Mitochondrial genome of the fluke pond snail, Austropeplea cf. brazieri (Gastropoda: Lymnaeidae).

BACKGROUND: Lymnaeid snails of the genus Austropeplea are an important vector of the liver fluke (Fasciola hepatica), contributing to livestock production losses in Australia and New Zealand. However, the species status within Austropeplea is ambiguous due to heavy reliance on morphological analysis and a relative lack of genetic data. This study aimed to characterise the mitochondrial genome of A. cf. brazieri, an intermediate host of liver fluke in eastern Victoria. METHODS: The mitochondrial genome was assembled and annotated from a combination of second- and third-generation sequencing data. For comparative purposes, we performed phylogenetic analyses of the concatenated nucleotide sequences of the mitochondrial protein-coding genes, cytochrome c oxidase subunit 1 and 16S genes. RESULTS: The assembled mt genome was 13,757 base pairs and comprised 37 genes, including 13 protein-coding genes, 22 transfer RNA genes and 2 ribosomal RNA genes. The mt genome length, gene order and nucleotide compositions were similar to related species of lymnaeids. Phylogenetic analyses of the mt nucleotide sequences placed A. cf. brazieri within the same clade as Orientogalba ollula with strong statistical supports. Phylogenies of the cox1 and 16S mt sequences were constructed due to the wide availability of these sequences representing the lymnaeid taxa. As expected in both these phylogenies, A. cf. brazieri clustered with other Austropeplea sequences, but the nodal supports were low. CONCLUSIONS: The representative mt genome of A. cf. brazieri should provide a useful resource for future molecular, epidemiology and parasitological studies of this socio-economically important lymnaeid species.

The prevalence and infection rates of amphistome species in intermediate snail hosts: a systematic review and meta-analysis.

The systematic review and meta-analysis were conducted to determine the estimates of the prevalence and infection rates of natural and experimental infections of amphistome species in intermediate host snails (IHs) across different continents. A search of peer-reviewed literature on natural and experimental infections of freshwater snails with amphistome species was conducted from four electronic databases from 1984 to 2023. The estimates of the prevalence and/or infection rates were based on 36 eligible peer-reviewed articles, which met the inclusion criteria and reported on natural and experimental infections of amphistome species in freshwater snails. The results showed that a total of 1,67,081 snail species from the peer-reviewed articles were examined for natural infections and 7,659 snail species for experimental infections. The overall pooled prevalence of amphistome infections from naturally infected snails was 2% (95% CI: 0-4), while the overall pooled prevalence of amphistome infections from infections was 40% (95% CI: 18-64). The highest pooled prevalence of natural infection was 3%, which was recorded in Europe (95% CI: 1-7%). The highest overall prevalence of naturally infected amphistome was 6% (95% CI: 0-20%) for Paramphistomum epiclitum. The Americas had the highest pooled prevalence of experimental amphistome infection among freshwater snails (66%; 95% CI: 26-96%). The highest pooled infection rate of 65% (95% CI: 12-100%) was recorded for Paramphistomum cervi in experimental infections. Galba truncatula was the only snail that qualified for meta-analysis for natural infection with Calicophoron daubneyi, with a pooled prevalence of 3% (95% CI: 1-8%). Galba truncatula infected with C. daubneyi and P. cervi, and Bulinus tropicus infected with Calicophoron microbothrium in the experimental infection qualified for the meta-analysis, with an overall infection rate of 66% (95% CI: 34-92%) and 30% (95% CI: 0-74%), respectively. The pooled prevalence of amphistome species infection in the intermediate host (IH) snails based on detection techniques was higher with PCR compared to the dissection and shedding of cercariae. The results from the quality effects model revealed a high heterogeneity and publication bias between studies. This meta-analysis provided valuable insights into the prevalence and infection rates of amphistome species in snail IHs across different geographical regions.

Advances in Detecting Cystic Echinococcosis in Intermediate Hosts and New Diagnostic Tools: A Literature Review.

