Epizootic Hemorrhagic Disease

calendar icon 29 September 2022
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EHD is a viral disease that has long been recognised as perhaps the most important infectious disease of white-tailed deer in the US. In some years, there are significant numbers of death losses in deer populations due to EHD. Mule deer, antelope, and other deer species can also become affected. Cattle can become affected uncommonly.


EHD is a virus exclusively spread by biting flies of the Culicoides family. These are more commonly known as biting midges, sand gnats, sand flies, or no-see-ums. The virus is not directly contagious; it needs to be spread through the bite of one of these flies. Once the fly bites an infected animal, whether cattle or deer, the virus can reproduce inside the fly. The fly then is able to transmit even more virus particles than it picked up in the first place.

As cooler weather prevails, the activity and the survival of the vector will diminish; therefore, transmission and numbers of new cases will decline with the onset of freezing temperatures.

Clinical signs

In cattle the clinical signs are much milder than in deer and death losses are very infrequent. Excessive salivation is the most common sign. Other signs include stiffness, lameness, crusty peeling muzzle, crusty skin on teats, fever and loss of appetite.

Sores and ulcers in the mouth are also common.


There is no vaccine for the EHD virus itself in cattle. However, veterinarians working with affected herds have been prescribing anti-inflammatory medications and antibiotics in hopes of preventing problems with secondary bacterial infections that may crop up where the lesions occur. Providing a palatable, accessible source of feed and for these animals is important because of the pain that goes along with the sores in the mouth.

Fly control may help prevent the disease spreading.

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