Trematode Species Research Articles

The occurrence of digenean trematodes in some cyprinid fish from Belchishta Wetland (Macedonia)

Abstract. Belchishta Wetland is the biggest wetland ecosystem in Macedonia and hosts a variety of plant and animal species. Belchishta Wetland is included in the Emerald National Network of R.N. Macedonia and is suggested for nomination as a Natura 2000 site. This study aimed to determine the occurrence of digenean trematodes, as well as their prevalence and intensity of infestation in some cyprinid fish from Belchishta Wetland. During the parasitological investigations on the intestinal tract of some cyprinid fish species (chub - Squalius squalus; Ohrid minnow - Pelasgus minutus, and minnow - Phoxinus lumaireul) from Belchishta wetland, 3 species of digenean trematodes were established, as follows: Allocreadium isoporum was found in chub (Squalius squalus) with the prevalence of 9.09 % and intensity of infestation 1.50; Plaigioporus stefanskii was found in Ohrid minnow (Pelasgus minutus) with the prevalence of 9.52%, and intensity of infestation 2.00; and Pseudochetosoma salmonicola was found in minnow (Phoxinus lumaireul) with the prevalence of 10.00% and intensity of infestation 2.00. The total prevalence in all cyprinid fish amounts to 9.33%. Findings of all digenean trematodes represent a first record for the parasite fauna of fish from Belchishta Wetland, while Plaigioporus stefanskii and Pseudochetosoma salmonicola are found for the first time in Macedonian waters.

Macrozoobentos Composition In The Babura River Sumatra Utara

To determine the composition of macrozoobenthos in the waters of the Babura river. The parameters measured are biological parameters, namely macrozoobenthos composition supported by physical and chemical parameters in the Babura river waters. The parameters measured in this research are biotic parameters, namely the type of macrozoobenthos and abiotic parameters, namely physical and chemical parameters. Physical parameters such as: temperature, turbidity, and chemical parameters such as: pH (degree of acidity), (DO), BOD, COD, and phosphate. Taking macrozoobenthos in shallow water using a quadrant and in deep water using an Eckman grab. Physical/chemical parameters are measured in situ and ex situ. Ex-situ is carried out in the BTKL laboratory. This type of research is ex-post de facto or only reveals existing data. Macrozoobenthos composition found in the Babura river: 1. There are six species of insects, namely Chironomus sp, Aeshna grandis, Dragonfiy nymph macronia, Agrion sp, Damsefly nymph, Dragonfly; 2. There are eight species of gastropods, namely: Thiara winteri, Thiara sp, Melanoides tuberculata, Melanoides rustica, Melanoides gramnifera, Brotia testudinaria, , Planorbis sp, Lymnaea rubiginosa; 3. There are two species of Hirudinea/Clitellata, namely Leeches and Glossiphoniidae; 4 There is one species of trematode, namely Pomatiopsis lapidaria Say; 5. There is one species of crustacean, namely Gammarus sp; 6. There is one species of nematode, namely the rolled worm; 7. There is one species of Oligochaeta, namely Tubifex sp; 8. There are three species of Turbilaria, namely Planaria sp, Dugesia sp, Mesostoma sp, so the macrozoobenthos composition consists of 8 classes with a total of 23 species. Physical/chemical parameters still support macrozoobenthos life in the waters of the Babura river.

Description and phylogenetic position of an unusual genus and species of allocreadiid trematode from a characid freshwater fish in South America