Cystic echinococcosis (CE) is a zoonotic disease affecting humans and animals. Despite a lack of clarity about many details of parasite-intermediate host interactions, the nature of the immune responses triggered by hydatid infection has revealed new perspectives. This study discusses the latest advances in elucidating the immunologic mechanism of echinococcosis and its detection and potential approaches to enhance serodiagnosis accuracy. Moreover, nanobiosensors have been evaluated according to their potential to improve treatment efficiency and aid in an early diagnosis of cystic echinococcosis. The serum of an intermediate host can diagnose CE by analyzing antibodies induced by Echinococcus granulosus. Among the most notable features of this method are its noninvasive ability and high sensitivity, both of which make it an excellent tool for clinical diagnosis. Several serological tests, including ELISAs and immunoblotting, can detect these antibodies to assess the disease's state and determine the treatment outcome. A thorough understanding of what cross-reactivity means and the stage of the disease are crucial to interpreting serological results. Nanobiosensors have also proven better than conventional biosensors in detecting hydatid cysts. Additionally, they are highly sensitive and versatile when detecting specific biomarkers, improving diagnostic accuracy. These immunomodulatory molecules, induced by E. granulosus, are a good candidate for diagnosing cystic echinococcosis because they alter intermediate host immune responses. Hydatid cyst detection is also enhanced through nanobiosensors, which provide better accuracy.

[Investigation of the population diversity of intermediate host snails and crabs of Paragonimus along Jiulong River, Zhangjiang River and Dongxi River basins in southern Fujian Province].

OBJECTIVE: To investigate the population distribution of intermediate host snails and crabs of Paragonimus along the Jiulongjiang River, Zhangjiang River, and Dongxi River basins in Bopingling Mountain, southern Fujian Province, so as to provide baseline data for researches on parasitic disease prevention and control and enlargement of samples in the parasitic resource bank. METHODS: A total of 23 villages in 8 counties (districts) along the Jiulong River, Zhangjiang River, and Dongxi River basins in Zhangzhou City, Fujian Province were selected as survey sites during the period from November 2020 through March 2023, and snail and freshwater crabs were sampled from 1 to 3 streams and ditches neighboring residential areas in each village. Morphological identification of snails was performed according to the external morphological characteristics of collected snail shells, and the unidentified snail species sampled from the natural foci of paragonimiasis in Yunxiao County were subjected to se-quence analysis of the mitochondrial cytochrome oxidase 1 (CO1) gene. The crab species was identified by observing the morphological characteristics of the terminal segment of the first pleopod of male crabs, and Paragonimus cercariae and metacercariae were detected in collected snails. RESULTS: The shells of the unidentified snails sampled from the natural foci of paragonimiasis in Yunxiao County were approximately 50 mm in height and 18 mm in width, thick and solid, long tower cone-shaped, and had 8 to 10 whorls. CO1 gene sequence analysis identified the snail species as Sulcospira hainanensis. A total of 6 freshwater snail species belonging to 5 genera within 3 families, identified 23 survey sites, including Semisulcospira libertina, Paludomus zhangchouensis and S. hainanensis that belonged to the Family Pleurceridae, Tricula fujianensis and T. huaanensis that belonged to the subfamily Triculinae, Family Pomatiopsidae, and Melanoides tuberculata (Family Thiaridae), and 11 species of freshwater crabs belonging to 5 genera within 2 families were identified, including Sinopotamon genus of S. jianglense, S. pinheense, and S. zhangzhouense, Huananpotamon genus of H. planopodum and H. zhangzhouense, Nanhaipotamon genus of N. huaanense and N. longhaiense, and Minpotamon genus of M. nasicum and M. auritum that belonged to the Family Potamidae, and Somanniathelphusa genus of S. huaanensis and S. zhangpuensis (Family Parathelphusidae). In addition, the prevalence of P. westermani cercariae infections was 0.08% (2/2 317) in P. zhangchouensis from Danyan Village in Changtai District and 0.09% (1/1 039) in S. hainanensis from Jinkeng Village in Yunxiao County, and the prevalence of P. westermani metacercariae infections was 25.81% (8/31) in S. jianglense from Danyan Village in Changtai District, and 26.31% (5/19) in S. zhangzhouense from Jinkeng Village in Yunxiao County, respectively. CONCLUSIONS: There is a population diversity in the intermediate host snails and crabs along the Jiulongjiang River, Zhangjiang River, and Dongxi River basins in Bopingling Mountain, southern Fujian Province, and P. zhangzhouensis and S. hainanensis are, for the first time, confirmed as the first intermediate hosts of P. westermani.

Green synthesis of silver nanoparticles using Croton urucurana and their toxicity in freshwater snail species Biomphalaria glabrata.

