Cercariae are motile infectious larval stages of digenetic trematodes that emerge from their molluscan first intermediate host to seek the next host in their life cycle. A crucial transmission strategy of trematodes involves releasing the maximum number of cercariae at times that coincide with the presence and activity of the next hosts, thereby increasing the likelihood of successful infection and continuation of the parasite's life cycle. We investigated the cercarial emergence of two furcocercous (with forked tail) trematodes Tylodelphys clavata (von Nordmann, 1832) and unidentified species of Sanguinicola Plehn, 1905 from naturally infected Ampullaceana balthica (Linnaeus) and Radix auricularia (Linnaeus) snails under natural light and constant temperature conditions. Both trematodes, which are important fish pathogens, showed distinct daily emergence rhythms influenced by light intensity, with emergence peaking at sunset and night for T. clavata and at night for Sanguinicola sp. The daily emergence rhythms of T. clavata cercariae were consistent in both summer and autumn, indicating adaptability to natural changes in seasonal photoperiods. The interspecific differences in emergence patterns are likely related to the behavioural patterns of upstream, i.e., next in the life cycle, fish hosts. Cercarial output also varied between trematode species and seasons, likely due to combined effects of snail size, intensity of trematode infection in snails and size of cercariae rather than seasonal temperatures. The trematodes were molecularly characterised using mitochondrial (cox1) and nuclear (28S rDNA and ITS1-5.8S-ITS2) regions to confirm their identity and facilitate future studies. This study highlights the importance of light-regulated and host-synchronised cercarial emergence rhythms for increased trematode transmission success and reveals significant variation in cercarial output influenced by environmental and biological factors, contributing to a deeper understanding of trematode ecology and disease management.

• Keywords
• DNA, Sanguinicola sp., Tylodelphys clavata, cercariae, snails, transmission,
• MeSH
• Cercaria physiology   MeSH
• Snails * parasitology   MeSH
• Host-Parasite Interactions MeSH
• Seasons MeSH
• Light MeSH
• Trematoda * physiology   genetics   classification   growth & development   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH

Trematodes of the order Diplostomida are well known as serious pathogens of man, and both farm and wild animals; members of the genus Schistosoma (Schistosomatidae) are responsible for human schistosomosis (schistosomiasis) affecting more than 200 million people in tropical and subtropical countries, and infections of mammals and birds by animal schistosomes are of great veterinary importance. The order Diplostomida is also rich in species parasitizing other major taxa of vertebrates. The "Aporocotylidae" sensu lato are pathogenic in fish, "Spirorchiidae" sensu lato in reptiles. All these flukes have two-host life cycles, with asexually reproducing larvae usually in mollusks and occasionally in annelids, and adults usually live in the blood vessels of their vertebrate hosts. Pathology is frequently associated with inflammatory reactions to eggs trapped in various tissues/organs. On the other hand, the representatives of Diplostomidae and Strigeidae have three- or four-host life cycles in which vertebrates often serve not only as definitive but also as intermediate or paratenic hosts. Pathology is usually associated with migration of metacercariae and mesocercariae within the host tissues. The impact of these trematode infections on both farm and wild animals may be significant.

• Keywords
• Aporocotylidae, Blood flukes, Diplostomidae, Sanguinicolidae, Schistosoma, Schistosomatidae, Skin penetration, Spirorchiidae, Strigeidae, Trematodes,
• MeSH
• Trematode Infections * parasitology   veterinary   MeSH
• Host-Parasite Interactions MeSH
• Humans MeSH
• Schistosomatidae genetics   MeSH
• Life Cycle Stages MeSH
• Trematoda physiology   pathogenicity   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Review MeSH

The emergence of cercariae from infected mollusks is considered one of the most important adaptive strategies for maintaining the trematode life cycle. Short transmission opportunities of cercariae are often compensated by periodic daily rhythms in the cercarial release. However, there are virtually no data on the cercarial emergence of bird schistosomes from freshwater ecosystems in northern latitudes. We investigated the daily cercarial emergence rhythms of the bird schistosome Trichobilharzia sp. "peregra" from the snail host Radix balthica in a subarctic lake under both natural and laboratory seasonal 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. These patterns were consistent under both field and laboratory conditions. While light intensity triggered and prolonged cercarial emergence, the temperature had little effect on cercarial rhythms but regulated seasonal output rates. This suggests an adaptive strategy of bird schistosomes to compensate for the narrow transmission window. 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.

