Hemorrhagic disease of cervids

• White-tailed deer are the main wildlife species affected in Minnesota.
• Elk and bison cases are less common and they may have milder symptoms.
• Occasional deaths from AHD have been reported in moose in other states.

• Some deer show no signs at all.
• Mild cases: Fever, lameness, reduced activity, or reduced appetite.
• Severe cases: Swelling around the head, trouble breathing, internal bleeding, bloody diarrhea and sudden death.
• Survivors may develop overgrown hooves or abnormal antlers with retained velvet (e.g. “cactus bucks”).

EHD and BTV are transmitted by biting midges (Culicoides spp.), with cases seen from late July to November when midges are active. Frost will kill the virus and the midge that carries it, ending the infection period. AHD is spread through direct contact at any time of year. Cases are most common in younger cervids.

• Fever drives sick deer to water, so multiple sick or dead deer seen near water during the late summer and fall may indicate HD.
• Sick deer with cracked or sloughing hooves.
• Sick deer with bloody diarrhea.

Epizootic hemorrhagic disease, once found mostly in the Southeast, is now more common in the upper Midwest. EHD was first reported in Minnesota in 2018 in a captive deer in Goodhue County, followed by an outbreak in wild deer in Stearns and Houston counties in 2019. The first confirmed BTV cases in Minnesota wild deer were in 2024. AHD has not been detected in MN; however, a captive deer case occurred in Wisconsin in 2025.

Outbreaks of EHD vary from a few cases to large die-offs, but deer populations usually recover within a few years. Bluetongue virus cases are sporadic and rarely cause significant die-offs. Adenovirus hemorrhagic disease has caused large die-offs in mule deer and black-tailed deer and occasional deaths in moose but is less common in other species.

• Humans cannot contract these viruses; however, visibly sick deer or multiple carcasses may also be seen with other diseases of concern. Avoid handling or consuming sick wildlife.
• Cattle can contract EHD or BTV, but they usually experience mild disease. Sheep can develop severe disease from BTV.