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

OBJECTIVE: To determine the contribution of Mycobacterium bovis to active tuberculosis in the Australian population during 1970-1994, and to collate and analyse demographic data from bacteriologically proven cases.DESIGN: Summary data for tuberculosis cases notified by Australian public health agencies during 1970-1985 and 1991-1994 were obtained from the database of notifiable diseases maintained by the Department of Health and Family Services. More detailed demographic data for cases confirmed by bacteriology during 1970-1994 were supplied by the Australian Mycobacterium Reference Laboratory Network.RESULTS: At least 236 cases of bovine tuberculosis (TB) occurred in the Australian population during 1970-1994 (mean 9.4 cases; range 3-22 cases annually). 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 years (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 the Australian population during 1970-1994. Most cases were apparently due to reactivation of infection acquired through occupational exposure. Thus, although virtual eradication of M. bovis from Australia's cattle herds has now reduced the risk of exposure, it can be expected that human cases of bovine TB will continue to be detected for years to come. The bovine strain should be considered as the possible agent of TB in foreign-born Australians.