Mar 29, 2025 4 min read

By Dave Bates

For the Observer-Reporter

newsroom@observer-reporter.com

If you have been hunting whitetail deer in Pennsylvania for any amount of time, you are likely familiar with the term Epizootic Hemorrhagic Disease, commonly referred to as EHD. According to the official site of the Commonwealth of Pennsylvania, Hemorrhagic Disease, or some form of similar disease, has been reported as far back as 1890.

Across the board, Hemorrhagic Disease (HD) in general can be caused by two viruses: Epizootic Hemorrhagic Disease (EHD) and Bluetongue Virus (BT). The EHD virus was isolated in an outbreak in New Jersey in 1955. In Pennsylvania, Hemorrhagic Disease has only been found to be spread in Epizootic Hemorrhagic virus form.

How exactly does EHD manifest itself in the deer population? While EHD is one of the more common diseases found in whitetail deer in the eastern United States it does not appear to affect humans. It can, however, cause widespread deer deaths during outbreaks. In our Southwestern Pennsylvania region, whitetail deer are the primary victims of EHD. Species more commonly found in the western United States, such as pronghorn antelope and bighorn sheep, can become infected with EHD, as well. Elk do not seem to be as susceptible, according to scientists, but cases have been reported. EHD in Southwestern Pennsylvania stems back to 1996 (undocumented) but documented cases in 2002, 2007 and 2012 have been recorded in our region.

Greene County Game Warden Brandon Bonin said “Hundreds of dead deer were observed in our area last year, likely due to EHD. It was a bad year for EHD.”

As per the official Commonwealth site, “The EHD and BT viruses are both transmitted by biting flies or midges in the group called Culicoides. Female midges pick up the viruses by ingesting the blood of an infected animal and they then transmit the viruses when they feed on an uninfected animal. Midges are found near mud, which is their preferred breeding habitat, so outbreaks usually occur when deer congregate in wet areas at the driest part of late summer and early fall, when seasonal midge activity is also at its peak. They end when the first hard frosts take their toll on the midges and the virus dies with the insects.

The species of Cullicoides that is considered the primary vector of EHD is not thought to normally occur in Pennsylvania, but is occasionally brought into the state on wind currents. As a result, Pennsylvania deer do not have any immunity to the virus because outbreaks usually occur at intervals which are longer than the average deer’s lifespan. This lack of immunity explains the high mortality rates during EHD outbreaks in Pennsylvania.

Once deer are infected with EHD, symptoms usually begin to appear within seven days, however, some animals remain asymptomatic. Signs of EHD can include, but are not limited to, swollen face and or neck, lethargy, weakness, fever, respiratory distress, foaming at the mouth, lameness, mouth ulcers, bleeding from the nose/mouth, swollen, blue tongues, etc.

Infected deer tend to die in about eight to 36 hours, revealing extensive hemorrhaging from major organs, hence the EHD moniker. There is currently no treatment or cure for EHD.

Logically, concentrations of deer tend to exacerbate the problem of disease spread. While well intended, the feeding of deer is discouraged because the increased deer contact found around feeding sites can lead to higher levels of interaction with the aforementioned midge. Feeding deer might have quite the exact opposite effect that is intended. That is to say, feeding may increase the number of incidents of the disease.

While the science is indeed sad, watching an animal suffer from this malady is a truly pitiful thing. I have witnessed deer suffering from EHD with no will to move, head supported by a fence rail. Watching them lean on a tree, attempting to hold themselves upright was heartbreaking. The only thing sadder is discovering the trail of resultant dead carcasses lining a stream bank and unfortunately it is not difficult to follow the stench up the valley with one’s nose.

Let’s do all we can as sportsmen and women to keep this awful disease at bay when and wherever possible as scientists continue to search for a means to combat the disease.

The website of the Commonwealth of Pennsylvania can be accessed for further information.

Dave Bates writes a weekly outdoors column for the Observer-Reporter. He can be reached at alphaomegashootingsolutions@gmail.com