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Introduction: Cercarial dermatitis (swimmer's itch) is a water-borne parasitic skin disease caused by larvae (cercariae) of a nonhuman species of schistosome. The prevailing symptoms are nodulopapular skin lesions accompanied by pruritus. The condition occurs virtually worldwide and is considered to be an emerging public health problem in Europe. In most cases, the symptoms are associated with cercariae of avian schistosomes of the genus Trichobilharzia spp. Aim: The aim of this review article is to present the most important information on the course of the disease, its diagnostics, treatment and epidemiology. Additionally, it offers an account of preventive measures targeted at reducing the risk of infection. Material and methods: A literature search was conducted using electronic databases such as PubMed, Google Scholar and Willey Online Library. Altogether, 40 articles were subject to analysis. Results and discussion: The data obtained from the literature survey process were systematised and presented in 5 sections. Clinically, effective control of swimmer's itch should comprise measures from the fields of diagnostics, treatment, epidemiology and prevention. Conclusions: Swimmer's itch poses diagnostic difficulties, primarily due to the low specificity of its symptoms. Owing to a lack of conclusive data on the fate of cercariae penetrating human skin and a growing number of documented cases of cercarial dermatitis worldwide, further intensive research into the matter is warranted. [ABSTRACT FROM AUTHOR]

Background: Combating infectious diseases and halting biodiversity loss are intertwined challenges crucial to ensure global health. Biodiversity can constrain the spread of vector-borne pathogens circulation, necessitating a deeper understanding of ecological mechanisms underlying this pattern. Our study evaluates the relative importance of biodiversity and the abundance of Bulinus truncatus, a major intermediate host for the trematode Schistosoma haematobium on the circulation of this human pathogen at aquatic transmission sites. Methods: We combined mathematical modelling and a molecular based empirical study to specifically assess the effect of co-infections between S. haematobium and other trematodes within their B. truncatus snail hosts; and B. truncatus abundance at transmission sites, on the production of S. haematobium infective cercariae stages released into the aquatic environment. Results: Our modelling approach shows that more competitive trematode species exploiting B. truncatus as an intermediate host at the transmission site level leads to higher co-infection rates within snail hosts, subsequently reducing the production of S. haematobium cercariae. Conversely, an increase in B. truncatus abundance results in lower co-infection rates, and a higher proportion of S. haematobium cercariae released into the environment. Our empirical data from the field support these findings, indicating a significant negative effect of local trematode species richness (P-value = 0.029; AIC = 14.9) and co-infection rates (P-value = 0.02, AIC = 17.4) on the dominance of S. haematobium based on our GLMM models, while B. truncatus abundance positively influences S. haematobium dominance (P-value = 0.047, AIC = 20.1). Conclusions: Our study highlights the importance of biodiversity in influencing the transmission of S. haematobium through the effect of antagonistic interactions between trematodes within bulinid snail hosts. This effect intensifies when B. truncatus populations are low, promoting co-infections within snails. In line with the One Health concept, our results suggest that maintaining high level of freshwater biodiversity to sustain global trematode diversity at transmission sites can help reducing the circulation of Schistosoma species locally. [ABSTRACT FROM AUTHOR]

Background: Mali is known to be a schistosomiasis-endemic country with a limited supply of clean water. This has forced many communities to rely on open freshwater bodies for many human-water contact (HWC) activities. However, the relationship between contact with these water systems and the level of schistosome infection is currently receiving limited attention. This study assessed human-water interactions including cercarial emergence pattern and their influences on urinary schistosomiasis transmission in two communities in the Kayes district of Mali. Methods: We carried out a parasitological study first in children in September 2021, then a cross-sectional study of quantitative observations of human-water contact activities in the population, and finally a study of snail infectivity at contact points in September 2022. The study took place in two communities, Fangouné Bamanan and Diakalèl in the Kayes region of western Mali. The chronobiological study focused on cercarial release from naturally infected snails. Released cercariae were molecularly genotyped by targeting the cox1 region, and the ITS and 18S ribosmal DNA gene (18S rDNA) regions of the DNA. Links between sociodemographic parameters, human water-contact points and hematuria were established using multivariate statistical analysis or the logistic regression model. Results: The main factor predisposing the 97 participants to water contact was domestic activity (62.9%). Of the 378 snails collected at 14 sampling sites, 27 (7.1%) excreted schistosome cercariae, with 15.0% (19/126) at Fangouné Bamanan and 3.3% (8/252) at Diakalel. The release of Schistosoma cercariae shows three different patterns in Fangouné Bamanan: (i) an early release peak (6:00–8:00 AM), (ii) a mid-day release peak (10:00 AM–12:00 PM) and (iii) a double peak: (6:00–8:00 AM) and (6:00–8:00 PM) cercariae release; and two release patterns in Diakalel: early release (6:00–8:00 AM) and (ii) mid-day release (12:00–2:00 PM). All cercariae released during early diurnal (6:00–8:00 AM) or nocturnal emission patterns (6:00–8:00 PM) were hybrids parasite having an cox1 S. bovis or S. curassoni associated with an ITS and 18S rDNA of S. haematobium while the cercariae released during diurnal, or mid-day patterns (8:00 AM–6:00 PM) were pure S. haematobium. Conclusions: Our study showed that domestic activity is the main source of exposure in the Kayes region. Two and three cercariae emission patterns were observed at Diakalel and Fangouné Bamanan respectively. These results suggest that the parasite adapts to the human-water contact period in order to increase its infectivity. [ABSTRACT FROM AUTHOR]

Bilharzia is a parasitic flatworm that causes schistosomiasis, a neglected tropical illness worldwide. Praziquantel (PZQ) is a commercial single treatment of schistosomiasis so alternative drugs are needed to get rid of its side effects on the liver. The current study aimed to estimate the effective role of Ficus carica nanoparticles (Fc-NPCs), silver nanoparticles (Ag-NPCs) and Ficus carica nanoparticles loaded on silver nanoparticles (Fc-Ag NPCs) on C57BL/6 black female mice infected by Schistosoma mansoni and treated with PZQ treatment. It was proved that schistosomiasis causes liver damage in addition to the PZQ is ineffective as an anti-schistosomiasis; it is recorded in the infected mice group and PZQ treated group as in liver function tests, oxidative stress markers & anti-oxidants, pro-inflammatory markers, pro-apoptotic and anti-apoptotic markers also in liver cells' DNA damage. The amelioration in all tested parameters has been clarified in nanoparticle-protected mice groups. The Fc-Ag NPCs + PZQ group recorded the best preemptive effects as anti-schistosomiasis. Fc-NPCs, Ag-NPCs and Fc-Ag NPCs could antagonize PZQ effects that were observed in amelioration of all tested parameters. The study showed the phytochemicals' nanoparticles groups have an ameliorated effect on the health of infected mice. [ABSTRACT FROM AUTHOR]

Background: Schistosomiasis is a parasitic disease which is spread through skin contact with water containing Schistosoma cercariae. Drug treatment has been the main control method, but it does not prevent reinfection. The use of soap can be a complementary measure to reduce transmission. Therefore, this study investigates the quantitative effect of different soaps on the mortality of Schistosoma mansoni cercariae. Methodology: Four soaps including two powder soaps (Kleesoft and Omo) and two bar soaps (B29 and Rungu) which are used in a schistosomiasis-endemic Tanzanian village were studied. S. mansoni cercariae were exposed to powder soaps of 0 (control), 10, 50, 75, 100 and 1000 mg/L and to bar soaps of 0 (control), 100, 500 and 1000 mg/L. The highest concentration of 1000 mg/L was selected based on the laboratory-estimated average soap concentration during handwashing. Cercariae were observed under a microscope after 0, 5, 15, 30, 45 and 60 minutes of exposure to determine their survival. Conclusions: All four soaps can kill S. mansoni cercariae and this lethal effect was related to soap concentration and exposure time. At the highest concentration of 1000 mg/L, all cercariae were dead at 5 minutes post-exposure with two powder soaps and Rungu, while 100% cercarial death was achieved between 5 minutes to 15 minutes for B29. Almost all cercariae survived after being exposed to 10 mg/L powder soaps and 100 mg/L bar soaps for 60 minutes. Powder soaps were more lethal than bar soaps. Considering the widely varying concentrations of soap during real-world hygiene activities and the necessity for a very high soap concentration to eliminate all cercariae in a short 5-minute exposure, providing the efficacy of soap in preventing schistosomiasis becomes challenging. Future studies should investigate whether soap can influence alternative mechanisms such as creating a barrier to skin, thereby providing protection. Author summary: Schistosomiasis is a major public health problem in low-resource countries where there is insufficient access to safe water, sanitation and hygiene (WASH). Preventive chemotherapy with praziquantel has been the main control method, but it cannot protect against reinfection. With the increasing awareness of the importance of a multi-faceted control strategy, WASH has been recommended as one of the core strategic interventions for schistosomiasis control. The use of soap, one hygiene practice, might play a role in prevention by reducing human exposure to cercariae, thereby lowering the infection risk at transmission sites. However, to the best of our knowledge, there are no detailed guidelines on how to use soap to prevent schistosomiasis in endemic areas. Therefore, this study aimed to explore the efficacy of four commercial Tanzanian soaps against Schistosoma mansoni cercariae to understand soap lethality. The results provide scientific evidence of soap protection against schistosome cercariae and suggest that future studies should investigate other potential mechanisms by which soap may provide protection against cercariae (e.g. damaging them sufficiently to hinder penetration into the skin or protecting skin against cercarial penetration). [ABSTRACT FROM AUTHOR]