Green silver nanoparticles (G-Ag NPs) have contributed to the development of ecological technologies with low environmental impact and safer for human health, as well as demonstrating potential for the control of vectors and intermediate hosts. However, knowledge about its toxicity in the early stages of gastropod development remains scarce. Therefore, the current study aimed to investigate the toxicity of G-Ag NPs synthesized from Croton urucurana leaf extracts in snail species Biomphalaria glabrata, which is an intermediate host for Schistosoma mansoni parasite. G-Ag NPs were synthesized using two types of plant extracts (aqueous and hydroethanolic) and characterized using multiple techniques. Bioassays focused on investigating G-Ag NPs and plant extracts were carried out with embryos and newly hatched snails, for 144 h and 96 h, respectively; toxicity was analyzed based on mortality, hatching, development inhibition, and morphological changes. Results have shown that both G-Ag NPs were more toxic to embryos and newly hatched snails than the investigated plant extracts. G-Ag NPs deriving from aqueous extract have higher molluscicidal activity than those deriving from hydroethanolic extract. Both G-Ag NPs induced mortality, hatching delay, development inhibition, and morphological changes (i.e., hydropic embryos), indicating their molluscicidal activities. Moreover, embryos were more sensitive to G-Ag NPs than newly hatched snails. Thus, the toxicity of G-Ag NPs to freshwater snails depends on the type of extracts and the snail's developmental stages. These findings can contribute to the development of green nanobiotechnologies applicable to control snails of medical importance.

Prevalence and risk factors of fasciolosis in a bovine population from farms in Taiping, Malaysia.

Fasciolosis is a zoonotic disease, considered an emerging neglected tropical disease threatening ruminant productivity and causing economic losses. Controlling fasciolosis is challenging due to the complex life cycle of Fasciola, which involves snail intermediate hosts. The high rainfall status in Taiping makes it an optimal region for snail abundance, which increases the opportunity to complete Fasciola's life cycle. Previous studies showed that liver condemnation caused by fasciolosis was highly prevalent in the Taiping abattoir compared to other investigated main abattoirs of Peninsular Malaysia. Therefore, the present study determined the prevalence of bovine fasciolosis and risk factors in farms from Larut and Matang (Taiping), Malaysia. Sampling was carried out from February until August 2020. In this cross-sectional study, a total of 371 fecal samples from bovines (dairy cattle, beef cattle, buffalo) were examined from 23 farms selected based on location, farmer consent, and history of anthelmintic usage. Animal's intrinsic and farm management details were recorded, and interview sessions were conducted with farmers to collect information on the potential risk factors. Individual fecal samples were examined for the presence of Fasciola egg using Flukefinder® sedimentation. There was moderate prevalence of bovine fasciolosis in Taiping (36.9%, n = 137/371). Significant risk factors (p < 0.05) were observed, which include buffalo group (OR = 9.5, 95% CI: 9.44-9.55), age of >3 years (OR = 5.5, 95% CI: 5.43-5.57), thinner animals with body condition score of 1 to 4 (OR = 1.2-14.9, 95% CI: 1.09-15.08), and larger grazing area (OR = 1.3, 95% CI: 1.30-1.31). Additional risk factors include the presence of more than one ruminant species in the same farm (OR = 2.0-2.1, 95% CI: 2.00-2.22), extensive housing system (OR = 4.0, 95% CI: 3.77-4.23), farm age (OR = 1.2, 95% CI: 1.20-1.21), and also co-infection with Paramphistomes (OR = 1.4, 95% CI: 1.10-1.71). The present study underscores the importance of local bovine fasciolosis epidemiology, which could be used to conduct future veterinary and public health programmes to inform effective parasitic management aimed at reducing the prevalence of fasciolosis.

Echinococcus species in wildlife.

Transmission of Echinococcus spp. in life cycles that involve mainly wildlife is well recognized for those species with small mammals as intermediate hosts (e. g. E. multilocularis), as well as for E. felidis and the 'northern' genotypes of E. canadensis (G8 and G10). In contrast, the remaining taxa of E. granulosus sensu lato are best known for their domestic life cycles, and the numerous wild mammal species (mainly ungulates) that have been recorded with cystic echinococcosis in the past were mainly considered a result of spill-over from the dog-livestock transmission system. This view was challenged with the advent of molecular characterization, allowing discrimination of the metacestodes, although the contribution of wild mammals to various Echinococcus life cycles has remained uncertain for scarcity of wildlife studies. Numerous records of cysts in wild ungulates date back to the 20th century, but cannot with certainty be allocated to the Echinococcus species and genotypes that are recognized today. This means that our current knowledge is largely restricted to studies of the past two decades that kept adding gradually to our concepts of transmission in various geographic regions. In particular, new insights were gathered in the past years on E. granulosus s.l. in wildlife of sub-Saharan Africa, but also on transmission patterns of E. multilocularis in previously neglected regions, e. g. North America. Here, an update is provided on the current state of knowledge on wild mammals as hosts for all Echinococcus species, listing >150 species of wild hosts with references, as well as estimates on their epidemiological impact and our current gaps of knowledge.

