Invaders as Diluents of the Cercarial Dermatitis Etiological Agent

Abstract

Research on alien and invasive species focuses on the direct effects of invasion on native ecosystems, and the possible positive effects of their presence are most often overlooked. Our aim was to check the suitability of selected alien species (the snail Physa acuta, the bivalve Dreissena polymorpha, and the gammarid Dikerogammarus villosus) as diluents for infectious bird schistosome cercariae—the etiological factor of swimmer’s itch. It has been hypothesized that alien species with different feeding habits (scrapers, filterers and predators) that cohabit the aquatic environment with intermediate hosts of the schistosomatid trematodes are capable of feeding on their free-swimming stages—cercariae. In the laboratory conditions used, all experimental animals diluted the cercariae of bird schistosome. The most effective diluents were P. acuta and D. villosus. However, a wide discrepancy in the dilution of the cercariae between replicates was found for gammarids. The obtained results confirm the hypothesis that increased biodiversity, even when alien species are involved, creates the dilution effect of the free-living stages of parasites. Determining the best diluent for bird schistosome cercariae could greatly assist in the development of current bathing areas protection measures against swimmer’s itch.

Scratching the Itch: Updated Perspectives on the Schistosomes Responsible for Swimmer’s Itch around the World

“…This has prompted a suggestion that P. antipodarum might have a role to play in defending European lakes from itch outbreaks [ 18 , 114 ]. A similar role for other species acting as biological diluents for itch-causing cercariae has also been proposed [ 115 ].…”

Somatic Dimorphism in Cercariae of a Bird Schistosome

“…In contrast, there are also certain disadvantages for the transmission associated with local ecosystem biodiversity in a form of dilution effect of parasite infective stages that leads to a reduction in parasite population size [ 50 , 62 , 63 , 64 , 65 ], including dilution of bird schistosomes [ 66 ]. In Lake Takvatn, cercariae of Trichobilharzia sp.…”

Friends or enemies: Multi‐species interactions among biofoulers, endoparasites and their gastropod hosts

“…Many studies emphasize that nontarget species contribute to the dilution effect on parasites (Gordon et al, 2016;Kopp & Jokela, 2007;Marszewska et al, 2018;Stanicka et al, 2021;Westby et al, 2019).…”

“…They can displace native species (Karatayev et al, 2002), introduce nonnative pathogens and parasites (Goedknegt et al, 2016; Maciaszek et al, 2021) and modify existing host–parasite interactions (Goedknegt et al, 2016). There is a growing interest in possible positive impacts of nonnative organisms, especially long‐established species, at a local scale (De Pádua et al, 2021; Gendron & Marcogliese, 2017; Marszewska et al, 2020; Pintor & Byers, 2015; Stanicka et al, 2021).…”

“…The parasites can change the physiology, reproduction, behaviour and/or morphology of their hosts (Brian et al, 2021; Poulin, 2013; Sousa et al, 2011), affecting individuals and populations of host organisms, as well as communities and ecosystems (Brian et al, 2022; Poulin, 1999). The system becomes more complex when nonnative species are involved, modifying existing relationships and creating new interactions in the community (Stanicka et al, 2021). Nonnative species can affect communities directly via predation, biofouling and competition, or indirectly by changing habitat structure and parasite–host dynamics (Croll et al, 2005; Goedknegt et al, 2017; Karatayev et al, 2002; Zaiko et al, 2009).…”