Snails are the first intermediate host in the life cycle of trematodes. Previous research found that Trichopodus microlepis fish, cultured in earthen ponds in Tan Nhut Commune, Binh Chanh District, Ho Chi Minh City, Vietnam had a high infection rate with metacercariae of Centrocestus formosanus and Procevorum sp. It is necessary to investigate whether habitats supplying water to the ponds may contribute to the transmission by carrying intermediate hosts and/or cercariae into these ponds or not. A study of cercariae and snail composition in rice fields and canal supplying water directly to these Trichopodus microlepis ponds was carried out with six samplings in the years 2022 and 2023. A total of 1,151 snails were collected, and nine snail species belonging to 8 genera and 6 families were identified. Three snail species in both rice fields and canal were infected with trematode (cercariae stage) including Bithynia siamensis, Lymnaea viridis and Indoplanorbis exustus. The overall prevalence in the dry season (25.9%) was significantly higher than in the wet season (10.6%) (P<0.05). Three cercariae morphotypes were recovered from snails: xiphidio (in all three snails), echinostome (in Lymnaea viridis and Indoplanorbis exustus), and pleurolophocercous in Bithynia siamensis. This finding shows that Bithynia siamensis is one of the infected sources for Trichopodus microlepis fish cultured in ponds, as pleurolophocercous is also the cercariae in the family of Heterophyidae (including Centrocestus formosanus and Procevorum sp.). Further research should be done to clarify the transmission of fish-borne zoonotic diseases to cultured Trichopodus microlepis in other habitats including the actual fishponds, and sources of trematodes in order to produce Trichopodus microlepis free of metacercariae, contributing to clean aquaculture development and safe food for local people in the area. [ABSTRACT FROM AUTHOR]

Schistosomiasis is an infection caused by contact with Schistosoma-contaminated water and affects more than 230 million people worldwide with varying morbidity. The roles of T helper 2 (TH2) cells and regulatory immune responses in chronic infection are well documented, but less is known about human immune responses during acute infection. Here, we comprehensively map immune responses during controlled human Schistosoma mansoni infection using male or female cercariae. Immune responses to male or female parasite single-sex infection were comparable. An early TH1-biased inflammatory response was observed at week 4 after infection, which was particularly apparent in individuals experiencing symptoms of acute schistosomiasis. By week 8 after infection, inflammatory responses were followed by an expansion of TH2 and regulatory cell subsets. This study demonstrates the shift from TH1 to both TH2 and regulatory responses, typical of chronic schistosomiasis, in the absence of egg production and provides immunological insight into the clinical manifestations of acute schistosomiasis. Editor's summary: Schistosomiasis infection causes more than 230 million infections worldwide, but immune responses during acute infection are not well understood. To better observe these responses, Houlder et al. used controlled human Schistosoma mansoni infections with either male or female cercaria-stage parasites. T helper 1 (TH1) cell–biased inflammatory responses dominated at early time points (4 weeks after infection), and male and female parasites induced similar responses. At 8 weeks after infection, TH2 and regulatory cell responses were more dominant and were consistent with responses seen during chronic infection. These results highlight the shift in immune responses occurring over the course of infection. —Christiana Fogg [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

• Persea americana, Curcuma longa and Allium sativum extracts showed anti-cercariae activity. • Methanol extracts of Persea americana bark and Curcuma longa exhibited the most potent scavenging activity. • Persea americana, Curcuma longa and Allium sativum extracts exhibited potent anti-inflammatory activity. • Plant extracts showed low toxicity on kidney Vero cells and murine macrophage cell lines. Schistosomiasis is a devastating parasitic infection, particularly in Sub-Saharan Africa. Despite the use of Praziquantel, the elimination of schistosomiaisis remains a challenge. The use of medicinal plant as treatment in disease endemic regions has provided a basis for investigating the antischistosomal properties of the plants-derived materials. This study therefore stands as a starting point for the search of new drugs against schistosomiasis. This study sought to evaluate the cercaricidal activity of methanolic extracts of Persea americana, Curcuma longa and Allium sativum. Twenty cercariae were exposed to plant extract concentrations ranging from 3.9 to 103 µg/ml. The antioxidant study was carried out using DPPH, ABTS, and FRAP assays. Anti-inflammatory activity was conducted by assessing the potential through albumin denaturation inhibition assay. The in vitro safety and phytochemical composition of plant extracts were also assessed. Cercaricidal tests revealed significant anti-cercariae activity of plant extracts at sublethal concentrations with LC 50 values ranging from 7.67 ± 3.40 to 56.07 ± 2.53 µg/ml with C. longa extract being the most potent cercaricidal. Antioxidant activity of plant extracts revealed that methanol extracts of P. americana bark and C. longa have the most potent antioxidant scavenging activities with SC 50 values ranging from 91.47 ± 5.83 to 138.75 ± 5.73 µg/ml. Anti-inflammatory analysis showed that plant extracts exhibited most potent anti-inflammatory activity by inhibiting protein denaturation. At 125 µg/ml, A. sativum, C. longa, P. americana root, bark, stem and leaf extracts showed 33.89, 108.26, 93.37, 108.18, 93.96 and 118.15 % inhibitions respectively, while the standard drug Diclofenac sodium (125 µg/ml) produced 24.67 % inhibition. Plant extracts also showed low toxicity on kidney Vero cells and murine macrophage cell lines with IC 50 values ranging between 132.15 ± 40.66 and 549.3 ± 43.70 µg/ml. The phytochemical composition of plant extracts shows that the plants are rich in at least five of saponins, cardiac glycosides, phenolics, flavonoids, alkaloids and tannins. These results suggest that methanolic extract of C. longa and P. americana showed a potent activity against S. mansoni cercariae with potent antioxidant scavenging activities and can mitigate the inflammatory effect of schistosome eggs within egg-infested tissue, combating the devastating effect of S. mansoni infection. [ABSTRACT FROM AUTHOR]

To estimate the diversity of trematodes parasitizing the invasive mollusk Viviparus viviparus, the occurrence frequency of trematode larvae (cercariae and metacercariae) in the Tura River has been surveyed near the city of Tyumen in Western Siberia. In total, 53 snails with a shell height of 17–32 mm have been examined. Three trematode species are found: Cercaria nigrospora cercariae (3.77%), Neoacanthoparyphium echinatoides cercariae (5.56%), N. echinatoides metacercariae (58.5%, 47–279), and nonencysted Leucochloridiomorpha constantiae metacercariae (62.3%, 2–69). [ABSTRACT FROM AUTHOR]

Bulinus are intermediate snail hosts of Schistosoma haematobium. Despite their vectorial role, the transmission dynamics and infectivity of these intermediate snail hosts remain understudied in the Ase River. This longitudinal study evaluated the geospatial and seasonal transmission patterns and infectivity of three S. haematobium vectors between November 2020 and October 2022 in the Ase River catchment, Delta State, Nigeria. Eleven (11) geospatial water contact coordinates were mapped for monthly spatiotemporal collection of Bulinus species along the Ase River and its catchment, for two years. Snail sampling was performed for 45 min at each study site using scooping/hand-picking techniques and subsequently counted, identified and recorded. Snails of the Bulinus genus were individually placed in a beaker containing distilled water and exposed to light to shed cercariae which were identified to be human schistosome type. The number of infected snails for each month and season was also documented to analyze the spatiotemporal and seasonal transmission dynamics of infectivity. Out of the 2345 Bulinus snails collected, a total of 41.45% were found to be infected with S. haematobium. The monthly infectivity of Bulinus snails varied significantly (P < 0.05) throughout the study period (P = < 0.0001; F = 23.11; df = 11). Further analysis showed a strong significant association (χ2 = 23.57; df = 11; p = 0.015) between the study years. The Principal Component Analysis (PCA) results suggest that Bulinus infectivity within the Ase River catchment area was primarily associated with the months of February and January. B. truncatus consistently had the highest transmission potential, followed by B. globosus and B. senegalensis. ANOVA confirms that the monthly/study site infectivity and transmission potential in B. truncates, B. globosus and S. senegalensis were statistically, significant (P < 0.05). These results demonstrated a clear distinction in the patterns and relationships between the different months in terms of snail infectivity and seasonal transmission potential. This understanding will help in the continuous monitoring and targeted interventions to control schistosomiasis transmission in Ase River. [ABSTRACT FROM AUTHOR]