IMPLICATIONS OF TREATING PARASITIC INFECTION IN NORTHERN BOBWHITE (COLINUS VIRGINIANUS) ON OVERALL HELMINTH LIFE CYCLE.

This study was conducted to determine how reducing the parasite burden in a definitive host may affect the prevalence in intermediate hosts. Here we used the eyeworm Oxyspirura petrowi and cecal worm Aulonocephalus pennula as model species. Northern bobwhite quail (Colinus virginianus) were provided an anthelmintic medicated feed in wild systems because of convincing evidence that these parasites were suppressing their populations. Eyeworm and cecal worm prevalence were measured in Orthopterans, which act as intermediate hosts, using polymerase chain reaction. Individuals were collected from a control site, a site treated for 2 yr, and a site treated for 5 yr. Orthopteran community composition was significantly different among the sites; however, an interaction between subfamily and site was not significant for the eyeworm. There was a significant reduction in eyeworm-infected Orthopterans on the 5-yr site compared with the other 2, suggesting that treatment of a definitive host may indeed affect the prevalence of eyeworms during other life-cycle stages. There was an interaction between the Orthopteran subfamily and the site for the cecal worm, so results were analyzed within each subfamily. A significant reduction in the prevalence of cecal worms was only found in the Cyrtacanthacridinae subfamily on the 5-yr site when compared with the other sites. However, the greatest prevalence in the Gomphocerinae and Oedipodinae subfamilies across all 3 sites was 4.1%. This indicates an unknown degree of cecal worm host specificity. Therefore, conclusions could not be made through the simple assessment of prevalence.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry traces the geographical source of Biomphalaria pfeifferi and Bulinus forskalii, involved in schistosomiasis transmission.

BACKGROUND: Freshwater snails of the genera Bulinus spp., Biomphalaria spp., and Oncomelania spp. are the main intermediate hosts of human and animal schistosomiasis. Identification of these snails has long been based on morphological and/or genomic criteria, which have their limitations. These limitations include a lack of precision for the morphological tool and cost and time for the DNA-based approach. Recently, Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight (MALDI-TOF) mass spectrometry, a new tool used which is routinely in clinical microbiology, has emerged in the field of malacology for the identification of freshwater snails. This study aimed to evaluate the ability of MALDI-TOF MS to identify Biomphalaria pfeifferi and Bulinus forskalii snail populations according to their geographical origin. METHODS: This study was conducted on 101 Bi. pfeifferi and 81 Bu. forskalii snails collected in three distinct geographical areas of Senegal (the North-East, South-East and central part of the country), and supplemented with wild and laboratory strains. Specimens which had previously been morphologically described were identified by MALDI-TOF MS [identification log score values (LSV) ≥ 1.7], after an initial blind test using the pre-existing database. After DNA-based identification, new reference spectra of Bi. pfeifferi (n = 10) and Bu. forskalii (n = 5) from the geographical areas were added to the MALDI-TOF spectral database. The final blind test against this updated database was performed to assess identification at the geographic source level. RESULTS: MALDI-TOF MS correctly identified 92.1% of 101 Bi. pfeifferi snails and 98.8% of 81 Bu. forskalii snails. At the final blind test, 88% of 166 specimens were correctly identified according to both their species and sampling site, with LSVs ranging from 1.74 to 2.70. The geographical source was adequately identified in 90.1% of 91 Bi. pfeifferi and 85.3% of 75 Bu. forskalii samples. CONCLUSIONS: Our findings demonstrate that MALDI-TOF MS can identify and differentiate snail populations according to geographical origin. It outperforms the current DNA-based approaches in discriminating laboratory from wild strains. This inexpensive high-throughput approach is likely to further revolutionise epidemiological studies in areas which are endemic for schistosomiasis.

Carbohydrate metabolism evaluation of terrestrial snail Subulina octona (Gastropoda, Subulinidae) experimentally infected by the Paratanaisia bragai digenetic trematode (Digenea, Eucotylidae).

