Changes in specific anti-egg antibody levels following treatment with praziquantel for Schistosoma haematobium infection in children.

Fifty-seven children 6-15 years old resident in a Schistosoma haematobium endemic area in eastern Zimbabwe were treated with praziquantel at 40 mg/kg body weight. Levels of IgA, IgE, IgG1, IgG2, IgG3, IgG4, and IgM antibodies against soluble egg antigen (SEA) were assayed by ELISA before treatment and at 18 and 36 weeks following treatment. Prevalence of infection (as determined by urine egg counts) was 65% before treatment, all children were confirmed egg negative six weeks after treatment, and reinfection prevalence was 4% at 18 weeks and 21% at 36 weeks after treatment. At 18 weeks after treatment, there was a massive increase in IgG1 levels and significant increases in IgE and IgG4 levels and significant decreases in IgA and IgG2 levels. Similar patterns occurred at 36 weeks after treatment. Egg positive children showed a more marked increase in IgG1 and (for older children) a more marked decrease in IgG2 levels. There were no other effects of age or sex. IgA and IgG1 levels fell significantly between 18 and 36 weeks following treatment but not to pretreatment levels. The results show that specific anti-egg antibody responses are highly sensitive to the effects of praziquantel treatment. A possible consequence is that the susceptibility of children to infection with S. haematobium is altered by chemotherapy; this requires further investigation.