Simple Summary: Leptophallus nigrovenosus is a trematode parasite found in snakes that requires feeding on amphibians to acquire the parasite. Firstly, this study investigated, in detail, the sensory receptors on the cercariae of these parasites, shedding light on the adaptations that allow them to find their host species. Secondly, the metacercariae of Salamandra salamandra were studied using histology to examine inflammatory responses in the eyes and potential eye damage. This study involved collecting snails (Planorbius metidjensis) and observing the emergence of cercariae. Salamander larvae were then exposed to these cercariae, and the larvae were later examined for the presence of metacercariae. Notably, this study is the first to report the presence of L. nigrovenosus in the snail P. metidjensis, a previously unrecorded host. These findings revealed that members of the genus Salamandra can serve as secondary intermediate hosts for L. nigrovenosus. Such infections in amphibians can lead to various eye issues, including cloudiness, inflammation, and tissue damage, ultimately affecting their survival. This research highlights the need for further investigation into trematode infections in amphibian eyes, which would provide valuable insights into their prevalence, transmission dynamics, and impact on host populations. (1) Background: Leptophallus nigrovenosus, an esophageal parasite that primarily affects water snakes of the genus Natrix, has a known life cycle that involves snail and amphibian hosts. However, the biological aspects, chaetotaxic patterns, and pathogeny of this parasite in its hosts have not been fully elucidated. (2) Methods: Snails (Planorbarius metidjensis) were collected in Spain and examined for cercaria emergence. The larvae were used to experimentally infect Salamandra salamandra, and metacercariae were isolated. Their chaetotaxy was studied using microscopy and scanning electron microscopy. The eye histology was also examined. (3) Results: The cercariae displayed distinctive morphological characteristics. The results of this study revealed three types of ciliated sensory papillae on the cercarial teguments, suggesting an adaptation for host detection and orientation. The metacercariae isolated from subcutaneous tissues showed oval bodies covered in spines. The chaetotaxy patterns matched those of Leptophallinae species. This is the first report of the presence of L. nigrovenosus in the snail P. metidjensis. Additionally, this study detected metacercariae in the eyes of S. salamandra, emphasizing the need for further research on trematode infections in amphibian eyes. (4) Conclusions: Members of the genus Salamandra can serve as secondary intermediate hosts for L. nigrovenosus, and the presence of metacercariae in amphibian eyes may have implications for the survival and habitat management of these amphibians. Understanding this parasite's prevalence, transmission dynamics, and impacts on host populations is crucial for conservation strategies. [ABSTRACT FROM AUTHOR]

Schistosomiasis is a neglected tropical disease caused by parasitic worms of the genus Schistosoma. In Brazil, there are reports of infection by the Schistosoma mansoni species, which has the Biomphalaria glabrata snail as one of its intermediate hosts. The present work aimed to test the effects of different Abelmoschus esculentus seed extracts and fractions on adults and embryos of B. glabrata and S. mansoni cercariae. A total of four crude extracts and thirteen fractions with different organic solvents were used for the bioassays. The extracts were analyzed using high-performance liquid chromatography coupled to mass spectrometry. Molluscicidal activity was assessed in 24-well plates, after which the LC50 and LC90 were calculated. Assays with B. glabrata embryos and S. mansoni cercariae were also performed. These findings indicate the presence of flavanoids in the hexane, ethyl acetate, and ethanol crude extracts. For the molluscicidal activity assays, eight fractions had an LC90 value less than that recommended by the WHO. The methanol fraction of the dichloromethane extract (FrMeOH EDM) had the most promising results, with an LC90 of 37.15 mg/L and 100% mortality in embryos of B. glabrata and cercariae. FrMeOH, EDM, and other fractions are possible candidates for new drugs for the combat of schistosomiasis. [ABSTRACT FROM AUTHOR]

Background: Exotic and ornamental fish are highly popular companion animals resulting in a significant transcontinental trade of fish, invertebrates and aquatic plants. A major issue is the diseases associated with these organisms, as they have a major impact on health of the fish in both public and private household aquaria. A secondary issue is the trade with these products, which potentially may expand the distribution area and spread a range of diseases to new habitats. Results: We here describe how Poecilia reticulata (guppy), produced in a private household aquarium, were invaded by cercariae of an exotic trematode released by imported Melanoides tuberculata snails. The fish presented with severe clinical signs (tremor, flashing, scraping of body against objects). A standard parasitological examination and morphometric identification showed scale pocket infections with a digenean trematode species within the genus Transversotrema. Molecular identification by PCR, sequencing and phylogenetic analyses of a 2646 bp sequence encoding ribosomal RNA (partial 18 S, ITS1, 5.8 S, ITS2, partial 28 S) was performed. The 1107 bp sequence of mitochondrial DNA (cox1) showed that the parasite differed from previously described Transversotrema species in M. tuberculata. Morphometrics of adult and larval specimens of this isolate also differed from previously described freshwater species within the genus. The new species was described and is named after Copenhagen, for its geographic origin. Conclusions: The genus Transversotrema comprises a range of species, adapted to a microhabitat in scalepockets of teleosts. A combination of morphological and molecular characterization techniques has been shown to provide a good differentiation between species. The fish were not purchased from a pet shop but produced in the home aquarium. This indicated that an infection pressure existed in the aquarium, where the source of infection was found to be exotic intermediate host snails M. tuberculata, which originally were imported and purchased from a pet shop. The potential spread of fish diseases associated with trade of fish and snails to new geographic regions, where climate conditions are favourable, is discussed. [ABSTRACT FROM AUTHOR]

The change in the distribution of organisms in freshwater ecosystems due to natural or manmade processes raises the question of the impact of alien species on local communities. Although most studies indicate a negative effect, the positive one is more difficult to discern, especially in multispecies systems, including hosts and parasites. The purpose of the study was to check whether the presence of an alien host, Potamopyrgus antipodarum , reduces the intensity of Echinoparyphium aconiatum metacercariae in a native host, Radix spp. We additionally tested the impact of water temperature and the biomass of the alien host on the dilution effect. We experimentally studied (1) the lifespan of echinostome cercariae in different temperatures, (2) the infectivity of cercariae toward the alien host and native host, and (3) the impact of different biomass of the alien host on the intensity of metacercariae in the native host. We found that cercarial survival and infectivity were temperature dependent. However, cercarial survival decreased with increasing temperature, contrary to cercarial infectivity. Echinostome cercariae entered the renal cavity of both the native host and alien host, and successfully transformed into metacercariae. The number of metacercariae in the native host decreased with the increasing biomass of the alien host. Our results indicate that lymnaeids may benefit from the co-occurrence with P. antipodarum , as the presence of additional hosts of different origins may reduce the prevalence of parasites in native communities. However, the scale of the dilution effect depends not only on the increased spectrum of susceptible hosts but also on the other variables of the environment, including water temperature and host density. [ABSTRACT FROM AUTHOR]

Cercarial dermatitis (CD), or "Swimmer's itch" as it is also known, is a waterborne illness caused by a blood fluke from the family Schistosomatidae. It occurs when cercariae of trematode species that do not have humans as their definitive host accidentally penetrate human skin (in an aquatic environment) and trigger allergic symptoms at the site of contact. It is an emerging zoonosis that occurs through water and is often overlooked during differential diagnosis. Some of the factors contributing to the emergence of diseases like CD are related to global warming, which brings about climate change, water eutrophication, the colonization of ponds by snails susceptible to the parasite, and sunlight exposure in the summer, associated with migratory bird routes. Therefore, with the increase in tourism, especially at fluvial beaches, it is relevant to analyze the current epidemiological scenario of CD in European countries and the potential regions at risk. [ABSTRACT FROM AUTHOR]

Cercariae of Plagiorchis spp. are frequently reported in European freshwater snails, but their true diversity is difficult to estimate due to subtle differences in morphology. We molecularly characterized 67 isolates of Plagiorchis cercariae collected from four lymnaeid snail hosts, Ampullaceana balthica, Ampullaceana lagotis, Radix auricularia and Lymnaea stagnalis in freshwater ecosystems in the Czech Republic and Poland. Based on mitochondrial cox1 and nuclear 28S sequences, ten species or species-level lineages were identified, including the first molecular evidence of P. vespertilionis from snail hosts and two species-level lineages reported for the first time. Previously undescribed species and species-level lineages are characterized morphometrically. We confirm the overlapping spatial distribution of Plagiorchis spp. in their snail hosts from Central Europe with those from Western and sub-Arctic Europe. Our results increase the known diversity of Plagiorchis spp. in Europe to 25 species/lineages in snails, but further research is needed to establish links between life cycle stages and to assess the host specificity of these parasites. [ABSTRACT FROM AUTHOR]

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.