• Keywords
• Trichobilharzia, bird schistosome, cercariae, emergence, light, temperature, trematodes,
• Publication type
• Journal Article MeSH

Phenotypic polymorphism is a commonly observed phenomenon in nature, but extremely rare in free-living stages of parasites. We describe a unique case of somatic polymorphism in conspecific cercariae of the bird schistosome Trichobilharzia sp. "peregra", in which two morphs, conspicuously different in their size, were released from a single Radix balthica snail. A detailed morphometric analysis that included multiple morphological parameters taken from 105 live and formalin-fixed cercariae isolated from several naturally infected snails provided reliable evidence for a division of all cercariae into two size groups that contained either large or small individuals. Large morph (total body length of 1368 and 1339 μm for live and formalin-fixed samples, respectively) differed significantly nearly in all morphological characteristics compared to small cercariae (total body length of 976 and 898 μm for live and formalin samples, respectively), regardless of the fixation method. Furthermore, we observed that small individuals represent the normal/commonly occurring phenotype in snail populations. The probable causes and consequences of generating an alternative, much larger phenotype in the parasite infrapopulation are discussed in the context of transmission ecology as possible benefits and disadvantages facilitating or preventing the successful completion of the life cycle.

• Keywords
• Trichobilharzia, bird schistosome, cercariae, phenotype, polymorphism, trematodes,
• Publication type
• Journal Article MeSH

Direct consumption on free-living cercariae stages of trematodes by non-host organisms interferes with trematode transmission and leads to reduced infections in the next suitable hosts. Consumer functional responses provide a useful tool to examine relationships between consumption rates and ecologically relevant prey densities, whilst also accounting for abiotic factors that likely influence consumption rates. We investigated how temperature influences the consumer functional response of the amphipod Gammarus lacustris towards the cercariae of three freshwater trematodes (Diplostomum, Apatemon and Trichobilharzia). Amphipods displayed different functional responses towards the parasites, with Type II responses for Diplostomum and Type I responses for Apatemon prey. Temperature did not alter the consumption rate of the amphipod predator. Trichobilharzia was likely consumed at similar proportions as Diplostomum; however, this could not be fully evaluated due to low replication. Whilst Type II responses of invertebrate predators are common to various invertebrate prey types, this is the first time a non-filter feeding predator has been shown to exhibit Type I response towards cercarial prey. The prey-specific consumption patterns of amphipods were related to cercarial distribution in the water column rather than to the size of cercariae or temperature influence. The substantial energy flow into food webs by non-host consumer organisms highlights the importance of understanding the mechanisms that modulate functional responses and direct predation in the context of parasitic organisms.

• Keywords
• Cercariae, Gammarus lacustris, Predator-prey, Transmission interference,
• MeSH
• Amphipoda physiology   MeSH
• Cercaria classification   growth & development   physiology   MeSH
• Species Specificity MeSH
• Trematode Infections parasitology   transmission   MeSH
• Food Chain MeSH
• Predatory Behavior classification   physiology   MeSH
• Temperature MeSH
• Trematoda classification   growth & development   physiology   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH

Human cercarial dermatitis is a parasitic disease that causes an allergic reaction in the skin (swimmer's itch) as a consequence of contact with cercariae of bird schistosomes present in water, mainly of the genus Trichobilharzia Skrjabin et Zakarow, 1920. The main objective of the study was to confirm the presence of the zoonotic disease agent following reports of human infections in recreational water in Slovakia. We identified two species of freshwater snails at Košice Lake, Radix auricularia (Linnaeus, 1758) and Physa acuta (Draparnaud, 1805). Trematode infections were observed only in R. auricularia. Of the 62 snails collected, 11 (17.7%) were infected with 5 different species of larval stages of trematodes. The blood fluke Trichobilharzia franki was found in 2 (3.2%) of the examined snails. The present record provides the first evidence that T. franki from the pulmonate snail R. auricularia represents a source of human cercarial dermatitis in recreational water in Slovakia. Our finding complements the easternmost records of both swimmer's itch and the confirmed occurrence of a bird schistosome in a waterbody in Europe. The present work suggests that the health risks associated with trichobilharziasis need to be further studied by detailed monitoring of the occurrence of the major causative agent of human cercarial dermatitis, T. franki.

