Diseases and Parasites of Deer

Every hunting season there is an eruption of questions concerning diseases in deer.

  • Does my deer have any diseases? deer fawn eating
  • Is my deer good to eat? 
  • What are theses strange lumps all over my deer? 
  • If I eat the deer will I get the Disease? 

I am going to go over some of the major diseases that effect the US deer population. I will show you how to identify and determine if the disease is hazardous for your consumption! 

Let’s first take a look at the viral diseases that plague the US deer population. Diseases like Chronic Wasting Disease (CWD), and Hemorrhagic Disease (HD) are the ones that you hear about the most, but there are others to watch out for too. 

Viral Infections Found in Deer

Chronic Wasting Disease (CWD) 

CWD infected deer disease
Chronic Wasting Disease (CWD) is a neurological disease of deer and elk producing small brain lesions in the infected. CWD was first identified as a fatal wasting syndrome in captive mule deer in Colorado in the late 1960′s and has been spreading sporadically in the wild population ever since. CWD can be highly transmissible within deer and elk populations. The mode of transmission is not fully understood, but evidence supports the possibility that the disease is spread through direct animal-to-animal contact or as a result of indirect exposure to prions in the environment (e.g., in contaminated feed and water sources). It is still unknown if humans are at risk to transmission of this disease but it is always better to be safe than sorry. To minimize your risk of exposure the CDC recommends that “hunters should consult with their state wildlife agencies to identify areas where CWD occurs and take appropriate precautions when hunting in such areas. Hunters and others should avoid eating meat from deer and elk that look sick or that test positive for CWD. Hunters who harvest deer or elk from known CWD-positive areas may wish to consider having the animal tested for CWD before consuming the meat (information about testing is available from most state wildlife agencies). 

Persons involved in field-dressing carcasses should wear gloves, bone-out the meat from the animal, and minimize handling of the brain and spinal cord tissues.” 

The best way to identify CWD is to look at its symptoms of weight loss over weeks or months, behavioral changes, excessive salivation, difficulty swallowing, polydipsia, and polyuria. Some animals will exhibit excessive ataxia and head tremors. Most animals with the disease die within several months of contracting the illness, sometimes from aspiration pneumonia. In rare cases the illness may last up to a year.

Hemorrhagic Disease (HD) also known as Epizootic Hemorrhagic Disease (EHD)

There are outbreaks of Hemorrhagic Disease (HD) across the country every year. 

[i.e… in Michigan (source: http://www.michigan.gov/emergingdiseases/0,4579,7-186–283966–,00.html);  “We have not received any new reports of Laboratory confirmed cases so we are still at 30 confirmed HD deer infection mappositive counties with a total reported dead figure of 12,646 deer”]. 

HD is transmitted by gnats or tiny biting flies (no see-ums in the south). Infected deer often show no symptoms, or only mild signs of illness (swollen head, neck, tongue, or eyelids, or have difficulty breathing). 

Humans are not at risk by handling infected deer, eating venison from infected deer, or being bitten by infected biting midges. However, deer that develop bacterial infections or abscesses secondary to HD may not be suitable for consumption. 

If you think that you have spotted an animal with HD do not harvest the animal and report it to your local DNR office. 

Blue Tongue Viruses (BTV) 

Blue Tongue Virus just like HD and EHD is transmitted by gnats or tiny biting flies. BTV can not be directly transmitted between animals so the exposure of the virus is dependent on the biting fly’s. Some signs of BTV include high fever, congestion, edema (or bleeding) of the face and tongue, and bleeding ulcers. In severe cases the tongue of the animal will turn blue, Thus the name. Just like HD if you think that you have spotted an animal with BTV do not harvest the animal and report it to your local DNR office.

 Mycobacterium Tuberculosis Infection (TB)

Mycobacterium tuberculosis Infection (TB) is a bacterial disease associated with deer, elk, and bison. Although rare in deer TB is highly infectious and can be transmitted to humans. TB is passed Mycobacterium tuberculosis Infection deer chestthrough respiratory contact between animals, thus population determines the size of any outbreak. TB can be determined by small lesions and abscesses, but even these may be missed by the average hunter when field dressing a deer. 