Schistosomiasis, one of the neglected tropical diseases which affects both humans and animals, is caused by trematode worms of the genus Schistosoma. The disease is caused by several species of Schistosoma which affect several organs such as urethra, liver, bladder, intestines, skin and bile ducts. The life cycle of the disease involves an intermediate host (snail) and a mammalian host. It affects people who are in close proximity to water bodies where the intermediate host is abundant. Common clinical manifestations of the disease at various stages include fever, chills, headache, cough, dysuria, hyperplasia and hydronephrosis. To date, most of the control strategies are dependent on effective diagnosis, chemotherapy and public health education on the biology of the vectors and parasites. Microscopy (Kato-Katz) is considered the golden standard for the detection of the parasite, while praziquantel is the drug of choice for the mass treatment of the disease since no vaccines have yet been developed. Most of the previous reviews on schistosomiasis have concentrated on epidemiology, life cycle, diagnosis, control and treatment. Thus, a comprehensive review that is in tune with modern developments is needed. Here, we extend this domain to cover historical perspectives, global impact, symptoms and detection, biochemical and molecular characterization, gene therapy, current drugs and vaccine status. We also discuss the prospects of using plants as potential and alternative sources of novel anti-schistosomal agents. Furthermore, we highlight advanced molecular techniques, imaging and artificial intelligence that may be useful in the future detection and treatment of the disease. Overall, the proper detection of schistosomiasis using state-of-the-art tools and techniques, as well as development of vaccines or new anti-schistosomal drugs may aid in the elimination of the disease.

The work discusses some issues related to the species diversity of helminth larvae developing in the body of freshwater molluscs and insects distributed in the territory of Karakalpakstan, a vast region in Uzbekistan. A total of 42 species of parasites in larval form were identified in the region; 27 species were recorded in aquatic molluscs and 15 species in insects. 29 species were recorded for the first time in Karakalpakstan. We established that the class Gastropoda in the water bodies of Karakalpakstan is represented by 17 species; 9 of them belong to the family Lymnaeidae, 6 species to Planorbidae and 2 to Physidae. 3,477 mollusс individuals of 11 species were infected with larval stages of trematodes. The prevalence of infection in Lymnaeidae (Radix and Lymnaea) ranged from 1.7% to 25.5%. A similar prevalence was recorded in Planorbidae (1.6–25.4%). Physa fontinalis showed a prevalence of infection of 1.3%. 27 species of parasites in cercarial forms were identified in molluscs. The largest number of cercariae of trematode species was found in molluscs from the family Lymnaeidae (14 species). They were followed by representatives of Planorbidae (12 species). The fauna of cercariae identified in molluscs from water bodies in Karakalpakstan was from 12 families of trematodes. The most common were the cercariae of those species of trematodes that complete their life cycle in wetland birds (20 species). Cercariae of 6 species of trematodes turned out to be parasites of mammals, mainly ungulates. 1 species of trematodes in a larval stage was recorded in each of the fish and amphibian groups. The richest species composition in the studied region was shown by trematode cercariae representing Schistosomatidae (6 species), which were followed by Echinostomatidae (4 species). Cercariae of other trematode families were represented by one, two and three species. It was established that the studied molluscs do not play an equal role as intermediate hosts of trematodes. The richest species composition was shown by populations of Radix auricularia (14 species), Planorbis planorbis (12 species), Anisus spirorbis (9 species), and Lymnaea stagnalis (5 species). Populations of L. bactriana, Pl. tangitarensis were infected by only one species. The prevalence recorded in the studied insects infected with helminth larvae ranged widely from 1.1% to 14.4%. The identified larvae turned out to be representatives of Cestoda (3 species), Trematoda (1 species) and Nematoda (11 species). The largest number of species (4) of helminth larvae were found in beetles from the family Scarabaeidae – Gongylonema pulchrum, Spirura rytipleurites, Choanataenia infundibulum and Echinolepis carioca, and mosquitoes – Dirofilaria immitis, D. repens, Dipetalonema ewansi and Setaria labiatopapillosa. 2 species were recorded in flies – Stephamofilaria stilesi and Parabronema skrjabini. The recorded species belong to the classes Nematoda and Cestoda. The intensity of infection ranged from single to 11–17 individuals. The work provides original data on the morphology and biology of the larvae of the studied mollusсs infected with cercariae of trematodes and insects with metacercariae of trematodes, cysticercoids of cestodes and larvae of nematodes, and presents the structure of communities of larval forms of parasitic worms.

Indoplanorbis exustus is a freshwater gastropod belonging to the family Planorbidae. This snail is widely distributed across the tropics and plays an important role as the intermediate host for trematodes. However, relatively little is understood regarding the genetic relationship between I. exustus and trematodes. The goals of this study were to investigate the current transmission status of trematode cercariae in I. exustus in Thailand and to examine the genetic diversity, genetic structure, and demographic history of I. exustus. We collected 575 I. exustus from 21 provinces across six regions of Thailand and investigated cercarial infections by using the shedding method. I. exustus from two provinces were infected with cercarial trematodes, and two types of cercarial stages were molecularly identified as furcocercous cercaria and xiphidiocercariae. Phylogenetic tree analysis based on 28S rDNA and ITS2 sequences demonstrated that furcocercous cercaria and xiphidiocercariae were closely clustered with a clade of Euclinostomum sp. and Xiphidiocercariae sp., respectively. Phylogenetic and network analyses of I. exustus haplotypes based on the COI, 16S rDNA, and ITS1 genes demonstrated four main clades. Only snails in clade A were distributed in all regions of Thailand and harbored trematode cercariae. The level of genetic diversity of I. exustus was relatively high, but most populations were not genetically different, thus suggesting the appearance of gene flow within the I. exustus populations. Overall, the haplotype network was star-shaped, thus suggesting the recent demographic expansion of populations. This result was also supported by the unimodal mode of the mismatch distribution graph and the large negative values of the neutrality tests. Therefore, the I. exustus snail was likely another freshwater snail of the invasive species in Thailand. This information will aid in monitoring the spread of the parasitic trematodes carried by I. exustus from different populations. [ABSTRACT FROM AUTHOR]

Background Some freshwater snails are as intermediate hosts of human and animal parasitic trematode. Studies on freshwater snails’ fauna and cercariae infection play an important role in detecting the sources of infection. Objective The present study aims to determine the prevalence of cercariae infection in freshwater snails from the Lymnaeidae and Physidae families in Guilan province, northern Iran, and assess the effects of physicochemical parameters of water on their abundance. Methods In a one-year period, freshwater snails from the Lymnaeidae and Physidae families were identified from 117 regions in Guilan province. Water samples from each region was also collected for physicochemical analyses. Identified snails were examined for cercariae infection by the shedding method. Results Of 39,486 collected snails, three species were found, including 19,726 Lymnaea auricularia (49.96%), 4911 Lymnaea palustris (12.44%), and 14849 Physa acuta (37.6%). The prevalence of cercariae infection was 2.36%. Identified cercariae were xiphidiocercariae (0.94%), echinostome (0.8%), furcocercous (0.44%), lophocercous (0.16%), and gymnocephalous (0.02%). The highest infection rate was found in the spring (3.37%). Temperature and pH of water had a negative significant relationship with the prevalence of cercariae infection, while the salinity and electrical conductivity of water had a positive significant relationship with the abundance of snails. Conclusion Three species of freshwater snails (Lymnaea auricularia, Lymnaea palustris, and Physa acuta) exist in the aquatic regions of Guilan province in different seasons. The physicochemical parameters of water have effects on the snails’ abundance and the prevalence of cercariae infection in them. [ABSTRACT FROM AUTHOR]

