What Is Mycobacterium Bovis?

Medically Reviewed by Jabeen Begum, MD on October 13, 2022
Written by Alicia Ramella
4 min read

Do you work closely with domestic animals? Have you recently consumed undercooked meat from a wild animal? If so, you may have been exposed to Mycobacterium bovis, a foodborne pathogen. 

Let's dive into what Mycobacterium bovis is, its symptoms, and how it's transmitted, diagnosed, and treated. Then, we'll look at ways to prevent contamination.

Mycobacterium bovis (M. bovis) is a bacterium belonging to the Mycobacterium tuberculosis group that causes bovine tuberculous disease in humans and animals. Most human tuberculosis (TB) cases come from Mycobacterium tuberculosis (M. tuberculosis). M. bovis also has an extensive range of hosts that can carry the bacteria and develop mycobacterium bovis tuberculosis.

Those affected may include:

  • Humans
  • Cattle 
  • Deer 
  • Bison
  • Pigs
  • Buffalo
  • Cats
  • Dogs
  • Goats
  • Badgers
  • Possums
  • Primates

M. bovis can also cause asymptomatic TB, which may not show any symptoms. This is called a "latent TB infection" (LTBI). People with LTBI cannot spread the disease and usually feel no symptoms. Over time, however, the latent form can turn into symptomatic TB.

TB can be transmitted through the air or infected food and milk. People can also become infected after receiving a cut from an infected animal or another type of open wound.

Some people who are infected with Mycobacterium bovis never display any symptoms. You may also have the infection and simply not notice any symptoms right away. Around four weeks in, though, some possible Mycobacterium bovis symptoms can include the following:

  • Fever
  • Night sweats
  • Weight loss 
  • Coughing 
  • Swelling of the lymph nodes 
  • Swelling of the abdomen
  • Diarrhea 
  • Fatigue

If the disease goes untreated for too long, you can die. However, this is a rare occurrence, as people receive successful treatment most of the time. Alternatively, the condition can go unnoticed, remaining dormant for an entire lifetime.

M. tuberculosis and M. bovine cause similar symptoms. Humans, other primates, and guinea pigs are highly susceptible to M. tuberculosis. Cattle, rabbits, and cats are more susceptible to M. bovis. Pigs and dogs are vulnerable to both strains. When humans contract M. tuberculosis, it is almost always spread from another human rather than an animal.

In terms of their respective symptoms, M. Bovis is more often an intestinal disease, whereas M. tuberculosis more commonly affects the lungs.

Mycobacterium bovis is a zoonotic disease that infects humans and animals and transmits between them. You can breathe in the pathogen, or the condition can be transferred via infected milk or food.

This risk of transmission can be significantly reduced by pasteurization: the process of heating milk to a temperature high enough to kill bacteria. M. bovis was actually one of the diseases that motivated the original implementation of the pasteurization process in the early 1900s because small children were contracting the disease from drinking contaminated milk. M. Bovis infections caused approximately 5–30% of all human TB cases in the United States and the United Kingdom during that time.

Even today, people working on farms or in close contact with animals are at a greater risk of infection. A recent study found that slaughterhouse workers, livestock farmers, and butchers had the most significant risk of becoming infected by M. bovis.

Also, in places where pasteurization is not mandatory, the risk of drinking contaminated milk is significant. TB developing from mycobacterium bovis transmission to humans has become quite rare, though. Today, less than 2% of reported human tuberculosis cases come from M. bovis.

A TB blood test and a TB skin test are available to determine whether you have tuberculosis, and they are broadly recommended to a subset of people who are more likely to develop symptomatic tuberculosis. These high-risk individuals include:

  • People who have HIV
  • Young children
  • People with suppressed immune systems
  • People who inject drugs
  • Elderly people

M. bovis is often treated the same way as M. tuberculosis because health care professionals often don’t know which one you have. Mycobacterium bovis treatment involves the use of a few antibiotics together, often including rifampicin, isoniazid, and ethambutol.

The M. bovis strain is resistant to the antibiotic pyrazinamide, one of the antibiotic medications used to treat M. tuberculosis.

The most common way to become infected with M. bovis is by drinking unpasteurized milk, so the best preventative measure is to avoid doing so. 

Additonally, if you hunt or work closely with animals, you should wear protective equipment to reduce your chances of contracting this disease. If you believe you have been exposed to M. bovis, seek medical attention as soon as possible.