• Keywords
• Bird schistosomes, Cercariae, Cercarial dermatitis, Trematodes, Trichobilharzia, Zoonosis,
• MeSH
• Dermatitis epidemiology   parasitology   MeSH
• Disease Outbreaks MeSH
• Snails parasitology   MeSH
• Trematode Infections epidemiology   parasitology   transmission   MeSH
• Lakes parasitology   MeSH
• Humans MeSH
• Skin Diseases, Parasitic parasitology   transmission   MeSH
• Schistosomatidae classification   genetics   isolation & purification   MeSH
• Schistosomiasis epidemiology   parasitology   transmission   MeSH
• Zoonoses epidemiology   parasitology   transmission   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Slovakia epidemiology   MeSH

No effective method has yet been developed to prevent the threat posed by the emerging disease-cercarial dermatitis (swimmer's itch), caused by infective cercariae of bird schistosomes (Digenea: Schistosomatidae). In our previous studies, the New Zealand mud snail-Potamopyrgus antipodarum (Gray, 1853; Gastropoda, Tateidae)-was used as a barrier between the miracidia of Trichobilharzia regenti and the target snails Radix balthica. Since the presence of non-indigenous snails reduced the parasite prevalence under laboratory conditions, we posed three new research questions: (1) Do bird schistosomes show totally perfect efficacy for chemotactic swimming behavior? (2) Do the larvae respond to substances emitted by incompatible snail species? (3) Do the excretory-secretory products of incompatible snail species interfere with the search for a compatible snail host? The experiments were carried out in choice-chambers for the miracidia of T. regenti and T. szidati. The arms of the chambers, depending on the variant, were filled with water conditioned by P. antipodarum, water conditioned by lymnaeid hosts, and dechlorinated tap water. Miracidia of both bird schistosome species chose more frequently the water conditioned by snails-including the water conditioned by the incompatible lymnaeid host and the alien species, P. antipodarum. However, species-specific differences were noticed in the behavior of miracidia. T. regenti remained more often inside the base arm rather than in the arm filled with water conditioned by P. antipodarum or the control arm. T. szidati, however, usually left the base arm and moved to the arm filled with water conditioned by P. antipodarum. In conclusion, the non-host snail excretory-secretory products may interfere with the snail host-finding behavior of bird schistosome miracidia and therefore they may reduce the risk of swimmer's itch.

• Keywords
• Chemo-orientation, Lymnaeid hosts, Miracidia, Potamopyrgus antipodarum, Trichobilharzia spp.,
• Publication type
• Journal Article MeSH

Parasites comprise a huge part of the biodiversity on earth. However, on a local scale, not much is known about their diversity and community structure. Here, we assess the diversity of larval trematode communities in an interconnected freshwater system of the River Ruhr in Germany and analyse how the parasites are spatially and temporally distributed in the ecosystem. A total of 5347 snail hosts belonging to six species revealed a highly diverse parasite fauna with 36 trematode species. More abundant snail species harboured more species-rich trematode faunas and communities, with the two dominant snail species, Radix auricularia and Gyraulus albus, accounting for almost 90% of the trematode diversity and harbouring spatially and temporally stable parasite communities. The results highlight the important role of stable keystone host populations for trematode transmission, structure and diversity. This local trematode diversity reveals information on definitive host occurrence and trophic interactions within ecosystems.

