Epizootic Hemorrhage Disease

Epizootic hemorrhagic disease (EHD) is a disease of deer and other ruminants that has been in the United States since 1955. Periodically since 1955, there have been outbreaks of the disease with high mortality in affected white-tailed deer. EHD is usually subclinical when it affects cattle, but has been known to cause severe clinical disease. An outbreak of EHD occurred in the summer of 1996 in a group of cattle in southern Indiana.

EHD, an insect-bome viral disease, is closely related to and closely resembles Bluetongue. They are orbivimses which are non-enveloped, double-stranded,RNA viruses. The biting midge,

Culicoidesvariipennis.is assumed to be the vector for the diseases, but ticks may also be capable of transmitting the diseases. EHD occurs in late summer and early fall because hiring midges and ticks are only present during the wanner months. This disease is reported from midwestem and southern states nearly every summer.

As mentioned earlier, EHD virus rarely causes disease in cattle, but sporadic outbreaks of severe disease with mortality rates of 10% have occurred. Ulcerative lesions associated with EHD appear in the skin, mouth and hooves. Clinical signs consist of fever, stiffness, lameness and thickened edematous skin. Folds may develop in the skin as it becomes edematous, and crusty lesions will form. If pregnant cows become infected, the pregnancy may result in fetal resorption or hydranencephaly. After clinical signs of the disease develop, cattle will usually recover within a few weeks. EHD may be confused with the clinical signs in plant photosensitization, foot-and-mouth disease, bovine virus  diarrhea,   malignant  catarrhal  fever, infectious bovine rhinotracheitis,parainfluenza-3 and vesicular stomatitis.

Diagnosis is made by isolation of the virus from heparinized blood or tissues such as lung, bone marrow or spleen. Serum samples can also be tested for antibodies to EHD virus by agar gel immunodiffusion. Both of these tests can be performed at the Purdue University Animal Disease Diagnostic Laboratory. Samples for virus isolation should include spleen, bone marrow and heparinized peripheral blood. Either serum or whole clotted blood should be submitted for antibody tests. The samples should be refrigerated, but not frozen.

The current case of possible EHD in southern Indiana is affecting deer and cattle. The cattle have the oral ulcerations and are very lame from three days to two weeks. Some of the cattle are too lame to stand. It appears that only the older animals are affected and the younger ones are clinically normal, similar to what is seen in Bluetongue infection in cattle. Clinical Bluetongue disease in cattle results from a prior exposure to an orbivirusfollowed by a later, second exposure to the same virus. The affected cattle in Southern Indiana were probably subclinically infected with EHD or Bluetongue virus and are now being re-exposed to EHD virus.

References:

Stott, Jeffrey L..Gibbs,E.P.H.:Bluetongue and Epizootic Hemorrhagic Disease. Foreign Animal Diseases, 1992: 111-124.

Radostits,O.M., Blood, D.C., Gay, C.C.: Bluetongue-Diseases Caused by Viruses and ChlamydiaI. Veterinary Medicine, 1994: 1028-1033.

Fisher, John R.,et.al.: An Epizootic of Hemorrhagic Disease in White-Tailed Deer (Odocoileusvirginianus) in Missouri: Necropsy Findings and Population Impact. Journal of Wildlife Diseases, 31 (1), 1995: 30-36.

- byDoug Powers, Class of 1997

- edited byW.G. Van Alstine,DVM,PhD