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Swimmer’s itch is a complex zoonotic disease manifested through several different routes of transmission involving a diversity of different host species. It seems increasingly likely that schistosomes have on two separate occasions colonized mammals. Basal lineages today are found in marine gastropods and birds, but subsequent diversification has largely taken place in freshwater, with some reversions to marine habitats. Collectively, schistosomes exploit 16 families of caenogastropod or heterobranch gastropod intermediate hosts.
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Recent years have witnessed a dramatic increase in our understanding of schistosome diversity, now encompassing 17 genera with eight more lineages awaiting description. The cercariae of many of these species can cause swimmer’s itch when they penetrate human skin. Our results fill a gap in our knowledge of the transmission dynamics and success of bird schistosomes under high latitude conditions that may serve as a basis for elucidating future potential risks and implementing control measures related to the spread of cercarial dermatitis due to global warming.Īlthough most studies of digenetic trematodes of the family Schistosomatidae dwell on representatives causing human schistosomiasis, the majority of the 130 identified species of schistosomes infect birds or non-human mammals. This suggests an adaptive strategy of bird schistosomes to compensate for the narrow transmission window. While light intensity triggered and prolonged cercarial emergence, the temperature had little effect on cercarial rhythms but regulated seasonal output rates. These patterns were consistent under both field and laboratory conditions. We demonstrated a circadian rhythm with the highest emergence during the morning hours, being seasonally independent of the photo- and thermo-period regimes of subarctic summer and autumn, as well as relatively high production of cercariae at low temperatures typical of northern environments. “peregra” from the snail host Radix balthica in a subarctic lake under both natural and laboratory seasonal conditions. We investigated the daily cercarial emergence rhythms of the bird schistosome Trichobilharzia sp. However, there are virtually no data on the cercarial emergence of bird schistosomes from freshwater ecosystems in northern latitudes. Short transmission opportunities of cercariae are often compensated by periodic daily rhythms in the cercarial release. The emergence of cercariae from infected mollusks is considered one of the most important adaptive strategies for maintaining the trematode life cycle.