The worldwide distributed family Allocreadiidae Looss, 1902 is predominantly parasitic in freshwater fish and occasionally in amphibians and reptiles. It contains 15 genera, of which only Allocreadium, Creptotrema, Wallinia and Creptotrematina have been reported in Argentina. The records of Allocreadium species still require further verification. The discovery of an allocreadiid digenean parasitizing Pseudocorynopoma doriae led us to erect a new genus for which the name Martorellia n. gen is proposed. It is characterized by poorly developed ventrolateral muscular lobes and a transversely elongated ovary, with the most characteristic feature being the presence of vitelline follicles in two fields (one anterior at level of ventral sucker and one posterior to the testis), which are not confluent in the middle. The phylogenetic tree reconstructed with 28S rDNA sequences placed the new genus as the sister taxa of Creptotrematina. Although both genera are separated by a small genetic distance, it is comparable with those separating other allocreadiid genera. The discovery of Martorellia liciae gen et sp. nov. provides further evidence of the great diversity of Allocreadiidae in South America. The analysis of new samples from different South American hosts with an integrative taxonomic approach as the one used here allows a better understanding of the evolutionary history and biogeography of allocreadiids in the Americas.

Platyhelminthes of common buzzard (Buteo buteo): Checklist of species in Europe and new parasite-host associations in Romania

BackgroundPlatyhelminthes are common parasites of diurnal birds of prey, including common buzzard (Buteo buteo). They are widely distributed in Europe. Despite the extensive study of flatworms across the continent, this study represents the first report for Romania and extends the biogeographic knowledge of Platyhelminthes in diurnal raptors. It also identifies common buzzards as a new host of Parastrigea flexilis in Europe. Materials and methodsBetween 2017 and 2020, 63 common buzzards (Buteo buteo) found road killed or dead due to other causes were collected from Romania. All specimens were necropsied and examined for internal helminths, which were preserved in ethanol for molecular identification and formaldehyde for morphological identification. ResultsSpecies identified included Cestoda: Cladotaenia globifera (33.3%) and five species of Trematoda: Neodiplostomum attenuatum (12.7%), Strigea falconis (6.4%), Parastrigea flexilis (3.2%), Neodiplostomum spathoides (3.2%) and Brachylaima fuscata (1.6%). ConclusionsThis study provides new data about diversity, phylogenetics and geographical distribution of Platyhelminthes parasitizing Buteo buteo in Romania. To our best knowledge, it identifies B. buteo as a new host of Parastrigea flexilis and reports the first genetic sequence of Neodiplostomum spathoides.

Prevalence and distribution of trematodes hosted by Bithynia siamensis in Southern Thailand.

This study aimed to investigate the occurrence of larval trematode infections in bithyniid snails across five provinces in southern Thailand. A total of 1,413 Bithynia siamensis snails were collected between October 2021 and October 2022 using handpicking and scooping methods. Among these, 844 were identified as B. s. siamensis and 569 as B. s. goniomphalos. The snail samples were examined for parasitic infections in the laboratory using shedding and crushing methods. Among the 27 sampling sites, snails from 6 sites were infected with various trematode species (infection rate: 4.95%, 70/1,413). Evaluation of the morphological and internal organ characteristics of the cercariae allowed for the categorization of the trematodes into five species of trematodes (belonging to four families). The identified species included Echinochasmus pelecani (family: Echinostomatidae), Echinostoma revolutum (family: Echinostomatidae), Haematoloechus similis (family: Haematoloechidae), Loxogenoides bicolor (family Lecithodendriidae), and Stictodora tridactyla (family: Heterophyidae), and the infection rates for these species were 3.26% (46/1,413), 0.35% (5/1,413), 0.42% (6/1,413), 0.78% (11/1,413), and 0.14% (2/1,413), respectively. The cercariae from the identified trematode species were studied for DNA analysis. The phylogenetic lineage reveals relationships among the species, confirming the morphological distinctions.

TAXONOMIC ANALYSIS OF HELMINTHS FOUND IN DOMESTIC POULTRY IN THE FERGANA VALLEY

The modern species composition of domestic poultry helminths in the Fergana Valley was studied, and it was found to consist of 45 species. These include 12 species of cestodes, 15 species of trematodes, and 18 species of nematodes. During the research, representatives of the families Davaineidae, Ascaridiidae, Heterakidae, Strongylida, and Capillaridae (Raillietina tetragona, Skrjabinia cesticillus, Ascaridia galli, Heterakis gallinarum, Syngamus trachea) were found in almost all domestic poultry. The research on the distribution, biology, and host damage properties of these helminths is essential for developing control measures.

