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National Wildlife Research Center NWRC)

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photo of deer

Controlling Wildlife Vectors of Bovine Tuberculosis

Bovine tuberculosis (bTB) is a contagious disease of both animals and humans caused by the bacterium, Mycobacterium bovis. There are 3 main types of TB: human, avian, and bovine. Bovine TB is the most infectious and capable of infecting most mammals. Bovine TB is a chronic disease, seldom becoming apparent until it has reached an advanced stage in animals. The disease originated from the Old World and was imported in cattle during European settlement in the United States and Canada.

Evidence suggests that deer can transmit the disease to cattle. Livestock and members of the deer family can get bTB from saliva or airway secretions transferred directly from one animal to another. They can also get the disease indirectly from eating contaminated feed. Bovine TB has been diagnosed in deer (about 1.7%), elk , raccoons, opossums, black bear, red fox, and bobcats (about 1%) and coyotes in 7 counties from the lower Michigan peninsula. In fact, scientists at the NWRC found that nearly 30% of coyotes in the bTB-affected zone in Michigan were infected with bTB.

In 2000, The United States Secretary of Agriculture enacted Declarations of Emergency for bovine tuberculosis, citing threats to livestock and human health and safety. In an effort to eradicate bTB, NWRC was directed to conduct research that would lead to a reduction or elimination of the potential transmission of this disease from wildlife to cattle.

NWRC scientists have found that the use of fences, guard dogs, and scare devices are useful in reducing deer/cattle interactions. However, infection in deer persists, and occasional cattle infection occurs. Also, NWRC scientists have nearly completed work on a population simulation model (SWARM) in an attempt to predict the spread or possible elimination of bTB in Michigan. Research also began, in cooperation with APHIS Veterinary Services, and is continuing, on development of an oral BCG vaccine for deer. Other studies are being conducted by NWRC scientists that will evaluate the applicability of using infrared technology to better be able to detect infected deer and cattle that may aid in screening animals infected with M. bovis.

The presence of bTB in Michigan’s white-tailed deer remains a serious problem. The disease threatens Michigan’s livestock industry and the region’s deer and elk herds which have significant social, ecological, cultural, and economic value to the citizens of Michigan. Bovine TB found in cattle populations in other areas of the U.S., especially where deer numbers are high, could also threaten to become established in deer as has occurred in Michigan. For example, in 2005, bTB was found in Minnesota’s cattle populations.

Although much has been accomplished by NWRC scientists, often in cooperation with various state and other federal agencies, much needs to be done. Bovine TB infected deer continue to spread the disease county by county in Michigan and whether prevalence of infection in deer is declining seems uncertain. Reduction of the infection rate in cattle has apparently declined significantly, but because of infected wildlife, the threat of infection to cattle and humans, and the threat of spread of the disease remain high.

Project Leader: Dr. Mike R. Dunbar,
(mike.r.dunbar@aphis.usda.gov)
USDA/APHIS/WS/NWRC
Fort Collins, Colorado 80521
(970) 266-6360

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Last Modified:

November 7, 2007