Wildlife Habitat_Content Page_Disease Bovine tuberculosis (TB)

Bovine tuberculosis (TB)

Bovine Tuberculosis (bovine TB) is a respiratory disease caused by the bacterium Mycobacterium bovis. Bovine TB can infect most mammals, including white-tailed deer and humans. The federal government has done nationwide testing of cattle herds to control bovine TB, but it still occurs sporadically in cattle and wildlife, such as elk and deer.

TRANSMISSION

Bovine TB does not spread easily. It is a chronic, slowly progressing disease, which means it can take months or years to worsen, grow or spread. It is most commonly spread between animals through nasal secretions. This can occur through close nose-to-nose contact, coughing and sneezing in close contact and sharing contaminated feed.

CLINICAL SIGNS

Most deer with bovine TB show no visible signs of illness. The disease progresses very slowly, and in later stages, deer may show signs of respiratory illness, such as coughing, nasal discharge, and difficulty breathing and may look thin or emaciated. Bovine TB causes lesions most commonly found in lymph nodes of the head in harvested deer but may also appear as tan or yellow lumps (small abscesses) on the inside surface of the rib cage and/or the lungs. Very rarely, abscesses may be identified in other organs.

DISEASE MANAGEMENT

The Department annually screens for bovine TB on all harvested deer samples that are submitted for chronic wasting disease testing. Since 1996, more than 150,000 deer in Wisconsin have been screened for bovine TB and no evidence of the disease has been found. Early detection of bovine TB in deer and herd management are the only effective tools for keeping bovine TB out of Wisconsin deer.

Michigan has found TB in its free-ranging white-tailed deer since 1994, and Minnesota has found TB in its free-ranging white-tailed deer since 2005.

PUBLIC HEALTH

Transmission of bovine TB from animals to people can occur, but it is rare. Bovine TB is most commonly spread to humans through consuming unpasteurized milk or milk products from infected animals, and close contact with infected animals or people.

Bovine TB is generally transmitted through the air by coughing and sneezing, and it is highly unlikely a person would contract the disease from field dressing or eating the meat of an infected deer. However, it is always a good idea to wear gloves when field-dressing any animal.

ADDITIONAL INFORMATION