Trematode metacercariae parasitic in the estuarine crustacean Cyathura muromiensis Nunomura, 1974 (Peracarida: Isopoda: Anthuroidea)

This is the first report of trematodes parasitic in the estuarine isopod crustacean Cyathura muromiensis, and the fourth report from anthuroid isopods worldwide. From 52 of 54 host individuals collected qualitatively on the tidal flat of the Muromi River estuary, Fukuoka, Japan, 389 cysts of metacercariae were extracted (sample prevalence = 96.3 %). Host individuals contained from one to 71 metacercarial cysts. The range in cyst diameter was 172.3–252.1 μm, and the distribution of cyst sizes contained only one component. Cysts occurred in pereonites 2–7 and the pleon of the host, but not in the head, pereonite 1, or telson. There was no correlation between the number of cysts and host sex or size. Sequences of the nuclear “ITS1 region,” from the 3´ region of 18S rRNA to the 5´ region of internal transcribed spacer I gene (ITS1), from five cysts ranging in size from nearly the lowest diameter to the greatest diameter in our sample showed p-distances of 0.0–0.2 %, suggesting that all cysts obtained were conspecific. A phylogenetic reconstruction based on nuclear 28S rRNA gene sequences showed that the trematode belongs in the genus Microphallus. The definitive host of our trematode species is likely a bird, since the definitive hosts of microphallids are chiefly birds, and birds are known to prey on Cyathura isopods.

The abundance of snail hosts mediates the effects of antagonist interactions between trematodes on the transmission of human schistosomes

BackgroundCombating 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.MethodsWe 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.ResultsOur 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).ConclusionsOur 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.Graphical

Innovative molecular and immunological approaches of heterophyiasis infecting some Egyptian marketed fishes

Heterophyiasis is a highly endemic disease in the Nile Delta, Egypt, where people consume raw or undercooked Oreochromis niloticus and Mugil cephalus. Birds and rats play a crucial role in fish-borne zoonotic trematode transmission since they serve as natural and experimental hosts. This study aimed to update the epidemiological information, morphological description, molecular identification and gene expression of two distinct heterophyid metacercariae in Giza, Wadi Al-Rayan, and Lake Manzala, Egypt, whereas various heterophyid infections could be expected. The present Centrocestus formosanus, Heterophyes heterophyes, and Heterophyes nocens with accession numbers OR947651.1, OR947700.1, and OR947719.1, respectively, matched with those recorded in the GenBank. Findings of the current investigation indicated that various cytokines like IL-1β, MHC-II, and TNF-α rapidly elevated in the infected pigeon’s intestines. Additionally, the infection expanded due to the parasite’s ejection from the host and the host’s clinical affliction, which induced humoral immune responses. Interestingly, investigation of other trematode species is in extreme demand in terms of zoonoses. We suggest controlling snails, managing migratory birds, and examining and frying fishes to the point when the encysted metacercariae is destroyed.

Paronatrema davidbowiei n. sp. (Trematoda: Syncoeliidae), a new parasite of the pelagic thresher (Alopias pelagicus) and its phylogenetic relationships within the suborder Hemiurata Skrjabin & Guschanskaja, 1954

A new species of hemiurid trematode found on the gills and in the aorta of the pelagic thresher Alopias pelagicus from the eastern Pacific, off Costa Rica, is described based on an integrative taxonomic approach that includes the use of light and scanning electron microscopy, and 28S rDNA sequencing. Phylogenetic analysis was also performed to explore, for the first time, the relationships of a member of the subfamily Otiotrematinae within the suborder Hemiurata. Paronatrema davidbowiei n. sp. can be distinguished from the congeners by having tegumental spines on the dorsal surface of the forebody, papillae on the oral sucker, and different morphology or number of testicular follicles. BLAST analysis revealed that sequences of Paronatrema davidbowiei n. sp. had the highest degree of similarity with Hirudinella spp. (Hirudinellidae). Results from Maximum Likelihood and Bayesian phylogenetic analyses, returning trees with the exact same topology and strong branch support, distinguished between the two superfamilies included in the suborder Hemiurata: Azygioidea and Hemiuroidea. Our analysis placed the new species in a clade with Copiatestes filiferus, the only existing sequence of the family Syncoeliidae.

