The effects of parasite infections on cognitive processes in children.

Two studies were carried out in the Nyuswa area of Natal to investigate the effects of parasitic infection on cognitive function in children. In the first study, children infected with intestinal helminths were given tests of information processing and perceptual speed before and after treatment with a single 500 mg dose of Mebendazole. The pattern of results was consistent with the hypothesis that parasitic infections combine with nutritional deficits to impair the efficiency of cognitive processes. There was, however, some confounding of variables, and the single drug treatment reduced but did not eliminate the parasites. The second study removed the confounding effects due to age and nutrition and employed a more comprehensive drug-treatment programme. A memory task and a test of sustained attention were administered. Poor performance on the attention task showed a significant association with parasite status, but no association was observed with educational attainment or memory function. The study also examined various ways of assessing parasite load, and an index weighted for estimated pathogenicity was found to give the best estimate. The results provide evidence of the effects of parasitic infection on attentional processes.