What is ehd in deer

Overview

Epizootic Hemorrhagic Disease (EHD) is a serious viral infection that affects various species of ruminants, with white-tailed deer being the most severely impacted. The disease is caused by the Epizootic Hemorrhagic Disease virus (EHDV), which belongs to the Reoviridae family. EHD has been documented in North America since the 1950s and remains a significant concern for wildlife management and deer populations.

Transmission and Spread

EHD is transmitted through the bites of infected Culicoides midges, tiny flying insects that are most active during warm months. These midges cannot transmit the virus between deer directly; instead, they serve as vectors that pick up the virus from infected animals and pass it to others. The disease does not spread through direct contact between deer, and infected carcasses do not pose a transmission risk. Outbreaks are seasonal, typically occurring from late summer through early fall when midge populations are highest.

Symptoms and Progression

Infected deer typically show symptoms within 5-10 days of exposure. Early signs include high fever (often exceeding 104°F), lethargy, and loss of appetite. As the disease progresses, deer may experience severe swelling in the face, tongue, and throat, making breathing and swallowing difficult. Other symptoms include lameness, excessive salivation, and hemorrhaging in the mouth and gastrointestinal tract. The disease often results in death within 7-10 days of symptom onset, though some deer may recover if they survive the acute infection phase.

Impact on Deer Populations

EHD can cause significant mortality in deer herds during outbreak years. White-tailed deer show the highest mortality rates, sometimes exceeding 50% in severely affected populations. Mule deer are also susceptible but typically show lower mortality rates. Other ruminants including cattle, sheep, and elk can contract the virus but usually experience milder symptoms. The disease can have long-term population effects, particularly when combined with other stressors like drought, habitat loss, or hunting pressure.

Management and Prevention

Currently, there is no vaccine or specific antiviral treatment for EHD. Management strategies focus on minimizing risk and supporting affected populations. Wildlife managers monitor for disease outbreaks and may implement hunting restrictions in affected areas. Reducing midge breeding habitat by eliminating stagnant water sources can help decrease transmission risk. Providing supplemental food and water during outbreaks may help some deer survive, though this is not always practical at a landscape scale.