▶️ West Nile Virus detected in Crook County horse

West Nile virus, a disease spread by mosquitoes, has been detected in a horse in Crook County according to Oregon Public Health officials and the Crook County Health Department.

The horse, which became ill in September, is the first to test positive for the disease in Crook County since testing began in 2004.

The horse had spent time in both the Prineville and the Post/Paulina areas, and had not traveled outside of the county during its exposure period.

West Nile virus is transmitted through the bite of infected mosquitoes. Horses, and humans, become infected from mosquitoes that have previously fed on infected birds. Even though it is late in the season, Crook County health officials are advising people in our area to take precautions against mosquitoes to avoid the risk of infection.

“It is critical that all horses be vaccinated,” said Dr. Rene Villagrana, a local veterinarian . “If your horse has not been vaccinated, you are encouraged to vaccinate before mosquito season next spring. If your horse is displaying signs of illness, call your veterinarian immediately.”

Now, with a confirmed case of the virus in Crook County, officials are urging horse owners to vaccinate their animals.

Health officials say 95% of horses that are infected with West Nile Virus will die from the disease.

“A lot of horse people have taken this seriously and have gotten their horses vaccinated,” said Karen Yeargain communicable disease coordinator with the Crook County Health Department. “But I know there’s a lot of you out there that have said, ‘Well it’s not really here yet’. But heads up, we do have documentation now that we have a horse who was sick and diagnosed. If you haven’t yet, get your horses started on the vaccine in mid-winter or early spring.”

West Nile virus can infect the central nervous system of horses and cause symptoms of encephalitis that include weakness or paralysis of hind limbs, hyper-excitability and convulsions. Not all horses with clinical signs of encephalitis have West Nile. In Oregon, about 95% of horses diagnosed with WNV had not been vaccinated. Symptomatic West Nile illness in horses is usually fatal.

Horses are considered “dead-end” hosts, which mean they don’t develop enough virus in the bloodstream to infect mosquitoes. Only birds are known to pass the virus to mosquitoes, which can then transmit the disease to other birds, animals, or humans.

About one in five people infected with West Nile virus may show symptoms. People at risk of serious illness include individuals 50 and older, and people with immune-compromising conditions, such as diabetes and high blood pressure.

According to Yeargain, West Nile symptoms may include fever above 100 degrees and severe headache, stiff neck, mental confusion, muscle weakness, shaking, paralysis or rash. People should contact their health care provider if experiencing any of these symptoms. So far, there have been no residents of Crook County diagnosed with West Nile illness.

In 2019, Oregon has had 8 human cases of West Nile virus in three counties. The virus was found in, 83 mosquito pools (samples of about 50 mosquitoes each) and seven horses. In 2018, there were two human cases of West Nile virus in Harney and Clackamas counties; one bird, 58 mosquito pools and two horses were positive in that year. The virus also can be found in, but not transmitted by, chickens, squirrels and dogs.

Climate change effects such as increased temperature and changes in rainfall have led to longer mosquito seasons and are contributing to the spread of West Nile virus, health officials say. They agree these and other climate change indicators must be considered to help people better prepare for future transmission of the disease.

Additional information about West Nile virus is available at:

Oregon Health Authority website: http://public.health.oregon.gov/DiseasesConditions/DiseasesAZ/WestNileVirus/Pages/survey.aspx

U.S. Centers for Disease Control and Prevention: http://www.cdc.gov/ncidod/dvbid/westnile/ index.htm

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