APHIS Factsheet

Veterinary Services March 2014

Questions and Answers: 

Bovine Tuberculosis

Signs and Symptoms

Q. What is bovine tuberculosis (TB)?

A. Bovine TB is a contagious, chronic bacterial disease 

caused by Mycobacterium bovis. The infection 

commonly involves the lungs, but it may spread to 

other organs. Animals often don’t show signs until the 

infection has reached an advanced stage.

Q. What animals can it affect?

A. Bovine TB primarily affects cattle, but it can be 

transmitted to any warmblooded animal, including 

people.

Q. What are the symptoms of bovine TB? 

A. Bovine TB is difficult to diagnose with clinical signs 

alone. In the early stages of TB, clinical signs are 

not visible. In later stages, clinical signs may include: 

emaciation, lethargy, weakness, anorexia, low-grade 

fever, and pneumonia with a chronic, moist cough. 

Lymph nodes may also be enlarged.

Q. What should I do if my animals show these 

symptoms?

A. If you suspect TB in your herd, you should isolate 

the animal immediately and then call your veterinarian 

for a proper diagnosis.

How Bovine TB Can Spread 

Q. How does TB get into cattle herds?

A. TB can be introduced into a herd by infected animals 

or people. In the United States, the two most common 

methods of introduction are:

1) Purchase of or exposure to infected cattle, or

2) Exposure to infected free-ranging wildlife.

The bacteria that causes bovine TB is found in the 

saliva of infected animals and spread through airborne 

particles from the respiratory tract. The bacteria 

can also spread through feed or watering sites 

contaminated with saliva and other bodily discharges 

(urine, manure) or by drinking raw, unpasteurized milk 

from infected animals. The risk of exposure is greatest 

in enclosed areas, such as barns with poor ventilation.

Q. How can I reduce the risk of my cattle herd being 

infected with TB?

A. Following these best practices will help keep TB out 

of your herd:

•	 Have your livestock tested for TB and, if 

possible, keep a closed herd and raise your 

own replacement stock.

•	 Buy your animals from an accredited TB-free 

herd, test the new animals prior to purchase, and 

finally, isolate them for 60 days and retest before 

commingling them with your herd. 

•	 Restrict or eliminate all contact between your 

herd and other herds.

•	 Clean with a disinfectant any trailers or facilities 

that have housed newly purchased animals or 

animals that did not originate from your herd.

•	 Keep on-farm visitors away from your herd 

whenever possible. This includes milk haulers, 

feed delivery personnel, and anyone who may 

have contact with other herds.

•	 Make sure your fences are in good condition 

to separate your herd from wildlife. If the 

wildlife in your area is affected by TB, contact 

the U.S. Department of Agriculture (USDA) 

Wildlife Services office in your State for advice 

on reducing wildlife contact with your herd. 

You can reach Wildlife Services staff by calling 

1-866-4USDA-WS (1-866-487-3297).

Q. Are dairies more susceptible to bovine TB?

A. The layout and activities of a dairy operation offer 

a greater chance for exposure to bovine TB than those 

of a beef operation. Dairy cows spend more time in 

enclosed areas or in crowded conditions, where there 

is a higher risk of exposure. Unpasteurized milk and 

unpasteurized colostrum, which are two main sources 

of nourishment for calves, can also spread the disease.

Bovine TB Testing

Q. How does USDA test for bovine TB?

A. USDA uses two methods to test for bovine TB. The 

main method of testing is a tuberculin skin test, where 

the animal receives an injection of tuberculin in the skin 

and is checked for a reaction 72 hours later. There is 

also a nationwide surveillance program in slaughter 

plants. If lesions consistent with bovine TB appear on a 

carcass, a sample is sent to USDA’s National Veterinary 

Services Laboratories for confirmation.
Q. How many animals in the United States are 

tested for bovine TB each year?

A. Each year, more than 1 million animals receive a 

skin test, and approximately 11,000 cattle are sampled 

during slaughter surveillance.

Q. Typically, when are animals tested for bovine TB?

A. Animals are tested if they are:

•	 Suspected of having bovine TB;

•	 Part of an epidemiological investigation, such as 

a TB trace from an affected herd;

•	 Required to for participation in a show or exhibition;

•	 Required to for a change of ownership;

•	 Preparing for interstate movement; or

•	 Part of surveillance activities at slaughter.

Wildlife and TB

Q. Does wildlife spread TB to commercial cattle?

A. Wildlife and cattle with TB can pass the infection to 

each other.

Q. What is the risk of TB transmission from local 

wildlife?

A. In areas where free-ranging deer are known to be 

infected with TB, deer that have direct contact with 

cattle could pose a risk of transmitting the disease. 

While the risk of transmitting TB is greatest in enclosed 

areas, such as barns, livestock can become infected 

if they share common watering or feeding places 

contaminated with saliva and other bodily discharges 

from infected wildlife.

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Q. How can I find out if the wildlife in my area 

has TB?

A. Contact your State’s game and fish commission or 

department of natural resources. You can find specific 

contact information for State and local government 

agencies on the U.S. Government’s official Web portal 

at www.usa.gov.

Q. What steps can I take to keep my cattle safe from 

TB in wildlife?

A. Always practice good biosecurity and avoid keeping 

livestock in the same enclosure as wildlife. Try to 

keep wildlife away from outdoor feeding and watering 

containers, such as troughs and pools. Additionally, 

store your animal feed in areas that wildlife cannot 

access. Should wildlife get into stored feed, discard that 

feed immediately, and do not give it to your cattle.

Learn More

For more information on bovine TB, please visit USDA’s 

Animal and Plant Health Inspection Service Web site 

at www.aphis.usda.gov. Click on “Animal Health,” then 

“Animal Disease Information,” and then “Tuberculosis.”