Research Article

Moderate to heavy infections of Trichuris trichiura affect cognitive function in Jamaican school children

C. Nokesa1, S. M. Grantham-McGregora2, A. W. Sawyera1, E. S. Coopera1, B. A. Robinsona3 and D. A. P. Bundya3

a1 Wellcome Trust Research Centre for Parasitic Infections, Department of Biology, Imperial College, Prince Consort Road, London SW7 2BB

a2 Tropical Metabolism Research Unit, University of the West Indies, Kingston, Jamaica, West Indies

a3 Mandeville Public General Hospital, Mandeville, Manchester, Jamaica, West Indies

A double-blind placebo trial was conducted to determine the effect of moderate to high loads of Trichuris trichiura (whipworm) infection on the cognitive functions of 159 school children (age 9–12 years) in Jamaica. Infected children were randomly assigned to Treatment or Placebo groups. A third group of randomly selected uninfected children were assigned to a Control for comparative purposes. The improvement in cognitive function was evaluated using a stepwise multiple linear regression, designed to control for any confounding variables. The expulsion of worms led to a significant improvement in tests of auditory short-term memory (P < 0.02; P < 0.01), and a highly significant improvement in the scanning and retrieval of long-term memory (P < 0.001). After 9 weeks, treated children were no longer significantly different from an uninfected Control group in these three tests of cognitive function. The removal of T. trichiura was more important than Ascaris lumbricoides in determining this improvement. The results suggest that whipworm infection has an adverse effect on certain cognitive functions which is reversible by therapy.

(Received October 12 1991)

(Revised November 15 1991)

(Accepted November 15 1991)