Status of bovine tuberculosis in North America.

The eradication of bovine tuberculosis from North America is in the advanced stages as Canada and the United States struggle to remove the last vestiges of the disease from the domestic livestock population. Canada realistically anticipates total eradication from the national cattle herd within the next few years. The United States must yet effectively deal with the increased tuberculosis exposure potential from imported steers and from bovine tuberculosis newly discovered in its captive cervid industry. This paper reviews the history and development of tuberculosis eradication programs in North America. The basic evolution is described from area testing to slaughter surveillance with follow-up epidemiological investigations as the program foundation. The current status of both countries is described and recognized deterrents to final eradication are discussed.

Mycobacterium bovis infections in San Diego: a clinicoepidemiologic study of 73 patients and a historical review of a forgotten pathogen.

We have presented 73 patients (48 adults and 25 children) with microbiologically documented M. bovis infections identified over the 12-year period from 1980 through 1991. Epidemiologic investigation of these patients revealed that the majority (80%) were of Hispanic origin. The non-Hispanic patients either had traveled extensively outside the United States, were born in the United States during its endemic period or in other countries with endemic bovine tuberculosis, or were exposed to a close relative with a positive PPD and known exposure to M. bovis. For Hispanic patients, the presence of reactivation disease in adults and primary disease in children indicate that this mycobacterium remains endemic in Mexican beef and dairy herds, a position supported by United States monitoring of Mexican cattle transferred across the border. Our review of the historical and contemporary efforts to eradicate this animal and human pathogen from the livestock industry in the United States and abroad shows that the implementation of similar methods could be effective in Mexico. The detailed presentations of selected patients and summaries of the clinical manifestations in the remainder of our 73 patients reveal striking similarities to historical accounts and to more contemporary studies of reactivated disease in England. Although M. bovis infections are still expressed predominantly in extrapulmonary sites (cervical and mesenteric nodes, the peritoneum, and the GU tract), as many as 50% of adult patients will present only with pulmonary disease. Underlying immunosuppressive disorders were particularly prominent in adults with extrapulmonary disease. For example, HIV positive patients accounted for 12 of 48 adults and 1 adolescent patient in our series. Overall, M. bovis infections accounted for almost 3% of all tuberculous disease reported in San Diego County during the study period. The intrinsic resistance of M. bovis to PZA could threaten the response of patients with bovine tuberculosis to the short-course chemotherapeutic regimens now recommended by the CDC and the American Thoracic Society. We strongly recommend continued surveillance for this forgotten pathogen because the importation of Mexican cattle, the migration of Hispanic immigrants from border areas to the United States interior, and the persistence of extrapulmonary disease in immunocompetent and HIV-infected United States citizens assure its persistence in this country.

Tuberculosis in greater kudu.

Four greater kudu (Tragelaphus strepsiceros) died while maintained in captivity at a zoo. Necropsy revealed tuberculous lesions in the lungs, spleen, and thoracic lymph nodes. Histopathologic findings included granulomas with Langhans' giant cells, necrosis, and mineralization. Acid-fast organisms isolated from tissues of each kudu were identified as Mycobacterium bovis.