Among the effects of the larval development of digenetic trematodes on their intermediate hosts, changes in the carbohydrate metabolism in the snails stand out. The aim of this study was to analyze, every 10 days after infection (d.p.i.), the effects of Paratanaisia bragai infection on the glycogen content in the digestive gland and cephalopedal mass in Subulina octona snail, and also verify the glucose concentration and the enzyme D- and L-lactate dehydrogenase activity (EC1.1.1.27 and EC1.1.1.28) (LDH) and the concentration of some metabolites(oxalic, succinic, pyruvic and lactic acid) presents in the hemolymph. Histochemical analisys were also performed. We verified a total increase of 54.81% in glucose concentration in infected snails and an oscillating pattern in the glycogen content in the cephalopedal mass and in the digestive gland. LDH activity shows an increase of 10 d.p.i. (+ 74.32%) and 40 d.p.i. (+ 47.81%) and decrease at 20 d.p.i. and 30 d.p.i. The concentrations of oxalic, succinic and pyruvic acids showed significant and progressive reductions; however, lactic acid had a significant increase. Histological and histochemical analysis showed a tissue disorganization in the cephalopedal mass of infected snails and morphological changes in the digestive gland. These results confirm that infection causes metabolic pathway changes in the snails due to activation of an alternative anaerobic pathway for producing energy, indicated by the increased lactic acid content and LDH activity.

Investigation of the population diversity of intermediate host snails and crabs of Paragonimus along Jiulong River, Zhangjiang River and Dongxi River basins in southern Fujian Province / 中国血吸虫病防治杂志

Objective To investigate the population distribution of intermediate host snails and crabs of Paragonimus along the Jiulongjiang River, Zhangjiang River, and Dongxi River basins in Bopingling Mountain, southern Fujian Province, so as to provide baseline data for researches on parasitic disease prevention and control and enlargement of samples in the parasitic resource bank. Methods A total of 23 villages in 8 counties (districts) along the Jiulong River, Zhangjiang River, and Dongxi River basins in Zhangzhou City, Fujian Province were selected as survey sites during the period from November 2020 through March 2023, and snail and freshwater crabs were sampled from 1 to 3 streams and ditches neighboring residential areas in each village. Morphological identification of snails was performed according to the external morphological characteristics of collected snail shells, and the unidentified snail species sampled from the natural foci of paragonimiasis in Yunxiao County were subjected to se-quence analysis of the mitochondrial cytochrome oxidase 1 (CO1) gene. The crab species was identified by observing the morphological characteristics of the terminal segment of the first pleopod of male crabs, and Paragonimus cercariae and metacercariae were detected in collected snails. Results The shells of the unidentified snails sampled from the natural foci of paragonimiasis in Yunxiao County were approximately 50 mm in height and 18 mm in width, thick and solid, long tower cone-shaped, and had 8 to 10 whorls. CO1 gene sequence analysis identified the snail species as Sulcospira hainanensis. A total of 6 freshwater snail species belonging to 5 genera within 3 families, identified 23 survey sites, including Semisulcospira libertina, Paludomus zhangchouensis and S. hainanensis that belonged to the Family Pleurceridae, Tricula fujianensis and T. huaanensis that belonged to the subfamily Triculinae, Family Pomatiopsidae, and Melanoides tuberculata (Family Thiaridae), and 11 species of freshwater crabs belonging to 5 genera within 2 families were identified, including Sinopotamon genus of S. jianglense, S. pinheense, and S. zhangzhouense, Huananpotamon genus of H. planopodum and H. zhangzhouense, Nanhaipotamon genus of N. huaanense and N. longhaiense, and Minpotamon genus of M. nasicum and M. auritum that belonged to the Family Potamidae, and Somanniathelphusa genus of S. huaanensis and S. zhangpuensis (Family Parathelphusidae). In addition, the prevalence of P. westermani cercariae infections was 0.08% (2/2 317) in P. zhangchouensis from Danyan Village in Changtai District and 0.09% (1/1 039) in S. hainanensis from Jinkeng Village in Yunxiao County, and the prevalence of P. westermani metacercariae infections was 25.81% (8/31) in S. jianglense from Danyan Village in Changtai District, and 26.31% (5/19) in S. zhangzhouense from Jinkeng Village in Yunxiao County, respectively. Conclusions There is a population diversity in the intermediate host snails and crabs along the Jiulongjiang River, Zhangjiang River, and Dongxi River basins in Bopingling Mountain, southern Fujian Province, and P. zhangzhouensis and S. hainanensis are, for the first time, confirmed as the first intermediate hosts of P. westermani.