Helminth Fauna of Buffaloes Bubalus bubalis (Linnaeus, 1758) in the Northeastern Foothills of the Lesser Caucasus of Azerbaijan

The article is devoted the study of the helminth fauna of buffaloes in the north-eastern foothills of the Lesser Caucasus. The study was conducted in 15 buffaloes by partial necropsy in different zones (plain, foothills, mountainous) and 23 species of helminths were detected. The helminth fauna consisted of 4 species of trematodes, 5 species of cestodes and 14 species of nematodes. The extent intensity and nature of spread of detected helminth species were analyzed.

Biogeography of larval trematodes in the freshwater snail, Semisulcospira libertina: a comparison of the morphological and molecular approaches

While biogeographic patterns of free-living organisms are well documented, the biogeography of parasitic fauna remains largely unclear. Due to morphological similarities, parasites are often difficult to identify without the aid of molecular genetics, further complicating the interpretation of their biogeographic patterns. We investigated trematode parasites infecting the East Asian freshwater snail Semisulcospira libertina to understand their biogeography and to evaluate how molecular approaches influence the interpretation of biogeographic patterns of the trematode fauna. We identified 46 genetically delimited species from 19 morphologically distinguishable trematodes infecting S. libertina and found that their species richness was negatively correlated to latitude. We also found that potential definitive host (fishes) richness and host body size were positively correlated with trematode species richness, suggesting that host attributes are essential factors shaping the biogeographic pattern in trematodes. These trends were observed irrespective of species identification methods, demonstrating that classical morphological identification can also effectively identify the latitudinal gradient pattern in trematodes. We further detected the distance decay of similarity in trematode communities, although this trend was only detectable in the biogeographic dataset based on molecular identification. Our study showed that morphological identification sufficiently reflects the latitudinal richness gradient while molecular identification is essential to estimate accurate local species richness and increase the resolution of the large-scale pattern of population similarities in the trematode communities.

Helminths of the black-headed gull (Chroicocephalus ridibundus) from breeding colonies in north-central Poland

Among parasites of the digestive tract of the black-headed gull (Chroicocephalus ridibundus) in Poland, the best known are species of digenetic trematodes and cestodes. Nematodes of this bird species are not well known. Black-headed gulls, due to their varied diet, migration, life in a flock, and changes of habitat, can become infected with various species of helminths, and like synanthropic birds, they can spread the dispersal stages of parasites across urban and recreational areas. In the present study, an attempt was made to identify the helminth fauna of C. ridibundus from breeding colonies in north-central Poland. The aim of the study was to describe the taxonomic structure of parasites of the digestive tract of the black-headed gull and determine the quantitative parameters of their occurrence. A total of 43 black-headed gulls were examined post-mortem for gastrointestinal helminths, resulting in the identification of four cestodes (Paricterotaenia porosa, Lateriporus clerci, Anomotaenia micracantha, and Wardium fusum), three trematodes (Diplostomum pseudospathaceum, Plagiorchis laricola, and Apophallus muehlingi), and three nematodes (Eucoleus contortus, Cosmocephalus obvelatus, and Porrocaecum ensicaudatum). Lateriporus clerci (in adult form), C. obvelatus and P. ensicaudatum (in larval form) were recorded for the first time in the black-headed gull in Poland.

