Integrated disease mapping in a polyparasitic world.

In the past, and still today, people living in the developing world have been, and continue to be, repeatedly exposed to a number of endemic parasitic diseases which impose an intolerable economic, health and social burden on their societies (Stoll, 1947; Sachs and Malaney, 2002). Among the parasitic diseases, malaria due to Plasmodium falciparum inflicts the largest burden (Snow et al., 2005). Concurrently, hundreds of millions of people are plagued by a number of so-called neglected tropical diseases (NTDs). The most significant of these are Chagas disease in South America, human African trypanosomiasis, leishmaniasis, lymphatic filariasis, onchocerciasis, schistosomiasis, soil-transmitted helminthiasis and trachoma. The scale of the problem is illustrated in Table 1, which summarises current population statistics, including at-risk populations, estimated numbers of people infected, annual morbidity and mortality rates and burden estimates due to malaria and the above-mentioned NTDs. In recent years, there has been an upsurge in public and private spending in global health, with particular efforts aimed at tackling HIV/AIDS, tuberculosis and malaria (Lu et al., 2006). With enhanced funding coming on stream also for the NTDs, new partnerships and global alliances have been formed to tackle a number of NTDs, with preventive chemotherapy playing a key role (Brady et al., 2006; Hotez et al., 2006; WHO, 2006). This funding has coincided with calls to improve the coordination and integration of national control programmes, placing emphasis on simultaneous morbidity control due to NTDs (e.g. schistosomiasis and soil-transmitted helminthiasis) or to eliminate NTDs as a publichealth problem (e.g. lymphatic filariasis) (Brady et al., 2006; Lammie et al., 2006). To help allocate public-health resources, an essential first step is to delineate and understand the spatial distribution of different parasitic diseases (Brooker et al., 2006; Hay and Snow, 2006; Utzinger and de Savigny, 2006).