In fact, most TB infected deer appear to be healthy and only on closer inspection can it be determined that the deer is infected. When field dressing a deer you should be looking for tan and yellow lumps on the inside surface of the rib cage and or on the lung tissue. 

IF you have come in contact with a TB infected Deer you need to immediately report it to your local DNR and get tested at  a doctors office. 

 Cutaneous Fibromas 

Cutaneous Fibromas infected deerCutaneous – Fibromas are wart-like growths caused by a virus that often infects deer through an open wound or insect bite. 

The warts range in size and consistence from less than one-half inch to 8 inches or greater in diameter and as few as one and as many as 200 have been reported. The only concern for us is an animal with extensive bacterial infection, which would render the deer unsuitable for human consumption. Deer with multiple warts would be highly recognizable! 


Rabies in deer like most animals is usually fatal. Rabies is a virus that causes inflammation in the brain. Animals suffering from rabies will have deterioration of the brain and will begin to behave bizarrely. Deer with rabies can often become aggressive, in creasing the chances to spread the disease to other animals and possibly humans. All mammals can be infected with the rabies virus. Hunters should not harvest animals infected by rabies, and take extra precautions when disposing of the carcasses of the animal. It is important that if you sight or come into contact with an infected animal that you report it immediately so that it can be dealt with properly. 


Bacterial Disease

Brucella Infection (brucellosis) 

A bacterial disease associated with bison, deer, and other wild animals. BI is spread through animal to animal or an animal coming into contact with an infected animals waste. Every one is susceptible to BI as it can be transmitted to humans on contact or through consumption. The symptoms of BI are flu in nature such as intermittent fever, chills, excessive sweating, weakness, weight loss, fatigue, headache, abdominal pain, back pain, loss of appetite or joint pain. The illness may be chronic and persist for years.

Brain Abscesses 

Brain abscesses are bacterial infections in the skull and brain. In white-tailed deer, brain abscesses most often occur in bucks (90 percent of cases) and are often seasonal, primarily due to the stages of antler development and fighting.
In the southeastern United States, brain abscesses are estimated to account for about 10 percent of natural mortality of mature bucks. Infection symptoms may include poor coordination, circling movements, blindness, lethargy (significant lack of energy) and emaciation.

Lyme Disease

Lyme disease is an illness caused by a spirochete bacterium (Borrelia burgdorferi). This disease is transmitted to people and animals primarily by the bite of the black-legged tick, Ixodes scapularis. There has never been a documented case of a human contracting Lyme disease through the handling or consumption of venison.

Transmissible Spongiform Encephalopathies (TSEs)

transmissible spongiform encephalopathies (TSEs). TSEs cause brain degeneration in deer, elk and moose. The disease was first detected in a captive mule deer facility in Colorado in 1967 and since has been documented in free-ranging and captive white-tailed deer, elk and moose in several states.


Arterial Worms

Arterial worms (Lump jaw)live in the arteries of white-tailed deer. Deer contract arterial worms when bitten by infected horseflies (nematode 
Elaeophora schneideri). The adult worms reside in the carotid arteries of the deer. The female worms produces microfillariae (worm in larvae form) that lodge themselves in the capillaryies of the skin (commonly found in the head region) deer with lump jaw are easily recognizable due to the facial swelling that occurs due to food impassion with the infected area. Although this parasite is not one that can be transmitted to humans it is a common problem with white-tailed deer.


Lungworms are parasitic nematode worms that infest different species and are commonly found in cattle and deer. After ingestion of an infected larva the infected larvae will then penetrate the intestinal wall where larvae migrate into the lungs through the bloodstream. the infected lungworms reside in the lungs until there adulthood. The eggs of the adult hatch and produce more lungworms. Common symptoms are coifing, wheezing and weight loss. These symptoms are caused by the lungs filling with mucus causing blockage f the airway and lungs. Lungworms can infect humans, although Lungworms are not a common problem in the US they are a growing concern in other parts of the world. 

Ticks and Lice

About 18 tick species have been reported to infect white-tailed deer. There are several species of lice that have been reported from deer (Solenopotes Binipilosus – sucking louse, Tricholipeurus Lipeuroides and T. parallenus – chewing lice) these are both parasites that are picked up in the woods and can be transmitted to humans through direct contact. 