Proterometra macrostoma is a digenetic trematode that is widely distributed in the eastern United States. The objective of this study was to assess how the cercariae of P. macrostoma within their redia in the infected intermediate snail host (Elimia semicarinata) respond during an initial 7-d exposure of their snail host to 20°C (mimicking a fall temperature), followed by a cold-water exposure of 7.5°C over a 28-d period (mimicking a winter temperature), and within a week after returning to warmer water at 20°C (mimicking a spring temperature). Specifically, we investigated whether cercarial development inside the redia ceases or continues during exposure of the snail host to a winter temperature, which was determined based on changes in the cercarial composition in each redia in the infected snails and the amount of cercarial shedding. Naturally infected snails (E. semicarinata) were collected from North Elkhorn Creek, Scott County, Kentucky, during June and July 2019. Baseline cercarial emergence was recorded over 7 d at 20°C for 55 snails with patent infections. Infected snails were then maintained at 7.5°C for 28 d and checked daily for any cercarial emergence followed by a post–cold treatment analysis of cercarial emergence over 7 d at 20°C. No cercariae were released during the 28-d cold treatment. Significantly more (mean ± SE) cercariae were released per snail during the 7 d following the cold treatment (4.60 ± 0.33) compared to the period prior to cold treatment (3.63 ± 0.35). At the termination of the experiment, 94.6% of infected snails were found to have living rediae with a mean ± SE infection intensity of 7.13 ± 0.51 rediae/snail (range 1–18). Additional sets of snails (pre–cold treatment = 4 snails; post–cold treatment = 5 snails) were dissected at the beginning of the pre– and post–cold treatment periods to observe individual cercarial populations within rediae. No significant differences were found in the average number of the 4 cercarial stages described within rediae pre– vs. post–cold treatment. These results suggest that additional cercariae within rediae mature during winter months, but this was not detectable by our staging criteria. [ABSTRACT FROM AUTHOR]

We elucidate the life cycle of Leuceruthrus stephanocauda (Faust, 1921) Womble and Bullard 2022, provide the first description of its adult, and redescribe its cercaria based on specimens infecting centrarchiform and perciform fishes and pleurocerid snails in the southeastern United States. Based on morphological and nucleotide-based (28S rRNA gene and internal transcribed spacer 2 [ITS2]) evidence, adults of L. stephanocauda infect the stomach of spotted bass, Micropterus punctulatus (Rafinesque, 1819), green sunfish, Lepomis cyanellus Rafinesque, 1819, and longear sunfish, Lepomis megalotis (Rafinesque, 1820) from Chewacla Creek (Tallapoosa River, Alabama) and mottled sculpin, Cottus bairdii Girard, 1850 (juvenile), from Raccoon Creek (Chattooga River, Georgia). The adult of L. stephanocauda differs from its congeners by having an elongated body and an asymmetrical vitellarium. The cercariae of L. stephanocauda shed from yellow elimia, Elimia flava (Lea, 1862) (Cerithioidea: Pleuroceridae) in Chewacla Creek and Moores Mill Creek (Tallapoosa River) and from Elimia caelatura georgiana (Lea, 1862) in Raccoon Creek. Naturally shed cercariae of L. stephanocauda are unique by having bilateral, discontinuous fields of black tail stem pigmentation posterior to the withdrawn distome and along the margins of the paired furcae, prominent subtriangular spines on the anterior end of the tail stem anterior and posterior to the distome, and broadly rounded to lanceolate furcae that are longer than wide and that bear numerous marginal and submarginal protuberances. Our 28S phylogenetic analysis recovered L. stephanocauda as a sister to Leuceruthrus micropteri Marshall and Gilbert, 1905, within monophyletic Leuceruthrinae Goldberger, 1911. No species of Leuceruthrus Marshall and Gilbert, 1905, has been reported previously from the Tallapoosa River. [ABSTRACT FROM AUTHOR]

The role of parasites as prey for nonhost species has received increasing attention over the last 3 decades as (1) such a reduction of infectious agents decreases disease transmission by reducing parasite numbers and (2) the importance of parasites in energy flow within aquatic food webs is acknowledged. Previous predation studies of digenetic trematode cercariae have assessed species in which large numbers of cercariae are released daily by individual snails. By contrast, the cercaria of the azygiid trematode Proterometra macrostoma averages less than 1 cercaria released per infected snail per day. The objective of this study was to evaluate the preference of crayfish (i.e., Procambarus spp. and Faxonius juvenilis) as predators of 3 different prey items of similar size and swimming ability including the comparatively large cercaria (i.e., 3–9 mm) of P. macrostoma. Four experiments were conducted, 2 with F. juvenilis and 2 with Procambarus spp. Each experiment consisted of 25 crayfish, which were individually exposed to 1 of 5 treatment levels consisting of a control (i.e., no prey), individual prey (i.e., cercariae, Daphnia magna, or Xenopus laevis tadpoles only), or a mixture of all 3 prey over a 7-hr exposure at 20°C and continuous light. In both the single-prey and mixed-prey experiments, cercariae were consumed at a similar or faster rate than tadpoles and D. magna, and these differences were most notable within the first hour postexposure. These results suggest that P. macrostoma cercariae are a legitimate component of the food web in freshwater habitats, and may play an important role in energy flow between trophic levels in such systems. [ABSTRACT FROM AUTHOR]

Postharmostomum larueiMcIntosh, 1934, utilizes terrestrial gastropods as first and second intermediate hosts. The flamed tigersnail, Anguispira alternata, is the only known first intermediate host. Among many reported second intermediate hosts, A. alternata is the most commonly reported and most heavily infected. The present investigation was undertaken to examine the breadth of second intermediate host use of P. laruei through experimental infections. Snails of 9 species were exposed to cercariae shed from infected A. alternata specimens in trials of varying durations. Developing worms were recovered from positive control A. alternata specimens, as well as members of 8 other species of terrestrial gastropods. Four of these (a succineid, Xolotrema fosteri, Oxychilus draparnaudi, and Neohelix albolabris) are new host records for P. laruei. The first record of incompatibility of P. laruei and potential second intermediate hosts is recorded, as members of the succineid and of X. fosteri were found to harbor dead worms at early stages of development. The ease with which P. laruei experimentally infects gastropods that are rarely found infected in the wild (e.g., N. albolabris, Webbhelix multilineata, Deroceras reticulatum), and even exotic snails (O. draparnaudi) combined with the seeming resistance to infection exhibited by other snails suggest that the specificity of host recognition is low, but also that both physiological incompatibility and ecological limitations restrict functional host use to A. alternata individuals in the wild. [ABSTRACT FROM AUTHOR]

Red swamp crayfish Procambarus clarkii were collected from Cattail Marsh in Beaumont, Texas and necropsied. Eight (13%) of 62 crayfish collected were infected with metacercariae of Crepidostomum cornutum. Excysted metacercariae were stained and mounted for morphologic identification or preserved for molecular analysis. Morphometric values were consistent with those reported previously in the literature. Sequences of the 28S ribosomal RNA gene were aligned with the National Center for Biotechnology Information GenBank database. Blast analysis returned a result of 99% similarity for C. cornutum. This study provides the first report of C. cornutum metacercariae infecting P. clarkii in Texas substantiated by a voucher specimen and sequence data. Molecular data from this study should prove helpful in identification of adult stages from fish and cercariae from bivalves in future studies. [ABSTRACT FROM AUTHOR]

We have studied the differential influence of light and temperature on the regulation of daily cercarial emission of ten species of littoral trematodes of the White Sea (Cryptocotyle lingua, C. concava, Himasthla elongata, H. continua, Cercaria parvicaudata, Levinseniella brachysoma, Maritrema subdolum, Microphallus claviformis, M. similis, and Paramonostomum alveatum) and two freshwater species from Lake Chudskoe (Diplostomum pseudospathaceum and Moliniella anceps). The experiments tested short-term (2 h) exposure to illumination (darkness and light 800 lux) and temperature (10, 20, 25°C) on the intensity of cercariae emission from infected molluscan host. The experimental setup and experimental design made it possible to separate the effects of the studied factors of all gradations. It was found that light plays a significant role in stimulating the emission of cercariae with pigmented eyes and echinostomatoid larvae Moliniella anceps and Himasthla spp., which are expected to have nonpigmented photoreceptors. However, even in these larvae in the dark, the emission was controlled by temperature. For almost all studied species, the high significance of the interaction between temperature and light factors in the regulation of cercariae emission was revealed. With the same values illumination can act as an emission trigger, and at other temperatures it can act as an inhibitor. It has been suggested that the temperature dependence of the rhythm and intensity of daily cercarial emission is especially favorable in polar latitudes, where most of the seasonal window of trematode transmission occurs during the polar day with minor changes illumination during the day. [ABSTRACT FROM AUTHOR]

