Some factors affecting prevalence of and immune responses to Schistosoma mansoni in schoolchildren in Gorgora, northwest Ethiopia.

ABSTRACT

There are population variations in human immune responses to infection with Schistosoma mansoni prior to and following treatment. The aims of the present study were a) to study some of the factors correlating with antibody levels against the parasite infection, b) to determine whether there were changes in antibody responses to the parasite in infected young people following drug treatment, and c) to identify some of the social, demographic and clinical factors associated with infection in this age group. The study population comprised 10 to 14 year old children attending Gorgora Primary School. One hundred sixty fife of the 325 children screened by Kato smear were found to be excreting S. mansoni eggs, a prevalence of 50.8%. The infected children were treated with Praziquantel, and examined for infection six weeks later. Levels of IgG and IgA antiworm antibodies were determined by ELISA from blood samples drawn prior to and six weeks after treatment. IgG antibody titres in the infected children were higher in the older children and were higher in males than in females. Antibody titres did not show significant change six weeks after treatment. A significantly higher proportion of the boys is infected, and the infected boys had higher egg counts than the infected girls. There was no correlation between egg excretion and any of the clinical symptoms measured. The age of the children significantly affected prevalence, whereas sex and swimming habit had only marginal effects. Place of residence, clinical profiles and presence of other parasites did not affect prevalence. Male sex and older age were associated with higher IgG titer to parasite antigens.