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 e ndemic 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 a nd at 18 and 36 weeks following treatment. Prevalence of infection (as dete rmined by urine egg counts) was 65% before treatment, all children were con firmed egg negative six weeks after treatment, and reinfection prevalence w as 4% at 18 weeks and 21% at 36 weeks after treatment. At 18 weeks after tr eatment, there was a massive increase in IgG1 levels and significant increa ses in IgE and IgG4 levels and significant decreases in IgA and IgG2 levels . Similar patterns occurred at 36 weeks after treatment. Egg positive child ren showed a more marked increase in IgG1 and (for older children) a more m arked decrease in IgG2 levels. There were no other effects of age or sex. I gA and IgG levels fell significantly between 18 and 36 weeks following trea tment but not to pretreatment levels. The results show that specific anti-e gg antibody responses are highly sensitive to the effects of praziquantel t reatment. A possible consequence is that the susceptibility of children to infection with S. haematobium is altered by chemotherapy; this requires fur ther investigation.