The discovery of more than 100 elk in northeastern New Mexico has animal health officials scrambling to determine how the animals died. Biologists on the scene say the elk were found within a half-mile area and no evidence indicates they were shot.

New Mexico Department of Fish and Game biologists responded to a first responder call Tuesday (Aug. 27) and have been collecting tissue and water samples from the animals and the surrounding area, located near Las Vegas, New Mexico, about 70 miles east of Santa Fe.

"At this time we're looking into all possible causes, including epizootic hemorrhagic disease (EHD)," said Fish & Game Wildlife Disease Specialist Kerry Mower. "What we do know from aerial surveys is that the die-off appears to be confined to a relatively small area, and that the elk were not shot by poachers."

A large number of cases of epizootic hemorrhagic disease (EHD) were reported in the U.S. Midwest last year, an unexpected development, say biologists, considering the prevailing drought conditions in the area.  Epizootic hemorrhagic disease viruses (EHDV) are widespread in white-tailed deer and periodically cause serious epidemics in wild populations as well as affecting farmed deer populations. EHD can also cause disease in cattle.

If you are enjoying reading this article, please check out Southwest Farm Press Daily and receive the latest news right to your inbox.

In the U.S., EHD in cattle is typically uncommon, rarely fatal, and usually associated with an epidemic in deer, as was reported last year in Iowa.

The epizootic hemorrhagic disease viruses belong to the genus Orbivirus, family Reoviridae. Ten serotypes of EHDV are known worldwide. The viruses of the EHDV serogroup are transmitted by biological vectors, usually biting midges in the genus Culicoides. In North America, C. variipennis is the major vector. Some species of gnats and mosquitoes can also transmit EHDV. Infected deer can be viremic for up to two months.

Three syndromes may be seen in cervid populations, like deer and elk. Peracute disease is characterized by high fever, anorexia, weakness, respiratory distress, and severe and rapid edema of the head and neck. Swelling of the tongue and conjunctivae is common. Cervid with the peracute form usually die rapidly, typically within 8-36 hours. Some animals may be found dead with few clinical signs.

In the acute form, symptoms can also include extensive hemorrhages in many tissues including the skin, heart, and gastrointestinal tract. There is often excessive salivation and nasal discharge, both of which may be blood-tinged. Animals with the acute form can also develop ulcers or erosions of the tongue, dental pad, palate, rumen, and omasum. High mortality rates are common in both the peracute and acute forms. The chronic form of the disease results in cervid being ill for several weeks but gradually recovering. After recovery, these deer sometimes develop breaks or rings in the hooves caused by growth interruption and may become lame.

In severe cases, animals slough the hoof wall or toe; some of these animals may be found crawling on their knees or chest. Cervid with the chronic form may also develop ulcers, scars, or erosions in the rumen; extensive damage to the lining of the rumen can cause emaciation even when there is no shortage of food.