Tuberculosis due to Mycobacterium bovis in the Australian population: cases recorded during 1970-1994

OBJECTIVE: To determine the contribution of Mycobacterium bovis to active t uberculosis in the Australian population during 1970-1934, and to collate a nd analyse demographic data from bacteriologically proven cases. DESIGN: Summary data for tuberculosis cases notified by Australian public h ealth agencies during 1970-1985 and 1991-1994 were obtained from the databa se of notifiable diseases maintained by the Department of Health and Family Services. More detailed demographic data for cases confirmed by bacteriolo gy during 1970-1994 were supplied by the Australian Mycobacterium Reference Laboratory Network. RESULTS: At least 236 cases of bovine tuberculosis (TB) occurred in the Aus tralian population during 1970-1994 (mean 9.4 cases; range 3-22 cases annua lly). The bovine strain has accounted for around 1% of Australian cases of TB during this period. Laboratory sources provided demographic data for 150 cases with positive bacteriology. For this group, the mean age was 54 year s (range 22-86), and the male:female ratio was 2.4:1. The majority of cases (74%) involved pulmonary disease. Australian-born persons accounted for 68 % of the total cases and typically had histories of employment in meat and/ or livestock industries. CONCLUSION: M. bovis was responsible for less than 1.5% of cases of TB in t he Australian population during 1970-1994. Most cases were apparently due t o reactivation of infection acquired through occupational exposure. Thus, a lthough virtual eradication of M. bovis from Australia's cattle herds has n ow reduced the risk of exposure, it can be expected that human cases of bov ine TB will continue to be detected for years to come. The bovine strain sh ould be considered as the possible agent of TB in foreign-born Australians.