Deer are susceptible to a variety of diseases and parasites. Nevertheless, disease does not typically account for a large percentage of deaths. During a deer study in northern Missouri, radio transmitters were placed on more than 200 deer. Less than 4 percent died from disease.
This chapter covers only a few of the more common parasites and unusual conditions that people, especially hunters, might observe in deer. Few situations actually render deer unsuitable for the table. Only rare exceptions occur, but if you have questions about the deer you harvested, contact your local conservation agent or the nearest Conservation Department office.
Normal organs and structures occasionally are misinterpreted as abnormal. Lymph nodes, which are found throughout the body, are sometimes taken to be multiple tumors or abscesses. The nodes, which are part of the body's system used to fight off disease, are located under the skin, between muscle groups and in the body cavity. They are beige to light brown and range from 1/4 to 1 inch in diameter. Lymph nodes may become enlarged and darkened when the deer is fighting an infection.
White-tailed deer do not spread Lyme disease but may be a host for tick species that carry human diseases such as Lyme disease.
Hemorrhagic Disease
Hemorrhagic disease is a general term for epizootic hemorrhagic disease and bluetongue virus. Both diseases are closely related, have similar clinical signs and are spread by a small, biting midge fly. White-tailed, mule and black-tailed deer all are susceptible. Cattle and goats are not affected or show only mild signs of being sick. Sheep are susceptible only to bluetongue virus.
Hemorrhagic disease outbreaks tend to occur from August to September and may go unnoticed because carcasses quickly decompose and are scavenged. Some infected deer may not show obvious symptoms, while others may die in one to three days. Typical symptoms include fever, excessive salivation, swollen neck, tongue or eyelids, sloughed or interrupted growth of hooves, reduced activity and/or emaciation. Because sick deer are feverish, they are often found near water. Not all deer die from the disease, but losses of up to 50 percent have been documented. Researchers speculate that 20 percent of the deer herd was lost in some areas of Missouri during past outbreaks.
The most common evidence that deer have survived the disease is sloughing, or cast and regrowth of the hooves. Their hooves are rough and may regrow much like a finger nail regrows after falling off. The deer are generally in good shape, and the hoof problem is simply a residual effect of the disease. In some cases, the deer have sores on their tongues, dental pads or insides of their cheeks. Their health may vary from excellent to poor depending on the degree to which the sores affect feeding.
Humans do not get hemorrhagic disease, so handling and consumption of meat from deer that have recovered from the disease pose no health hazard. Any animal in a poor, diseased condition, regardless of the cause, may be unfit for consumption. If you find a dead deer and the cause of death is not apparent, report it to your local conservation agent.
Lyme Disease
Deer often are implicated in the spread of Lyme disease. One of the tick species that harbors and spreads the disease is called the "deer tick" in some regions. However, there has never been a documented case of a human contracting Lyme disease through the handling or consumption of venison. The disease actually is caused by bacteria and is spread through certain species of ticks. Deer, other wildlife and domestic animals often are hosts for the ticks that carry Lyme disease and may expand its range.
Deer can become infected with Lyme disease, but they do not carry large numbers of the bacteria. The disease isn't passed from one deer to another or to humans. Deer may have large numbers of ticks and other parasites, and certain deer handling precautions will minimize your exposure to them.
- Hang a deer carcass for a day or two to let many of the ticks drop off. Refrigeration may discourage ticks from dropping.
- Wear latex gloves while dressing and processing deer. Gloves prevent any possible disease transmission through open cuts or abrasions. Wearing gloves is strictly precautionary because there are no documented cases of people acquiring diseases or parasites from dressing deer.
- Treat clothing with permanone or a similar tick spray to prevent most ticks from biting. Take a shower after being in the woods, and check your body closely.
- Cook meat thoroughly. Although there is no evidence to suggest that deer diseases or parasites can be transmitted through venison, thoroughly cooking meat will ensure this.
Nasal Bot Flies
Although unpleasant looking, nasal bot fly larvae do not harm deer and do not infect humans. ( Southeast Wildlife Disease Study photos)
Nasal bot flies (Cephenemyia spp.) are common parasites that infest the nasal passages of deer. They most often are found by taxidermists while preparing heads for mounting, although hunters occasionally notice them.
Adult female flies deposit small larvae in the nostrils of the deer. The larvae enter the nasal passages and pass through several stages of development and growth. They are liberated when the deer sneezes. They then form a pupa and emerge as an adult fly.
Although quite large (up to 1 1/2 inches) and unpleasant looking in the final stages of development, nasal bots cause little harm to the deer and do not infect humans. They also do not affect meat quality.
Cutaneous Fibromas
Cutaneous fibromas, which are caused by a virus, are confined to the skin and do not affect the meat.
These wartlike growths can cover large portions of the body, but usually are small, single to multiple, and range from a fraction of an inch to several inches in diameter. They are caused by a virus that often infects the deer through a wound. Fibromas are more common in bucks because they are more likely to incur wounds while fighting other bucks and rubbing antlers.
Although sometimes grotesque in appearance, fibromas generally do no harm to deer. The virus that causes them to grow in whitetails does not infect other wild animals, domestic animals or humans. Fibromas are confined to the skin and, therefore, are removed when the deer is processed for consumption. They do not affect the quality of the meat.
Tapeworms
Several tape worms can infect whitetails, but one of the most visible is the juvenile stage of the canine tapeworm (Taenia hydatigena). This stage, called the bladderworm, appears as a white oval in the liver or on membranes within the deer's abdominal cavity.
Bladderworms, the juvenile stage of canine tapeworms, are seen above as a white oval on the liver.
Deer become infected by consuming plants contaminated with eggs. The eggs hatch and burrow through the deer's gut wall, enter blood vessels and emerge within the liver. They move to the surface of the liver and enter the body cavity. A coyote or dog can become infected by eating tissues from the abdomen of an infected deer. Deer infected with bladderworms experience minimal ill effects. In addition, bladderworms do not infect humans and do not affect venison quality.
Another species of tapeworm (Echinococcus granulosus), confined mostly to the northern United States and Canada, can be harmful to humans. However, humans become infected by ingesting eggs originating from a dog or coyote, not from consuming deer meat. Cysts in deer caused by this tapeworm are harmless to humans but indicate the parasite is present in the region and infection by other means may be possible.
Abdominal Worms
Hunters dressing deer may encounter the parasite Setaria yehi in the abdominal cavity. It does not affect the quality of the venison.
These slender, white parasites (Setaria yehi) range from 5 to 10 inches in length. They usually are located in the abdominal cavity, so hunters are most likely to find them as they dress their deer. In some cases, 75 percent of deer may have the parasite, but usually the infection rate is lower. Younger deer are more likely to harbor the parasite than older deer.
The life cycle of this parasite is not completely understood. It is thought that mosquitoes serve as intermediate hosts and transmit larval stages of the parasites to deer, the final hosts for the adult worms. Like most parasites, Seteria seldom harm the host deer and are of no significance to other animals or humans. Consumption of meat from a deer infected with Seteria is safe.
Traumatic Injuries
Deer that have suffered injuries due to accidents occasionally are taken by hunters. Injuries may be due to hunter-inflicted wounds or to run-ins with automobiles or fences. Many of these injuries heal without complication, but occasionally they cause infections characterized by dead tissue and pus in and around the wound.
Small, localized infections pose no problems, but large infections
that appear to have spread may affect the general health of the
deer and render it unfit for consumption. Common sense and good
judgment must be used to determine if the animal's injury makes
it unsuitable for the table.