The elucidation of life-cycles of digeneans, with their successive larval stages, is facilitated by the use of molecular markers. Samples of sporocysts containing cercariae and metacercariae belonging to Monorchis Monticelli, 1893 were collected from naturally infected bivalves, Cerastoderma glaucum (Bruguière, 1789), and adult forms of Monorchis spp. were collected from sparid fishes of the genus Diplodus. All specimens were collected in the Gulf of Gabès, southern Tunisia. The identities of the examined molluscs and fishes were determined via molecular barcoding of their COI gene. Sequences of COI and ITS1 genes were also obtained for both larval and adult stages of collected parasite specimens. Genetic sequence data generated for the collected larval specimens only differed minimally from the sequence data of adults identified as Monorchis parvus; we attribute the difference to intraspecific variation. The morpho-anatomical study showed that the different stages of M. parvus collected from the Tunisian coasts had the same morphology as those reported in European waters with a lag in maturity and lower measurements. The species is recorded and molecularly characterised for the first time off the Tunisian coasts. [ABSTRACT FROM AUTHOR]

Experiments with underyearlings of Oncorhynchus mykiss and cercariae of the trematode Diplostomum pseudospathaceum show that the first parasites that infect the fish have an excitatory influence on it and triple the rate of cercaria income with water through the oral cavity and gills. This effect is considered as manipulation of fish behavior at the stage of parasite transmission from the first intermediate host (mollusk) to the second (fish) one. Experimental data on the effect of fish odor on locomotor activity and the vertical distribution of cercariae have been obtained. Analysis of the data made it possible to determine a set of conditions that ensure the successful infection of fish by diplostomum larvae. [ABSTRACT FROM AUTHOR]

Lymnaeids are aquatic snails playing an important role in the transmission of many parasitic trematode species of veterinary and medical importance. In this study, we assessed the presence of cercarial flukes in naturally infected lymnaeid snails from Phayao province, Thailand, and determined the species diversity of both the intermediate snail hosts and parasite larvae. A total of 3,185 lymnaeid snails were collected from paddy fields at 31 sites in eight districts of Phayao province between October 2021 and December 2022. Larval fluke infection was assessed using the cercarial shedding method. The collected snails as well as emerging cercariae were identified at the species level via morphological and molecular methods. The sequences of snail internal transcribed spacer region 2 (ITS2) and cercarial 28S ribosomal RNA gene (28S rDNA) and cytochrome C oxidase1 (Cox1) were determined by PCR amplification and sequencing. Three species of lymnaeid snails were detected in this study, including Radix (Lymnaea) rubiginosa (Michelin, 1831), Radix (Lymnaea) swinhoei (Adams, 1866) and Austropeplea viridis (Quoy & Gaimard, 1832), of which R. rubiginosa was the most abundant, followed by A. viridis and R. swinhoei. The overall rate of trematode cercarial infection in the lymnaeid snails was 2.8% (90/3,185); the cercarial infection rate in R. rubiginosa and A. viridis was 3.5% (60/1,735) and 3.1% (30/981), respectively. No larval fluke infection was observed in the studied R. swinhoei (0/469). Nine morphotypes of cercariae were detected at 15 sites from four districts. The emerging cercariae were molecularly identified as Clinostomum sp., Aporocotylidae sp., Apharyngostrigea sp., Trichobilharzia sp., Apatemon sp., Pegosomum sp., Petasiger sp., Echinostoma revolutum and Plagiorchis sp. These findings emphasize the occurrence and diversity of trematode cercariae among naturally infected lymnaeid snails in Phayao province and could contribute to broadening our understanding of the host-parasite relationships between trematodes and their first intermediate hosts as well as developing effective interventions to control trematode parasitic diseases. [ABSTRACT FROM AUTHOR]

Malacological and parasitological studies were conducted from April 2020 to March 2021 to determine the abundance and distribution of molluscs and cercariae of Schistosoma spp and Fasciola gigantica. Collected molluscs are exposed to strong light to induce cercarial release. Mollusc densities were higher at station 1 (Gamak) than in station 8 (Patakai), with Bellamya unicolor and Biomphalaria pfeifferi more abundant and Bulinus truncatus, B. tropicus, and B. globosus less abundant. The overall prevalence of cercariae (19.87%) is higher in station 3 (Yaye orchard), station 9 (Gougni), station 4 (Madiogo), station 5 (Madiogo pasture), and station 6 (Ziam 3). It varies significantly between 15.76% in station 8 and 25.77% in station 3, between 8.48% in B. truncatus and 25.53% in B. globosus, and between 19.27% for cercariae of Schistosoma spp and 21.60% for those of F. gigantica. Cercarial emissions in L. natalensis and B. pfeifferi were higher in hot and cold dry seasons; on the other hand, cercarial emissions in B. globosus were higher in hot dry seasons (31.48%) and rainy seasons (23.38%). Emissions of cercariae from S. haematobium are related to areas of human activity and defecation, while those of F. gigantica in L. natalensis, Schistosoma haematobium in B. tropicus, and S. mansoni in B. pfeifferi are related to grazing areas. Mayo-Vreck is a site that favors the endemicity of fascioliasis and human schistosomiasis. [ABSTRACT FROM AUTHOR]

Simple Summary: Far Eastern trematodes of the genus Echinochasmus were studied. As the analysis of the nuclear 28S rRNA gene sequence showed, the examined Far Eastern individuals did not belong to the species E. beleocephalus despite their morphological similarities and represented a new species, Echinochasmus pseudobeleocephalus n. sp. An analysis of phylogenetic relationships in Echinochasmidae supported their status as an independent species. The subdivision of individuals of the genus Echinochasmus into two groups was also confirmed on the basis of the number of head-collar spines and the tail length in cercariae. Adult individuals of Echinochasmus pseudobeleocephalus n. sp. were obtained during an experimental study on trematodes' life cycle. An analysis of the morphometric characteristics of the developmental stages and involvement of first intermediate hosts, snails of the genus Boreoelona, in their life cycle, revealed the identity of the obtained trematodes to the European species Echinochasmus beleocephalus previously discovered in the south of the Russian Far East. However, an analysis of molecular data, in particular sequences of the 28S rRNA gene, showed that the Far Eastern trematodes examined do not belong to European E. beleocephalus despite their morphological similarities. An analysis of phylogenetic relationships within the family Echinochasmidae supported the status of E. pseudobeleocephalus n. sp. as an independent species. Our new data confirmed that the individuals attributed to Echinochasmus can be subdivided into two groups on the basis of the number of head-collar spines and the tail length in cercariae on an intergeneric level. [ABSTRACT FROM AUTHOR]

Predation is considered one of the key drivers shaping the relationships between animals. There is increasing evidence that non‐host aquatic taxa use free‐living parasite stages as prey, including motile cercariae of digenean trematodes. However, species‐specific predator differences in cercarial consumption are poorly understood, especially when invasive consumers are involved.We used experimental approaches to investigate the possible predator‐induced reduction in trematode‐host encounters in freshwater benthic communities. Four gammarid species, two native European (Gammarus jazdzewskii and G. pulex) and two invasive Ponto‐Caspian (Dikerogammarus villosus and Pontogammarus robustoides), were selected as predators of echinostomatid cercariae (Echinoparyphium aconiatum).We hypothesised that (i) all predators will prey on cercariae, but the amount of prey consumed will vary, the invaders will be more voracious than native species, and (ii) the effect of predator‐induced dilution of cercariae will depend on the environmental condition, i.e., the presence of the natural target host (the planorbid snail Planorbarius corneus) and alternative food resource; the exposure of predators to these two basic environmental factors will reduce their consumption rates of cercariae.The extent of the dilution effect caused by gammarids was highly predator species‐dependent and also varied depending on experimental conditions. Overall, all gammarids preyed on cercariae and reduced infection levels in the target snail host, but the invaders were more efficient than the native species. Furthermore, decreased consumption rates of cercarial prey were observed in the presence of both the target snail hosts and alternative food resources, except for invasive P. robustoides consuming more cercariae when a snail host was present.The observed differences among predators in the consumption of cercariae may be a result of complex interaction traits of parasites, predators and target hosts, such as different predatory behaviour of invasive and native amphipods, change in parasite behaviour in response to the presence/chemical signals of the target host and a predator‐induced "ecology of fear" interfering with the dilution effect of parasites.We provided evidence that gammarids can cause a significant reduction in parasite‐host encounters. The high consumption rates, especially in the presence of easily available alternative food resources, emphasise the importance of free‐living cercariae as an energy resource in aquatic food webs. The observed predator differences in the consumption of cercariae are further evidence of the higher competitive ability of invasive species. Simultaneously, our results indicate that the appearance of new predators in the environment may interfere with established host‐parasite interactions. [ABSTRACT FROM AUTHOR]

