Epizootic hemorrhagic disease
Epizootic hemorrhagic disease (EHD) is a disease caused by viruses in the genus orbivirus. It is transmitted to deer by biting midges of the genus Culicoides. Both white-tailed deer and mule deer are susceptible to EHD, but white-tailed deer seem to be more vulnerable. Cattle can be infected by the virus but rarely die from it. EHD is not known to infect humans.
This disease most commonly occurs in the late summer and early fall. The timing of this disease is most likely related to the abundance of the midge vectors, with the disease usually ending after the first frost. EHD can be acute, leading to death quickly with deer in good body condition and coat. It may also be chronic with the deer becoming emaciated and lame.
Clinical signs are therefore widely varied. They may include fever, hemorrhaging around the orifices and lack of fear of humans. Generally, high fevers lead deer to water before they die. However, this may not always be the case where die-offs occur over a large geographic region. A confirmed diagnosis requires fresh lymph nodes or blood from sick or freshly killed deer exhibiting clinical sings.
Deer mortalities were first recorded in Nebraska in the early 1950s. There has been some level of the disease present in the deer population since then. The largest recorded outbreak occurred in 1976 when between 30 to 40 percent of the deer population was estimated to have died. The last 10 year reporting level of deer mortality is presented in the following table. Another significant outbreak occurred in 2012. Portions of northcentral and northwest Nebraska saw a smaller die-off in 2013. Herds are recovering statewide.
Facts
- Hemorrhagic disease (HD) includes both epizootic hemorrhagic disease (EHD) and bluetongue (BTV) viruses. The resulting disease produced by EHD and bluetongue viruses is indistinguishable, thus the general term for is Hemorrhagic Disease (HD), as the specific virus can only be determined from laboratory evaluation. HD is caused by a virus transmitted by a small biting fly (midges in the genus culicoides).
- Infected deer typically develop a high fever and seek out water sources for relief, therefore, deer that have died due to HD are often found near or in creeks, ponds and lakes.
- Deer that succumb to HD normally die of internal bleeding. Infected animals may also exhibit symptoms including swollen tongue, eyelids, head and neck; lethargy; loss of fear of humans; incoordination or lameness; and lesions or ulcers on the tongue,dental pad and stomach.
- A hard frost or freezing temperatures will kill the midge, and without the midge to transfer the virus, deer mortality due to HD should significantly decrease.
Frequently asked questions
There is no evidence to suggest a human health risk from the handling or consumption of HD-infected deer, as HD viruses are not known to infect humans, however, deer that appear to be sick or unhealthy should not be consumed.
Please report sick and dead deer (with unexplained cause of death) to the nearest Game and Parks office. If a hunter harvests an apparently sick deer, they should contact their local Conservation Officer.
A confirmed diagnosis of HD can only be done with laboratory testing, although a strong tentative diagnosis can be made based on physical and behavioral symptoms and close proximity to water.
HD is primarily a disease of white-tailed deer, but it sometimes affects pronghorn, mule deer, bighorn sheep and elk. Livestock rarely contract EHD. Cattle rarely exhibit clinical signs from either EHD or bluetongue, although a small percentage of animals may develop fever, lameness or sore mouths. EHD and Bluetongue do not affect cats or dogs.
No, a significant decrease of deer infected with HD will result once an area receives a hard frost or freezing temperatures killing the midge. There is no cure or vaccine for HD.
A drought is not required for deer to contract HD; however, significant outbreaks are often associated with years of droughts/hot temperatures. This is because droughts/high temperatures appear to facilitate the transmission of the disease as the biting fly is more abundant, and deer concentrate around water sources during these conditions.
No, CWD is an entirely different disease. The infectious agent causing CWD is an abnormal protein, known as a prion, while HD is caused by a virus.
