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White-tailed Deer & Disease Concerns in Connecticut

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Connecticut’s white-tailed deer population is faced with several existing and potential diseases, some of which could pose a serious threat, while others may only impact a smaller number of individuals. It is important to know what these diseases are and how they may or may not affect people; what precautions should be taken when handling harvested deer; and how to identify the symptoms (or the cause). The Northeast Wildlife Disease Cooperative is an excellent resource for obtaining important news, research results, and information about various diseases affecting not only deer, but other species of wildlife in our area of the country: https://www.northeastwildlife.org/.

Eastern Equine Encephalitis (EEE): EEE is an infectious, often fatal disease in horses, pigs, and humans that is transmitted by biting mosquitos. Wild ruminants, such as deer, can also become infected, but EEE rarely causes death. Only three states have reported mortality in deer associated with EEE (GA, WI, MI), although a few other states have reported finding EEE in deer populations (ME, MA, VT, RI). Symptoms of EEE in deer include walking in circles, lack of awareness, muscle paralysis, lethargy, and incoordination. It is possible, although rare, that humans could become infected with the EEE virus through their eyes, open skin wounds, or lungs when coming into contact with brain or spinal cord material from an infected deer. Follow deer handling recommendations provided on Chronic Wasting Disease.

Epizootic Hemorrhagic Disease: In October 2017, the first ever cases of Epizootic Hemorrhagic Disease (EHD) were confirmed in Connecticut. At the time, dead deer were reported in Portland, Middletown, Chester, Haddam, and Lyme all displaying symptoms associated with EHD. EHD is one of the most important infectious diseases affecting white-tailed deer and it spreads through a bite from an infected midge. No infected animals were reported in 2018 and 2019. The disease progresses rapidly in infected deer, which exhibit such symptoms as a swollen head, neck, tongue, or eyelids; bloody discharge from the nasal cavity; ulcers on the tongue; and hemorrhaging of the heart and lungs followed by death within three to five days. The virus also creates high feverish conditions, causing infected deer to sometimes be found in or near water sources.

Concern over EHD should not limit hunter willingness to harvest deer during the hunting season. The disease does not infect humans, and people are not at risk by eating venison from or handling infected deer, or by being bitten by infected midges. The disease rarely causes illness in domestic animals, such as cattle, sheep, goats, horses, dogs, and cats. However, hunters are advised to exercise caution if they observe a deer that is behaving abnormally or appears sick and to avoid shooting, handling, or consuming that animal. When field dressing deer, hunters should wear latex or rubber gloves and disinfect any instruments that come in contact with the animal. More information on EHD is on the DEEP website at https://www.ct.gov/deep/LIB/deep/hunting_trapping/pdf_files/ehdv.pdf.

Bovine Tuberculosis (TB): TB can infect most animals and is caused by a bacteria that affects the respiratory system. Although rare in deer, it is a chronic progressive disease that can cause gradual debilitation and emaciation, coughing, nasal discharge, and difficulty breathing. Only two states have reported TB in deer (MI, MN). Although the threat of humans contracting TB from deer is very rare, a man recently contracted TB most likely from inhaling infectious pathogens while removing the deer’s organs. Follow deer handling recommendations provided on Chronic Wasting Disease.

Chronic Wasting Disease (CWD): CWD is a naturally-occurring disease of the brain and nervous system in deer, elk, and moose that belongs to a family of diseases known as transmissible spongiform encephalopathies. This disease attacks the brains of deer, elk, and moose, producing small lesions that eventually result in death. CWD does not cause an immediate widespread die-off of deer, but there may be long-term impacts to the herd if the disease is allowed to spread. There are no proven solutions to eradicating the disease once present in wild populations. The method of CWD transmission is unknown; however, strong evidence suggests that abnormally-shaped proteins called “prions” are responsible. The agent responsible for this disease may spread directly through animal to animal contact or indirectly through soil or other surface to animal contact. It is thought that the most common mode of transmission from an infected animal is via saliva and feces. CWD can spread from region to region by the movement of captive deer or through the improper disposal of a harvested deer transported from a CWD-infected area. CWD has been documented in 25 states and 4 Canadian provinces; the disease has not been found in Connecticut or New England. However, the Wildlife Division has been testing hunter-harvested and road-killed deer to monitor for CWD. Connecticut and many other states have taken measures to prevent the spread of CWD, such as banning the importation of live cervids (species in the deer/elk family) across state lines. In addition, an emergency regulation prohibits hunters from transporting into Connecticut any deer, elk, or moose carcasses or parts thereof from any state where CWD has been documented, unless the meat has been de-boned. A list of states where CWD has been documented and a description of precautions hunters should take can be found on Chronic Wasting Disease of this guide or on the DEEP website at wwww.ct.gov/deep/hunting. One of the most important precautions is to minimize the use of natural urine-based lures. (A possible new regulation MAY prohibit the possession and use of commercial natural-based deer urine or other bodily fluids. Check www.ct.gov/deep/hunting before the 2020 deer seasons start.) Avoid placing lures on clothes, skin, ground, or vegetation where deer can reach them. Up-to-date information can be found on the Chronic Wasting Disease Alliance website at http://cwd-info.org/.

