The impact of zinc supplementation on Schistosoma mansoni reinfection rate and intensities: a randomized, controlled trial among rural Zimbabwean schoolchildren.

OBJECTIVES

To assess the effect of zinc supplementation on susceptibility to S. mansoni reinfections among schoolchildren.

DESIGN

Randomized, double-blind, placebo-controlled trial.

SETTING AND SUBJECTS: 313 rural Zimbabwean schoolchildren (144 boys and 169 girls), 11-17 y).

INTERVENTIONS: Supplementation with zinc (30 or 50 mg) or placebo on schooldays for 12 months. Due to drought, a food programme was in operation during the last eight months of the study.

OUTCOME MEASURES: S. mansoni and S. haematobium reinfection rates and intensities.

RESULTS

There was no difference in reinfection rates between the zinc and placebo groups (25 vs 29%, P = 0.46). However, the median intensity of S. mansoni reinfection, although low in both groups, was significantly lower in the zinc than in the placebo group (7 vs 13 eggs per gram of faeces, P = 0.048). No difference in either S. haematobium reinfection rates or intensities were seen.

CONCLUSIONS

Zinc supplementation reduced the intensity of S. mansoni reinfections. Although the intensities of reinfection were very low, the finding probably reflects a biological effect of zinc that could be of public health importance in settings with higher transmission.