A major, and long-misunderstood killer of free-ranging whitetails is hemorrhagic disease. What is collectively referred to as hemorrhagic disease is actually two similar diseases — epizootic hemorrhagic disease and bluetongue virus. Both illnesses are spread by biting midges, commonly referred to as "no-see-ums." When one of these insects takes a blood meal from an HD-infected deer, it transmits the virus when it bites another deer.
Because the midges require warm weather to survive, HD is most prevalent in the Southeast, but it afflicts whitetails through much of their range from late summer through fall. In the acute, late-summer form, deer weaken and often die soon after transmission. An infected deer’s head and tongue swell, and its organs hemorrhage, especially the lungs. Infected deer are weak, disoriented, and run a high fever. As a result, they often seek water.
When an EHD epidemic hits, no deer is safe. In many cases, entire age classes — even the biggest deer — can be wiped out of the herd. In fact, that’s exactly what happened in some parts of Illinois and Indiana in 2009, and those areas are first now recovering from major losses of mature bucks. In cases like this, deer management can turn into a real balancing act between hunters’ desires and the herd’s best interests.
What’s more, during severe outbreaks, the disease can significantly lower deer populations across large regions. In 1976, for example, EHD killed off nearly 40 percent of Nebraska’s total whitetail population before the deer hunting season even started.
Although EHD outbreaks have traditionally plagued Southeastern states, the diseases have shown up as far north as Michigan in recent years. In fact, Michigan has reported outbreaks in nearly every decade since the first cases showed up in 1955.
For more Deer & Deer Hunting insights, check out Bob Zaiglin’s latest book, Whitetail Racks.