Free-living endohelminth stages: at the mercy of environmental conditions.

During their free-living phases, endohelminths are directly exposed to environmental conditions in their respective macrohabitats. Both natural environmental factors and pollutants released into the environment through anthropogenic activities can influence the success of the free-living stages. This overview examines the effects of natural variables and pollutants on two specific properties (survival and infectivity) of free-living stages of endohelminths, mainly trematodes, while fully recognizing that other parasitic life history stages in addition to the hosts can also be affected. As most parasite pollution studies have been carried out in aquatic habitats, this paper focuses on parasites of aquatic or amphibious hosts.