• MeSH
• Biodiversity * MeSH
• Ecosystem * MeSH
• Snails parasitology   MeSH
• Host-Parasite Interactions genetics   MeSH
• Larva parasitology   MeSH
• Humans MeSH
• Population Dynamics MeSH
• Rivers MeSH
• Fresh Water parasitology   MeSH
• Trematoda classification   pathogenicity   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Germany MeSH

Cercarial dermatitis (CD) is an allergic skin disease that rises in consequence of infection by invasive stages (cercariae) of trematodes of the family Schistosomatidae. CD has been considered a re-emerging disease, human cases have been reported from all continents, and tourism-threatening outbreaks occur even in frequented recreational areas. Although the symptoms of CD are generally known, the data on immune response in human patients are sporadic and incomprehensive. In the present study, we attempted to correlate the symptoms, personal history, and time course of CD in human patients with differential cell counts, dynamics of selected cytokines, and dynamics and quality of antibody response. By a systematic follow-up, we obtained a uniquely complex dataset from ten persons accidentally and concurrently infected by the same parasite species in the same locality. The onset of CD was significantly faster, and the symptoms were heavier in participants with a history of CD if compared to naive ones, who, however, also developed some of the symptoms. The repeatedly infected persons had elevated proportion of eosinophils 1 week post exposure (p.e.) and a stronger specific IgG but not IgM response, whereas specific IgE response was not observed. Increased serum levels of IL-4 occurred 1 and 3 week(s) p.e. in all participants. There was high variability in individual immunoblot patterns of IgG response, and no antigen with a universal diagnostic potential was confirmed. The presented analyses suggested that a complex approach can improve the accuracy of the diagnosis of CD, but component data should be interpreted carefully.

• Keywords
• Allergy, Diagnosis, Immunity, Schistosome, Skin, Trichobilharzia,
• MeSH
• Dermatitis immunology   parasitology   MeSH
• Adult MeSH
• Disease Outbreaks MeSH
• Immunoglobulin E blood   MeSH
• Immunoglobulin G blood   MeSH
• Immunoglobulin M blood   MeSH
• Trematode Infections diagnosis   immunology   parasitology   MeSH
• Interleukin-4 blood   MeSH
• Middle Aged MeSH
• Humans MeSH
• Young Adult MeSH
• Follow-Up Studies MeSH
• Antibodies, Protozoan blood   MeSH
• Surveys and Questionnaires MeSH
• Ponds parasitology   MeSH
• Schistosomatidae immunology   MeSH
• Animals MeSH
• Check Tag
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Young Adult MeSH
• Male MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Czech Republic MeSH
• Names of Substances
• IL4 protein, human MeSH Browser
• Immunoglobulin E MeSH
• Immunoglobulin G MeSH
• Immunoglobulin M MeSH
• Interleukin-4 MeSH
• Antibodies, Protozoan MeSH

In freshwater ecosystems, snails can significantly influence the competition between primary producers through grazing of periphyton. This activity can potentially be modified by trematodes, a large group of parasites which mostly use molluscs as the first intermediate host. Available studies, however, show contradictory effects of trematodes on snail periphyton grazing. Here, we used four different freshwater snail-trematode systems to test whether a general pattern can be detected for the impact of trematode infections on snail periphyton grazing. In our experimental systems, mass-specific periphyton grazing rates of infected snails were higher, lower, or similar to rates of non-infected conspecifics, suggesting that no general pattern exists. The variation across studied snail-trematode systems may result from differences on how the parasite uses the resources of the snail and thus affects their energy budget. Trematode infections can significantly alter the grazing rate of snails, where, depending on the system, the mass-specific grazing rate can double or halve. This underlines both, the high ecological relevance of trematodes and the need for comprehensive studies at the species level to allow an integration of these parasite-host interactions into aquatic food web concepts.

• Keywords
• Freshwater snails, Grazing rates, Host–parasite interaction, Periphyton, Trematodes,
• MeSH
• Ecology MeSH
• Ecosystem MeSH
• Snails parasitology   MeSH
• Trematode Infections parasitology   MeSH
• Host-Parasite Interactions physiology   MeSH
• Periphyton * MeSH
• Food Chain MeSH
• Eating physiology   MeSH
• Fresh Water parasitology   MeSH
• Trematoda isolation & purification   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH