Bureau of Tuberculosis Control

Mycobacterium bovis (M. bovis) Fact Sheet

What is M. bovis?

M. bovis is a germ that primarily causes tuberculosis in cattle, but it may also infect and cause illness among other animals, including humans. In humans, M. bovis can cause a type of tuberculosis that may affect the lungs, lymph nodes, and other parts of the body.

How common is M. bovis tuberculosis?

In the United States and in other industrialized nations where few cattle are infected and milk is pasteurized, M. bovis causes less than 1% of tuberculosis cases in humans.

Since 2001, there have been 35 identified cases of M. bovis tuberculosis in New York City, the majority of which have occurred in Mexican-born adults or children born in the U.S. to Mexican parents.

Who gets M. bovis tuberculosis?

Anyone can become infected with M. bovis, but it generally occurs among people who eat or drink unpasteurized (raw) milk products produced in regions or countries where M. bovis disease is common in cattle, such as Mexico. Young children and individuals with weakened immune systems are at higher risk for disease.

How is M. bovis transmitted to humans?

Humans are generally infected by eating or drinking contaminated, unpasteurized (raw) milk products from areas where M. bovis is present in cattle. M. bovis can also be spread through the air when a person with the disease in their lungs coughs or sneezes. However, airborne transmission is less common than transmission through food.

What are the symptoms of M. bovis tuberculosis?

General symptoms of M. bovis tuberculosis may include fever, night sweats, and weight loss. Other symptoms may manifest themselves depending on the part of the body affected by the disease: disease in the lungs may be associated with a cough; lymph node disease may cause swelling in the neck; and gastrointestinal disease may cause abdominal pain and swelling, and diarrhea. In rare instances, a person may die if the disease is left untreated.

How soon after infection do symptoms appear?

Symptoms generally appear months to years after infection with M. bovis, but some people may never show signs of illness.

How is M. bovis tuberculosis diagnosed?

M. bovis tuberculosis is diagnosed by isolating the bacteria from sites of infection in a patient, such as lymph nodes in the neck or abdomen, or from sputum produced by coughing. Samples are sent to a laboratory for testing to determine if the bacteria is present.

What is the treatment for M. bovis tuberculosis?

M. bovis tuberculosis is treated with a combination of antibiotics.

Should a person with M. bovis tuberculosis go to work or school?

A person with disease of the lungs should not attend work or school until they have started treatment and have been told by a physician that they are no longer contagious.

A person with disease in other parts of the body, such as the lymph nodes or gastrointestinal tract, cannot transmit the disease to other people and can attend work or school.

How can I protect myself from M. bovis?

Do not eat unpasteurized milk products, especially those manufactured in countries where M. bovis is present in cattle, such as Mexico.

How do I know if a product is made from unpasteurized (raw) milk products?

A product that is unlabeled, or does not state that the product is pasteurized on the label may be made from unpasteurized (raw) dairy products. Do not eat these products.

Only eat dairy products that are labeled "pasteurized."

• Some Mexican grocery stores and door-to-door vendors may sell unlabeled cheeses that may be produced in Mexico and may not be pasteurized.

Make sure that the following products - which may be transported from Mexico to New York City via courier services or "paqueterias" - have food labels that say "pasteurized":

• Cotija
• Crema Mexicana
• Queso fresco
• Queso blanco

What are the benefits of pasteurization?

Pasteurization is a heating process that kills harmful germs that may be present in milk. Consuming unpasteurized dairy products, particularly if you have a weakened immune system, may increase your risk of other diseases such as:

• Salmonellosis
• Listeriosis
• E. coli O157 infection

Diseases caused by these germs can be prevented by avoiding unpasteurized dairy products.