EHD On The Radar

Despite the seriousness and spread of Chronic Wasting Disease (CWD) in some parts of the country, there remains another fatal deer disease that continues to wallop whitetails at least to some degree almost every late summer and early fall. This other disease primarily affects deer in the South, where whitetails develop some immunity to it, but it can also loom large in Northern and Midwestern states, even out West, where it has devastated herds of whitetails in some of the nation’s most famous whitetail hunting grounds.

This disease is widespread and unforgiving, and some years it hits local whitetail populations with a vengeance.

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It’s early autumn as the deer season nears. With bridled excitement, you continue to check the trail cams and watch the evening parade of velvet antlers in your food plots, monitoring a bachelor group of bucks. Yet now they seem to have vanished. You’re confident that coyotes haven’t been running the property, so where have the deer gone? Even the does are sparse this evening on your food plot.

Then you spot the vultures circling overhead near the creek. To your dismay, you soon locate the carcasses of several whitetails along the water’s edge, including several of the nice bucks you’ve been watching progress all summer.

What killed them? It surely couldn’t be CWD, which has never been confirmed in Georgia.

Before long your calls to DNR help you determine that the deer were not victims of CWD or predators. Instead, they have fallen prey to hemorrhagic disease, either a strain of EHD or a very closely related virus called bluetongue.

Deer that recover from EHD may have cracked or sloughing hooves. Other factors can adversely affect deer hooves, and a pathological examination is the only reliable way to determine if EHD was present. Photo by Dr. Kevin Keel, Southeastern Cooperative Wildlife Disease Study.

Most experts will tell you EHD or bluetongue won’t have a significant impact on a deer population over a large area. That’s no consolation if it hits hard on your hunting property, especially when you start finding big bucks dead by the creek and realize that this disease affects and kills older, mature deer at a much higher rate, especially mature bucks.

This year, EHD began hitting eastern Kentucky and eastern Tennessee fairly hard in August. As a professional wildlife photographer, I spend countless hours in the woods and saw the eastern Tennessee outbreak firsthand. The reports from Kentucky are growing. Then Ohio started to get EHD reports, and so did western Pennsylvania. Those early reports in August indicate that those outbreaks could be serious.

Fortunately, at the time this article was written in late September, Georgia hadn’t experienced severe or widespread reports of EHD.

Georgia’s state deer biologist, Charlie Killmaster, said, “We’ve received a few reports of mortalities in northwest Georgia, the area of the state with the lowest innate immunity, but it’s hard to say what kind of year it might be. All the rain from the hurricane could have slowed an outbreak—all the reports I’m aware of were in the dry spell before the hurricane.”

If history repeats itself here, then this disease will run its normal course without hitting Georgia deer too badly. Although some southern deer may get hit, outbreaks should not be severe—only sporadic and not intense. Let’s hope.

A Brief History Of EHD

In 2007, parts of the country experienced one of the worst outbreaks of EHD ever. In the years since, this disease has been impacting more northern regions and the Midwest.

The state of Michigan didn’t dodge the bullet with EHD, and in recent years, cases there have been on the rise. Although EHD has historically been sporadic for Michigan, since 2000 it has gone from mild to severe. In 2009, south central and southwestern portions of Michigan lost an estimated 450 deer. In 2010, there was a die-off of roughly 1,025 deer. Then came 2012. In these same regions of Michigan, the loss to EHD was estimated at 11,000 whitetails—a significant rise.

Parts of eastern Montana were devastated by EHD in 2011. Estimates are that at least 90 percent of white-tailed deer in eastern regions of Montana were affected. The famous Milk River region of Montana, seen for decades featured on famous hunting shows, lost virtually all of its giant, mature bucks in an EHD outbreak.

Back in 2007, the outbreak of EHD unfolded throughout the country. From Georgia to the Carolinas, Alabama, Tennessee, Kentucky, Indiana, Illinois, Ohio, Maryland and many other states, hemorrhagic disease was intense and widespread.

Although EHD kills a certain number of deer each year and is usually sporadic, the summer of 2007 wasn’t sporadic—it was dramatic. Scores of outdoorsmen and landowners discovered the remains of whitetails, and big bucks were hit hard.

The Predator Factor

Beginning in the 1990s, there was an aggressive promotion to shoot more does in the South. In fact, around the turn of the century, some game agencies and deer-hunting organizations were claiming that hunters literally couldn’t shoot too many does.

Even though numerous deer habitats did need liberal doe harvest, foresight wasn’t on the table. It wasn’t long until some hunters starting seeing a decline in deer numbers, and fawns became few and far between. Yet, wildlife agencies continued to allow record numbers of female deer to be harvested. A factor that wasn’t anticipated was the impact coyotes, combined with other predators like bobcats and black bears, could have on deer mortality.

It wasn’t until the folks at GON and AON magazines did their homework and broke the stories of new Auburn University research that attitudes of relentless doe harvest began to change. That research, based in part on studies at Fort Rucker, showed that high antlerless harvest in combination with predators could drive deer populations down to a level so low that predators wouldn’t allow the herd to recover, even if future deer harvest was eliminated completely. The term for this is called a “Predator Pit” scenario. This was the warning call to be much more selective in doe harvest, and to definitely not take deer populations for granted. When a Predator Pit takes hold, coyotes, bobcats and black bears can stop a local deer population from rebounding to its previous numbers. The only way out is control of the predators and very conservative to no harvest of does.

Coyotes are not native to Georgia, and southern deer are still adapting to these predators. Research shows that coyotes will impact your fawn recruitment—and in many cases dramatically. Hunters and land managers must monitor deer numbers and fawn recruitment closely.

