From Deseret News archives:
W. Nile is confirmed in additional 16 horses
That brings the total to 24, compared to last year's five confirmed equine infections.
At press time, the department had the addresses of the horse owners and it was being assumed the animals were kept nearby. Seven were in Utah County, four in Salt Lake County, two in Weber County, and one each in Uintah, Duchesne and Washington counties.
The virus cannot be transmitted from horses to humans. Rather, certain types of birds serve as a reservoir and when mosquitoes bite them, the insects become infected and can carry the virus to horses, chickens and humans they bite. In areas where horses are being infected, people are at risk, too.
It's not too late to have horses vaccinated against West Nile to get at least limited benefits this season, said state veterinarian Mike Marshall. If this year is typical, mosquitoes will be a concern for another month or so. "We get 80 percent of our West Nile cases in August and September."
Last year, 160,000 doses of equine vaccine were sold in Utah. Typically, a horse gets the vaccination, followed three weeks later by a second dose, then an annual booster, Marshall said. There are about 250,000 horses in Utah. How many have been vaccinated this year won't be known until numbers are tallied at the end of the season.
The infection has also been found in horses in Wyoming, Colorado, New Mexico, Arizona, Nevada, California and Idaho.
Horses are hard-hit with an encephalitis that affects their central nervous system, according to department spokesman Larry Lewis. The most typical symptom in a horse is weakness, indicated by a widened stance, stumbling, leaning to one side and toe dragging. Severely afflicted horses may be paralyzed. Other symptoms include depression, fearfulness and sometimes fever.
About a third of the horses with symptoms die.
Although the vaccination takes about five weeks to be fully effective, Marshall said, "if I had an unvaccinated horse, I would vaccinate it right now. I believe it does help to some degree, thought there's not good immunity for a while."
Usually the very young and very old get sickest, he said, but it can strike any horse. And even those that survive usually show some neurological effects, Marshall said. "Tics or chorea, involuntary movement of the leg that shakes all the time and (the animal) can't control it. Those that live through it quite often wind up with some neurological problem. Then there's the question, 'Do I want my 15-year-old daughter on that horse?' "
