Abstrakt
Birds and snails are suitable hosts for many parasites, including helminths in general and trematodes in particular. Among trematodes, members of the family Schistosomatidae with two-host life cycles (snails as intermediate hosts and birds as definitive hosts) are successful and abundant pathogens.
Their transmission between birds and snails in nature can be influenced by many abiotic and biotic factors. In snails, the prevalence of schistosome infections and production of cercariae can be influenced by host immunological susceptibility/physiological suitability, snail age/size, interspecific competition of trematode larvae, etc.
Schistosomes are able to survive in overwintering snails, serving as a source of infection in spring. Birds may also differ in susceptibility to and prevalence rates of schistosome infections.
They are long-range vectors of schistosomes. Climate changes influence behaviour of migratory birds, lead to shifts in season- or temperature-dependent processes in snails and schistosomes, and influence the frequency of schistosome transmission and intensity of infection.
Also, eutrophication can increase the growth of snail populations and transmission of bird schistosomes. Dispersal of bird schistosomes to new regions and an increased availability (local abundance) of the snail hosts, together with the use of new water reservoirs (e.g., in higher latitudes) for recreational purposes, may contribute to a higher number of outbreaks of cercarial dermatitis.