BACKGROUND: In Europe, avian schistosomes of the genus Trichobilharzia are the most common etiological agents involved in human cercarial dermatitis (swimmer's itch). Manifested by a skin rash, the condition is caused by an allergic reaction to cercariae of nonhuman schistosomes. Humans are an accidental host in this parasite's life cycle, while water snails are the intermediate, and waterfowl are the final hosts. The study aimed to conduct a molecular and phylogenetic analysis of Trichobilharzia species occurring in recreational waters in North-Eastern Poland. METHODOLOGY: The study area covered three water bodies (Lake Skanda, Lake Ukiel, and Lake Tyrsko) over the summer of 2021. In total, 747 pulmonate freshwater snails (Radix spp., Lymnaea stagnalis) were collected. Each snail was subjected to 1-2 h of light stimulation to induce cercarial expulsion. The phylogenetic analyses of furcocercariae were based on the partial sequence of the ITS region (ITS1, 5.8S rDNA, ITS2 and 28SrDNA). For Radix spp. phylogenetic analyses were based on the ITS-2 region. RESULTS: The prevalence of the Trichobilharzia species infection in snails was 0.5%. Two out of 478 (0.4%) L. stagnaliswere found to be infected with Trichobilharzia szidati. Moreover, two out of 269 (0.7%) snails of the genus Radix were positive for schistosome cercariae. Both snails were identified as Radix auricularia. One of them was infected with Trichobilharzia franki and the other with Trichobilharzia sp. CONCLUSIONS: Molecular identification of avian schistosome species, both at the intermediate and definitive hosts level, constitutes an important source of information on a potential threat and prognosis of local swimmer's itch occurrence, and helps to determine species diversity in a particular area.

• Klíčová slova
• Avian schistosomes, Cercariae, Cercarial dermatitis, Trichobilharzia,
• MeSH
• DNA helmintů genetika   MeSH
• fylogeneze * MeSH
• hlemýždi parazitologie   MeSH
• infekce červy třídy Trematoda parazitologie   veterinární   epidemiologie   MeSH
• jezera parazitologie   MeSH
• lidé MeSH
• Schistosomatidae * genetika   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Polsko epidemiologie   MeSH
• Názvy látek
• DNA helmintů MeSH

As host community diversity decreases, parasite diversity may also decline. The life cycles of trematodes involve multiple hosts from different orders, with many trematodes displaying narrow host specialization. In the 1960s and 2010s, we performed full-body necropsies of juvenile or first-year birds of four wetland bird species, Anas platyrhynchos, Aythya fuligula, Fulica atra, and Chroicocephalus ridibundus which originated from the southern Czech Republic, and examined them for the presence of trematodes. We compared the trematode species richness and diversity of the analyzed component communities. We found complete disintegration of host-parasite networks, which led to declining populations and local extinctions of the majority of trematode species, particularly those with narrow host preferences. For example, in black-headed gulls, 67% of trematode species recorded in the 1960s were absent in gulls that were examined in the 2010s. In contrast, we did not identify any trematode species that were absent in the 1960s but present in the 2010s. This collapse provides new insight into the recent debate regarding whether human-caused extinctions should be considered a problem when locally extinct host species are replaced by an equal or even higher number of nonnative species, thus maintaining local alpha diversities but leading to biotic homogenization and consequently reducing beta diversity. By documenting the collapse of the host-parasite network, we provide a strong argument that biodiversity cannot be assessed by simple measures alone, as only local-scale conservation measures allow the preservation of host-pathogen interactions and nutrient cycles and thus prevent the loss of low-visibility species, such as helminths.

• Klíčová slova
• Aquaculture, Fishponds, Helminths, Sustainability, Trematoda, Wetlands,
• MeSH
• biodiverzita MeSH
• Charadriiformes parazitologie   MeSH
• extinkce biologická * MeSH
• interakce hostitele a parazita MeSH
• kachny parazitologie   MeSH
• mokřady MeSH
• ptáci parazitologie   MeSH
• stadia vývoje MeSH
• Trematoda klasifikace   izolace a purifikace   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Česká republika MeSH
• Evropa MeSH

In contrast to the well-studied trematode fauna of lymnaeid snails, only little is known about the role of small planorbid snails as first intermediate hosts for trematodes in temperate freshwater systems. This study aims at closing this gap by assessing the diversity and composition of larval trematode communities in Gyraulus albus and Segmentina nitida in a Central European reservoir system, and by providing an updated comprehensive review of the published trematode records of these snail hosts. A total of 3691 planorbid snails (3270 G. albus; 421 S. nitida) was collected in three consecutive years from four reservoirs of the River Ruhr catchment area in Germany. Gyraulus albus showed a higher overall trematode prevalence (11.7%) and more diverse trematode fauna (12 species) compared to S. nitida, which harboured three species and showed a lower trematode prevalence (1.7%). Altogether, 13 trematode species belonging to four families were identified in both hosts. Seven trematode species encountered in this study represent novel records for these hosts, and/or constitute first records of these larval stages from Germany. Trematode component communities in G. albus were stable across seasons and years, indicating excellent conditions for trematodes in this snail host and the continuous presence of the final hosts of the most dominant trematode species. Overall, this study reveals the importance of small planorbid snails, in particular G. albus, as first intermediate hosts for a species-rich trematode fauna in European freshwater systems, and highlights the parasites' contribution to the ecosystem's biodiversity.

