Author
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Waters, Wade |
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Submitted to: Book Chapter
Publication Type: Book / Chapter Publication Acceptance Date: 7/5/2012 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Tuberculosis (TB) in animals and humans may result from exposure to bacilli within the Mycobacterium tuberculosis complex (i.e., M. tuberculosis, M. bovis, M. africanum, M. pinnipedii, M. microti, M. caprae, or M. canetti). Mycobacterium bovis is the species most often isolated from tuberculous cattle and it is infectious to humans (zoonotic). Within the United States, bovine tuberculosis is nearly eradicated in cattle; however, sporadic cases are detected primarily due to on-going importation of tuberculous cattle from Mexico, spillover from a wildlife reservoir host (i.e., white-tailed deer, Odocoileus virginianus) in the NE region of the lower peninsula of Michigan, and transmission from captivecervids infected with M. bovis. Primary control strategies for bovine TB include: diagnosis via tuberculin skin test and/or interferon-gamma release assays, isolation of affected herds, sub-isolation of infected animals within affected herds (i.e., Bang Method), slaughter of infected animals, slaughter surveillance, and movement / border testing policies. While often viewed as a pulmonary disease in humans, TB is primarily a disease of the lymphatic system. With ruminants, tuberculous lesions are most commonly detected within pulmonary and cranial lymph nodes as well as lungs. Postmortem diagnosis is based upon: (1) gross and microscopic evaluation for tuberculous lesions, (2) detection of the organism by mycobacterial culture of tissues with follow-up confirmation/characterization using molecular techniques, and (3) detection of M. tuberculosis complex specific DNA by PCR on histologic sections. Many countries have official bovine TB eradication / control programs including uniform methods and rules for application. Prevention and control efforts are designed to identify affected herds and remove infected animals or depopulate the entire herd (stamping out). These efforts are generally achieved via routine slaughter surveillance to identify affected herds, targeted testing schemes to remove TB test positive animals (reactors), movement restriction of affected herds, thorough epidemiologic investigations of reported cases to determine risks for other impacted herds, and depopulation of affected herds. Additionally, movement testing with certification of a negative TB test(s) may be required prior to entry of animals into certain countries or regions, particularly with animals entering from bovine TB-affected regions. Additional research is needed in the areas of diagnostic testing, environmental sampling, vaccine development, and management practices that may decrease the risk of disease spillover from wildlife reservoirs to cattle. |
