Studies on the pathogenesis of experimental epizootic hemorrhagic disease of white-tailed deer

Observations were made of clinical signs, gross and microscopic lesions in white-tailed deer infected with epizootic hemorrhagic disease (EHD) virus. Typically, animals became weak and lethargic and developed hyperemia of the oral and nasal mucosa, tongue, ears and sclera of the eyes six to seven days following intramuscular inoculation with virus. Body temperature increased initially and then fell to subnormal levels just prior to death.A decrease in levels of circulating blood platelets was correlated with the occurrence of fever and the appearance of platelet and fibrin thrombi in small vessels of many organs of the body. Thrombosis resulted in tissue degeneration, necrosis and hemorrhages in the terminal stages of the disease. Tissues most seriously affected were oral, nasal and tongue mucosa, mandibular salivary glands, myocardium and epithelium of the forestomachs. The lesions resembled those of blue-tongue in deer. Inoculation of domestic sheep with EHD virus-infected deer spleen tissues was without clinical effect. Blood collected from the sheep, representing the third blind passage of EHD virus in sheep, was not infective for deer.