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Bovine Tuberculosis

WHAT IS BOVINE TUBERCULOSIS?

Bovine TB is an infectious disease that is caused by the bacterium Mycobacterium bovis (M. bovis). Bovine TB primarily affects cattle, however, other animals may become infected. M. bovis causes a disease that can be transmitted between wildlife populations and food animals (e.g., cattle). Disease due to M. bovis in animals typically presents in the lungs but may also occur in the intestines or other parts of the body.

Report Sick or
Dead Deer or ELK

	CALL Kentucky Fish and Wildlife at 1-800-858-1549 from 8 a.m. to 4:30 p.m. (Eastern) on weekdays.
	CONTACT your area’s regional biologist.
	SUBMIT observations online via our reporting application.
	Found an injured animal? Contact a permitted wildlife rehabilitator.

DISEASE INFORMATION

What are the symptoms of bovine TB in deer?

Bovine TB is a progressive, chronic disease. It can take months to years from time of infection to the development of clinical signs. Unlike most bacteria, bovine TB grows very slowly and only replicates every 12-20 hours. 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. In severely infected deer, lesions can usually be found throughout the animal’s entire body.

Lung lobes with pearl-like abscesses on the surface.
Photo c/o of the Minnesota DNR

How is bovine TB spread?

Bovine TB is spread primarily through the exchange of respiratory secretions between infected and uninfected animals. This transmission usually happens when animals are in close contact with each other. Animals may also become infected with TB by ingesting the bacteria. Thus, animal density plays a major factor in TB transmission. Bacteria released into the air through coughing and sneezing can spread the disease to uninfected animals. Research also suggests that bovine TB can also be contracted from ingesting contaminated feed. Survival of TB in the environment is reduced by exposure to sunlight. Reports on the length of bacterium (M. bovis) survival vary from 18 - 332 days at temperatures ranging from 54-75 F.

Can bovine TB spread from infected cattle to wild deer and vice versa? Although bovine TB was once relatively common in U.S cattle, it has historically been a very rare disease in wild deer. Prior to 1994, only eight wild white-tailed and mule deer had been reported with bovine TB in North America. In 1995, bovine TB was detected in wild deer in Michigan. The M. bovis strain isolated from the infected Indiana and Kentucky herd is a unique strain and does not match that found in Michigan. Kentucky has no history of tuberculosis infection in deer or other wildlife.

How is bovine TB diagnosed?

Bovine TB infected deer not showing lesions in the chest cavity can be diagnosed by performing a visual inspection of the lymph nodes in the deer’s head. Affected lymph nodes, when cut, will contain one or more variably sized pus-filled nodules. Suspicious looking lymph nodes are removed for further testing at approved laboratory facilities.

How is bovine TB treated?

There are no effective vaccines for disease prevention and no effective medications for treatment of bovine TB in wild deer. Instead, a combination of wildlife disease surveillance and deer management strategies can be used to eliminate the disease if present in wild deer. Wildlife surveillance monitors the spatial distribution and prevalence of the disease, while hunters are also asked to examine their deer.

Has bovine TB been detected in Kentucky?

In May of 2010, bovine TB was found in a beef cattle herd in Kentucky's Fleming County. This was the first positive case in Kentucky since 1987. Wildlife surveillance around the affected premises did not detect any additional infected wildlife. In April of 2016, bovine TB was detected on a cattle farm consisting of two premises in Southeastern Indiana. As part of the response to that event, wildlife was removed and tested from the affected areas and a wild white-tailed deer doe removed from the affected premise tested positive for bovine TB. This marked the first time the disease was found in wild deer in Indiana. Kentucky has no history of tuberculosis infection in deer or other wildlife.

Does bovine TB pose a risk to people or other animals?

Bovine TB primarily affects cattle, however, other animals may become infected, such as white-tailed and mule deer. Until the disease was detected in white-tailed deer in Michigan in 1994, it has historically been very rare in wild deer. Other mammals are most likely to contract bovine TB from feeding on infected tissues from deer carcasses. In Michigan, bovine TB has also been found in black bear, bobcat, coyote, opossum, raccoon, and red fox. Worldwide, bovine TB has been reported in a variety of mammals and is established in populations of European badgers in the UK, cape buffalo in South Africa, brush-tailed possums in New Zealand, and wood buffalo and elk in Canada.

Although bovine TB was once relatively common in U.S cattle, it has historically been a very rare disease in wild deer. Prior to 1994, only eight wild white-tailed and mule deer had been reported with bovine TB in North America. The M. bovis strain isolated from the infected Indiana and Kentucky herd is a unique strain and does not match that found in Michigan.

In the U.S. today, the threat of humans contracting bovine TB from animals is extremely remote. Most human tuberculosis is caused by the bacteria M. tuberculosis, which is spread from person to person and rarely infects animals. Bovine TB is caused by the closely related bacteria M. bovis, which is capable of infecting all mammals including people. The United States has actively pursued a bovine tuberculosis eradication program since 1917. This program, together with food safety initiatives such as the pasteurization of milk, has been very effective in reducing the likelihood of people contracting tuberculosis from M. bovis.

INFORMATION FOR HUNTERS

How can I tell if my deer is infected with bovine TB?

Hunters do not always readily recognize small lesions in deer. Abscesses may not be visible to hunters when field dressing deer. Infected animals may have yellow to tan, pea-sized nodules in the chest cavity or lungs. Lymph nodes of the head and neck can be swollen and soft. In fact, most infected white-tailed deer appear healthy. In Michigan, only 42% of the bovine TB positive deer had lesions in the chest cavity or lungs that would be recognized as unusual by most deer hunters. These deer had tan or yellow lumps on the inside surface of the rib cage and/or in and on the lung tissue.

What precautions should I take when field dressing deer or handling meat?

In the U.S. today, the threat of humans contracting bovine TB from animals is extremely remote. However, good field-dressing techniques are important to avoid contact with TB and other wildlife pathogens. The best way to insure your safety is to wear disposable rubber gloves when gutting a deer or elk and wash your hands after field dressing or handling raw meat. Special attention should be paid to the lungs and chest cavity where small lesions may be evident in an infected animal. As a precaution, all meats (including deer), should be thoroughly cooked to an internal temperature of 165 degrees F. This effectively kills all known bacteria, including TB and E. coli.

Is it safe to eat venison?

Yes, venison from deer harvested in Kentucky is safe to eat. Kentucky has no history of tuberculosis infection in deer or other wildlife. While it is possible to transmit bovine TB from animals to people, the likelihood is extremely rare. It is highly unlikely that a person field dressing or eating the cooked meat of animals infected with bovine TB would become infected. The TB bacterium is very rarely found in meat (muscle tissue). Since bovine TB is primarily spread through respiration, the bacterium is generally found in lung tissue. As a precaution, all meats (including venison), should be thoroughly cooked to an internal temperature of 165 degrees F. This effectively kills all known bacteria, including TB and E. coli.

How can hunters help?

Hunters can help by reporting any unusual lesions on deer to the Kentucky Department of Fish and Wildlife Resources wildlife veterinarian at 1-800-858-1549. If possible, keep the carcass or affected tissues on ice. We will advise you about the appropriate use of the animal and may collect tissues for diagnostic testing if warranted.

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