Epizootic Hemorrhagic Disease
What is Epizootic Hemorrhagic Disease?
Epizootic Hemorrhagic Disease (EHD) as well as Bluetongue Virus (BT) are illnesses caused by two similar viruses impacting white-tailed deer with EHD being more common in deer. These viruses are transmitted by the biting midge, Culicoides. Because these insect vectors and the virus are killed after the onset of frost, outbreaks are seasonal, typically occurring in late summer or early fall.
These viruses act quickly with symptoms developing approximately a week after infection and death occurring within 48 hours of symptoms developing. Intermediate symptoms include weakness and lethargy, unresponsiveness, fever, and edema. The associated fever often drives weakened deer to seek out water, and victims of these illnesses are often found dead next to or in water. While EHD is most often fatal for deer, some do survive and develop immunity to the virus.
Where has Epizootic Hemorrhagic Disease been found?
EHD and BT are commonly associated with the southeastern, midwestern, and Great Plains states, though cases have been reported further north into Pennsylvania, New York, Connecticut, Delaware, New Jersey, and recently New Hampshire and Vermont. These diseases have not yet been detected in Maine.
Can Epizootic Hemorrhagic Disease be treated?
There is no effective and broadly applicable treatment for EHD or BT in deer. Due to the fast-acting nature of these diseases, surveillance of wild deer is not practical, and confirmation of these diseases typically comes from testing deer found dead in the wild.
What is the impact on deer and the population?
Outbreaks of these diseases may vary in size. In areas where the disease has been present for long periods and where some deer have developed natural immunity, outbreaks are often more limited; in areas where the disease has not been present and where natural immunity does not exist, outbreaks may be more severe. Seasonal climate variation may also impact the size and intensity of outbreaks; hot, droughty summer conditions may limit water availability and concentrate deer and Culicoides midges at relatively few water bodies, which may lead to increased disease transmission and more intense outbreaks in the fall.
An annual jurisdictional survey conducted by the Southeastern Cooperative Wildlife Disease Study in 2020 reported an estimated 1,001-5,000 deer deaths associated with EHD in New York, and all other participating jurisdictions reported mortality estimates of 101-500 or less than 50 deer (survey options were presented as ranges). Statewide deer population impacts are typically low, though impacts may be more significant in the localized area of an outbreak.
Can Epizootic Hemorrhagic Disease spread to humans, pets, or livestock?
These viruses are not spread between animals, they are spread through the bite of an insect vector, the Culicoides midge. These viruses are capable of infecting livestock such as cattle and sheep and may impact other animals such as dogs. Sickened cattle often display no clinical symptoms, but weakened animals may exhibit symptoms such as lameness, fever, and lesions about the skin, mouth, and hooves.
Neither of these viruses affect humans.
What can I do?
EHD is often confirmed when groups of dead deer are found in the wild. If you find multiple dead deer in a small area with no obvious discernable cause of death particularly during the late summer or early fall, please contact your local regional office of MDIFW to report the case and consult with a biologist. Similarly, while these illnesses are fast-acting, it may happen that you spot a deer exhibiting early symptoms; any time you see any deer in the wild that is exhibiting symptoms such as unresponsiveness to people and extreme lethargy and weakness, please contact your nearest regional office to consult with a biologist.