Tuberculin skin-test reactions are unaffected by the severity of hyperendemic intestinal helminth infections and co-infections.
Author(s): Zevallos K, Vergara KC, Vergara A, Vidal C, Garcia HH, Evans CA
Affiliation(s): Department of Microbiology, Universidad Peruana Cayetano Heredia, Lima, Peru.
Publication date & source: 2010-08, Am J Trop Med Hyg., 83(2):319-25.
Publication type: Randomized Controlled Trial; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.
The tuberculin skin test (TST) quantifies cell-mediated immunity to tuberculosis antigens. Helminths suppress cell-mediated immunity, so we studied the effect of helminth infection and deworming on the TST in a randomized, double-blind, placebo-controlled study in an indigenous Amazon community (N = 195). Stool microscopy diagnosed helminths in 98% and co-infection with multiple species in 24% of study subjects. The TST was positive (> or = 10 mm) for 49%, and responses increased with age (P < 0.001), Bacille Calmette Guerin (BCG) vaccination (P = 0.01), and tuberculosis contact (P = 0.05). TST results had no association with helminth-egg concentrations, species, or co-infections (all P > 0.1). One month after deworming with albendazole (three daily 400-mg doses), helminths were reduced, but 63% remained infected with helminths. Albendazole did not cause a change in TST size (P = 0.8) or positivity (P = 0.9) relative to placebo. Thus, TST reactions were unaffected by albendazole therapy that partially cured intestinal helminth infections, and TST interpretation was unaffected by high-burden helminth infections and co-infection with multiple helminth species.