The effect of schistosoma mansoni infection on cognitive processes: a case of primary school children in Machakos district, Kenya.

Abstract

The purpose of the study was to find out whether Schistosoma mansoni infection has an effect on cognitive functions of primary school children.

A pre-and post- double-blind placebo trial was conducted, on 155 school children (age 7-11 years) in Masongaleni settlement scheme, Kibwezi Division, Machakos District. Infected children were randomly assigned to Treatment I (n=61) and Treatment II (n=60) groups. A third group of uninfected children (n=34) served as a control for comparison purposes. A period of six months was allowed between the pre- and post- intervention tests.

Infection was assessed using the Kato thick smear technic. Cognitive function was assessed using a battery of seven tests. These were Verbal Fluency, Selective Attention, Digit-Span Forward, Digit-Span Backward, Free Recall, Picture Search and Coding. Another test Draw-a-person test was included to measure intellectual maturity. Background information was collected using a questionnaire. Achievement and absenteeism were determined from school records.

One-Way-Analysis of variance was used to assess the improvement in cognitive levels and Sheffe's test for post-hoc comparisons. There were two null hypotheses.

Comparison of the mean difference scores between pre- and post-test in the three groups showed that there were no significant differences among the groups in any of the tests. The first hypothesis was therefore rejected at 0.05 level of significance.

On comparing the performance of those severely and mildly infected in the group that received praziquantel, a difference was observed. Treatment resulted in positive improvement of scores on tests of children who suffered severe infections. However, significant differences in scores were observed only for the Free Recall and Coding tests (p>0.05). The improvement tables showed that 64.7% and 88.2% of the intensely infected children improved their performance on the Free Recall and Coding tests respectively while, 57.6% and 66.7% of the mildly infected improved their scores on the two tests respectively. This, therefore, showed that upon treatment the severely infected improved their scores much more than those who had mild infections. The second hypothesis was therefore accepted for the two tests.

The effect of treatment could also be seen in reduced absenteeism. For the study period, an overall improvement of attendance was observed. The placebo group recorded a 1.9% improvement in attendance, 2.0% for the praziquantel group and 0.9% for the control group. This showed that a slightly bigger change was recorded for those who received the praziquantel.

In general than comparison of the pre- and post- scores showed a reduction of differences between the infected and uninfected. After treatment these differences were reduced to almost zero. That is only six months after treatment; the infected children improved their scores such that their performance was no longer significantly different from that their performance was no longer significantly different from that of the uninfected control group.

One major implication of this study is that cognitive functions are affected by infection and can be improved by simple therapy. Educational planners should therefore incorporate sufficient health programs in educational policies. These will ensure efficient use of educational resources by children and may result in improved school performance.