Parasites as indicators of biodiversity and habitat complexity in coastal ecosystems

AbstractResearchers often use surrogate species for assessing biodiversity—organisms that can indicate the presence of additional taxa or provide insight into environmental processes. As indicators of anthropogenic impact, “cross‐taxon” surrogates are theorized to be effective shortcuts for determining how communities respond to environmental change. However, few studies have implemented cross‐taxon surrogates given the challenge of validating the strength of the relationship between surrogates and their target taxa. Trophically transmitted parasites require multiple invertebrate and vertebrate taxa to complete their life cycles (e.g., annelids, mollusks, fishes, shorebirds), making them ideal cross‐taxon surrogates of community diversity. By sampling for these parasite surrogates, it is theoretically possible to infer the composition of the overall host community based on the species of parasites present. In our study, we tested the use of parasites as cross‐taxon surrogates of biodiversity by sampling for digenetic trematodes in the mudsnail Ilyanassa obsoleta, collected from coastal shoreline environments with or without artificial structures (e.g., bulkheads, seawalls). We found that trematode richness, evenness, and diversity were all greater in snails sampled from natural shorelines versus those with artificial structures. While parasite communities clustered by shoreline type (with vs. without artificial structures), we found no differences in multivariate dispersion, or beta‐diversity, between groups in our system. At the species level, trematodes requiring polychaetes and estuarine fishes as downstream hosts dominated parasite communities at shorelines with artificial structures. These taxa are ubiquitous but more abundant in degraded environments. In contrast, trematode species requiring mollusks and shorebirds as hosts was only documented from shorelines without artificial structures (i.e., natural), which may indicate that these areas are less degraded and have greater overall host diversity. High parasite diversity in easily collected hosts (e.g., mudsnails) provides evidence that the secondary (polychaetes, crustaceans) and tertiary (fishes, shorebirds) hosts required by the parasites are present in the system. Our study also helps validate the concept of surrogate species by demonstrating how a single species can represent broader taxonomic groups.

TREMATODE SPECIES DETECTION AND QUANTIFICATION BY ENVIRONMENTAL DNA-qPCR ASSAY IN LAKE CHANY, RUSSIA.

Environmental DNA (eDNA) surveys promise to be a sensitive and powerful tool for the detection of trematodes. This can contribute to the limited studies on trematode ecology, specifically in aquatic ecosystems. Here, we developed species-specific primer and probe sets for Moliniella anceps, Opisthioglyphe ranae, and Plagiorchis multiglandularis cercariae and applied a novel eDNA qPCR assay to detect larval trematodes quantitatively. We evaluated the effectiveness of the assays using filtered lake water samples collected from different sites of Lake Fadikha and Kargat River Estuary in Lake Chany, Russia, showing high species specificity and sensitivity in all 3 assays. Further, all 3 assays had high efficiencies ranging from 94.9 to 105.8%. Moliniella anceps, O. ranae, and P. multiglandularis were detected in the environmental water samples through real-time PCR. Thus, we anticipate that our approach will be beneficial for biomonitoring, measuring, and managing ecological systems.

Specifics of <i>Anisakis simplex</i> larvae infection in the Pacific herring <i>Clupea pallasii</i> Valenciennes, 1847 from Lake Tunaicha

The purpose of the research is to analyze specifics of Anisakis simplex larvae infection in the body cavity of the lake Pacific herring in Lake Tunaicha (from materials of 1980 to 1995).Materials and methods. Conventional parasitological methods were used for collecting the material. The dissection recorded the number of nematodes in the fish. Parasitological studies of the herring from Lake Tunaicha (southern Sakhalin) were conducted from 1980 to 1995. A total of 4,438 fish caught in the Krasnoarmeyskaya channel and Lake Tunaicha were examined.Results and discussion. The parasite fauna in the herring from Lake Tunaicha included six parasite species of which two nematode species (Anisakis simplex l., Hystorethylacium aduncum l.), one acanthocephala species (Corynosoma strumosum juv.), one trematode species (Brachyphalus crenatus) and two parasitic copepod species (Ergasilus wilsoni and E. hypomesi). Among all the above species, A. simplex larvae were of greatest interest for study. The helminth is a typical species of the Pacific herring and poses a threat to human and animal health. The results of the studies found no difference in the infection of herring females or males in Lake Tunaicha. A change in the infection rate was demonstrated in the herring by age and linear dimensions depending on the fish life cycle (spawning and wintering migration periods). The first cases were recorded for herrings infected with Anisakis sp. larvae sized from 14 cm.