• Klíčová slova
• Community composition, Digenea, Europe, Parasite diversity, Planorbidae, Reservoir,
• MeSH
• biodiverzita * MeSH
• ekosystém MeSH
• hlemýždi parazitologie   MeSH
• infekce červy třídy Trematoda parazitologie   veterinární   MeSH
• larva MeSH
• řeky MeSH
• roční období MeSH
• sladká voda MeSH
• Trematoda fyziologie   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Německo epidemiologie   MeSH

Digenean trematodes are common and abundant in aquatic habitats and their free-living larvae, the cercariae, have recently been recognized as important components of ecosystems in terms of comprising a significant proportion of biomass and in having a potentially strong influence on food web dynamics. One strategy to enhance their transmission success is to produce high numbers of cercariae which are available during the activity peak of the next host. In laboratory experiments with 13 Lymnaea stagnalis snails infected with Trichobilharzia szidati the average daily emergence rate per snail was determined as 2,621 cercariae, with a maximum of 29,560. During a snail's lifetime this summed up to a mass equivalent of or even exceeding the snail's own body mass. Extrapolated for the eutrophic pond where the snails were collected, annual T. szidati biomass may reach 4.65 tons, a value equivalent to a large Asian elephant. Emission peaks were observed after the onset of illumination, indicating emission synchronizing with the high morning activities of the definitive hosts, ducks. However, high cercarial emission is possible throughout the day under favorable lightning conditions. Therefore, although bird schistosomes, such as T. szidati constitute only a fraction of the diverse trematode communities in the studied aquatic ecosystem, their cercariae can still pose a considerable risk for humans of getting cercarial dermatitis (swimmer's itch) due to the high number of cercariae emitted from infected snails.

• MeSH
• biomasa MeSH
• cerkárie růst a vývoj   MeSH
• chronobiologické jevy MeSH
• ekosystém MeSH
• Lymnaea parazitologie   fyziologie   MeSH
• neparametrická statistika MeSH
• plavání MeSH
• Schistosomatidae růst a vývoj   MeSH
• stadia vývoje MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

We examined the small-scale temporal and spatial variability in composition and structure of larval trematode communities in Lymnaea stagnalis and Planorbarius corneus in two fish ponds in the Czech Republic and compared the patterns of richness and similarity to continental and regional trematode faunas of these hosts. The levels of parasitism in the populations of both hosts were high, the former parasitized predominantly by allogenic species maturing in a wide range of birds and the latter infected by relatively more species completing their life cycles in micromammals. Communities in both hosts exhibited a congruent pattern of seasonal change in overall infection rates and community composition with lower levels of infection in spring. Both temporal and spatial variation was closely related to the structure of snail populations, and no significant differentiation of community composition with respect to pond was observed. Comparisons with large-scale inventories revealed overall congruent patterns of decreased richness and similarity and increased variability at the smaller scales in both host-parasite systems. The relative compositional homogeneity of larval communities in both snail hosts irrespective of scale suggests that historical data at small to medium regional scales may provide useful estimates of past richness and composition of larval trematode communities in these snail hosts.

• MeSH
• Lymnaea parazitologie   MeSH
• plži parazitologie   MeSH
• roční období MeSH
• Trematoda izolace a purifikace   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Česká republika MeSH

Studies on life cycles of trematodes have a long tradition in Germany; (Odening 1978) listed a total of 177 trematodes, which can potentially complete their life cycles in German inland waters. However, almost no recent data on the occurrence of larval stages in molluscs are available. Therefore, a survey of trematodes in Southeast Germany was carried out in 2004. A total of 31 species of ten families (29 species of cercariae, seven species of metacercariae, and five species found of both) were found in 311 (4.9%) molluscs of 15 species. The dominant cercariae were Plagiorchis elegans, Echinoparyphium aconiatum, Opisthioglyphe ranae, and Diplostomum pseudospathaceum. Echinoparyphium pseudorecurvatum is reported, for the first time, under its valid scientific name from Germany. In previous studies from the same region, 88 species of cercariae of 16 families were found in 19 species of molluscs (52 cercariae with valid names and 36 not identified to species level). It is proposed that there is still a very similar spectrum of the most common species of cercariae typical for Central Europe as found 20, but also 100-150 years ago.

• MeSH
• biodiverzita MeSH
• ekosystém MeSH
• larva MeSH
• měkkýši parazitologie   MeSH
• řeky parazitologie   MeSH
• stadia vývoje MeSH
• Trematoda růst a vývoj   izolace a purifikace   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Německo MeSH