raven from Pend Oreille County and a crow from Snohomish County.
Infected horses were also reported in Island and Whatcom counties.
In August 2006, the State Department of Health reported the state's
first
human case of West Nile virus acquired in Washington.
What are the symptoms of West Nile virus in horses?
Most horses do not become ill and show no symptoms. Those that do become ill show signs such as loss of appetite, loss of coordination, confusion, head pressing, fever, stiffness and muscle weakness. About a third of horses that become ill die.
What are the treatments for West Nile virus in horses?
There is no known cure for this virus. Fluids and anti-inflammatory drugs
have been used to reduce the signs of the virus.
Is there a vaccine to protect horses from West Nile virus?
Yes. The U.S. Department of Agriculture has approved a vaccine for use on horses.
Approval means the vaccine is pure and safe and there is scientific evidence that it is effective.
The vaccine is available through licensed veterinarians.
When should the vaccine be given?
Now is a good time to talk to your veterinarian. The vaccine requires two doses three to six weeks apart, and immunity will not be achieved until five weeks after the second dose. An annual booster is needed just prior to mosquito season.
What else can I do to protect my horse?
The best way to minimize the threat of West Nile virus is to control mosquito populations and prevent your horse from being exposed to adult mosquitoes.
How can I reduce the mosquito population?
Change the water in livestock troughs, fountains, birdbaths and wading pools weekly. Aerate ornamental pools. Discard old tires and other containers around your home where water can accumulate and serve as a breeding ground for mosquitoes. Drill holes in the bottom of containers that are left outside. Clean clogged roof gutters annually. Clean and chlorinate swimming pools that are not in use. Be aware that mosquitoes can breed in the water that collects on swimming pool covers.
How can I keep my horse from being exposed to adult mosquitoes?
Housing animals in a structure with well-maintained screens could help to reduce exposure to mosquitoes. However, use of these structures may increase exposure unless precautions are first taken to eliminate mosquitoes. Precautions may include using fans to reduce the ability of mosquitoes to feed on horses or treating the area with an insecticide.
Horse owners may choose the option of applying an insect repellent to decrease exposure of horses to adult mosquitoes. Repellents should be used according to the labels. And, due to the challenges of covering the entire horse and limits in the length of time that
repellents are effective, repellents should not be your only line of defense against mosquitoes.
Should I try to keep my horse inside?
A recent study suggests that keeping horses in a stall at night could reduce their risk of infection. However, various species of mosquitoes feed at different times of the day or night, and it is not yet clear what types of mosquitoes transmit West Nile virus.
What should I do if I believe my horse has West Nile virus?
To report a potential case of West Nile virus in horses, call the State Veterinarian’s Office at (360) 902-1878, or the U.S. Department of Agriculture in Olympia at (360) 753-9430.
Where can I get more information?
For information about West Nile virus surveillance or human health issues, contact the Washington State Department of Health Communications Office at (360) 236-4076.
The state Department of Health’s West Nile virus Web site (http://www.doh.wa.gov/EHP/TS/ZOO/WNV/WNV.HTML) has more information. Other sources include the U.S. Department of Agriculture’s Web site at http://www.aphis.usda.gov/oa/wnv/, or the Centers for Disease Control and Prevention Web site at http://www.cdc.gov/ncidod/dvbid/westnile/qa/wnv_dogs_cats.htm
Washington State Department of Agriculture
PO Box 42560
Olympia, Washington 98504-2560
(360) 902-1815
FAX (360) 902-2150
lwaring@agr.wa.gov
