Keeping Wisconsin Deer Healthy

Wisconsin is home to over 1.5 million white-tailed deer. A source of pride for Wisconsin's citizens and the state's official wild mammal, whitetails provide many forms of enjoyment to Wisconsin citizens from wildlife watchers to hunters.

How Do We Keep Wisconsin's Deer Herd Healthy?

Monitoring the health of the deer herd is the job of the DNR's Bureau of Wildlife Management, including the Wildlife Health Section. In cooperation with hunters, annual health testing is done on deer harvested in the fall hunt. Sick and dead deer reported to DNR wildlife managers are also examined for disease throughout the year.

For information on Chronic Wasting Disease, a disease of deer currently of great concern in southern Wisconsin, please view the CWD pages. The information below describes three additional infectious diseases of deer: Bovine Tuberculosis, Hemorrhagic Disease, and Cranial Abscessation Syndrome.

You can help keep the deer herd healthy. Early detection is the best defense we have in controlling these infectious diseases. If you see a deer with any of the disease signs described here or any other significant health problems that concern you, contact your local DNR office.

Bovine Tuberculosis

Bovine Tuberculosis (TB) is a contagious respiratory disease caused by the bacterium Mycobacterium bovis. Bovine TB can infect most warm-blooded animals, including humans. The federal government has done nationwide testing of cattle herds to control bovine TB, but it still occurs sporadically in cattle and wildlife such as elk and deer. TB has been diagnosed in captive elk and red deer herds in several states including Wisconsin. Michigan has found TB in their free-ranging white-tailed deer since 1994, and Minnesota has found TB in their free-ranging white-tailed deer since 2005.

What are the signs of Bovine Tuberculosis in deer?

Bovine TB is a progressive, chronic disease. It can take months to years from the time of infection until the development of clinical signs. The lymph nodes in the animal’s head usually show infection first, and as the disease progresses lesions will begin to develop on the surface of the lungs and chest cavity.

Are Wisconsin wild deer infected with TB?

We do not believe our wild deer are infected with TB. Since 1996, over 150,000 deer in WI have been screened for bovine TB, and no evidence of the disease has been found. WDNR will continue annual TB screening. As a hunter, you may be asked by DNR personnel to provide a sample from your deer for TB and other disease screening. This is voluntary, but your cooperation is important in detecting this disease.

Is deer TB a human health hazard?

Transmission of bovine TB to people can occur, but it is rare. TB is generally transmitted through the air by coughing and sneezing, and it is highly unlikely a person would contract the disease from field dressing or eating the meat of an infected deer. However, it is always a good idea to wear gloves when field dressing any animal. There is no specific test that can be easily done to check for TB in deer meat. Michigan recommends that venison harvested from their TB infected area should not be smoked or made into sausage or jerky, but be thoroughly cooked until it is no longer pink, and juice from the meat runs clear.

Brain Abscesses or Cranial Abscessation Syndrome

Brain abscesses are usually caused when Actinomyces pyogenes bacteria enter a wound in the velvet of a buck's antlers, through a broken antler, or through the pedicle (antler base) after antlers shed. After entering through a wound, the bacteria can actually damage the bone of the skull sufficiently to penetrate and cause an abscess in the brain.

Have brain abscesses been found in Wisconsin wild deer?

Adult antlered deer from all over Wisconsin have been diagnosed with cranial abscessation syndrome (CAS). Bucks appear blind, are uncoordinated, and may show abnormal behavior such as aggression toward people and stationary objects, or not moving when approached by people or dogs. Signs of CAS include swollen eyes, broken antlers weeping fluid, swollen joints, foot sores, and lameness. Pus may be observed at the pedicle or in eye sockets.

CAS is more common in bucks than does, likely because the bacteria enter wounds that result from sparring between bucks; according to studies in other states, CAS may account for up to six percent of natural mortality in bucks.

Is CAS a human health hazard?

If you harvest an adult buck with pus weeping from antler pedicles or eye sockets, the deer may have this bacterial infection. Though the meat may be contaminated with the CAS-causing bacteria, the infection is usually limited to the head. No part of the head should be eaten. The other meat is likely safe to eat, as normal cooking temperatures will destroy the bacteria.

