Objective: To determine the relative susceptibility of Schistosoma mansoni infections to treatment with the oxamniquine (OXA) and praziquantel (PZQ).
Design and setting: Three separate cross sectional studies were performed in six primary schools located in two Schistosoma mansoni endemic areas in Eastern Kenya: Kangundo (low morbidity) and Kibwezi (high morbidity).
Subjects: One thousand two hundred and fourteen infected children aged 6-20 years were involved.
Intervention: Each child received either 15-mg OXA/kg body weight twice within an interval of six hours or a single dose of 40 or 60 mg PZQ/kg body weight. Three duplicate Kato stool examinations were done before and four or five weeks after treatment to assess treatment efficacy.
Results: The cure rates in different schools with OXA were 71.7-79.7% in Kangundo and 56.7-61.9% in Kibwezi. In children treated with PZQ, the 40-mg/kg-dose regimen achieved cure rates of 77.6-87.2% in Kangundo and 67.1-81.1% in Kibwezi, whereas the 60-mg/kg dose regimen attained cure rates of 93.2% in Kangundo and 76.3% in Kibwezi. Both OXA and PZQ efficacy declined significantly with age in Kangundo, whereas the age effect was not seen in Kibwezi.
Conclusion: The poorer cure rates in Kibwezi than in the Kangundo children were not due to known previous drug exposure to either OXA or PZQ. The varying efficacy may be attributed to innate low drug susceptibility, possibly related to schistosome strain differences between the two areas.