Epizootic Hemorrhagic Disease (EHD) is a viral illness that primarily affects white-tailed deer in North America. Caused by an orbivirus, it is characterized by extensive internal bleeding. EHD outbreaks are seasonal, typically emerging in late summer and early fall across various regions of the United States and Canada. While it can lead to deer mortality, its occurrence is often localized, impacting populations to varying degrees depending on environmental conditions.
How EHD Spreads
Epizootic Hemorrhagic Disease is not spread through direct contact between deer. The virus is transmitted exclusively through the bite of tiny insects known as biting midges, specifically from the genus Culicoides. These insects are often referred to as “no-see-ums” due to their small size.
The transmission cycle begins when a midge feeds on the blood of an infected deer, acquiring the virus. The virus then replicates within the midge. When this infected midge subsequently bites a healthy deer, it injects the virus, transmitting the disease. Midge populations thrive in warm, wet conditions, particularly around muddy areas, which serve as their preferred breeding grounds. Outbreaks of EHD typically cease with the arrival of the first hard frost, as freezing temperatures kill off the adult midge population, breaking the transmission cycle.
Recognizing EHD in Deer
Deer infected with EHD often display a range of signs. Common indicators include lethargy, weakness, and a loss of appetite. Affected deer may also exhibit a high fever, prompting them to seek out water sources. Swelling of the head, neck, tongue, and eyelids is frequently observed, and some deer may develop a bluish discoloration of the tongue.
Lameness can occur as a result of swollen joints or sloughing of the hoof walls. Infected deer may appear disoriented, unresponsive, or show an unusual lack of fear towards humans. Sudden deaths are a hallmark of EHD, and it is common to find deceased deer in or near water bodies. Symptoms can develop rapidly, with death often occurring within days of onset.
EHD and Other Animals
Epizootic Hemorrhagic Disease does not pose a known threat to human health. The EHD virus is not transmissible to humans, meaning there is no public health risk from contact with infected deer or from consuming venison. Proper handling and cooking practices are always advisable for any wild game.
EHD primarily impacts deer species, particularly white-tailed deer, but related viruses can occasionally affect other ruminants. Livestock such as cattle and sheep may become infected with the EHD virus, but clinical disease in these species is generally mild. Symptoms in cattle, if present, might include fever or lameness, but they do not spread the virus to deer. Domestic pets like dogs and cats are not at risk of contracting EHD.
Reporting and Public Action
If you encounter sick or dead deer that you suspect may be affected by EHD, reporting these observations to your local wildlife agency or state game commission is helpful. This reporting assists wildlife officials in monitoring the spread and severity of outbreaks, providing valuable data for disease management efforts. Many agencies offer online reporting systems or direct phone contacts for this purpose.
It is advisable to avoid directly handling sick or deceased deer without proper precautions. While EHD does not affect humans, other pathogens might be present, so wearing gloves if contact is unavoidable is a sensible measure. Hunters should continue to follow standard safe handling practices for venison, such as thoroughly cooking meat.