Epizootic Hemorrhagic Disease
 

Causative Agent

  • Epizootic Hemorrhagic Disease (EHD) is a viral disease of wild ungulates caused by viruses of the genus Orbivirus.

  • Bluetongue, a viral disease of wild ungulates caused by another Orbivirus, has similar signs and symptoms.

  • The diseases caused by both Bluetongue and EHD are collectively known as hemorrhagic disease.

Click on the photo to enlarge.

Hemorrhage in the eyes of a white-tailed deer infected with EHD

Distribution

Geographic:

  • EHD is widely distributed in both temperate and tropical regions of the world.

  • EHD in free-ranging wildlife has only been reported in North America.

  • EHD has been reported in bighorn sheep and white-tailed deer in the Okanagan region of BC.

Seasonality:

  • EHD occurs in late summer and early fall. This is thought to be related to seasonal wind patterns moving the insect vector northwards from endemic areas in the USA.
Hosts and Transmission

Hosts:

  • Primarily white-tailed deer and mule deer; less frequently elk, pronghorn antelope and bighorn sheep.

  • Severity of the EHD is quite variable and may be related to herd immunity.

Transmission:

  • EHD is transmitted by various species of Culicoides midges (“no-see-ums”).

  • The virus enters the blood of hosts from the midge. In some species, viral replication may occur in the walls of blood vessels.

  • Blood vessels are damaged leading to numerous small and large hemorrhages - hence, the hemorrhagic nature of this disease.

Signs and Symptoms

  • Signs are variable, ranging from none to sickness or sudden death.

  • Sick and dead animals are often found near water.

  • Other signs include:

    • swelling of the face, tongue, neck and conjunctiva of the eyes

    • lack of appetite

    • weakness and incoordination

    • excessive salivation, often blood-tinged

    • nasal discharge, often blood-tinged

    • bloody diarrhea

    • lameness

    • extensive hemorrhaging in many tissues including the skin, gastrointestinal tract, heart, testicles

    • ulcers in the tissues of the mouth, tongue and stomachs

    • breathing difficulty

    • recumbancy (lying down)

    • overgrowth/cracked hooves

Meat Edible?

  • EHD does not infect humans, and eating venison from deer with EHD is not dangerous. However, secondary infections that may occur as the disease progresses can render venison unfit for consumption.

  • The meat should not be fed to dogs.

Human Health Concerns and Risk Reduction

  • EHD virus is not associated with human disease.

Samples for Diagnosis

  • The whole body should be submitted for post mortem.

  • Immunological tests can verify if EHD virus is present in the following tissues which should be REFRIGERATED NOT FROZEN:
    - blood collected with anti-coagulant and the spleen (best)
    - lymph node, lung or bone marrow

Further Reading

Howerth, E. W., D. E. Stallknecht, and P. D. Kirkland. 2001. Bluetongue, epizootic hemorrhagic disease, and other Orbivirus-related diseases. Pp. 77-97 in E. S. Williams and I. K. Barker (eds.), Infectious Diseases of Wild Mammals. 3rd Ed. Iowa State University Press, Ames, IA.

Missouri Deptartment of Conservation - EHD in livestock and deer

 

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