Background


Schistosomiasis is considered the second most important infectious disease worldwide after malaria in terms of public health and economic impact (WHO 2012). Six hundred million people are at risk of getting infected with schistosomiasis, with the majority living in sub-Saharan Africa.

Schistosomiasis is caused by parasitic trematodes of the genus Schistosoma that use humans as their primary hosts and freshwater snails as their intermediate hosts. The pathogen multiplies in these intermediary hosts before cercaria are released into the water that actively search for humans. A direct transmission among humans is not possible. A snail can serve as a host for different pathogenous and nonpathogenous trematodes at the same time.

The balance between efficient host snails and antagonistic species is governed by additional ecological stressors (Barbosa 1987). The loss of biodiversity and the ecological degradation of freshwater habitats are known to support schistosomiasis and other water-borne diseases (WHO 2001, Johnson & Thieltges 2009). Freshwater pollution and spread of infectious diseases is highly relevant. Agricultural runoff presents a crucial source of freshwater pollution (Liess & Schulz 1999).

In Africa, agriculture is the key economic activity and irregular heavy rainfalls potentially increase the runoff of pollutants into surface waters. However, information on pesticide concentrations and other pollutants in tropical freshwater streams and their effects on the macroinvertebrate community are often fragmentary and inadequate (London et al. 2005, Musa et al. 2011). Thus, the project SENTINEL was designed to investigate the freshwater pollution and the links to the distribution of Schistosoma host snails in Western Kenya