Outbreaks of epizootic hemorrhagic disease or blue tongue always worry hunters, but these deadly diseases rarely set back a population long. Learn more about how deer are affected — and if there’s anything hunters can do.
Despite the seriousness and spread of CWD, there remains one fatal disease that continues to wallop whitetails along with affecting the men and women who hunt them. Though it is predominantly an issue in the South, it can loom North — devastating herds of whitetails…
It’s late summer and, with bridled excitement, you continue to check the food plots and trail cams — monitoring a bachelor group of velvet antlered bucks.
But today, they seem to have vanished for no apparent reason.
Coyotes haven’t been running the property, so where have the deer gone?
Even the does are sparse — only one here and there.
Finally, you spot a few vultures circling overhead near a creek basin. Within moments, you locate several whitetails along the water’s edge.
Unfortunately, the deer are quickly decomposing — confirming your worst fears.
Fortunately, you haven’t witnessed an outbreak of chronic wasting disease —CWD has not been documented in Mississippi.
Instead it’s likely you have found evidence of a predominantly Southern disease commonly known as epizootic hemorrhagic disease (EHD).
Back in 2007, a large outbreak of EHD unfolded throughout the country — causing the death of several thousand whitetails.
In the Carolinas, Georgia, Tennessee, Kentucky, Indiana, Illinois, Ohio and Maryland, as well as 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 was dramatic. Scores of outdoorsmen and landowners discovered the remains of many whitetails.
Wildlife biologists with state agencies reported that it was one of the worst years since 2002’s EHD epidemic.
Though most outbreaks are not severe, occasionally it hits hard enough to adversely affect hunters — limiting harvesting opportunities for a season or two.
While whitetails do rebound from EHD outbreaks, a disturbing trend could be on the horizon.
Recent studies have shown that if deer numbers drop too low through disease, harsh winters or other means like liberal antlerless harvest, fawn recruitment can struggle.
In other words, it becomes difficult for a natural surplus of newborns to work back into the population if the region has a sufficient number of predators like coyotes.
This cycle is referred to as the “predator pit.” When the pit takes hold, predators like coyotes, bobcats and bears can seriously hinder and even stop the deer population from rebounding to its previous numbers.
The analogy is like getting your haircut and having it consistently trimmed to where it never grows back to its original length.
Where deer densities have been historically high, disease outbreaks like EHD in conjunction with the predator pit could actually benefit both deer and hunters in balancing the herds to a healthy population. But where whitetails are less prolific, EHD outbreaks combined with liberal antlerless harvest and predators can undoubtedly minimize future hunting opportunities.
This is especially true for some public lands where large numbers of hunters are competing for a limited number of deer.
Studies conducted by the Southeastern Cooperative Wildlife Disease Study have determined that Southern deer have, in some cases, developed antibodies to EHD — which minimizes the die-off for deer herds.
Despite these antibodies, overall, the disease is still fatal — periodically affecting large portions of whitetail herds.
So how does EHD run its course? What enhances it, and are symptoms obvious or not?
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 blue tongue.
These viruses are powerful agents that cause internal bleeding. The viruses affect blood platelets and is believed to cause internal ruptures referred to as hemorrhaging.
Some whitetails infected with EHD might not even show symptoms, while other deer quickly manifest signs of sickness.
Simply, the virus is highly variable — and, surprisingly, there are cases where some deer actually survive EHD and build up an immunity.
Research and on-hand observations have shown that symptoms do vary, but typically they are as follows: sluggish behavior, and an enlarged head, neck and particularly the tongue, which is known to hang out from the mouth.
Deer might also exhibit respiratory problems. Deer are known to release saliva and mucous from their nasal passages, and occasionally blood can be seen.
Of course, a deer’s lack of mobility and the neglect of eating are other indicators that EHD might present.
Severe stages of EHD also reveal emaciation with the body and lesions or ulcers on the tongue.
Of course, cases can be mild to chronic.
Once the hooves of a whitetail peel, the disease is at a serious stage. Yet because the majority of EHD is internal, sometimes symptoms are not even noticeable until it is too late.
Although EHD is more likely to occur with high deer densities and hot, dry weather, that isn’t law.
Research biologists have determined the disease can manifest with normal to abundant rainfall as well as in deer herds whose population densities are properly balanced.
But one aspect that holds true is that EHD tends to strike from late summer to early fall. Once the first frost occurs, then the tiny, biting flies that carry the viruses are no longer a threat.
Without advocating global warming, some biologists are concerned that as warmer temperatures prevail — especially into the fall and winter months — insect carriers of the disease will be active longer. In turn more numbers of whitetails could be adversely affected.
Also, EHD is notorious for striking a region hard and then returning several years later — although usually not as harshly.
If EHD is suspected in a herd, the only way to really know is to have a biologist or a wildlife veterinarian examine carcass.
Many other deer diseases can cause minor but similar symptoms to EHD because the disease affects each deer differently.
Even so, the most-common warning signs of EHD are a sudden loss of deer on a property or lease; within just a few weeks, the visibility of whitetails can diminish.
The infected animals will seek water and can be found near water sources. Yet if predators such as coyotes roam the area, determining the actual cause of death can be difficult. Coyotes are quick to scavenge a deer carcass — at times just leaving a few bones.
Can EHD negatively affect a deer population? Scientific studies show that EHD usually accounts for roughly a 25-percent mortality rate in a localized deer herd, but on rare occasions half of the deer population can succumb to the disease.
To date, humans are not at risk for contracting EHD, even after consuming infected venison. However, most state agencies recommend not eating infected deer due to various bacterial infections secondary to the disease.
Therefore, if you suspect a deer you’ve harvested has EHD, contact your local state wildlife agency for assistance.
So what can be done to curtail this persistent plague on wild free-ranging whitetails?
For the most part, all one can do is to allow nature to takes its course. However, by intensely monitoring deer numbers, biologists and managers can regulate harvest quotas.
So once EHD strikes a specific region, deer manages can limit the number of deer taken until the herds recuperate, taking into consideration predators.
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