Hemorrhagic Disease

September 2007

Kip Adams, QDMA Director of Education and Outreach, Northern Region

Deer had a relatively easy start to 2007 across most of their range. Some northern areas received abundant snowfall during February, but it was a relatively easy winter in most areas. Starting in April however, it’s been a much different story. A late frost in April decimated hard mast crops across much of the Southeast. That was followed by drought conditions across portions of the Southeast,Midwest and Northeast. Late July and August rains helped immensely, but overall forage production will be far below the norm.

The latest kick to deer populations in 2007 was the outbreak of hemorrhagic disease. According to the Southeast Cooperative Wildlife Disease Study (SCWDS), hemorrhagic disease is an infectious, viral disease of deer and elk. It is a blood-borne disease transmitted to deer by biting midges or flies. Hemorrhagic disease is the most important infectious disease of white-tailed deer and outbreaks occur nearly every year in the Southeast. Hemorrhagic disease is caused by either of two closely related viruses, epizootic hemorrhagic disease (EHD) virus or bluetongue virus. Since the disease features produced by these viruses are indistinguishable, a general term, hemorrhagic disease often is used when the specific virus responsible is unknown. Since EHD and bluetongue viruses are transmitted by biting flies (gnats, no-see-ums) hemorrhagic disease is seasonal and occurs in late summer and early fall. It was first reported in the U.S. in 1955 in New Jersey and has been confirmed in over 30 states since. The Southeast is most affected but the disease ranges as far north as Pennsylvania and New Jersey in the Northeast, across the Midwest to Montana and southern Canada , and to Washington, Oregon and California on the west coast.

The severity of disease outbreaks is influenced by the number of deer exhibiting immunity to the disease, the virulence of the infecting virus, the number of livestock nearby (because they can carry the virus), and the abundance of midge vectors. Herd density may also play a role as high-density herds may have higher mortality rates, but the relationship between deer density to the severity of hemorrhagic disease is not clear-cut. The disease occurs annually but its distribution and severity are highly variable.

Regional deer herds are impacted differently. According to SCWDS records, in coastal regions of the Southeast, most adult deer have antibodies to the disease and disease outbreaks are rare. In piedmont regions many adult deer have antibodies but disease outbreaks occur every 5-10 years. In mountainous regions antibodies are rarely formed in deer and disease tends to occur in sporadic outbreaks, often with higher death losses. Besides being illegal, this is one reason why releasing “big northern bucks” to increase the body and antler size in southern deer herds does not work. Northern deer are poorly suited to deal with southern climates and disease vectors.

Initially, infected deer may appear normal or show mild signs of illness. Five to ten days following exposure animals may appear depressed; feverish; have a swollen head, neck, tongue or eyelids; have difficulty breathing or lose their appetite and fear of man. Deer may have ulcers on their tongue, an eroded dental pad, or interrupted hoof growth. Internally, deer may have fluid-filled lungs, cardiac hemorrhage, a congested rumen or scarred rumen lining depending on virulence of the virus and duration of infection. Deer not previously exposed to the disease often die within 5-10 days. Mule deer, bighorn sheep and pronghorn antelope are also susceptible to hemorrhagic disease. Even though chronic wasting disease (CWD) and hemorrhagic disease share many symptoms, the two aren’t related. CWD is caused by abnormal prions and is neither viral nor bacterial, while hemorrhagic disease is caused by a virus.

There are three forms of hemorrhagic disease – peracute, acute and chronic. Depending on virulence of the viral strain, the peracute form can kill deer in 1-3 days. Acute is the classic form and deer may live for several days. The chronic form is typified by growth interruptions on the hooves and deer often survive this form. Deer that survive develop immunity to the disease and does may pass temporary immunity to their fawns through their milk. Most deer that die do so around water because they develop high fevers and seek water to cool their bodies.

Since the disease is spread by insects, there is little we can do to prevent it and outbreaks will end with the onset of cold weather. A good, hard frost will kill or drive the majority of insects responsible for the disease into winter inactivity.

In 2007, numerous states have reported hemorrhagic disease mortality including Alabama, Delaware, Georgia, Indiana, Kentucky, Maryland, New Jersey, North Carolina, Ohio, Pennsylvania, South Carolina, Tennessee, Virginia and West Virginia. The Pennsylvania Game Commission suggests the outbreak is especially severe because of the heat and drought conditions and report that more than 1,000 deer have succumbed to hemorrhagic disease in southwestern Pennsylvania. The Tennessee Wildlife Resource Agency reported they had received EHD reports from across the state and fears one of the state’s worst outbreaks on record.

It’s important to note that humans are not at risk by handling infected deer, eating venison from infected deer, or being bitten by infected midges. Our dogs and cats are not at risk either. For more information on hemorrhagic disease see an article by David Osborn, wildlife research coordinator for the University of Georgia on our website at http://www.qdma.com/articles/details.asp?id=111.

Reference: Most of the information in this article was taken from the Southeastern Cooperative Wildlife Disease Study’s (SCWDS) website and publications. SCWDS is located at the College of Veterinary Medicine at the University of Georgia and can be found at http://www.uga.edu/scwds/.

Kip’s Korner is written by Kip Adams, a certified wildlife biologist and Director of Education and Outreach for the Northern Region for the Quality Deer Management Association (QDMA). The QDMA is a non-profit wildlife conservation organization dedicated to promoting sustainable, high-quality, white-tailed deer populations, wildlife habitats and ethical hunting experiences through education, research, and management in partnership with hunters, landowners, natural resource professionals, and the public. The QDMA can be reached at 1-800-209-DEER or http://www.QDMA.com.