There have been many recent reports of deer found dead throughout Missouri; many of these deer have been reported to have died from bluetongue, but in all likelihood, most of these animals were infected with a disease known as epizootic hemorrhagic disease, or EHD. This viral disease is potentially devastating to the white tail deer population both wild and captive, and can affect domestic ruminants.
Epizootic hemorrhagic disease (EHD) is caused by a virus in the family Orbivirus, and is related to the more commonly known Bluetongue virus that affects both wild and domestic ruminants. This disease occurs in many parts of the United States and has been diagnosed in parts of Canada. EHD is most prevalent in the late summer and early fall, when the population of biting midges, or no-see-ums, is highest. These small gnats of the genus Culicoides bite infected animals and spread the disease by biting another animal to transmit the virus.
Whitetail and mule deer are most affected, but elk, bighorn sheep and antelope can also be affected. Domestic cattle, sheep and goats can also be affected by EHD, though the disease is rarely fatal in domestic ruminants. Symptoms can vary from none to very severe. The most common symptoms are loss of appetite, lethargy, swelling of the tongue, face and eyes, excessive salivation, and ulceration of the mucus membranes in the mouth and tongue. Especially in deer, the nasal and oral discharges are often bloody. These hemorrhages can occur throughout the body. As the disease progresses, weakness becomes more apparent, the animal becomes recumbent, and can die. Cases in domestic livestock are marked with fever, inappetence, ulcers of the tongue and oral cavity, increased respiratory rate and effort, and lethargy. These symptoms may persist for several days before they abate and the animal returns to normal.
Diagnosis can be made based on clinical signs and confirmed with serologic blood tests or immunologic tests on tissue samples. EHD does not infect humans, and there is no danger in eating meat from an animal that is infected and showing no clinical symptoms. Deer with clinical symptoms should not be consumed for food as secondary infections are common and would render the meat inedible.
In regards to prevention, fly control can help to reduce the number of biting midges that can infect animals. For herds of captive deer, isolation from wild deer populations can reduce transmission due to proximity. Reduction of stress and good nutrition can help to reduce disease severity by propping up natural immunity. A veterinarian should examine suspected cases. Treatment for EHD is purely symptomatic and seeks to make the animal comfortable while its immune system fights the virus. More information about EHD can be obtained by contacting your veterinarian.
Mike Bloss, DVM, owns and operates Countryside Animal Clinic, with his wife, Kirstin Bloss, DVM. The mixed animal practice is located in Aurora, Mo.