THE EFFECTIVENESS OF ANNUAL VERSUS BIENNIAL MASS CHEMOTHERAPY IN REDUCING MORBIDITY DUE TO SCHISTOSOMIASIS - A PROSPECTIVE-STUDY IN GEZIRA-MANAGIL, SUDAN

The most serious complication of schistosomiasis is periportal fibrosi s, which affects a large number of subjects in endemic areas, Populati on-based chemotherapy remains the most effective way of controlling th is disease. In an attempt to find the best way to deliver chemotherapy to the endemic population, we compared the impact of repeated annual versus biennial mass chemotherapy on morbidity due to schistosomiasis in two villages in Gezira, Sudan. One village was given five rounds of mass chemotherapy annually in the years 1990-1994 while the other vil lage was given three rounds of mass chemotherapy biennially from 1988 to 1994. Before treatment, these villages had similar intensity of inf ection and prevalence. One round of either annual or biennial treatmen t reduced the intensity of infection, but not prevalence or morbidity. After two rounds of annual chemotherapy, infection rates, bloody diar rhea, and fibrosis in those 20 years of age and less were significantl y reduced. Two rounds of biennial chemotherapy had a similar effect on rates and bloody diarrhea; however, fibrosis was reduced only after t he third round of biennial chemotherapy. Prevalence of hepatosplenomeg aly increased after both treatment regimens. Reinfection was most prom inent in those 5-14 years of age. These findings support the general n otion that repeated chemotherapy may be needed in areas of high transm ission of schistosomiasis. We recommend two rounds of annual mass chem otherapy to significantly reduce infection and morbidity.