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West Nile Virus takes the lives of four Utah horses in a month

By Bronson Teichert

Sept. 22, 2016

Horse owners in northern Utah are scrambling to keep their animals safe from West Nile Virus following reports of six confirmed cases, resulting in four deaths, since Aug. 24.

Both conventional insect abatement protocols and unconventional methods are being used to prevent mosquitoes from spreading the virus, which is spread by mosquitos that turn standing water into breeding and hatching grounds.

Removing anything that holds standing water, including old tires, hinders population growth, according to Kerry Rood, a professor of veterinary health at Utah State University.

“Adding mosquito larvae-feeding fish to standing water,” is one way that might help drive down transmission rates. “In theory they would then reduce the mosquito hatch and you could keep some of those standing bodies of water.”

Diseases carried by mosquitoes, and particularly the Zika virus, have been widely discussed in the past year. But it’s West Nile that is prevalent and causing problems locally.

The first two cases of the virus were confirmed in a 4-year-old quarter horse and a yearling on Aug. 24, said state veterinarian Barry Pittman.

“A total of six horses have been confirmed with the virus,” he said, “and none of them were vaccinated beforehand.”

All six cases were from separate owners according to Pittman.

“Horses should be vaccinated annually for the virus.” Rood said. “Ideally the vaccine should be administered prior to mosquito season.”

Eighty percent of West Nile detected in horses occurs in August and September. Once vaccinated, yearly booster shots are required according to Rood. 

Traditional and well-tested actions can be taken by ranchers and farmers to protect their horses.

“An effective, affordable and safe vaccine is already available,” Pittman said.

On top of that, protective measures should include mosquito control and clean-up areas around barns and stables to minimize mosquito populations, he said.

Pittman said humans and horses are dead-end hosts. A dead-end hosts means that the virus will effect them and cause disease but the mosquito feeding on a person cannot go to another person and transmit the virus because not enough of it gets in the blood.

“Horses work also as an excellent sentinel," Rood said. "If your horse gets sick with West Nile Virus what does it tell you? There are mosquitoes that have the virus so you should be careful in your mosquito prevention."

“Approximately one-third of horses who show signs of illness will die,” Pittman said. “People who contract the virus will have flu-like symptoms and the virus will most likely just run its course without any future damage.”