Transmission of tuberculosis in the prison of Antananarivo (Madagascar)

The prevalence of tuberculosis in the Antananarivo prison is 16 times highe r than that in the general population of Madagascar. We compared the cluste ring of Mycobacterium tuberculosis strains within and outside the prison an d studied the transmission of strains in the prison. M. tuberculosis strain s isolated in 1994 to 1995 from 146 prisoners and from 260 nonprisoner pati ents from Antananarivo were typed using the genetic markers IS6110 and dire ct repeat. We compared the strains isolated from prisoners and nonprisoners and found that the clustering rate was higher within (58.9%) than outside the prison (40%) suggesting that the transmission rate was higher in prison . Of the 146 incarcerated patients, 82 were grouped into 22 clusters. We ch ecked for possible tuberculosis transmission between prisoners with identic al strains by epidemiological investigation of the various prison clusters. We found that 9.5% of the incarcerated patients could have been sources of infection and that only 15.1% could have been infected in the prison. One hundred and twenty-seven prison patients were new cases. Epidemiological da ta suggested that 37% of them resulted from a reactivation of an old infect ion, due to poor living conditions or recent transmission from an index cas e outside the prison. (C) 2000 Editions scientifiques et medicales Elsevier SAS.