Submitted to: Review Article
Publication Type: Review Article
Publication Acceptance Date: November 20, 2007
Publication Date: January 1, 2008
Citation: Palmer, M.V. 2008. Mycobacterium bovis Shuttles between Domestic Animals and Wildlife. Microbe. 3(1):27-34.
Interpretive Summary: Complex interactions involving humans, domestic animals and wildlife create environments favorable to the emergence of new diseases. Today, reservoirs of Mycobacterium bovis, the causative agent of tuberculosis in animals and a serious disease communicable to humans, exist in wildlife. The presence of these wildlife reservoirs is the direct result of spillover from domestic livestock, human factors such as translocation of wildlife, supplemental feeding of wildlife and wildlife populations reaching densities beyond normal habitat carrying capacities due to human intervention. As many countries attempt to eliminate M. bovis from domestic livestock, efforts are impeded by spillback from wildlife reservoirs. It will not be possible to eliminate M. bovis from livestock until transmission between wildlife and domestic animals is halted. Such an endeavor will require a collaborative effort between agricultural, wildlife, environmental and political interests. Novel tools such as improved diagnostic methods an vaccines may be needed.
In the early 20th century there were large numbers of tuberculous cattle in many countries. An association was made between the number of M. bovis infected humans and the prevalence of tuberculosis in cattle. Mandatory pasteurization of milk caused the prevalence of human tuberculosis due to M. bovis to decline in developed countries. In some countries eradication has been prevented by several factors not least of which is the presence of a wildlife reservoir of M. bovis. In Great Britain evidence suggests that M. bovis is endemic among badgers (Meles meles), and that tuberculous badgers are the source of infection for cattle. In New Zealand, brushtail possums (Trichosurus vulpecula), first taken to New Zealand in the mid-19th century now occupy over 90% of New Zealand’s land mass and serve as a source of M. bovis for domestic livestock. In Michigan, USA free-ranging white-tailed deer (Odocoileus virginianus) represent the first reservoir of M. bovis in free-living wildlife in the United States. Deer to cattle transmission of M. bovis has been documented. Wildlife reservoirs of M. bovis represent a serious challenge to the eradication of M. bovis. The presence of wildlife reservoirs is the direct result of spillover of M. bovis from domestic livestock and efforts to eradicate M. bovis from domestic livestock are impeded by spillback from wildlife reservoirs. The test and slaughter policies of tuberculosis control, effectively used with livestock, are insufficient where wildlife reservoirs exist. It will not be possible to eradicate M. bovis from livestock until transmission between wildlife and domestic animals is halted. Such an endeavor will require a collaborative effort between agricultural, wildlife, environmental and political interests.