The impact of iron supplementation on reinfection with intestinal helminths and Schistosoma mansoni in western Kenya

A randomized, placebo-controlled, double-blind trial was carried out in 199 4-96 among 231 children and 181 adults in order to determine the effects of iron on reinfection rates and intensities of hookworm, Ascaris lumbricoide s, Trichuris trichiura and Schistosoma mansoni. Adults given 60 mg elementa l iron twice-weekly for 12 months had significantly lower reinfection rates of A. lumbricoides (16(.)7% vs 31(.)9%, P = 0(.)046), T. trichiura (6(.)9% vs 20(.)6%, P = 0(.)03) and S. mansoni(38(.)3% vs 61(.)8%, P = 0(.)008) co mpared to adults given placebo. In contrast, adults allocated to iron had a significantly higher reinfection rate of hookworm at the 4-month examinati on (11.1% vs 0%, P = 0(.)009), but the difference was not significant at 8- and 12-month follow-up examinations. Iron supplementation had no effect on reinfection intensities in adults. Surprisingly, iron supplementation had no effect on either reinfection rates or intensities in children. Multiple logistic regression analyses controlling for baseline infection status conf irmed the effect in adults of iron on A. lumbricoides, T. trichiura and S. mansoni reinfection rates. The effect is suggested to be due to reduced ris k behaviour, to improved immune function or to unfavourable host gut condit ions caused by an increased oxidative stress. In each case, the lack of eff ect in children remains to be explained. In contrast, iron supplementation apparently was short-lived in favour of hookworm infection, an effect that. needs further clarification. The findings suggest that iron supplementatio n has a role to play in helminth control programmes and that intraluminal f actors may contribute to the regulation of some helminth infections.