Questions and answers about epizootic hemorrhagic disease in cattle
Cases of epizootic hemorrhagic disease, or EHD, were reported this summer in South Dakota cattle herds and in white-tailed deer. EHD is viral disease spread by flies. Russ Daly, South Dakota State University Extension veterinarian, answers some frequently asked questions about the disease and its origins:
• Biting flies spread viral disease in deer and cattle this year.
• EHD can make cows sick, but it kills deer.
• Symptoms in cattle include sores in the mouth.
Q. What is EHD?
A. EHD is a viral disease that has long been recognized as perhaps the most important infectious disease of white-tailed deer. In some years, including 2012, significant death losses in deer due to EHD are reported. Mule deer, antelope and other deer species can also become affected, but usually not to as severe an extent as white-tailed deer. Cattle can become affected uncommonly, but clinical illness is very rare in other species.
Q. What are the signs of EHD in deer?
A. Usually, the disease in deer develops so quickly that death losses are the only signs noted. If observed, affected deer may show signs of excessive salivation and nasal discharge, sometimes bloody in nature. Weakness and difficult breathing also are common. Hemorrhages throughout the entire body are often noted in the carcasses of deer that have died from EHD. Mortality rates are high.
Q. Does EHD do the same thing to cattle?
A. No. The clinical disease in cattle is generally much milder, and death losses are very infrequent. In the current outbreak, the most common sign noted in cattle is that of excessive drooling. Other signs include stiffness or lameness, a crusty peeling muzzle, crusty skin on the teats, fever and a reluctance to eat.
Q. What do veterinarians see in these animals?
A. The most common problem associated with EHD in cattle in this South Dakota outbreak has been that of sores in the mouth. These sores can be found under the upper lips, on the roof of the mouth, or along the gums in the lower jaw as well. Cows may show redness, blistering and leatheriness in their teats. In some cases, sores have been noted in the feet where the skin meets the hoof (coronary band).
Q. Is there any treatment for infected cattle?
A. Not against the EHD virus itself. However, veterinarians working with affected herds have prescribed anti-inflammatory medications and antibiotics in hopes of preventing problems with secondary bacterial infections that may crop up where the lesions occur. Providing a palatable, accessible source of feed for these animals is important because of the pain that goes along with the sores in the mouth.
Q. Is there any vaccine for EHD in cattle?
Q. What is the outcome for cattle with EHD?
A. Reports from veterinarians are generally encouraging. Most of the infected cattle have recovered, with some taking longer to recover than others. There are very few reports of cows that are permanently affected. Deaths in cattle due to EHD have been confirmed by the SDSU Animal Disease Research and Diagnostic Laboratory, but these death losses are considered very uncommon overall.
Q. Why did this disease show up in South Dakota this year?
A. The area of the state in which the most cases are identified is also the area of the state experiencing very dry conditions. The insect vector likes to breed in moist dirt, such as that found in drying creek beds, or along the shores of receded rivers and creeks. Some scientists have speculated that the level of immunity in the cattle population may currently be on a down cycle, allowing more animals to show clinical signs, although this has not been definitively proven.
Q. What is going to happen next year? Will we see more, or less, of this syndrome? Will we see any effects next calving season in the cows that were infected?
A. It is unclear at this point, and much depends on conditions for the vector next year. One could suppose that a high percentage of cattle will have been exposed to EHD this year whether they have shown signs of illness or not. Whether this results in an increased resistance to EHD in future years remains to be seen. In a 2007 Ohio outbreak, there were no instances in which EHD was confirmed to have contributed to reproductive losses in the following calving season.
Q. Does EHD affect people or meat or milk from the infected animals?
A. No. EHD does not affect people. Meat and milk from animals that are recovering or have recovered is safe to consume.
This article published in the November, 2012 edition of DAKOTA FARMER.