Identification of Sarcocystis spp. in synanthropic (Muridae) and wild (Cricetidae) rodents from Argentina.

The occurrence of Sarcocystis species was investigated in synanthropic (Muridae) and wild (Cricetidae) rodents from Argentina. Nine species were captured (n = 356). Sarcocysts were detected in muscles of 8.7% (31/356) and 3.7% (4/106) of the rodents by histopathology and direct microscopic observation, respectively. PCR-sequencing targeting the 18S rRNA, cox1, and ITS1 regions was performed on samples with positive histopathology. Four different 18S rRNA sequences or sequence groups with high intra-group identities (99.6-100%) were detected in Mus musculus, Oxymycterus rufus, Akodon azarae, and Necromys lasiurus. Eight sequences showed 99.5-99.7% identity with S. dispersa. Thirteen sequences showed low identity (95.3-96.4%) with other Sarcocystis spp. The obtained coxI sequences (n = 9) were almost identical to each other and showed a high similarity with S. strixi (99.2-99.5%) and S. lutrae (99.1%), despite the 18S rRNA sequences from the same samples suggested the occurrence of at least two species. This suggests that coxI may not show high variability in Sarcocystis spp. that use rodents as intermediate hosts. Six ITS1 sequences were obtained, showing high identity but low coverage with several Sarcocystis spp. Multilocus sequence typing and BLAST analysis did not lead to an accurate species identification. Possible reasons are the detection of new species or the limited molecular information available from previously described Sarcocystis spp. Phylogeny suggests that the detected Sarcocystis spp. may use raptor birds or snakes as definitive hosts. This study represents the first molecular identification of Sarcocystis spp. in naturally infected rodents of the Cricetidae and Muridae families in South America.

One-health approach on the future application of snails: a focus on snail-transmitted parasitic diseases.

Snails are fascinating molluscs with unique morphological and physiological adaptive features to cope with various environments. They have traditionally been utilized as food and feed sources in many regions of the world. The future exploitation of alternative nutrient sources, like snails, is likely to increase further. Snails, however, also serve as an intermediate host for several zoonotic parasites. A category of parasitic infections, known as snail-transmitted parasitic diseases (STPDs), is harmful to humans and animals and is mainly driven by various trematodes, cestodes, and nematodes. The environment plays a crucial role in transmitting these parasites, as suitable habitats and conditions can facilitate their growth and proliferation in snails. In light of diverse environmental settings and biologically categorized snail species, this review evaluates the dynamics of significant STPDs of zoological importance. Additionally, possible diagnostic approaches for the prevention of STPDs are highlighted. One-health measures must be considered when employing snails as an alternative food or feed source to ensure the safety of snail-based products and prevent any adverse effects on humans, animals, and the environment.

Core gut microbes Cloacibacterium and Aeromonas associated with different gastropod species could be persistently transmitted across multiple generations.

BACKGROUND: Studies on the gut microbiota of animals have largely focused on vertebrates. The transmission modes of commensal intestinal bacteria in mammals have been well studied. However, in gastropods, the relationship between gut microbiota and hosts is still poorly understood. To gain a better understanding of the composition of gut microbes and their transmission routes in gastropods, a large-scale and long-term experiment on the dynamics and transmission modes of gut microbiota was conducted on freshwater snails. RESULTS: We analyzed 244 microbial samples from the digestive tracts of freshwater gastropods and identified Proteobacteria and Bacteroidetes as dominant gut microbes. Aeromonas, Cloacibacterium, and Cetobacterium were identified as core microbes in the guts, accounting for over 50% of the total sequences. Furthermore, both core bacteria Aeromonas and Cloacibacterium, were shared among 7 gastropod species and played an important role in determining the gut microbial community types of both wild and cultured gastropods. Analysis of the gut microbiota at the population level, including wild gastropods and their offspring, indicated that a proportion of gut microbes could be consistently vertically transmitted inheritance, while the majority of the gut microbes resulted from horizontal transmission. Comparing cultured snails to their wild counterparts, we observed an increasing trend in the proportion of shared microbes and a decreasing trend in the number of unique microbes among wild gastropods and their offspring reared in a cultured environment. Core gut microbes, Aeromonas and Cloacibacterium, remained persistent and dispersed from wild snails to their offspring across multiple generations. Interestingly, under cultured environments, the gut microbiota in wild gastropods could only be maintained for up to 2 generations before converging with that of cultured snails. The difference observed in gut bacterial metabolism functions was associated with this transition. Our study also demonstrated that the gut microbial compositions in gastropods are influenced by developmental stages and revealed the presence of Aeromonas and Cloacibacterium throughout the life cycle in gastropods. Based on the dynamics of core gut microbes, it may be possible to predict the health status of gastropods during their adaptation to new environments. Additionally, gut microbial metabolic functions were found to be associated with the adaptive evolution of gastropods from wild to cultured environments. CONCLUSIONS: Our findings provide novel insights into the dynamic processes of gut microbiota colonization in gastropod mollusks and unveil the modes of microbial transmission within their guts. Video Abstract.

