Placebo-Controlled Double-Blind Study to Determine the Efficacy of Topical Niclosamide 1% Lotion in the Prevention of Naturally Occurring Schistosoma mansoni Infection in Egyptian Farmers

A randomized, double blind, placebo controlled field trial of a topical antipenetrant lotion 1 % niclosamide applied daily to the upper and lower limbs of farmers occupationally exposed to S. mansoni cercarial infested water was conducted in the Nile Delta to assess safety and efficacy in preventing re-infections. Farmers aged 1840 years were treated to cure their S. mansoni infections 3 months prior to the onset of the trial. Subjects were randomly assigned to receive niclosamide or placebo lotion which was self- applied daily for 5 months. A total of 186 subjects met the inclusion criteria and completed the trial. The exposure to schistosomal infested water occurred during routine irrigation activities from June to November 1991. Stool specimens were evaluated monthly during and for two months following the lotion application period. The subjects applying the niclosamide lotion were comparable to those applying placebo lotion in age (average of 30 years for both) total water contact (185.2 vs. 173.8 hours), reported lotion application compliance (88 % vs. 92 %) and reported water contact involving skin exposure other than upper and lower limbs (23 % vs. 27 %). The schistosomal reinfection rate was lower in the niclosamide group (53.3 %) compared to the placebo lotion group (71.3 %), (p .02). Increased protection might be obtained with total body application for shorter, less intense water contact exposures.