Toxic pollution and parasitism in freshwater fish.

As aquatic habitats throughout the world are increasingly contaminated with toxic chemicals, toxicologist strive to determine what impact these substances will have an biological systems. So far, the effects of this type of pollution on fish parasites has received little attention, despite their important status as determinants of fish health. Robert Poulin discusses the many ways in which toxic pollution may affect infections of metazoan parasites in freshwater fish. Effects on fish immunity, parasites survival and intermediate host populations are not independent, and currently the outcome of toxic pollution and parasitism in fish is impossible to predict. Future research will have to answer several questions if we are to understand and forecast pollution-mediated changes in parasitism, an urgent challenge for ecotoxicologists and fish parasitologists alike.