Game and Fish tracking EHD in deer, pronghorn

JACKSON HOLE, Wyo. — The Wyoming Game and Fish Department is tracking an outbreak of epizootic hemorrhagic disease (EHD), a virus that primarily impacts white-tailed deer and pronghorn. Multiple samples from dead deer and pronghorn confirmed the outbreak in the Arvada area as well as areas near Douglas, Laramie and Cheyenne.

The presence of the disease is not uncommon in times of drought and hot weather, especially where wildlife congregates around small water holes where the disease-carrying biting midge lives.

Wyoming’s wildlife managers see EHD in big game every year. However, some years have greater impacts than others, and 2021 could be one of them.

“This year seems worse, but we are just at the beginning of the outbreak,” said Hank Edwards, Wildlife Health Laboratory supervisor. “Monitoring will be important to chart the impacts.”

Game and Fish is tracking the spread of the disease online and has a map of identified locations. The map locations represent lab-confirmed distribution, but not the intensity of the disease. Once an area is documented, the lab won’t continue to sample there.

EHD is not spread by animal-to-animal contact; rather, transmission occurs when a host-animal with the virus is bitten by a midge.

“The midge collects a ‘blood meal,’ like a mosquito,” Edwards said. “When the midge bites another animal, the virus spreads.”

EHD typically occurs in the fall, especially in dry conditions coupled with drought, where there tend to be more outbreaks. As water holes shrink, animals become more concentrated, so it is easy for midges to transmit the disease.

The disease impact in Wyoming is not expected to be uniform. The disease is known to wax and wane in deer and pronghorn populations, and not all animals that are exposed to the virus will die. Some develop an immunity. Wildlife managers expect areas with high white-tailed deer will be impacted the hardest and some isolated pronghorn areas. The disease cycles every 7-10 years.

The number of deer and pronghorn affected is expected to increase until the first hard frost kills off midge populations. This fall, hunters should be aware of the disease, but shouldn’t be concerned about contracting EHD or spreading it to their pets.

Humans are not at risk of contracting the disease. If disease managers identify substantial impacts to wildlife, it could curtail hunting seasons. Game and Fish will continue to monitor the extent of the disease across the state.