Mycobacterial infection, epidemiological trends -New Zealand

Abstract

The incidence of tuberculosis in New Zealand has fallen steadily over the last 25 years from 52 cases per 100,000 in 1962 to 7.8 cases per 100,000 in 1987. The rate of decline has been greater in Maoris than Europeans, but Maoris still have almost double the rate of infection - 5.5 per 100,000 c.f. 3.3 per 100,000. Resistance to isoniazid or rifampicin occurs in about 10% isolates, but resistance to other anti-tuberculous drugs is rare in N.Z. acquired M. tuberculosis. The isolation of M. bovis has also declined. In the Auckland area there were 13 infections in 1970 and 12 in 1980 but since 1986 there have been fewer than 5 cases each year. Atypical mycobacteria are being isolated more frequently. Only 2 isolates were cultured in 1970 compared with 15 in 1988 but only 5 of these 15 were associated with known H.I.V. infection. During 1889 blood cultures yielded 9 isolates of M. avium intracellular from H.I.V. positive patients. Most atypical mycobacteria were resistant to four or more antituberculous drugs. Although tuberculosis is uncarmon, physician awareness trust be maintained because delay in diagnosis increases the risk of spread of this disease.