Sick deer in Athens County: historic outbreak impacts hunting season

Autumn’s chills, radiant sunsets and fantastic floral displays comprise a sensory experience that for many residents of southeast Ohio would not be complete without the taste of local game—especially white-tailed deer.

This year, however, deer season has been marred by a historic outbreak of a disease that is killing deer across the state: epizootic hemorrhagic disease. EHD can be fatal to deer and other ruminants, but is harmless to humans.

Though humans cannot contract EHD, deer may walk on their knees and develop secondary systemic or localized bacterial infections from abrasions, said Michael Tonkovich, Ohio Department of Natural Resources Deer Program administrator. This could pose a threat to people. A hunter could notice that a deer has severe EHD upon field dressing, as its body would be full of blood from collapsed blood vessels. 

Overall, the average hunter would “be able to know that there’s something wrong with (a) deer,” Tonkovich said. 

Reported sightings of sick and dying deer began rising in Athens County the week of Sept. 5-11, with 10 reports, according to ODNR data. The next week, Sept. 12-18, saw 35 reports. Reports peaked at 96 sightings the week of Sept. 19-25. The following week, reports dropped back down to 10, then to six, then five. Athens County’s last report occurred Oct. 14.

Despite the vast spread of EHD, this year’s outbreak isn’t necessarily more severe or fatal, Tonkovich explained. And a handful of counties are still without any EHD confirmations, he noted.

EHD follows some “seasonality,” Tonkovich said; dead deer reports start rolling in the late summer, historically around Labor Day. But reports from southwest Ohio came early this year—the second week of August, Tonkovich said.

“The degree to which it occurs, of course, varies from year to year,” Tonkovich said. This is due in part to the ODNR’s reliance on public reporting, he said; “If [people] don’t report, obviously we don’t know about them.”

Tonkovich noted that EHD “is relatively predictable; we’ve been seeing like a five-year cycle where it’s really bad. And I don’t know that that’s just pure coincidence or whether there’s actually something to it, but as it turns out, the last big outbreak that we had was in ‘17, so it’s not totally surprising that we had another one this year.”

What is EHD?

Epizootic hemorrhagic disease is a bloodborne virus spread through the bite of culicoides, commonly known as biting midges or no-see-ums. Along with chronic wasting disease, it is one of two major diseases of concern in Ohio deer, Tonkovich said. 

There are 10 known variations of EHD in the world, according to Cornell University. It is related to the bluetongue virus, which is also spread through the bite of a midge and affects ruminants. 

There are three forms of EHD, Tonkovich said. “Like many diseases, there’s the acute, which will kill the deer very, very quickly; the peracute, which is sort of in between; and then there’s the chronic form, where deer generally survive, but you’ll see symptoms of it.”

Clinical signs of EHD in white-tailed deer usually begin within a week of infection, according to Cornell. They may eat less, develop ulcers, weaken or lose their fear of humans. They often experience fever and swelling of the head, neck, tongue and/or eyelids. The disease can kill deer in as little as eight to 36 hours.

“And it’s not a pretty death, unfortunately,” Tonkovich said. “Essentially, the virus wreaks havoc with the lining of the blood vessels, and so they begin to hemorrhage amongst other things, and so when that happens in the brain, you start to see [that] mental capacity is compromised—they’re walking in circles, they’ll be drooling, their heads will be hanging down.” 

Deer may also have seizures—or drown. A telltale sign of EHD is a dead deer near a body of water, where they seek relief from the disease’s high fevers. Tonkovich noted that this is a major difference between the physical manifestations of EHD as opposed to CWD.

“A deer that’s dying from late stage chronic wasting disease will lose body condition, look like skin and bones, as opposed to this hemorrhagic disease because it kills them so quickly,” he said. “They’re still very healthy looking deer.” 

Deer that do not die of EHD and recover will likely survive the next outbreak, said Dr. Dennis Summers, chief of the Division of Animal Health at the Ohio Department of Agriculture.

“Those that do survive, do tend to have pretty good immunity for a long period of time,” Summers said. “So the odds are if they make it through one season, they’re probably going to make it through subsequent seasons because the virus doesn’t really change that much.”

Outbreaks tend to end as the weather gets colder. “The disease usually goes away about two weeks after the first really hard frost,” Summers said, adding that frost prompts culicoides to enter a dormancy stage.

Once dormancy begins, fewer insects are out and about in the environment, Summers explained. 

“But the virus remains present in the environment through a deer that may have developed an immunity but still carries the virus,” Summers said. “Or, some of those viral particles will stay alive in the midges themselves when they go to their dormancy phase, and then it kind of pops up again in the spring. And so the cycle just kind of becomes repetitive.”

There is no way to mitigate EHD without “pretty damaging [ecological] intervention,” said Mark G. Ruder of the Athens, Georgia-based Southeastern Cooperative Wildlife Disease Study.

There are roughly 140 species of culicoides in the United States, and “which one or ones are implicated at causing the most infection in deer, we’re not quite clear on, or whether even the distribution of those certain species is changing,” Ruder said. 

What is changing, Ruder explained, is the annual life cycle of midges, and “how long they can come out and play in a given year.” 

Looking forward

Tonkovich estimated that EHD first appeared in Athens County in 2002. It has long been present in deer in the southern United States, he noted.

And “once [EHD] gets into an ecosystem, it tends to stay there,” Summers said.

EHD cases in the south have been declining “because [deer] have slowly over the course of decades developed some immunity,” Summers said. According to Cornell, EHD “causes high mortality in northern deer.”

“We haven’t had it that long [in Ohio],” Summers said. “We’ve had it for several years. But in terms of decades of disease every year, we are not there yet. We are still lagging behind in terms of the immunity within the wild deer population.”

EHD is “a part of life for deer,” Ruder explained. But from a wildlife management and research perspective, questions remain: “What does [EHD] mean for deer, especially in some of these northern areas? As this disease becomes more frequent on the landscape, how are the populations going to respond over time? Moving forward, we need to keep our finger on the pulse.”

For Tonkovich, “[EHD] will continue to occur, most likely every year and at some point, well after my career.” He suspects that Ohio deer will adapt, like deer in the south, because “Once you’re challenged enough, those that can survive it will pass that trait and build immunity.” 

And deer are prolific survivors, Tonkovich noted—evolving “under intense predation pressure.”

“Unfortunately, we’ve taken away most all of the predators, except for humans, and so they’re still reproducing at a rate that allows them to come back very, very quickly—double their population in three years. That’s pretty rapid.”