Deer Diseases

Hemorrhagic Disease

Hemorrhagic disease occurs in deer populations every year during late summer and early fall in the Southeast U.S. The disease is often referred to as “blue-tongue,” however the responsible virus can only be identified in a laboratory, and epizootic hemorrhagic disease (EHD) viruses are typically responsible for hemorrhagic disease outbreaks in North Carolina rather than blue-tongue (BT) viruses. Hemorrhagic disease viruses are transmitted to deer by biting flies and cannot be transferred from one deer to another. Clinical signs of hemorrhagic disease are highly variable; infected deer may appear normal or show only mild signs of the illness (see Signs of Hemorrhagic Disease below). Acute infections can kill a deer in 1 to 3 days. Deer that survive acute infections develop immunity, but can experience long-term side effects such as lameness, suppressed appetite, or loss of energy.

In some cases, deer affected with Hemorrhagic disease will display little to no symptoms of an infection, especially if they were previously exposed to the disease. If a deer does show signs of infection, these often include: fever, swollen head or neck, loss of appetite, difficulty breathing, ulcers on their tongue or mouth, and an eroded dental pad. Mortality from hemorrhagic disease most commonly takes place near water sources (e.g. pond, lake, creek) because of high fever. Deer that do not have any prior immunity to the disease will typically die within 5-10 days after infection. 

The severity of hemorrhagic disease is affected by a variety of factors (e.g. herd density, midge abundance, previous exposure) and mortality rates vary regionally across the state as well as across years. Deer herds that have been previously exposed to hemorrhagic disease can fight off an infection. Meanwhile, deer which have not been previously exposed to the disease are more likely to die from the disease. Normal deer die-offs associated with hemorrhagic disease occur annually in North Carolina, with larger outbreaks occurring periodically every few years.

Hemorrhagic disease does not pose any significant health risks to people and domestic pets. Hunters do not need to be concerned about consuming venison from infected deer.  As always, hunters should be cautious of consuming venison from any animal with obvious signs of illness. 

Signs of Hemorrhagic Disease

• Swollen or bluish head, neck, tongue, or eyelids
• Breathing difficulty
• Loss of appetite or energy
• Erosions or ulcers on the tongue or mouth
• Peeling or splitting of hooves
• Scarring, hemorrhaging, or fluid build-up in internal organs

The Vector

Hemorrhagic disease is transmitted by biting flies known as biting midges, sand gnats, sand flies, no-see-ums, or punkies. Outbreaks of the disease typically occur seasonally during hot, dry weather when biting midges become numerous. Generally, the onset of winter and freezing temperatures decreases biting midge populations and brings an end to hemorrhagic disease outbreaks.

Suspicious Deer

Hemorrhagic disease should be suspected in instances of unexplained deer mortality during late summer or early fall, especially if any of the above signs are present or if a dead deer is found near water. Sick or dead deer should be reported immediately to your local District Biologist or the Wildlife Helpline at 866-318-2401. Delays in reporting hinder the ability to determine the cause of death or illness.

Herd Impacts

Deer herds in the Southeast U.S. have some immunities to hemorrhagic disease and disease events aren’t notable in most areas in most years. However, severe localized outbreaks periodically occur and result in significant losses in deer numbers. Typically, hunting effort is voluntarily reduced by deer hunters during and immediately following outbreaks, and deer herds recover within a few years.

Human Health

Hemorrhagic disease does not affect humans, and people are not at risk by handling or eating venison from an infected deer or being bitten by an infected biting midge. Deer that develop secondary bacterial infections or abscesses may not be suitable for consumption. It is difficult to determine the extent of secondary infections or distinguish hemorrhagic disease from other diseases. As a precaution, humans should not eat meat from animals that appear to be sick or die from unknown causes.

Livestock Health

The effects on domestic livestock are difficult to assess. In cattle, BT infections are usually subclinical (no obvious signs); however, a small percentage of animals can develop fever, lameness, sore mouths, and reproductive problems. There is less known about EHD in cattle, but antibodies found in some herds indicate that they may frequently be exposed to the virus. Domestic sheep are typically unaffected by EHD, but BT can be serious, causing effects similar to those in deer.

