A Culver-area horse was recently treated for West Nile virus, the first case of the disease in Central Oregon this year, and only the third case in the state this year.

Dr. Wendy Krebs, a veterinarian with the Bend Equine Medical Center, said Saturday the horse was brought to the clinic earlier in the week, and has since recovered and been returned to its home pasture.

Transmitted primarily by mosquitoes, West Nile virus spreads through the mosquito population via host animals, mostly birds. A mosquito that bites an infected bird can then pass on West Nile virus to the next animal it bites, Krebs said, though infected mammals are regarded as “dead-end hosts” that cannot transmit the infection to other mammals, and carry too little of the virus to pass it on to additional mosquitoes.

Only two other cases of West Nile have been reported in the state this year, Krebs said, one in Union County and one near Baker.

Krebs said the infected Culver horse had not recently traveled and was not vaccinated against West Nile virus. She said the vaccination is effective and widespread among horses in Central Oregon, but an annual booster is required to provide protection against the disease.

September and October are typically the peak months for West Nile infections among horses. Krebs said while mosquitoes are more prevalent earlier in the summer, by September, a larger portion of the mosquito population is carrying the disease.

Horses or other animals that have been infected with West Nile virus will typically display unusual behavior.

“Generally, it causes neurological symptoms, imbalance, falling down. One of the really classic signs in horses is a twitching muzzle,” she said.

West Nile virus is fatal in about 40 percent of cases among horses, Krebs said, but infected animals can develop irreversible neurological problems if not treated promptly.

“The sooner you get them in for treatment, the more optimistic the outlook,” she said.

— Reporter: 541-383-0387, shammers@bendbulletin.com