Gut microbiota in parasite-transmitting gastropods.

BACKGROUND: Gastropoda, the largest class within the phylum Mollusca, houses diverse gut microbiota, and some gastropods serve as intermediate hosts for parasites. Studies have revealed that gut bacteria in gastropods are associated with various biological aspects, such as growth, immunity and host-parasite interactions. Here, we summarize our current knowledge of gastropod gut microbiomes and highlight future research priorities and perspectives. METHODS: A literature search was undertaken using PubMed, Web of Science and CNKI for the articles on the gut microbiota of gastropods until December 31, 2022. We retrieved a total of 166 articles and identified 73 eligible articles for inclusion in this review based on the inclusion and exclusion criteria. RESULTS: Our analysis encompassed freshwater, seawater and land snails, with a specific focus on parasite-transmitting gastropods. We found that most studies on gastropod gut microbiota have primarily utilized 16S rRNA gene sequencing to analyze microbial composition, rather than employing metagenomic, metatranscriptomic, or metabolomic approaches. This comprehensive review provided an overview of the parasites carried by snail species in the context of gut microbiota studies. We presented the gut microbial trends, a comprehensive summary of the diversity and composition, influencing factors, and potential functions of gastropod gut microbiota. Additionally, we discussed the potential applications, research gaps and future perspectives of gut microbiomes in parasite-transmitting gastropods. Furthermore, several strategies for enhancing our comprehension of gut microbiomes in snails were also discussed. CONCLUSIONS: This review comprehensively summarizes the current knowledge on the composition, potential function, influencing factors, potential applications, limitations, and challenges of gut microbiomes in gastropods, with a specific emphasis on parasite-transmitting gastropods. These findings provide important insights for future studies aiming to understand the potential role of gastropod gut microbiota in controlling snail populations and snail-borne diseases.

Infection Rates of Fasciola Intermediate Host Snail Species and Their Distribution in Africa: A Systematic Review and Meta-Analysis.

This systematic review and meta-analysis aimed to collate the infection rates of Fasciola spp. in intermediate host snails and their distribution in Africa. The overall infectivity prevalences of Galba truncatula, Radix natalensis, and Pseudosuccinea columella are 52%, 8%, and 3%, respectively. The intermediate host snails native to Africa (R. natalensis and G. truncatula) have been examined more than the invasive P. columella. The studies included in the review ranged from 1999 to 2022. North Africa has the highest prevalence of G. truncatula, with an infection rate of 52%. The review reveals that naturally infected intermediate host snails (G. truncatula, R. natalensis, and P. columella) are found in various regions of Africa. G. truncatula accounts for 22% (from three countries) of the studies included in the review and it was only found in the North African region with the highest overall infection rate of 52%. More studies on infection rate and distribution are needed to effectively control and prevent future transmissions.

Long live the host! Proteomic analysis reveals possible strategies for parasitic manipulation of its social host.

Parasites with complex life cycles often manipulate the phenotype of their intermediate hosts to increase the probability of transmission to their definitive hosts. Infection with Anomotaenia brevis, a cestode that uses Temnothorax nylanderi ants as intermediate hosts, leads to a multiple-fold extension of host lifespan and to changes in behaviour, morphology and colouration. The mechanisms behind these changes are unknown, as is whether the increased longevity is achieved through parasite manipulation. Here, we demonstrate that the parasite releases proteins into its host with functions that might explain the observed changes. These parasitic proteins make up a substantial portion of the proteome of the hosts' haemolymph, and thioredoxin peroxidase and superoxide dismutase, two antioxidants, exhibited the highest abundances among them. The largest part of the secreted proteins could not be annotated, indicating they are either novel or severely altered during recent coevolution to function in host manipulation. We also detected shifts in the hosts' proteome with infection, in particular an overabundance of vitellogenin-like A in infected ants, a protein that regulates division of labour in Temnothorax ants, which could explain the observed behavioural changes. Our results thus suggest two different strategies that might be employed by this parasite to manipulate its host: secreting proteins with immediate influence on the host's phenotype and altering the host's translational activity. Our findings highlight the intricate molecular interplay required to influence the phenotype of a host and point to potential signalling pathways and genes involved in parasite-host communication.