(1) Background: Leptophallus nigrovenosus, an esophageal parasite that primarily affects water snakes of the genus Natrix, has a known life cycle that involves snail and amphibian hosts. However, the biological aspects, chaetotaxic patterns, and pathogeny of this parasite in its hosts have not been fully elucidated. (2) Methods: Snails (Planorbarius metidjensis) were collected in Spain and examined for cercaria emergence. The larvae were used to experimentally infect Salamandra salamandra, and metacercariae were isolated. Their chaetotaxy was studied using microscopy and scanning electron microscopy. The eye histology was also examined. (3) Results: The cercariae displayed distinctive morphological characteristics. The results of this study revealed three types of ciliated sensory papillae on the cercarial teguments, suggesting an adaptation for host detection and orientation. The metacercariae isolated from subcutaneous tissues showed oval bodies covered in spines. The chaetotaxy patterns matched those of Leptophallinae species. This is the first report of the presence of L. nigrovenosus in the snail P. metidjensis. Additionally, this study detected metacercariae in the eyes of S. salamandra, emphasizing the need for further research on trematode infections in amphibian eyes. (4) Conclusions: Members of the genus Salamandra can serve as secondary intermediate hosts for L. nigrovenosus, and the presence of metacercariae in amphibian eyes may have implications for the survival and habitat management of these amphibians. Understanding this parasite’s prevalence, transmission dynamics, and impacts on host populations is crucial for conservation strategies.

Cercariae of Plagiorchis spp. are frequently reported in European freshwater snails, but their true diversity is difficult to estimate due to subtle differences in morphology. We molecularly characterized 67 isolates of Plagiorchis cercariae collected from four lymnaeid snail hosts, Ampullaceana balthica, Ampullaceana lagotis, Radix auricularia and Lymnaea stagnalis in freshwater ecosystems in the Czech Republic and Poland. Based on mitochondrial cox1 and nuclear 28S sequences, ten species or species-level lineages were identified, including the first molecular evidence of P. vespertilionis from snail hosts and two species-level lineages reported for the first time. Previously undescribed species and species-level lineages are characterized morphometrically. We confirm the overlapping spatial distribution of Plagiorchis spp. in their snail hosts from Central Europe with those from Western and sub-Arctic Europe. Our results increase the known diversity of Plagiorchis spp. in Europe to 25 species/lineages in snails, but further research is needed to establish links between life cycle stages and to assess the host specificity of these parasites.

Anti-schistosomal effect of crude aqueous extract of Occimum gratissimum (scent leaf) and Andrographis paniculata (king of bitters) on Schistosoma haematobium were cercaricidally evaluated over a period of 2 hours (h). The mortality of the cercaria was dose and time dependent. At 100 milligram per milliliter (mg−mL), O. gratissimum and A paniculata exhibited 100% mortality. Statistically, extract concentrations (F = 53.55; P= 0.004) and plant species (F = 10.13; P = 0.049) had significant (p < 0.05) effect on cercaria mortality. Pearson correlation coefficient (R) analysis showed that the results of cumulative mean cercariae mortalities and exposure time were strongly correlated for both plants. Probit analysis, lethal concentration (LC50) of O. gratissimum and A. paniculata against S. haematobium cercaria was 41.50 and 44.10 mg−mL respectively. The median lethal time (LT50) values for O. gratissimum and A. paniculata extract concentrations at 120 minutes treatment implicated 100.0 mg−mL to be the most toxic concentration which generated an LT50 value of 50.47 and 55.0 minutes respectively. While the least effective concentration of A. paniculata was 25.0 mg−mL requiring 115.03 minutes to cause 50% mortality of cercariae. From the study, it can be deduced that O. gratissimum and A. paniculata elicited varying degree of anti-schistosomal properties at all concentrations against S. haematobium. S. haematobium cercariae were more susceptible to toxic effects of O. gratissimum leaf extracts than A. paniculata. Cultivation of these plants along river banks will help in controlling cercariae and possibly miracidia in endemic areas by way of leave shedding since these plants are hydrophilic, biodegradable, readily available and less laborious to cultivate.

Trematode parasites are one of the 'dark' areas of the tree of life, with perhaps over 90% of trematode species remaining to be discovered, described, and named. The parthenita and cercaria life stages of trematodes are particularly poorly documented, despite being biologically fascinating, medically and ecologically important, and serving as model systems even when undescribed and unnamed. Modern practice is to avoid assigning formal names to trematode parthenitae and cercariae, which is problematic and, I argue, often unnecessary. A new, formal naming practice for parthenitae and cercariae (proposed here) should improve our efforts to understand global trematode diversity and enhance basic ecological, evolutionary, and public-health research involving these parasites. Arguably the most unique biological features of trematode parasites involve their clonal parthenitae and cercariae. These life stages are biologically fascinating, medically and scientifically important, and often studied for years, lacking knowledge of their corresponding sexual adult stages. But sexual adults are the focus of trematode species-level taxonomy, partially explaining the relative neglect of documenting the diversity of parthenitae and cercariae and why researchers who do describe them give them only provisional names. Provisional names are unregulated, unstable, often ambiguous, and, I argue, often unnecessary. I suggest that we recommence formally naming parthenitae and cercariae using an improved naming scheme. The scheme should permit us to reap the benefits of formal nomenclature and thereby enhance research involving these diverse and important parasites. [ABSTRACT FROM AUTHOR]

Introduction: Lymnaea gedrosiana snails are hosts to a variety of trematode cercaria of public and veterinary health importance. In Guilan Province, Iran, a region with a high level of fish and bird farming and wetlands important for migratory birds, little is known about the trematode cercaria from L. gedrosiana. Methods: From April 2020 to October 2021, six freshwater sites in Guilan Province were sampled for Lymnaeidae snails three times per season (spring, summer, autumn and winter). Snails were exposed to light and heat to induce cercaria shedding and shredded cercaria were identified morphologically and molecularly. Results: In total, 5,712 Lymnaeidae snails were collected of which 3,288 (57.6%) were identified to be L. gedrosiana with 54.3% containing trematode cercaria. Snail and cercaria recovery were highest in the spring and summer. Trematode cercaria identified included Telorchis assula, Hypoderaeum conoideum, Apharyngostrigea pipientis, Sanguinicola cf. inermis, Opisthioglyphe ranae, Diplostomum pseudospathaceum, and Australapatemon burti. Discussion: The four trematodes D. pseudospathaceum, S. inermis, A. burti, and A. pipientis have not been previously reported in Iran; all four of these can infect migratory birds. The most common cercaria found, H. conoideum (18.3% of the snails) is of zoonotic importance. The third most common cercaria found, S. inermis (10.0% of the snails) is detrimental to fish production. Given the importance of the wetlands in the region for wildlife and migratory birds as well as the number of fish and bird farms in the area, efforts to control L. gedrosiana snails are needed to protect wildlife and human health. In addition, monitoring programs should be implemented to identify and prevent introductions of new trematode species. [ABSTRACT FROM AUTHOR]

This study focused on documenting and evaluating the cercaricidal activity of medicinal plants used for schistosomiasis treatment in an endemic area in Ghana. Through semistructured questionnaires, personal interviews with herbalists in communities surrounding the Barekese dam in the Atwima-Nwabiagya district, where the disease is endemic, were carried out. Thirty medicinal plants distributed in 19 families were reported to be used for schistosomiasis treatment in the survey. Information on the plants, including scientific names, common names, families, and the used plant part were recorded. The families Apocynaceae and Euphorbiaceae recorded the highest number of plants (14% each), followed by Asteraceae (10%), Loranthaceae (7%), and Rubiaceae (7%). In vitro cercaricidal activity of methanol extracts of nine out of the thirty plants was performed by exposing human Schistosoma mansoni cercariae obtained from Biomphalaria pfeifferi to various concentrations of extracts over a duration of 240 minutes. All the plants tested demonstrated time- and concentration-dependent cercaricidal activity. With lethality being set at <1000 μg/mL, the cercaricidal activity in order of decreasing potency was as follows: Withania somnifera (LC50 = 1.29) > Balanites aegyptiaca (LC50 = 7.1) > Xylia evansii (LC50 = 11.14) > Jathropha multifida (LC50 = 12.9) > Justicia flava (LC50 = 22.9) > Anopyxis klaineana (LC50 = 182.81) > Ximenia americana (LC50 = 194.98) > Loranthus lecardii (LC50 = 223.87) > Bridelia tenufolia (LC50 = 309.03) > Zanthoxylium zanthoxyloides (LC50 = 851.94). Phytochemicals, including alkaloids, tannins, triterpenes, saponins, phytosterols, and flavonoids were identified in the plants. The result of this study gives scientific credence to the traditional use of these plants in the treatment of schistosomiasis and proves that the rich botanical knowledge of medicinal plants provides an incredible starting point for the discovery of new anti-schistosomal drugs for the local population. [ABSTRACT FROM AUTHOR]

