EFFICACY OF PRAZIQUANTEL AGAINST SCHISTOSOMA-MANSONI IN NORTHERN SENEGAL

Two treatments with praziquantel (PZQ) 40 mg/kg, 40 d apart, were give n to individuals in a recently established (<6 years) Schistosoma mans oni focus in the Senegal River Basin (SRB). Efficacy of treatment was evaluated 4 weeks after each treatment. Among 130 individuals who prov ided stool samples on days 0, 118 and 153 and were treated on days 85 and 125, 113 (87%) were infected with S. mansoni before treatment. The overall geometric mean faecal egg count of the infected individuals w as 478 eggs/g. Four weeks after the first treatment (day 118), the ove rall cure rate was only 42.5% and the overall reduction in intensity o f infection was 70.7%. However, 4 weeks after the second treatment (da y 153), the overall cure rate rose to 76.1% and the overall reduction in intensity was 88.1%. The greatest increase in cure rate between the 2 treatments was in those individuals who were initially the most hea vily infected (> 1000 eggs/g). There was no apparent difference in cur e rate between younger (< 20 years) and older individuals (> 20 years) . No evidence for the existence of a PZQ tolerant strain of S. mansoni was found. Two treatments of PZQ 40 mg/kg, 40 d apart, were sufficien t to give an adequate cure rate and high reductions in the intensity o f infection. As there was insufficient time for reinfection between tr eatment and follow-up to result in egg production, the low cure rate o bserved after one treatment was probably the result of a combination o f high infection intensity and the maturation of pre-existing prepaten t S. mansoni infections.