Metapopulation Structure of Two Species of Pikeworm (Triaenophorus, Cestoda) Parasitizing the Postglacial Fish Community in an Oligotrophic Lake.

In the present study, we estimated the levels of infestation of the main fish species that are hosts for two Triaenophorus species: T. crassus and T. nodulosus. The prevalence of T. crassus and T. nodulosus infestations in the intestine of their definitive host-pike Esox lucius was similar (71.0% and 77.4%, respectively). At the same time, the prevalence of T. crassus infestation in muscle tissue was significantly different between the second intermediate hosts, Coregonus lavaretus pidschian (31.4%) and Cor. l. pravdinellus (91.2%), due to considerable differences in their diets. For T. nodulosus, we found significant variations in the levels of prevalence among the second intermediate hosts-100% for Lota lota, 81.8% for Cottus sibiricus 31.9% for Thymallus arcticus, and 24.5% for Perca fluviatilis-that we also explained using different diets. Moreover, analysis of the symmetry of parasite infestations did not reveal any asymmetry between the number of cysts in the left and right body surfaces of the "planktivorous" form/species of whitefish, whereas in the ''benthivorous", an asymmetry of parasite infestations was found.

Metagenomic Analysis Reveals Variations in Gut Microbiomes of the Schistosoma mansoni-Transmitting Snails Biomphalaria straminea and Biomphalaria glabrata.

Biomphalaria snails play a crucial role in the transmission of the human blood fluke Schistosoma mansoni. The gut microbiota of intermediate hosts is known to influence their physiological functions, but little is known about its composition and role in Biomphalaria snails. To gain insights into the biological characteristics of these freshwater intermediate hosts, we conducted metagenomic sequencing on Biomphalaria straminea and B. glabrata to investigate variations in their gut microbiota. This study revealed that the dominant members of the gut microbiota in B. glabrata belong to the phyla Bacteroidetes and Proteobacteria, which were also found to be the top two most abundant gut bacteria in B. straminea. We identified Firmicutes, Acidovorax and Bosea as distinctive gut microbes in B. straminea, while Aeromonas, Cloacibacterium and Chryseobacterium were found to be dependent features of the B. glabrata gut microbiota. We observed significant differences in the community structures and bacterial functions of the gut microbiota between the two host species. Notably, we found a distinctive richness of antibiotic resistance genes (ARGs) associated with various classes of antibiotics, including bacitracin, chloramphenicol, tetracycline, sulfonamide, penicillin, cephalosporin_ii and cephalosporin_i, fluoroquinolone, aminoglycoside, beta-lactam, multidrug and trimethoprim, in the digestive tracts of the snails. Furthermore, this study revealed the potential correlations between snail gut microbiota and the infection rate of S. mansoni using Spearman correlation analysis. Through metagenomic analysis, our study provided new insights into the gut microbiota of Biomphalaria snails and how it is influenced by host species, thereby enhancing our understanding of variant patterns of gut microbial communities in intermediate hosts. Our findings may contribute to future studies on gastropod-microbe interactions and may provide valuable knowledge for developing snail control strategies to combat schistosomiasis in the future.

Sarcocystis Species Richness in Sheep and Goats from Lithuania.

Contradictory data is available on the intermediate host specificity of Sarcocystis spp. in farm animals. Therefore, the current work aimed at molecularly testing samples of sheep and goats reared in Lithuania to identify Sarcocystis species described in other intermediate hosts but suspected to be non-canonical parasites to these small ruminants. For this purpose, muscle samples from 47 domestic sheep and nine goats were examined. Sarcocystis species were identified using direct and nested PCR targeting cox1 and sequencing of positive amplified products. Along with the detection of the canonical Sarcocystis spp. in their respective intermediate hosts, the DNA of S. capracanis and S. morae was detected in sheep, although these species were previously thought to be specific to goats and deer, respectively. In addition, DNA from S. arieticanis and S. tenella was found in goats, even though these two species were believed to be sheep-specific. Notably, under light microscopy, only sarcocysts of S. capracanis specific to goats were observed. Thus, future research on the life cycle and host-specificity of Sarcocystis spp. examined is warranted.