Hemorrhagic Disease Report for District 3, 2014 (PDF)

Hemorrhagic Disease 2012 (PDF)

Southeastern Wildlife Disease Study Information on Hemorrhagic Disease of Whitetail Deer (PDF)

Hunting and West Nile Virus

West Nile virus is an infectious disease of birds that can also infect humans. The virus is transmitted by mosquitoes. According to the North Carolina Division of Public Health, West Nile virus may cause flu-like symptoms in humans, such as headache, swollen glands and muscle aches, as well as a rash. Usually West Nile virus only causes mild disease in humans, but in rare cases the virus may cause encephalitis and even death. Elderly people and those with compromised immune systems are most likely to be severely affected by West Nile virus.

Cutaneous Fibromas

Cutaneous fibromas are wart-like growths that develop on the skin. In deer, these growths are caused by a strain of the papilloma virus that is spread by biting insects. White-tail deer are primarily affected by the virus, but it has been reported in other cervids (deer, elk, moose, etc). While unattractive, fibromas only impact the skin and not the overall health of the deer. Harvested deer are safe to eat unless a fibroma has developed a secondary bacterial infection.

Many species can develop fibromas from various viruses. The virus that causes fibromas in white-tailed deer can only be spread to other cervids.

Cutaneous fibromas are characterized by hairless, wart-like growths on the skin that vary in white, gray or black coloration. Fibromas can vary greatly in size and grow to be 8 or more inches in diameter. The growths can be solitary or found in clusters.

Fibromas generally do not impact the health of the deer and can even clear up on their own. They can become problematic if they impede the deer’s ability to eat, breathe, or see.

People, livestock and pets cannot contract the virus that causes cutaneous fibromas. /p>

Nasal Bots

Nasal bots are the larvae of a maggot style fly in the genus Cephenemyia. An adult fly will lay a group of eggs around the nose or mouth of a deer and the eggs are released when the deer licks the eggs. The larvae then move to the nasal passages and sometimes the sinuses where they develop into larger stages of mature larvae. Once fully mature, nasal bots will exit the deer, pupate in the ground for 2-3 weeks and emerge as adult flies.

Many wildlife species and humans can be hosts of bot flies. Different species of bot flies affect different wildlife species. Bot fly larvae found in white-tailed deer only affect members in the deer family (white-tailed deer, elk, mule deer, etc.). Other wildlife species that are commonly seen with bot fly larvae include squirrels and rabbits.

Bot fly larvae are white to yellowish-brown in color and range from 1-2 inches in length. 

The larvae typically cause little or no harm to deer, except for some minor discomfort associated with irritation of the sinuses and nasal passages. Some sneezing and coughing in deer is assumed to be the result of nasal bots. No sores, infection or other problems have been reported even when the parasites are large in number. 

Nasal bots that occur in deer do not affect humans or pets. However, there are species of bot flies that can affect human and pets. Cases in pets are uncommon and the fly species that can affect humans only occur in Mexico and Central America. Nasal bots that occur in deer are most often encountered by hunters while field dressing a deer. When a deer’s body cools down, these larvae sometimes migrate into the throat region or into the open body cavity of the deer. It is here that unsuspecting hunters often find the larvae. Nasal bots do not make the carcass unfit for human consumption. 

 COVID-19

The SARS-CoV-2 virus, that causes COVID-19 in humans, has been detected in wild white-tailed deer inIowa and Ohio. Some states began testing live deer following initial work by the US Department of Agriculture that confirmed the susceptibility of captive deer to the virus and still other research that detected antibodies to the virus in wild deer in Illinois, Michigan, New York, and Pennsylvania. So far, COVID testing in wild deer has been limited to only a few states, but increased testing is occurring locally and nationally.

COVID-19 Precautions for Handling and Processing Deer (PDF) December 2021