One Health monitoring reveals invasive freshwater snail species, new records, and undescribed parasite diversity in Zimbabwe

BackgroundSnail-borne trematodes afflict humans, livestock, and wildlife. Recognizing their zoonotic potential and possible hybridization, a One Health approach is essential for effective control. Given the dearth of knowledge on African trematodes, this study aimed to map snail and trematode diversity, focusing on (i) characterizing gastropod snail species and their trematode parasites, (ii) determining infection rates of snail species as intermediate hosts for medically, veterinary, and ecologically significant trematodes, and (iii) comparing their diversity across endemic regions.MethodsA cross-sectional study conducted in 2021 in Chiredzi and Wedza districts in Zimbabwe, known for high human schistosomiasis prevalence, involved malacological surveys at 56 sites. Trematode infections in snails were detected through shedding experiments and multiplex rapid diagnostic polymerase chain reactions (RD-PCRs). Morphological and molecular analyses were employed to identify snail and trematode species.ResultsAmong 3209 collected snail specimens, 11 species were identified, including schistosome and fasciolid competent snail species. We report for the first time the invasive exotic snail Tarebia granifera in Zimbabwe, which was highly abundant, mainly in Chiredzi, occurring at 29 out of 35 sites. Shedding experiments on 1303 snails revealed a 2.24% infection rate, with 15 trematode species identified through molecular genotyping. Five species were exclusive to Chiredzi: Bolbophorus sp., Schistosoma mansoni, Schistosoma mattheei, Calicophoron sp., and Uvulifer sp. Eight were exclusive to Wedza, including Trichobilharzia sp., Stephanoprora amurensis, Spirorchid sp., and Echinostoma sp. as well as an unidentified species of the Plagiorchioidea superfamily. One species, Tylodelphys mashonensis, was common to both regions. The RD-PCR screening of 976 non-shedding snails indicated a 35.7% trematode infection rate, including the presence of schistosomes (1.1%) Fasciola nyanzae (0.6%). In Chiredzi, Radix natalensis had the highest trematode infection prevalence (33.3%), while in Wedza, R. natalensis (55.4%) and Bulinus tropicus (53.2%) had the highest infection prevalence.ConclusionsOur xenomonitoring approach unveiled 15 trematode species, including nine new records in Zimbabwe. Schistosoma mansoni persists in the study region despite six mass deworming rounds. The high snail and parasite diversity, including the presence of exotic snail species that can impact endemic species and biomedically important trematodes, underscores the need for increased monitoring.Graphical

PREVALENCE OF OPECOELID TREMATODES (TREMATODA: DIGENEA: OPECOELIDAE) IN THE WOOLLY SCULPIN CLINOCOTTUS ANALIS FROM THE PACIFIC COAST OF THE BAJA CALIFORNIA PENINSULA.

Prevalence values for 3 digenean species of the family Opecoelidae were calculated during a half-year period from 20 individuals per month of the fish species Clinocottus analis, collected from an intertidal environment of Baja California, Mexico. Trematode species recovered were Opecoelus adsphaericus, Opecoelus cameroni, and Opecoelus pacificus. Of these, only O. adsphaericus was present throughout the study, whereas O. pacificus and O. cameroni were recorded for 1 or 2 mo, respectively, exhibiting relatively low prevalence values. The decrease in prevalence of O. adsphaericus coincides with the appearance of O. pacificus and O. cameroni; these last 2 species were found only in the largest hosts, and their presence represents new records for Mexican marine fauna.

