Potamopyrgus antipodarum as a potential defender against swimmer's itch in European recreational water bodies-experimental study.

Swimmer's itch is a re-emerging human disease caused by bird schistosome cercariae, which can infect bathing or working people in water bodies. Even if cercariae fail after penetrating the human skin, they can cause dangerous symptoms in atypical mammal hosts. One of the natural methods to reduce the presence of cercariae in the environment could lie in the introduction of non-host snail species to the ecosystem, which is known as the "dilution" or "decoy" effect. The caenogastropod Potamopyrgus antipodarum -an alien in Europe-could be a good candidate against swimmer's itch because of its apparent resistance to invasion by European bird schistosome species and its high population density. As a pilot study on this topic, we have carried out a laboratory experiment on how P. antipodarum influences the infestation of the intermediate host Radix balthica (a native lymnaeid) by the bird schistosome Trichobilharzia regenti . We found that the co-exposure of 200 P. antipodarum individuals per one R. balthica to the T. regenti miracidia under experimental conditions makes the infestation ineffective. Our results show that a non-host snail population has the potential to interfere with the transmission of a trematode via suitable snail hosts.