Tuesday, July 31, 2012

Drought-driven EDH threat concerns Ohio's deer managers

The drought-driven Epizootic Hemorrhagic Disease (EHD) that is killing deer as far north as Michigan’s Iona and Branch counties may very well yet set its sights on Ohio.

EHD is a typically fatal viral disease. It is found in wild ruminants like deer, causing extensive internal bleeding and is transmitted solely by a midge, a flying critter about the size of a course-ground black pepper flake.

A characteristic of the disease is its sudden onset. An infected deer loses its appetite and fear of humans, grows progressively weaker, salivates excessively, and finally become unconscious.

Due to an accompanying high fever, an infected deer is often found sick or dead along or in bodies of water.

Importantly, biologists also say, there is no evidence that humans can contract the EHD virus.

Mike Tonkovich, the Ohio Division of Wildlife’s white-tailed deer management administrator, says the threat of EHD showing up in Ohio’s deer herd is very real; and just as disturbingly, comes with a calling card of too-many unknowns.

“There’s a lot about the disease that we don’t know, like how the virus over-winters, and how is it maintained in nature,” Tonkovich says. “I’m holding my breath, hoping that we don’t see the virus, but I wouldn’t be at all surprised if we do.”

A key issue is that world-wide there are 1,200 midge species, and though they are not all here in the U.S.,

“We probably don’t know all of the species that are capable of transmitting the virus,” Tonkovich says.

The thing is, too, Tonkovich says, there has not been a “whole lot of research into midges.”

“There’s still a great deal we don’t know,” Tonkovich says.

And since midges are so tiny, winds can carry them aloft and send them many miles away. Such transmission means that a virus-carrying midge in some southern Ohio county could find itself sucking blood out of a Northeast Ohio deer in a matter of just days, Tonkovich says.

The previous serious EHD outbreak that happened in Ohio were in 2005 and 2007, Tonkovich says.

“So we may be due,” Tonkovich says.

Tonkovich says as well that an EHD outbreak typically occurs later in the summer, as was the case in 2007 when the disease began showing up around Labor Day.

Why late summer is prime EHD time is best explained thus; as pools of water dry up the deer concentrate around what limited water is still available, Tonkovich says.

“That is where the adult midges hang out, looking for their next blood meal,” Tonkovich says.

With that being said, not every deer that contracts the disease will die, though the mortality rate is high: “Up to 80 or 90 percent,” Tonkovich says.

Unfortunately, also says Tonkovich, science has not discovered protocols or any methodology that can arrest the spread of an EHD outbreak. It must simply run its course, Tonkovich says.

Consequently, on a local level, EHD could have a significant impact on the number of deer that hunters will see come autumn, Tonkovich says.

Beyond that limited sphere, there is less to worry about, says Tonkovich.

“Will it show up in this year’s overall deer harvest?” Tonkovich said rhetorically. “On the grand scale of things, ‘no.’”

- Jeffrey L. Frischkorn
Twiter: @Fieldkorn

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