Lymnaeid snails play a crucial role in the transmission of trematode cercariae as an intermediate host that can infect humans, ruminants like buffalo, and other animals, resulting in serious economic losses. The purpose of the study was to identify the morphological and molecular characteristics of snails and cercariae collected from water bodies near buffalo farms that were integrated with palm oil in Perak, Malaysia. The presence or absence of snails in 35 water bodies was examined via cross-sectional study. From three marsh wetlands, 836 lymnaeid snails were gathered in total. Each snail's shell was morphologically identified to determine its family and species. The cercarial stage inside each snail's body was observed using the crushing method and trematode cercariae types were determined. In addition, the target gene Cytochrome c oxidase subunit 1 (Cox1) and the ribosomal internal transcribed spacer 2 (ITS2) region were used to identify the snail species and cercarial types according to the species level. The findings indicated that the collected snails belong to the family lymnaeidae and Radix rubiginosa species. In snails, the cercarial emergence infection rate was 8.7%. Echinostome, xiphidiocercariae, gymnocephalous, brevifurcate-apharyngeate distome cercariae (BADC), and longifurcate-pharyngeal monostome cercariae (LPMC) are the five morphological cercarial types that were observed. The cercariae were identified using morphological and molecular techniques, and they are members of the four families which are Echinostomatidae, Plagiorchiidae, Fasciolidae, and Schistosomatidae. Interestingly, this is the first study on R. rubiginosa and several trematode cercariae in Perak water bodies near buffalo farms that are integrated with palm oil. In conclusion, our research shown that a variety of parasitic trematodes in Perak use R. rubiginosa as an intermediate host. [ABSTRACT FROM AUTHOR]

The objective of this study was to conduct a survey of parasites infecting the fat mucket, Lampsilis siliquoidea, during July 2022 at Lemon's Mill along 50 m of North Elkhorn Creek, a tributary of the Kentucky River in Scott County, Kentucky, U.S.A. Fifty-two specimens of L. siliquoidea were collected, and 3 different parasites were recovered. Sporocysts and rhopalocercous cercariae associated with Phyllodistomum sp. (prevalence = 13.5%) were recovered from the visceral mass and mantle cavity, respectively, nymphs and adults of the water mite Unionicola fossulata (prevalence = 96.2%; mean intensity = 3.92 ± 2.25) from the external surface of the gill demibranchs, and the aspidogastrid Cotylaspis insignis (prevalence = 84.6%; mean intensity = 8.50 ± 7.13) from the external surface at the gill-visceral mass junction. Prevalence and mean intensity were not significantly affected by host sex or host size. These results establish a baseline for parasite community structure in L. siliquoidea at the North Elkhorn Creek site. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the pulmonate snail species in the vicinity of the cercarial dermatitis outbreak area in southern Thailand. In 2020, an outbreak of cercarial dermatitis was reported in Chana district, Songkhla Province, caused by the ruminant schistosome Schistosoma indicum and its snail intermediate host Indoplanorbis exustus. In the present study, 1,175 pulmonate snails were collected between October 2021 and October 2022 from five provinces covering 34 locations in southern Thailand. Seven pulmonate snail species were identified based on shell morphology, including Amerianna carinata, Gyraulus bakeri, G. convexiusculus, G. hubendicki, Physella acuta, Indoplanorbis exustus, and Radix rubiginosa. Among these snails, eight species, and five types of cercariae were identified, viz. type (i) Echinostome cercariae consisted of Echinoparyphium recurvatum, Echinostoma spiniferum, and E. revolutum, type (ii) Brevifurcate-apharyngeate cercariae consisted of Schistosoma indicum and S. spindale, type (iii) Brevifurcate- pharyngeate-clinostomatoid-cercariae was represented by Clinostomum giganticum, type (iv) Longifurcate--pharyngeate cercariae (strigea cercaria) was Diplostomum baeri eucaliae, and type (v) Ophthalmoxiphidiocercaria. Among the seven pulmonated snail species, three were found to be infected, viz. G. convexiusculus, I. exustus, and R. rubiginosa, with infection rates of 1.14% (2/176), 0.25% (2/802), and 4.02% (7/174), respectively. [ABSTRACT FROM AUTHOR]

The article discusses the infection of wetland birds in Uzbekistan with the trematodes Schistosomatidae Stiles et Hassall, 1898. The research covered 282 individuals from the main groups of birds represented by the orders Pelecaniformes, Ciconiformes, Anseriformes, Gruiformes, Podicipediformes and Charadriiformes. The Schistosomatidae fauna of Uzbekistan includes 13 species: Bilharziella polonica (Kowalewsky, 1895), Trichobilharzia ocellata (La Valette, 1854), T. filiformis (Szidat, 1938), T. kowalewskii (Ejsmont, 1929), T. tatianae (Spasskaja, 1953), Macrobilharzia macrobilharzia Trawassos, 1923, Ornithobilharzia canaliculata (Rudolphi, 1819), O. baeri Fain, 1955, Dendritobilharzia pulverulenta (Braun, 1901), D. loossi Skrjabin, 1924, D. anatinarum Cheatum, 1941, Gigantobilharzia acotylea Odhner, 1910 and Gigantobilharziella monocotylea (Szidat, 1930). Predominant are representatives of the genera Trichobilharzia and Dendritobilharzia. The species composition of Schistosomatidae is most diverse in birds from the lower reaches of the Amu Darya, where a high rate of infection with larvae of some of these trematodes was also recorded in aquatic molluscs. 11 species of molluscs were registered in the studied regions: Galba truncatula (Muller, 1774), Stagnicola corvus (Gmelin, 1791), Radix auricularia (Linnaeus, 1758), Lymnaea stagnalis (Linnaeus, 1758), Physa fontinalis (Linnaeus, 1758), Physella acuta (Draparnaud, 1805), Planorbis planorbis (Linnaeus, 1758), P. tangitarensis Germain, 1918, Anisus spirorbis (Linnaeus, 1758), Gyraulus albus (Muller, 1774), Melanoides kainarensis Starobogatov et Izzatullaev, 1980, from the families Lymnaeidae (4 species), Planorbidae (4 species), Physidae (2 species) and Thiaridae (1 species). They are identified as intermediate hosts of Schistosomatidae and were infected with 7 species of flukes. The total rate of infection with larval stages of Schistosomatidae in molluscs was about 2.0%. The highest infection rate was observed in Melanoides kainarensis – 5.3%. Morpho-biological indicators for mature forms of B. polonica from different bird species (Anas platyrhynchos and Oxyura leucocephala) were confirmed by molecular genetic studies. The study identified foci of birds’ infection with Schistosomatidae and the occurrence of human cercarial dermatitis.

The Tunggu Pampang Reservoir is one of the reservoirs located in the city of Makassar. The functions of the reservoir area was tourist attractions and fish farming locations so that the local community uses them for swimming, fishing, selling, and gardening. The existence of various types of freshwater snails in the reservoir has the potential to act as intermediate hosts for trematodes in animals and humans. This study aimed to analyze the type of cercariae in freshwater snails. This research is a descriptive survey to determine the distribution of trematode larvae. The stages of this research began with the snails were collected from Tunggu Pampang Reservoir, Makassar City. Freshwater snails were collected at several points in the reservoir. Freswater snail collection using hand collecting method. The snails were put into a plastic bag with different types of snails and site of collection. The collected samples and cercariae were examined in the Tropical Disease Laboratory of the Study Program of DIII Medical Laboratory Technology, Megarezky University, South Sulawesi, Indonesia. Freshwater snails are placed on a petri dish and their shells were gently crushed with a stamper. Dropped with aquadest on the crushed snail shell. The next step was observed using a microscope to determine the presence of cercariae. Cercariae found then identified according to morphological classification as previously study. A total number of 500 freshwater snail were collected in Tunggu Pampang Reservoir. The results showed that overall snails infected with cercariae was 33,4%. The highest prevalence of cercariae in Indoplanorbis exustus was 94.3%. Total of Echinostoma cercariae found (n = 224) compared to furcocercous cercariae (n = 5). Cercariae of Echinostoma sp., Fasciola gigantica, Fasciolopsis buski living in Tungu Pampang Reservoir can cause diseases in humans and animals. Larval trematodes can be controlled in snails using reducing parasite contamination, monitoring surveillance, information dissemination, and preventive education.