Schistosomiasis and neglected tropical diseases: towards integrated and sustainable control and a word of caution

Abstract

In May 2001, the World Health Assembly (WHA) passed a resolution which urged member states to attain, by 2010, a minimum target of regularly administering anthelminthic drugs to at least 75% and up to 100% of all school-aged children at risk of morbidity. The refined global strategy for the prevention and control of schistosomiasis and soil-transmitted helminthiasis was issued in the following year and large-scale administration of anthelminthic drugs endorsed as the central feature. This strategy has subsequently been termed 'preventive chemotherapy'. Clearly, the 2001 WHA resolution led the way for concurrently controlling multiple neglected tropical diseases. In this paper, we recall the schistosomiasis situation in Africa in mid-2003. Adhering to strategic guidelines issued by the World Health Organization, we estimate the projected annual treatment needs with praziquantel among the school-aged population and critically discuss these estimates. The important role of geospatial tools for disease risk mapping, surveillance and predictions for resource allocation is emphasised. We clarify that schistosomiasis is only one of many neglected tropical diseases and that considerable uncertainties remain regarding global burden estimates. We examine new control initiatives targeting schistosomiasis and other tropical diseases that are often neglected. The prospect and challenges of integrated control are discussed and the need for combining biomedical, educational and engineering strategies and geospatial tools for sustainable disease control are highlighted. We conclude that, for achieving integrated and sustainable control of neglected tropical diseases, a set of interventions must be tailored to a given endemic setting and fine-tuned over time in response to the changing nature and impact of control. Consequently, besides the environment, the prevailing demographic, health and social systems contexts need to be considered.

Fig. 1

Country-specific prevalence estimates for schistosomiasis in Africa, stratified into low-prevalence (<10%), moderate-prevalence (10·0–49·9%) and high-prevalence (≥50%) in mid-2003 (A) (source: Steinmann et al. (2006), webappendix 2), and estimated annual treatment needs with praziquantel to be administered to school-aged children (B).

Fig. 2

Global burden estimates of the initial set of 13 neglected tropical diseases, including current uncertainties (A) (source: WHO, 2004; Hotez et al. 2006) and comparison of global burden estimates of the neglected tropical diseases with other major communicable diseases (B) (source: Lopez et al. 2006).

Fig. 3

Predicted risk maps for no infection (A), S. mansoni mono-infection (B), hookworm mono-infection (C), and S. mansoni-hookworm co-infections (D) in the region of Man, western Côte d’Ivoire (sources: Raso et al., , 2006​a, ​b).