Can my pet get bovine TB?
Dogs, cats and horses can be infected with bovine TB, but the risk is very low. Actually, dogs and cats are more likely to be infected by Mycobacterium tuberculosis, or human TB, through exposure to their human family members who have the disease; or by Mycobacterium avium, or avian (bird) TB, from eating infected birds. These forms of TB are caused by different species of bacteria, but the symptoms and effects of the diseases are similar.
What is Bovine Tuberculosis?
Bovine tuberculosis (TB) is a disease caused by the bacterium Mycobacterium bovis. In the U.S., the disease is found primarily in cattle, captive cervidae (deer and elk), bison and goats, but can affect any warm-blooded animal, including humans. In June 1998, bovine TB was confirmed in a beef cow in Alpena County. Since that time the disease has been confirmed in multiple cattle herds in Michigan. Bovine TB has also been detected in numerous captive and wild deer as well as wild carnivores such as coyote and bobcat, and in one case a domestic outdoor cat.
How Bovine TB is Spread
Bovine tuberculosis is most commonly spread through respiration. Invisible droplets (aerosols) containing TB bacteria may be exhaled or coughed out by infected animals and then inhaled by animals or humans.
Animals who come in close contact with infected wild deer on pasture, or those kept in close contact with other infected animals in enclosed areas like barns, are at greatest risk for exposure to bovine TB.
Livestock and deer may also infect each other when they share and ingest water or feed that has been contaminated with saliva and other discharges from infected animals.
Animals and humans can contract bovine TB when they drink unpasteurized milk from infected cows, or consume raw or undercooked meat from infected animals. Horses very rarely contract TB. In cases where horses have contracted bovine TB, they were most likely kept in close contact with infected cattle over a long period of time. Cats also rarely contract bovine TB, but when they do the most likely source is from drinking unpasteurized milk from infected cows or eating from carcasses or gut piles of animals infected deer. Dogs are most likely to contract bovine TB from ingesting carcasses or gut piles of animals infected by the disease also, but cases of bovine TB in dogs are also rare.
Symptoms of Bovine TB
Dogs, cats and horses infected by any form of tuberculosis may not show any outward signs of illness, or they may exhibit weight loss and a gradual decline in general health.
If the disease was contracted by breathing in the bacterium, symptoms could include shortness of breath, cough and other symptoms of lung disease.
When contracted by ingesting unpasteurized milk or raw meat from an infected animal, as would be the case with dogs and cats, the disease would affect the animal's digestive tract. TB lesions may be found in any organ or body cavity of diseased animals.
Testing for the Disease
There is a live test for tuberculosis in dogs, but it is not very reliable. There are no live tests currently available for diagnosing tuberculosis in cats or horses. Infection is usually determined through laboratory tests after the animal has died. There are currently no preventative bovine TB vaccines for animals.
How to Reduce the Risk of Exposure
The most effective way to reduce the risk of TB exposure in humans and domestic animals is to eliminate the disease in livestock and wildlife.
Humans, cats and other animals should not drink raw, unpasteurized milk; and cats and dogs should not be allowed to ingest possibly infected carcasses.
Dogs and cats should not be allowed to roam freely where they could feed on carcasses of dead animals. If you have cattle, goats, bison or captive cervidae, your entire herd should be tested for TB by an accredited veterinarian, to make sure the disease is not present in your herd.
For more information about bovine TB in Michigan, please contact:
MDARD Animal Health Liaison (517) 241- 4339
MDCH Communicable Diseases (517) 335-8165
MDNR Rose Lake Wildlife Research Station (517) 373-9358
MSU Contact your local county extension agent or ANR Communications at (517) 432-1555
USDA -(517) 324-5290