FAILURE OF MEBENDAZOLE IN TREATMENT OF HUMAN HOOKWORM INFECTIONS IN THE SOUTHERN REGION OF MALI

Preliminary studies indicated that single-dose (500 mg) mebendazole ga ve disappointing results in the treatment of hookworm infections (Neca tor americanus) in Mali. A placebo-controlled, randomized trial conduc ted with the participation of 103 infected subjects (background hookwo rm prevalence > 50%) confirmed that mebendazole (Vermox(R)) did not re duce parasite burdens significantly, as assessed through fecal egg cou nts. In contrast, a group of subjects treated with pyrantel (Combantri n(R)) experienced a significant reduction in fecal worm egg counts (ov erall, both sexes combined showed a 75% reduction). Male subjects carr ied significantly more intense infections compared with females, but t here was no gender difference in response to treatment. A standard egg hatch assay showed that N. americanus from our subjects in Mali was m ore resistant to benzimidazoles compared with a laboratory-maintained strain that had not been exposed to anthelmintics in more than 100 gen erations (50% effective dose = 0.12 and 0.07 mu g/ml of thiabendazole, respectively), suggesting that, among other possibilities, the develo pment of resistance to the benzimidazoles by N. americanus may have co ntributed to the drug failure. Whatever the underlying explanation, ou r results indicate that single-dose treatment with mebendazole is an i neffective treatment for hookworm infections and despite its relativel y cheap cost and wide availability, mebendazole should not be consider ed a drug of choice in the mass treatment of hookworm infections in th is region of Mali.