If predators aren’t being controlled and your fawn recruitment is very low, and if antlerless harvest is not moderated, an EHD outbreak could have dramatic impacts.

Although a local whitetail population will certainly recover from an EHD outbreak, the recovery time may lag if predator impacts are severe or doe harvest has been too liberal. Of course, there are also the unknowns, and sometimes EHD will wallop a deer population so hard that having good doe numbers will not really matter. Despite this reality, managers and hunters ought to be preparing for the worst with the hopes to minimize the impacts of a bad EHD outbreak. They can do that by trying to maintain an adequate number of reproducing females to make it through the impacts of predators and other environmental extremes like drought or poor food production years.

Some years may allow for a moderate doe harvest, while other years would require a more conservative approach to harvesting female deer.

An important part of preparation and proper management is to aggressively go after predators like coyotes. This approach was publicly advocated by the folks at Georgia Outdoor News in their annual Coyote Cull contest.

EHD And Its Symptoms

Studies conducted by the Southeastern Cooperative Wildlife Disease Study have determined that southern deer, in some cases, have developed antibodies to EHD, which minimizes the die-off from infected herds. Up north, the picture is different where there is less immune resistance to the disease, and a larger portions of a herd will fall prey to this disease during an outbreak. Southern deer have developed some antibodies to certain EHD strains, but the disease can still be fatal, periodically effecting large portions of whitetail herds in the South.

So how does EHD run its course? What enhances it, and are symptoms obvious?

Although there are several viral strains in the hemorrhagic classification, the two most common types affecting whitetails are referred to as EHD (epizootic hemorrhagic disease) and BT (bluetongue). These viruses are powerful, causing internal bleeding. The virus affects blood platelets and is believed to cause internal ruptures, known as hemorrhaging.

Some number of whitetails infected with EHD may not show symptoms, while other deer are fast to manifest signs of sickness. Simply, the virus is highly variable. In the South, there are often cases where deer survive EHD, building up an immunity to it.

Research and my personal observations indicate that EHD symptoms vary, but typically they include sluggish behavior, and an enlargement of the head, neck and particularly the tongue, which often hangs out from the mouth. Deer may also exhibit respiratory problems. Deer are known to release saliva and mucous from their nasal passages, and occasionally blood can be seen. A deer’s lack of mobility and not eating are other indicators of EHD. Severe stages of EHD also reveal emaciation of the body and lesions, or ulcers, on the tongue.

Cases of EHD can range from mild to chronic. Deer that are exposed to the EHD virus but do not die from the illness may show growth deformities and peeling of the hooves. Yet, because the majority of EHD is internal, sometimes symptoms are not even noticeable until the final stages.

Environmental Conditions

You’ve probably heard that EHD might be more likely to occur with hot, dry weather and with deer herds that are overpopulated, but that isn’t always true. Researchers have determined that the disease can manifest with normal to abundant rainfall, as well as in deer herds where population densities are properly balanced. Yet, it holds true that EHD tends to strike from late summer to early fall. Once the first frost occurs, the tiny biting insects that transmit EHD to deer are no longer a threat.

When warmer temperatures prevail later into the fall and winter months, the insect carriers of the disease will be active longer. In turn, more numbers of whitetails could be adversely affected.

Detecting EHD

If EHD is suspected in a herd, the only way to really know is to have a biologist or a wildlife veterinarian examine a carcass. Many other deer diseases can cause minor but similar symptoms to EHD, simply because the disease affects each deer differently and degrees of infection can range from mild to severe.

Even so, the most common sign of EHD is a sudden loss of deer on a property. Within just a few weeks, the visibility of whitetails can diminish. The infected animals will seek water and can be found near water sources. Some hunters periodically walk creek basins and watershed tributaries to scout for dead deer if EHD is suspected. Yet, if predators such as coyotes roam the area, then determining the actual cause of death could be difficult, and even finding a carcass can be easier said than done. Coyotes are quick to scavenge.

So, to what degree does EHD alone affect a deer population? Scientific studies show that an EHD outbreak can account for roughly a 25 percent mortality rate of a localized deer herd, but on rare occasions, half of the deer population can succumb to the disease. Here again, add in predators and other environmental factors, and EHD can have more of an impact.

Humans are not at risk for contracting EHD, even after consuming venison of infected animals. However, most state agencies recommend not eating infected deer due to various bacterial infections secondary to the disease. If you suspect that a deer has EHD, contact your local state wildlife agency for assistance.

By all means, EHD is nothing to take lightly. Although CWD is a devastating disease and something we hope to never see in Georgia, EHD currently affects more hunters and land managers. It is not just the loss of a natural resource and the added frustration for poorer hunting prospects, but EHD has financial impacts, as well.

Confronting EHD

So what can be done to curtail this persistent plague on wild, free-ranging whitetails? There are no measures that can prevent an EHD outbreak, and once it hits, all one can do is to allow it to take its course.

What should be done is a close monitoring of your deer herd prior to an EHD outbreak. Are you seeing fawns? Are you doing anything to control the impacts of coyotes? Poor acorn crops or drought negatively impact nutrition. The impacts of predators or severe poaching need to be weighed before EHD strikes. An analogy would be like preparing for a natural disaster, hoping to minimize a catastrophe and survive the elements. Yet despite all our stewardship of the land and careful management, this disease is still so unpredictable and powerful that the hunting industry is at the mercy of God that a local herd will not be decimated—just ask the property owners along the famous Milk River in Montana.

Although whitetails are highly adaptable and resist a horde of diseases and parasites, hemorrhagic disease should not be taken lightly.