Hot weather and drought are likely to blame for a resurgence of a natural and usually fatal disease among Southern Oregon's black-tailed deer herds.

Hot weather and drought are likely to blame for a resurgence of a natural and usually fatal disease among Southern Oregon's black-tailed deer herds.

Oregon Department of Fish and Wildlife biologists have evidence of at least 56 blacktails in Josephine and Jackson counties succumbing to the adenovirus since June.

In addition, another two dozen fawns in a rehabilitation center in Josephine County either died from the virus or were euthanized after showing signs of suffering from the virus, according to the ODFW.

This is the third year since 2009 that the disease has popped up among migratory and local, so-called "city deer" in the region and perhaps the largest since 2002, when more than 1,000 blacktails likely died from adenovirus.

The die-offs could end up large enough to cause regional impact to upcoming fall deer-hunting seasons, says Mark Vargas, the ODFW's Rogue District wildlife biologist.

"It could be drought and it could be hot weather, but in the really hot years it's worse, without a doubt," Vargas says.

"We just really hope we don't see a big die-off in these animals," he says. "But it really is all over."

The virus can spread easily — such as breathing air from an infected animal — so water buckets and grain piles placed by well-intentioned landowners can turn into viral hot spots that can kill groups of deer in days.

"That's why we don't encourage people to feed and water deer," Vargas says.

But drought years like this one can also cause deer to congregate around what natural sources of food and water are available to them, thereby exacerbating the outbreak outside of human interference, Vargas says.

First diagnosed in Northern California in the mid-1990s, adenovirus hemorrhagic disease is believed to have been responsible in the late 1980s for killing hundreds of deer whose deaths originally were attributed to a different disease known as blue tongue.

Along with 2002's outbreak, smaller outbreaks occurred locally in 2009 and last summer.

Infected deer can suffer from bloody diarrhea that can scour the animal or cause mouth lesions that keep it from feeding.

In some cases, the deer suffer massive internal hemorrhaging. In other cases, field necropsies have revealed a liter or more of liquid in the lungs of infected animals.

Humans and pets are not considered vulnerable to the virus. While similar strains of adenovirus affect cattle and sheep, there are no known instances of the virus spreading from deer to other species.

Vargas says biologists want to hear from landowners who find dead deer, but agency biologists will not test all the carcasses or remove them.

People who find dead deer should either take them to the landfill or bury them, Vargas says. If the deer are found inside city limits, residents should call their city public works department, he says. The number for Ashland is 488-5587.

Vargas says he would like to hear about such circumstances; call him at 541-826-8774.

Reach reporter Mark Freeman at 541-776-4470 or Follow him at