A Washington horse positively identified as a West Nile virus victim was euthanized north of Pasco.
A 10-year-old mare, the animal was the second West Nile case in the state in 2013, according to the Washington State Department of Agriculture. The horse had not been vaccinated against the disease, but is reported not to have left the state, assuring it did not contaminate horses in other parts of the U.S.
West Nile, fatal in most cases of many mammals and birds who contact the disease, is closely monitored by the Washington State University Animal Disease Diagnostic Laboratory in Pullman, which identified the malady in the latest find. The positive test results were reported in early October.
The other 2013 West Nile case in Washington was reported in late September for a horse pastured in Outlook, Yakima County.
"A killing frost will reduce the likelihood of further cases for the year," says Paul Kohrs, acting state veterinarian at WSDA. "Horse owners in areas of the state where this disease will overwinter should consider vaccinating for West Nile in 2014 at least a month before the onset of the mosquito season.
Mosquitoes vector West Nile disease after feeding on the blood of infected birds. The disease can also strike humans, but is not known to spread from horses to people or other animals, according to researchers.
Already this year, there have been 1,135 confirmed cases of human infection with West Nile virus nationally, a situation which has caused health agencies to urge caution in mosquito areas, and to assure that standing water in which they lay eggs is emptied. Particular attention to control mosquitoes is urged in the spring and summer months.
West Nile is fatal to horses in about a third of confirmed cases. Animals stricken by the disorder may not display signs of illness. Horses that do exhibit symptoms show loss of coordination and appetite, confusion, fever, stiffness and muscle weakness.