July 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 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 phone local KDWPT staff and report where and how many deer are involved. To help identify the extent of the disease, an online survey is also available for people to report fresh or decomposing carcasses. The public survey can be found at surveymonkey.com/s/WHZKVNS.
So far this year, KDWPT has received reports of dead or sick deer from at least 24 counties in northcentral and eastern Kansas. These counties include Jewell, Cloud, Cherokee, Shawnee, Clay, Washington, Wilson, Doniphan, Jackson, Miami, Franklin, Crawford, Labette, Linn, Douglas, Osage, Wabaunsee, Pottawatomie, Lyon, Riley, Anderson, Bourbon, Dickinson, and Marion. Most of these reports have involved a single sick or dead deer, with occasional reports of multiple mortalities.
Test samples can be taken from deer if the carcass is found soon after death. Samples are submitted to the Southeastern Cooperative Wildlife Disease Study (SCWDS) at the University of Georgia to determine cause of death and occurrence at the county level. Recent results from a case in Wilson County confirmed the epizootic hemorrhagic disease virus, serotype 2 (EHDV-2), a variation within a subspecies of the virus.There are two related classes of viruses that may cause hemorrhagic disease — epizootic hemorrhagic disease virus (EHDV) and bluetongue virus (BTV). The virus and serotype most often associated with death of deer in Kansas is EHDV-2.
Both BTV and EHDV infect cattle, but in North America, clinical disease in infected cattle is rare and generally mild when it does occur. 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 nutrient-rich substrate near stagnant water, and deer are often found near those sites in the late summer. Deer with HD frequently have a high temperature and may seek cool water. They also often allow people to get very close. Sick deer may be standing or lying down, many times right in water, 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. The virus can damage the deer’s blood vessel lining, which can result in leaking blood vessels and an accumulation of blood and fluid in tissues. This hemorrhagic appearance gave rise to the name for this disease.
This year many deer are responding severely to the disease. These animals will sometimes die within a couple days after they are first infected by the midges. 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 can give the deer some protection from the disease in future years. Other deer will survive the initial infection, only to develop complications from tissue damage during the early stages of infection, a form known as chronic HD.
The chronic signs of HD 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 a decreased ability to effectively digest food. Chronic HD can further lower the immune response of deer and leave them vulnerable to bacterial diseases such pneumonia. The virus itself is not a threat to people, but deer with bacterial infections are unfit for consumption.
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 EHDV and BTV, and a significant die-off in the western two-thirds of the state 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 deer are not being fed high levels of corn, which may lower their ability to mount an immune response if they become infected. KDWPT will continue to 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 KDWPT. “Occasionally, there are years when the disease causes high mortality. The department adjusts future management, such as antlerless-only seasons and numbers of permits, as a result of those events.”
Fox explains 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.
Logo courtesy of the Kansas Department of Wildlife, Parks and Tourism