Mycobacteria in northern Tanzania: Exposure and risk of disease among agropastoralists and programmatic challenges in investigation of re-treatment cases
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Background: The genus mycobacterium includes several species that can cause disease. Mycobacterium tuberculosis-complex is transmitted from person to person by air and usually affects the lungs. Non-tuberculous mycobacteria (NTM) are transmitted from natural sources in the environment and are often considered not a public health hazard. A number of mycobacterial diseases occur due to close contacts between humans, domestic animals and the environment.
Objective: The objective of this study was to examine patients suspected of having mycobacterial diseases and describe: 1) the association between mycobacterial diseases and patient characteristics, 2) experienced risk factors, 3) knowledge and perceptions about TB in agropastoral communities, and 4) at national level the investigation practices of retreatment cases of mycobacterial disease in Tanzania.
Methods: Three studies were conducted to address the stated objectives. In order to identify risk factors for mycobacteria, a cross-sectional study was conducted on 1711 patients examined for tuberculosis (TB) (TB suspects). The suspects were enrolled from Mt. Meru Hospital (the Arusha Regional Hospital), Enduleni Lutheran Hospital in Ngorongoro district, and Haydom Lutheran Hospital in Mbulu district. The study areas were purposively selected because of their strong human and animal habitat overlap. The participants were examined for mycobacteria by sputum microscopy and culture at Central Tuberculosis Reference Laboratory in Dar es Salaam. In a cross-sectional study, we selected 41 patients among the 277 confirmed mycobacteria positive from the study mentioned above. Interviews were conducted to compare the patients with 68 relatives and 55 neighbors about their perceived risk of exposure to mycobacteria and knowledge about mycobacterial diseases. In a study on the national TB and laboratory registers, we assessed the investigation practices for mycobacteria by reviewing of records of all TB patients notified as re-treatment cases, and the number submitting their sputum samples for culture and DST at the reference and three zonal laboratories between 2002 and 2010.
Results: We examined 1711 patients suspected of having TB of whom 927 (54.2%) were males. Out of all the study participants, 277 (16%) were found to have sputum samples positive for mycobacteria, 228 (13.3%) were smear positive and 123 (7.2%) were culture positive. Of the 123 mycobacterial culture positive, 15 (12.2%) had NTM. Of the 1711 study participants, 664 had known HIV sero-status, of whom 159 (23.9%) were HIV positive. Males were more likely than females to have sputum samples positive for mycobacteria. Comparing 41 patients with tuberculosis with 68 relatives and 55 neighbors, we found that participants aged over 50, those aged ≤20 years, 21-30; 31-40 were more likely to be positive for mycobacteria. Being mycobacterial positive was also associated with loss of appetite, living in a household with a family size of more than six individuals, being in contact with a person who had TB, sharing a room with domestic animals, sharing water sources with domestic animals, or a family member with persistent cough significantly. Knowledge about risk factors for mycobacterial diseases was generally low both among the 41 TB patients and among their 68 relatives and 55 neighbors. There was an association between believing to be at risk of mycobacterial disease and eleven assessed practices with some inherent risk of exposure to mycobacteria; there was higher risk among respondents who do not boil, filter or treat their drinking water, and among the respondents who had shared dwelling with a known TB patient, and livestock keepers. Of all the 164 respondents, 9 (5.5%) reported to be aware of traditional medicines or procedures in their community that a person with symptoms of TB may use and get relief. Drinking untreated water, consumption of raw animal products such as milk, meat and blood, smoking and drinking alcohol were among the habits reported as routes for mycobacterial diseases. We reviewed 40940 retreatment TB patients notified by the NTLP, and found that 3871 (10%) had their sputum samples received at the reference and zonal laboratories, for culture and DST, 3761 (9%) were processed for culture and 1589 (3.9%) were found to be culturepositive; 1415 (3.5%) had DST performed.
Conclusions: Among patients suspected and examined for TB, many had mycobacterial disease and over 10% had non-tuberculous mycobacteria (NTM). Predictors of having mycobacteria were loss of appetite, presence of a coughing family member, being an exclusive animal keeper, age below 40 years, and being a male. Knowledge of risk factors for mycobacterial diseases was generally low. Although awareness about mycobacterial diseases among the study community was high, specific knowledge on causes, prevention, and treatment of the disease was poor, and some misconceptions existed on modes of transmission and symptoms. Only 10% of notified retreatment cases had their sputum samples submitted for DST, implying that there are problems with the logistics of getting sputum samples to a central reference laboratory.