Lice feed on skin and epithelial debris (biting lice) or feed on blood (sucking lice). Infestations are often heaviest in the winter months with severe infestations causing irritation and hair loss. 
Transmission is again by direct contact with other infested deer. Lice are vary host specific and these species are restricted to infesting only deer.

Demodectic Mange 

Infestations with Demodex folliculorum are not common in deer but when they do occur, they usually result in considerable pathogenicity. This mite lives in the hair follicles and sebaceous glands of its host and varieties are reported from most animals. Excessive tissue growth occurs associated with the lesions. Lesions may become secondarily infected with bacteria, compounding the problem. In most instances, infestations with this mite are seen in either captive animals or isolated free-ranging individuals.

Psoroptic Mange 

Psoroptes conniculi is reported from deer with infestations ranging from being confined to the ear canals to total body involvement. The entire life cycle of this mite involves infestations of the skin. Most reports are from captive individuals and many reflect exposure to other infested domestic animals.

 Trypansosoma Cervi 

Trypansosoma cervi is a protozoan parasite that can be found free in the blood plasma of deer. The parasite consists of a single cell that is leaf-like in appearance. A free flagellum, which is used for locomotion, is attached to an undulating membrane. The parasite is not considered pathogenic to deer. Infection rates are generally low and culture procedures are often necessary to document its presence. Microscopic identification of the stained organism in blood films is necessary. The transmission of the parasite is probably via horseflies. 

Theileria Cervi 

Theileria cervi is another protozoan parasite found in the blood of deer. In this instance, the organism, referred to as a piroplasm, is found within circulating erythrocytes. The parasite is transmitted via the tick vector Amblyomma americanum. Transmission appears to be mainly from infected unfed adults that feed on newly born fawns in the spring. Once infected, the fawns develop a parasitemia sufficient to allow infection of other tick stages that feed on them, thus perpetuating the infection. Adult deer remain infected for life but usually have parasite infection levels of below 1%. The parasite is not pathogenic in healthy animals. 

 Babesia Odocoilei

Babesia odocoilei is another protozoan parasite that is tick-transmitted. In this instance, just as in T. cervi. the piroplasms are found in circulating erythrocytes. The tick vector appears to be Ixodes scapularis. The infection does not appear to be pathogenic in healthy animals. Diagnosis is difficult and may require culture procedures as well as microscopic detection of the organisms in stained blood films.

Nasal Bots

Nasal bot flies (Cephenemyia spp.) are common parasites that infect the nasal passages of deer.. Deer become infected when the adult fly that looks like a honey bee, deposits eggs on the nasal passages of the deer. The larvae that hatch migrate into the nasal passages and attach to the tissue by means of hooks located on their anterior end. They remain attached to the tissue until they are ready to pupate. At this time they migrate out of the nose or are sneezed out, falling onto the ground. After about one month of pupation, adult flies emerge and begin the cycle again. Although deer sometimes harbor large numbers of this parasite, it does not appear that much more than a mild irritation and discomfort is experienced by the infested animal. Larvae have been reported from locations other than the nasal passages of deer including the lungs, stomach, and esophagus. However, this is probably due to larval migration in animals that have been dead for an extended period of time. Based on a typical life cycle, the heaviest infestation are seen in the summer months.


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Posted in: Gregory Beckman, Scrolls
Gregory Beckman

About the Author:

Hi, I am Gregory Beckman, as the main owner of Military Hunting and Fishing let me tell you a little bit more about myself. I am currently an active duty member in the United States Coast Guard. I have been privileged to traveling the world. My experiences have shaped the way that I see the world and my memories will stick with me for a lifetime. Although I may not live in the country, the country lives in me. Traveling the world I have had the chance to experience the wonders of nature in many different places, meeting many different people and tasting wild game that the normal person would not get to experience. Although these experiences have kept me away from home, it has instilled a deep passion of hunting and fishing in my blood. Thank you for joining our site, and I look forward to interacting and sharing stories of our hunting adventures. Gregory A. Beckman
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