Is mass treatment the appropriate schistosomiasis elimination strategy?

Background. Several initiatives for the control of schistosomiasis worldwide are encouraging the use of praziquantel mass treatment to control the infection. The Philippines Department of Health adopted schistosomiasis mass chemotherapy using praziquantel in 2000 to eliminate the disease. This paper describes the mass treatment activities and factors associated with participation.

Methods. Mass treatment was offered to an eligible population of 30,187 residents of 50 villages in Western Samar, the Philippines in 2004. A sub-sample from all 50 villages participated in the Schistosomiasis Transmission and Ecology Project (STEP) research study. Advocacy, information dissemination and social mobilization activities were conducted prior to mass chemotherapy. Village leaders were primarily responsible for community mobilization. Mass treatment was offered in village meeting halls and schools. Participation proportions were estimated based on the 2002-03 census. Community involvement was measured using a participation index. A Bayesian hierarchical logistic regression model was fitted to estimate the association between socio-demographic factors and coming to the treatment site.

Findings. A village-level average of 53.1% of residents (range of 21.1% to 85.3%) came to the treatment site, leading to a mass treatment coverage ranging from 15.8% to 80.7%, with an average of 48.3%. At the individual level, participation proportions were higher among males, pre-school and school-aged children, non-STEP participants and among those who provided a stool sample. At the village-level, better community involvement was associated with increased participation whereas a larger census was associated with decreased participation.

Conclusion. The conduct of mass treatment in the 50 villages resulted in far lower participation than expected. This raises concern for the ongoing mass treatment initiatives now taking place in developing countries.