Nebraska’s cattle are facing an outbreak of Epizootic Hemorrhagic Disease (EHD), a viral disease that usually occurs in deer of North America. Severe epidemics periodically strike wild white-tailed deer populations, for whom the disease is often fatal. In rare cases, EHD is passed from deer to cattle by biting gnats, midges, or mosquitoes.
It is unclear why EHD is suddenly affecting cattle in the Midwest, however Nebraskan state agricultural officials believe that this past summer’s drought and extremely hot weather increased insect activity. The influx of transmitting insects spread the disease to more animals across greater distances than previously experienced.
Among cattle, the disease is largely benign. In some extreme cases, cattle may exhibit symptoms such as fever, swollen eyes, ulcers in the mouth, lameness, and labored breathing. However, cattle do not usually die from EHD and, according to the experts, the safety and quality of meat is unaffected by the illness.
Of greater concern than the uncommon appearance of EHD in cattle is the striking increase in reported deer mortalities in Nebraska, which rose from about 100 in an average year to 6,000 in 2012. “We’ve probably lost 25 percent of our deer,” said Bruce Trindle of the Nebraska Games and National Parks Commission. Roger Dudley of the Nebraska Department of Agriculture adds, “Certainly a ten-twenty-fold increase over what we’ve seen in the last few years.”
Epizootic Hemorrhagic Disease
There are ten known serotypes of EHD viruses, and only a few of these can cause illness in cattle. Of the strains common in North America, none are known to be fatal among cattle although some animals may remain lame and sickly for prolonged periods of time after infection.
In deer, on the other hand, symptoms of EHD are presented in one of three ways. In the peracute form of EHD, deer experience fever, anorexia, respiratory distress and severe swelling. This form typically causes death within 36 hours. Classical EHD exhibits similar symptoms, accompanied by hemorrhage in the tissues of the skin, heart, and gastrointestinal tract. This acute form is often identified postmortem by ulcers and erosions of the tongue and mouth. Finally, deer may also suffer from a chronic form of EHD, from which the animals usually recover after several weeks but often with lasting effects, including lameness and damage to parts of the alimentary canal.