Epidemiological evidence of the presence of non-tuberculous sensitivity to tuberculin in Queensland

Abstract

Summary The proportion of children in Brisbane, aged 13–14, who reacted to the multiple puncture test Old Tuberculin was 21 %. This percentage is much higher than those reported from southern Australian cities (2·5% to 7·6%). The proportion in tropical Queensland was still higher—Rockhampton 93%, Cairns 41%, Ayr 40%. In Roma, in south-west Queensland, it was 29 %. The proportion who reacted with induration of at least 6 mm. to PPD‘S' (prepared from a standard human strain) intracutaneously was 52% in Rockhampton, but in the other Queensland towns was low and comparable to the Old Tuberculin rates in southern capitals. The following evidence suggests that the high incidence of sensitivity to Old Tuberculin in these areas is not due solely to infection with human or bovine tubercle bacilli: (a) the generally low incidence of sensitivity to PPD‘S'; (b) the absence of an excess of active cases of tuberculosis in Queensland; (c) the significant absence of cases of nodal, osseous and peritoneal tuberculosis, such as are associated with bovine infection; (d) the pasteurisation of milk supplies in the towns investigated. Reactions to PPD-Battey varied from 30% in Brisbane to 81% in Rockhampton. However, the mean reaction size decreased as the percentage of reactors increased. The results in Brisbane showed a close correspondence with those of the multiple puncture with O.T. test. This correspondence was much less in tropical Queensland. In Brisbane, there was also a close correspondence between the results of the O.T. multiple puncture test and those obtained with PPD from Myco, tuberculosis var. avis . In a second survey in Cairns, a considerable degree of cross-reaction was observed between PPD preparations of Myco, tuberculosis on the one hand, and those of Myco. fortuitum or ‘yellow bacillus' on the other. The larger and more frequent reactions to these two PPD's than to PPD‘S' suggest that the organisms which may be causing sensitisation to Old Tuberculin in this area are more allied antigenically to Myco. fortuitum and ‘yellow bacillus' than to Myco. tuberculosis . Reaction to PPD- Nocardia was negligible. The high rate of sensitivity of Queensland children to Old Tuberculin may be due to infection with various mycobacteria which vary from place to place in their relative importance.