EMPORIA — Late August through early October is a time when people occasionally see sick and dead deer and wonder what is happening. The disease most often associated with these losses is a virus called hemorrhagic disease (HD). It is caused by a virus, and it is transmitted to deer and other ruminant animals by biting midges. People and their pets are not affected by this virus, and the disease stops in the fall after cold weather kills the midges.
The Kansas Department of Wildlife, Parks and Tourism (KDWPT) is asking anyone who sees a sick or dead deer to contact local KDWPT staff and report where and how many deer are involved. So far this year, KDWPT has received reports from 12 counties in eastern Kansas, and most of these reports involve a single sick or dead deer. Samples have been submitted to the Southeastern Cooperative Wildlife Disease Study at the University of Georgia. Initial results from two cases confirmed that the virus involved in this year’s cases is epizootic hemorrhagic disease virus (EHDV), serotype 2. (A serotype is a distinct variation within a subspecies of the virus.)
There are two related viruses that may cause HD; epizootic hemorrhagic disease virus (EHDV) and bluetongue virus (BTV). In the US, there are multiple serotypes of both EHDV (EHDV-1 and -2) and BTV (BTV-2, -10, -11, -13, and -17). Although all of these viruses can cause HD, the virus and serotype most often associated with death of deer is EHDV-2. Both BTV and EHDV infect cattle, but in North America, clinical disease in infected cattle is rare and generally mild. Sheep are not affected by EHDV, but severe disease can be caused by BTV. Midges can carry both viruses and feed on many species of ruminants, and the viruses may produce a variety of symptoms in deer.
When HD occurs, people normally find sick and dead deer along streams or near ponds. Midges reproduce in stagnant water, and deer are often found near those sites in the late summer. Deer with HD frequently have a high temperature and allow people to get very close to them. The deer may be standing or lying down, and they occasionally have an open mouth with their tongue hanging out and swollen.
The clinical signs of HD in deer can be highly variable depending on the virulence of the virus in a particular location or year and the susceptibly and immunity of the deer herd.
In late August, sick Kansas deer have responded severely to the disease. These animals will generally die within a couple days after they first show symptoms. That does not mean that all deer infected with the virus will die. Some deer will not show any symptoms, and their immune system will produce antibodies for this virus. Those antibodies give the deer protection from the disease in future years. Other deer will survive the initial problems with the virus but still develop chronic hemorrhagic disease.
The chronic signs typically observed by hunters in the winter or by people who encounter a sick deer in the spring include fever rings on the hooves (cracked or sloughed hooves on three or four feet) and emaciation. Thin deer are generally the result of the disease’s effects on the lining of the rumen (a digestive organ similar to a stomach in other animals). Those animals have no ability to digest food. Chronic HD can further lower the immune response of deer and leave them vulnerable to bacterial diseases such pneumonia.
What can be done about HD? There are no effective treatments or vaccines for HD. Even if there were, it would be nearly impossible to treat enough wild deer to have any effect on the annual outcomes of this disease. Some individual deer have high levels of immunity to the disease. Deer in western Kansas generally have antibodies for various serotypes of HD, and a significant die-off in that area is rare. Deer in eastern Kansas generally do not have antibodies for the disease, and when events like the one this year occur, there can be high numbers of sick and dead deer.
The best advice for people concerned about HD on their land is to make sure deer are not concentrated at feeders and that they are not being fed high levels of corn, which may lower their ability to mount an immune response if they become infected.
KDWPT will monitor the spread and extent of HD this year.
“HD probably occurs to some extent every year in Kansas,” explains Lloyd Fox, big game program coordinator for the agency. “Occasionally, there are years when the disease causes high mortality. This disease has been known to kill as many as 10 percent to 50 percent of a local deer herd. The department adjusts future management, such as antlerless-only seasons and numbers of permits, as a result of those events.”
Fox explained that HD is a traditional disease of deer, and while there may be high numbers of dead deer in a particular area, the deer herd will generally repopulate the area within a few years.