Effect of active case finding on prevalence and transmission of pulmonary tuberculosis in Dhaka Central Jail, Bangladesh.
BACKGROUND
Understanding tuberculosis (TB) transmission dynamics is essential for establishing effective TB control strategies in settings where the burden and risk of transmission are high. The objectives of this study were to evaluate the effect of active screening on controlling TB transmission and also to characterize Mycobacterium tuberculosis strains for investigating transmission dynamics in a correctional setting.


METHODS
The study was carried out in Dhaka Central Jail (DCJ), from October 2005 to February 2010. An active case finding strategy for pulmonary TB was established both at the entry point to the prison and inside the prison. Three sputum specimens were collected from all pulmonary TB suspects and subjected to smear microscopy, culture, and drug susceptibility testing as well as genotyping which included deletion analysis, spoligotyping and analysis of mycobacterial interspersed repetitive units (MIRU).


RESULTS
A total of 60,585 inmates were screened during the study period. We found 466 inmates with pulmonary TB of whom 357 (77%) had positive smear microscopy results and 109 (23%) had negative smear microscopy results but had positive results on culture. The number of pulmonary TB cases declined significantly, from 49 cases during the first quarter to 8 cases in the final quarter of the study period (p=0.001). Deletion analysis identified all isolates as M. tuberculosis and further identified 229 (70%) strains as 'modern' and 100 (30%) strains as 'ancestral'. Analysis of MIRU showed that 347 strains (85%) exhibited unique patterns, whereas 61 strains (15%) clustered into 22 groups. The largest cluster comprised eight strains of the Beijing M. tuberculosis type. The rate of recent transmission was estimated to be 9.6%.


CONCLUSIONS
Implementation of active screening for TB was associated with a decline in TB cases in DCJ. Implementation of active screening in prison settings might substantially reduce the national burden of TB in Bangladesh.
International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
Sayera
S
Banu
International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
Md Toufiq
MT
Rahman
International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
Mohammad Khaja Mafij
MK
Uddin
International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
Razia
R
Khatun
International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
Md Siddiqur Rahman
MS
Khan
National TB Control Program, Directorate General of Health Services, Mohakhali, Dhaka, Bangladesh.
Md Mojibur
MM
Rahman
Directorate of Prisons, Nazimuddin Road, Dhaka, Bangladesh.
Syed Iftekhar
SI
Uddin
International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
Tahmeed
T
Ahmed
International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh; Global Disease Detection Branch, Division of Global Health Protection, Center for Global Health, US Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America.
James D
JD
Heffelfinger
D015373:Bacterial Typing Techniques; D001459:Bangladesh / Q000453:epidemiology; D006801:Humans; D009169:Mycobacterium tuberculosis / Q000145:classification; D010802:Phylogeny; D015995:Prevalence; D011329:Prisoners / Q000706:statistics & numerical data; D011330:Prisons / Q000706:statistics & numerical data*; D014397:Tuberculosis, Pulmonary / Q000453:epidemiology* / Q000382:microbiology / Q000635:transmission*