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Humans, horses and birds see spike in West Nile virus cases in Utah

Posted at 10:46 PM, Sep 07, 2021

Health officials and veterinarians are warning the community about an uptick in West Nile virus cases among people and animals across the state.

The Utah Department of Health is reporting the highest number of positive West Nile virus mosquito pools ever seen in the state, according to a press release from the Department of Agriculture and Food.

READ: 6 human cases of West Nile Virus found in Utah

In addition to infecting people, mosquitoes are also passing the virus on to birds and horses.

This is the time of year that veterinarians like Dr. Lyle Barbour of Mountain Point Equine Hospital are making sure their four-legged clients aren't showing any telltale signs of West Nile virus.

"The staggering, stumbling, inability to rise, circling," Dr. Barbour listed off. "You see some other signs such as inappetence, lethargy."

A simple mosquito bite can cause neurological damage in a horse with an upwards of 33 percent chance of death, especially if the horse isn't vaccinated, he indicated.

"Horses that show clinical signs -- that have been diagnosed and have clinical signs -- a third of those horses aren't going to make it, even with treatment," he said.

That's why it's concerning that at least eight horses have tested positive for West Nile virus this season. UDOH is reporting six in the Weber-Morgan Health District, one in Salt Lake County, and one in the Bear River Health District.

While not reflected in UDOH numbers, the Utah Department of Agriculture and Food added that a seventh horse tested positive in Weber-Morgan as of September 7, bringing the total statewide number up to nine.

"This year is a little bit different. We have seen some more cases," Dr. Barbour said. While his clinic has not diagnosed any cases, it's something that the tight-knit community is talking about.

The spike isn't just worrisome for horse owners and veterinarians.

Salt Lake County Health Department Communications Manager Nicholas Rupp said they use cases in birds and horses as a barometer to determine how widespread West Nile infection and activity is in the community.

The Utah Department of Agriculture said that seven birds have tested positive for West Nile.

"The fact that we have a number of horses throughout the state, a number of birds throughout state confirmed have West Nile virus is concerning, because that means that there are a high number of mosquitoes in this vicinity who are infected with West Nile virus," Rupp said.

According to the latest UDOH numbers, 506 pools of mosquitoes have tested positive for West Nile Virus in Utah this season. Most of those pools-- 281-- were in Davis County. Salt Lake County saw the second highest at 192 positive pools.

So far, human cases sit at six across Utah. Rupp said five of those six are in Salt Lake County, with the remaining person living in Davis County.

In one of the five cases, the person suffered from West Nile fever, Rupp said. That involves a mild fever, headache, and body aches.

The other cases were more severe.

"Unfortunately, our other four of the five cases are what we call 'neuroinvasive,' which means that the virus has interfered with brain activity and those are very serious situations," Rupp said.

The neuroinvasive West Nile virus, Rupp said, can end in hospitalization and in rare cases, death. He said the four people infected are recovering from the neuroinvasive cases.

The good news is that 70 percent of people who contract West Nile virus never show symptoms at all, Rupp explained. He said people over the age of 50 or who have other conditions that weaken the immune system are at a higher risk of illness.

An EPA-registered mosquito repellent with DEET or IR3535, Rupp said, is the biggest way to ward off mosquitoes and cut down the likelihood of infection.

He also recommended draining or dumping any standing water on your property, keeping tall grasses and weeds short, and wearing pants at dawn and dusk when mosquitoes are most active.

For horses, Dr. Barbour explained that there's another way to prevent them from contracting West Nile virus.

"Vaccination is extremely crucial in the prevention of this disease," he said.

He said studies show the vaccine is 93-95 percent effective, and he recommended horse owners meet with their veterinarian to make sure their horse is protected.