HOST SPECIFICITY, INFECTION DYNAMICS, AND ALLERGENICITY IN Anisakis SPP. INFESTATION: A REVIEW

Fish and seafood are important in providing protein to human diets. However, they are susceptible to contamination by various parasites, such as nematodes, cestodes, and trematodes. Among these, Anisakis spp. and other species of trematodes belonging to the Anisakidae family are commonly identified in fish and shellfish, posing a significant health risk. This contamination poses a substantial risk to public health, particularly with the increasing prevalence of these parasites in marine fish. The globalisation of cuisines, including sushi, is one of the factors causing this development. The risk of Anisakis contamination has increased due to the global popularity of sushi, a form of Japanese food that features raw or undercooked fish. Gastric anisakiasis is the primary infection in humans, caused by the penetration of L3 larvae into the gastric wall. However, the indefinite symptoms associated with anisakiasis make precise identification challenging, complicating efforts to effectively treat this health issue. This study reviewed the host specificity, risk factors, infection mechanisms, and infestation areas of Anisakis spp. Various reputable sources, including Google Scholar, PubMed Central, ScienceDirect, Springer Link, and the Wiley Online Library, were used to explore the diverse host preferences and the impact of environmental changes. The larvae of Anisakis spp. exhibit diverse host preferences and environmental changes like global warming make hosts more vulnerable. Inadvertent exposure to these parasites occurs when individuals consume raw or undercooked fish and seafood. An extremely serious threat is posed by allergic anisakiasis, characterised by severe symptoms such as respiratory arrest, shock, and collapse. Research focusing on bioactive substances capable of blocking or neutralising the excretions and secretions of Anisakis sp. should be encouraged. Metalloproteinases (MMPs) and serine proteases, in particular, show promise for minimising adverse effects and reducing dependency on medication in treating allergic anisakiasis. Further research and intervention techniques are essential if health issues associated with Anisakis exist.

Freshwater trematodes differ from marine trematodes in patterns connected with division of labor.

Prior research suggests that trematode rediae, a developmental stage of trematode parasites that reproduce clonally within a snail host, show evidence of division of labor (DOL). Single-species infections often have two morphologically distinct groups: small rediae, the 'soldiers', are active, aggressive, and do not appear to reproduce; large rediae, the 'reproductives', are larger, sluggish, and full of offspring. Most data supporting DOL come from trematodes infecting marine snails, while data from freshwater trematodes are more limited and generally do not supported DOL. The shorter lifespan typical of freshwater snails may partially explain this difference: defending a short-lived host at the expense of reproduction likely provides few advantages. Here, we present data from sixty-one colonies spanning twenty species of freshwater trematode exploring morphological and behavioral patterns commonly reported from marine trematodes believed to have DOL. Trematode rediae were obtained from sixty-one infected snails collected in central Vermont, USA. A portion of the COI gene was sequenced to make tentative species identifications ('COI species'). Samples of rediae were photographed, observed, and measured to look for DOL-associated patterns including a bimodal size distribution, absence of embryos in small rediae, and pronounced appendages and enlarged pharynges (mouthparts) in small rediae. Additional rediae were used to compare activity levels and likelihood to attack heterospecific trematodes in large vs. small rediae. Many of the tests for DOL-associated patterns showed mixed results, even among colonies of the same COI species. However, we note a few consistent patterns. First, small rediae of most colonies appeared capable of reproduction, and we saw no indication (admittedly based on a small sample size and possibly insufficient attack trial methodology) that small rediae were more active or aggressive. This differs from patterns reported from most marine trematodes. Second, the small rediae of most colonies had larger pharynges relative to their body size than large rediae, consistent with marine trematodes. We also observed that colonies of three sampled COI species appear to produce a group of large rediae that have distinctly large pharynges. We conclude that these freshwater species likely do not have a group of specialized non-reproductive soldiers because small rediae of at least some colonies in almost every species do appear to produce embryos. We cannot rule out the possibility that small rediae act as a temporary soldier caste. We are intrigued by the presence of rediae with enlarged pharynges in some species and propose that they may serve an adaptive role, possibly similar to the defensive role of small 'soldier' rediae of marine trematodes. Large-pharynx rediae have been documented in other species previously, and we encourage future efforts to study these large-pharynx rediae.