Are intestinal helminths risk factors for developing active tuberculosis?

Objectives: To determine the prevalence of intestinal helminth infections in active tuberculosis patients and their healthy household contacts and to assess its association with active TB in an area endemic for both types of infections.

Methods: Smear-positive pulmonary TB patients and healthy household contacts were tested for intestinal helminths using direct microscopy and the formol-ether concentration techniques. Three consecutive stool samples were examined before the start of TB chemotherapy. Sputum microscopy was done using the sodium hypochlorite concentration techniques. Participants were also tested for HIV by commercial sandwich enzyme linked immunosorbent assay.

Results: The study population consisted of 230 smear-positive TB patients and 510 healthy household contacts. The prevalence of intestinal helminths was 71% in patients and 36% in controls. HIV seroprevalence was significantly higher in patients than in controls (46.7%vs. 11.6%, P < 0.001). Conditional logistic regression analysis showed a strong association between TB and intestinal helminth infection (OR = 4.2, 95% CI 2.7-5.9, P < 0.001), and between TB and HIV infection (OR = 7.8, 95% CI 4.8-12.6, P < 0.0001). The odds of being a TB patient increased with the number of helminth species per person: in individuals with mono-infection it was 4.3 (95% CI 2.8-6.8); in people infected with two species was 4.7 (95% CI 2.5-8.7), and in patients infected with three or more helminths was 12.2 (3.9-52.6).

Conclusion: Intestinal helminth infection may be one of the risk factors for the development of active pulmonary TB in addition to HIV infection. This finding may have important implications in the control of TB in helminth endemic areas of the world.