Epizootic Hemorrhagic Disease

Epizootic hemorrhagic disease (EHD) is a hemorrhagic disease of white-tailed deer (Odocoileus virginianus) caused by an infection of a virus from the genus Orbivirus (Shope et al. 1960, Howarth et al. 2001). It is an infectious, and sometimes fatal, virus that is characterized by extensive hemorrhages, and is found throughout the United States. It is important for deer hunters, farmers, farm property owners, and livestock owners to have knowledge about EHD because of the seriousness of this disease, its ability to cause large scale outbreaks in wild ruminants, and its ability to affect livestock and the production industry (EHD in White-tailed Deer: Michigan Wildlife Disease Manual). Epizootic hemorrhagic disease has been found in some domestic ruminants and many species of deer including white-tailed deer, mule deer, and pronghorn antelope (CFSPH 2006). Seropositive black-tailed deer, fallow deer, red deer, wapiti, and roe deer have also been found, which essentially means that they were exposed to the disease at some time in the past, but may not be involved in transmission. Outbreaks of EHD have been reported in cattle although it is rare for them to develop disease or die. Sheep may develop clinical signs; however, this is also rare (Howarth et al. 2001). Epizootic hemorrhagic disease is often called bluetongue; however, this is incorrect. Bluetongue virus is closely related to EHD, and has similar clinical signs, but it is a different disease. Bluetongue is a serious disease in cattle, as well as other ruminants, and can have a significant effect on international trade. Testing at animal health laboratories is necessary to distinguish between the viruses that cause bluetongue and EHD.