White-tailed deer

White-tailed deer, which are found throughout Northeastern Oregon, are especially susceptible to the Epizootic Hemorrhagic Disease, which is spread by biting gnats.

PULLMAN, Wash. — There’s been an uptick in the number of Pacific Northwest white-tailed deer dying of viruses that typically infect more animals during hot summers and periods of drought, experts say.

The deer get the viruses after getting bitten by gnats that flourish when the mud underneath dried-up watering holes, where the insects live, is exposed, according to the Northwest News Network.

And in dry times, more deer gather around those holes in search of water and are more likely to get bitten by gnats, experts say. The tiny insects can live in puddles of water as small as a deer’s hoof print, according to the Oregon Department of Fish and Wildlife.

One virus is called epizootic hemorrhagic disease, or EHD, and the other is called bluetongue disease. They aren’t contagious to people and can’t pass from deer to deer. The spread usually stops after the first hard freeze, which kills the gnats.

In late August, the Baker City Herald reported that EHD killed eight deer in the Baker Valley in less than a week.

Increasing drought has made the viruses more prevalent this summer and fall, and that’s a concern as climate change makes hot and dry conditions more common, said Kevin Snekvik, of Washington State University’s animal disease diagnostic lab.

“Your population starts having more and more animals that are susceptible to the virus because they don’t have any immunity developed,” Snekvik said.

Kristin Mansfield, Washington state veterinarian, said she gets reports of suspected cases in the middle of August, and reports slow at the end of October.

“When I got the first report this summer, I looked at the calendar, and it was Aug. 16. My thought was, ‘Oh, boy. Here we go. Right on schedule,’” Mansfield said.

EHD almost exclusively affects white-tailed deer and can rarely affect domestic cattle. Bluetongue affects deer and bighorn and domestic sheep, she said.

In Washington, reports of diseased deer have come in from east of the Cascade Mountains, including Spokane Valley, Deer Park, Colfax and Davenport. Idaho Fish and Game has reported around 250 to 300 white-tailed deer died last month, including in the Kamiah and Clearwater areas.

Oregon is seeing an increase in deer mostly infected with EHD, said Colin Gillin, an ODFW veterinarian.

Oregon shut down hunting season in the Blue Mountains last year because an estimated 2,000 deer died of that virus.

“There weren’t any deer there to have hunters go out and spend their time on,” Gillin said. “You just really have to keep an eye on it and try to track it. There’s nothing you can do about it.”

This year, the department also had reports of diseased black-tailed deer in Central Oregon, which is a little unusual, Gillin said. The viruses more often affect white-tailed deer, he said.

“We’ve seen it more and more and more over the last 10 years, the more that we’ve had drought conditions increase,” Gillin said.

Snekvik said he’s also concerned about increased rates of other diseases, such as the West Nile virus, as summer conditions become more favorable for the mosquitos that carry the virus.

West Nile first arrived in the Columbia Basin. Now, it’s been found in North Idaho and near the Canadian border, he said.

“We’re seeing that over time, that virus moves farther north, probably because the mosquitoes are carrying it farther because they can survive up there,” Snekvik said.

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