Hemorrhagic Disease of Deer

Hemorrhagic disease (HD) is an acute, infectious, often fatal, viral disease that affects white-tailed deer (and some other hoofed animals, including livestock). In areas where HD regularly occurs death rates are lower, usually less than 25% of the population. In areas where the disease rarely occurs, like here in Wisconsin, there can be much higher local death rates. High-density deer herds may have higher mortality rates. HD is caused by either bluetongue virus or epizootic hemorrhagic disease virus; however, the visible signs of the disease are virtually indistinguishable with both the viruses. HD is transmitted by biting flies often referred to as no-see-ums (Culicoides midges). The virus does not survive long outside the insect vector or the deer host.

What are the signs of Hemorrhagic Disease in deer?

Outward signs of Hemorrhagic Disease in deer can include mouth and tongue ulcers, loss of appetite and activity, or abnormal hoof growth. However, deer can die quickly with HD, and therefore HD infections without clinical signs are common. On internal examination, hemorrhage of internal organs is common, ranging from pinpoint bleeds to large areas of hemorrhage. Sick deer are often found near water sources, as they develop high fevers.

Are Wisconsin wild deer infected with HD?

HD has been reported in the United States since 1900, but the viruses that cause the disease were first discovered in 1955. Outbreaks of HD occur almost every year in the southeastern U.S. and more sporadically in the Great Plains and Great Lakes states. HD was definitively diagnosed for the first time in Wisconsin deer in 2002, when approximately 14 deer were found suddenly dead in Iowa County during September. HD has also been identified recently in farmed deer in Wisconsin.

Is Hemorrhagic Disease a concern to human health?

The viruses that cause hemorrhagic disease do not infect humans. Therefore, humans are not at risk when handling infected deer, eating venison from infected deer, or being bitten by infected Culicoides midges (no-see-ums).

How does the WDNR monitor Hemorrhagic Disease in WI?

Blood from hunter harvested deer may be used to estimate HD activity in a particular deer herd. WDNR has performed serologic surveys for HD in the southwestern Wisconsin deer herd, and in some other regions of the state, since 2000. Though the number of deer tested is small, to date we have not identified HD activity through these surveys. This suggests that HD does not occur commonly in Wisconsin. It also suggests that few deer survive infection with HD after the small outbreaks that likely occur sporadically in southern Wisconsin. There is still much we need to learn about HD in Wisconsin deer, so please continue to report any unusual observations of dead deer to your local DNR office.

What other health issues are common in WI deer?

Deer Fibromas

Fibromas are firm, nodular, fleshy masses attached to the skin. They are commonly described as warts. Fibromas vary in size from less than an inch to over four inches in diameter, and they can be found anywhere on the deer’s body (but are most common on the face, neck and forelegs). Fibromas are caused by a virus which is transmitted by insects. Infected deer usually mount an immune response, and the fibromas eventually disappear. Occasionally, a deer will be severely infected with multiple fibromas which interfere with the eyes or normal use of the legs, causing health problems for the deer. Fibromas cause no damage to the meat, which is safe to consume.

Nasal Bot Flies

Nasal bot flies (Cephenemyia sp.) are common parasites that are found in the nasal passages of deer. Adult female flies deposit eggs in the nostrils of the deer. The eggs hatch into larvae and then pass through several stages of development and growth while living in the nasal passages. Although quite large (up to 1 1/2 inches) and unpleasant looking in the final stages of development, nasal bots cause little harm to individual deer and do not infect humans. Bot flies do not affect meat quality, and it is safe to eat meat from an animal infected with bots.

Liver Flukes

Liver flukes are a parasite that may be found in the liver of some deer. Adult flukes are flat, oval-shaped, purple-gray in color, and look like ‘bloodsuckers’ or ‘leeches.’ The flukes vary in size from 15-30mm wide by 30-100mm long by 2-5mm thick. Even though the flukes may cause local damage to the liver, it is rare that the presence of liver flukes significantly affects the health of the deer. Consumption of venison from an infected deer poses no risk to humans. However, the liver of an infected deer should not be consumed as the fluke-damaged areas of the liver can be secondarily infected by bacteria which could impact human health.

What Can I Do to Help Keep Wisconsin's Deer Healthy?

Transmission of Bovine Tuberculosis, Hemorrhagic Disease, Cranial Abscessation Syndrome, and some parasites are enhanced when high deer numbers and artificial feeding cause congregation and prolonged contact of deer, so it is worth limited these situations. If you see deer with signs suggestive of significant deer diseases or other evidence of ill health, report your findings to the nearest DNR office.

Information on proper handling of venison. (PDF, 234KB)(Exit DNR)

Questions for Wildlife Health.

Questions for Wildlife Management