Cutaneous Fibromas: The Wildlife Division frequently receives questions concerning deer with odd warty growths. These are most often harmless tumors caused by a viral skin condition called cutaneous fibroma. Tumors are gray or black in color, range from 0.25 inches to over 8 inches in diameter, and they may grow alone or in groups on the skin of white-tailed deer. Most tumors consist of smooth peeling skin; however, it is not uncommon for tumors to also have a warty appearance. The tumors are most often found on the front half of the animal, more specifically on the head, neck, and shoulders, but can occur anywhere on the deer’s skin.

Cutaneous fibromas are caused by a virus found only in white-tailed deer; they are not a danger to humans, pets, or livestock. Fibromas are transmitted from deer to deer by insect bites; scratches from sharp objects, such as barbed wire fences, briars, or branches; or other close contact of open wounds between animals. The virus typically lasts about 2 months and, outside of appearance, rarely causes any health issues in the infected deer. However, large tumors on the head may result in eating difficulties or impaired vision. The tumors are rarely attached to any part of the animal underneath the skin, and are harmless to humans who may come into contact with the deer during the hunting season. Large open lesions on tumors may lead to bacterial infections, in which case the deer may be unsuitable for consumption. Bacteria-infected deer will be obvious due to a strong odor.

Rabies: This disease in mammals is caused by a virus affecting the central nervous system. Left untreated, rabies is almost always fatal. The disease is primarily transmitted through the bite of an infected animal; however, people may also be exposed from being scratched by a rabid animal or getting an animal’s saliva in an open wound or mucous membrane (eyes, nose, or mouth). Raccoons, skunks, bats, foxes, dogs, and cats are most likely to get rabies. Rabbits, opossums, and squirrels are seldom affected. Although rare, white-tailed deer infected with rabies have been documented in Connecticut. Hunters and trappers can minimize their risk of exposure to rabies by following several common sense rules and knowing what to do if they or their pets are exposed (see the DEEP website at www.ct.gov/deep/hunting).

Report Possibly Diseased Deer: The DEEP is encouraging anyone who observes deer appearing emaciated, behaving strangely, or lying dead along the edge of waterbodies to report the information, along with the closest address, to Andrew.labonte@ct.gov, the DEEP Wildlife Division at 860-418-5921, or the DEEP’s 24-hour Emergency Dispatch Center at 860-424-3333. The Wildlife Division expects to continue collecting deer heads to test for CWD and blood samples for EHD (from towns along the Connecticut River) during the fall hunting seasons. Those interested in donating deer heads or blood samples from harvested deer should contact Andrew LaBonte (Andrew.labonte@ct.gov) at 860-418-5921.

Cutaneous fibromas are gray or black tumors found in the skin of white-tailed deer. The tumors are most often found on the front half of the animal, more specifically on the head, neck, and shoulders.

New Tick Concerns

If apprehension about blacklegged (deer) ticks and their associated diseases (e.g., Lyme, babesiosis, ehrlichiosis) is not already high enough, additional tick-related concerns are on the horizon. The first confirmed, established breeding population of the lone star tick was documented in South Norwalk, Connecticut, in 2017. This southeastern species has been slowly expanding its range north, and the population in our state has been increasing, possibly due to milder winters over the past few years. Adult lone star ticks are brown with eight legs and similar in size to the American dog tick. Adult females have a silvery-white spot near the center of the back, while males have varied white streaks or spots around the top edge of the body. The lone star tick is very aggressive and non-specific when seeking hosts and will feed on a variety of birds, most frequently wild turkeys, small mammals (e.g., squirrels), larger mammals (e.g., coyote, white-tailed deer), and humans during various stages of its life cycle. Adult activity runs from April through August, peaking in June. Nymphs may be active from March to October, but peak activity is April through early July. Larvae are active mainly in August and September. The lone star tick is associated with a number of human and animal diseases, such as ehrlichiosis, southern tick-associated rash illness (STARI), spotted fever rickettsiosis, tularemia, theileriosis in deer (related to human babesiosis), and, more recently, red meat allergy. Bites from lone star ticks may produce or generate a hypersensitivity allergic response that causes a food allergy to a red meat protein called alpha-gal that is found in most mammals.

In 2018, the first case of a person being bitten by an exotic Asian longhorned tick was documented in Fairfield County. This invasive species was originally discovered in New Jersey in 2017 and has now been found in 8 other states (AR, CT, MD, NC, NY, PA, VA, and WV). It is a major pest on livestock and feeds on a wide variety of mammals, including humans. However, it is currently not known if this tick will transmit pathogens, such as those that cause Lyme disease, babesiosis, anaplasmosis, and/or the Powassan virus. Continued research and monitoring will be conducted by the Connecticut Agricultural Experiment Station to fully understand the risk this tick species presents.

Young male deer with lone star tick infestation in South Norwalk, CT.