Digenean Parasites Research Articles

Tubulovesicula lindbergi (Layman, 1930) (Digenea: Hemiuridae) in the Southwestern Atlantic Ocean: A Morphological and Phylogenetic Study Based on Specimens Found in Nebris microps (Actinopterygii: Sciaenidae) off the Brazilian Coast

This study presents the first record of T. lindbergi from the southwestern Atlantic Ocean, based on specimens collected from the smalleye croaker Nebris microps Cuvier (Sciaenidae), off the coast of Maranhão Island, State of Maranhão, Brazil. Our approach included a morphological analysis complemented by DNA sequencing (28S, ITS2 rDNA, and cox1 mtDNA). Our phylogenetic analysis revealed the affinity of T. lindbergi to its congener T. laticaudi Parukhin, 1969, a digenean parasite commonly found in hydrophiine snakes inhabiting the Pacific Ocean. The interspecific divergence between T. lindbergi and T. laticaudi measures 3.80% for 28S, 7.49–7.64% for ITS2, and 16.29–16.70% for cox1. Our findings expand the documented geographic range of T. lindbergi into the southwestern Atlantic Ocean, report a novel host record, and increase the number of hemiurids known from Brazil to 30 species. Additionally, this study represents the initial documentation of a marine digenean fish within the North Brazil Shelf.

Lethal effects of praziquantel and albendazole, on the cercariae of Echinochasmus sp. (Dietz, 1909) in-vitro.

Echinochasmidae are considered one of the digenean intestinal parasites of carnivorous mammals and humans. Some larvicidal medications, such as praziquantel and albendazole, were employed to interrupt the life cycle of Echinochasmidae, which may cause harmful and serious effects on the domestic fish, ducks, and humans in our ecosystem. Cercariae of Echinochasmus sp. (gymnocephalus type) were harvested by exposing snails to strong artificial illumination. The emerging cercariae were exposed in vitro to different concentrations of praziquantel and albendazole at the same period of incubation 12 h. Using probit analysis in SPSS version 25, the lethal concentrations 50 and 95% were determined. They were 0.036 and 0.82 ppm, respectively, for praziquantel and 5.3 and 9.2 ppm, respectively, for albendazole. The ultrastructural changes using scanning electron microscope on the tegumental surface of the treated cercariae with the two drugs were compared to the untreated cercariae. The untreated cercariae have a pear-shaped body with a long tail. The oral sucker is armed with a spiny collar and decorated with ciliated and unciliated sensory papillae. The cardinal ventral sucker has a thick, muscular wall. The cercarial tail is decorated with parallel longitudinal tegumental processes and spherical, unciliated papillae. In comparisons, cercariae treated with both drugs lost all healthy morphological features, but in varying degrees and effects between the two drugs. Our findings suggest that the use of both drugs can be recommended during the design of control strategies to combat this type of intestinal parasite.

A new genus and species of Microphalloidea (Digenea), parasite of Peropteryx spp. (Chiroptera: Emballonuridae) from the Neotropical region of Mexico revealed by morphological and phylogenetic analyses.

The present study aims to describe a new genus and species of microphalloid digenean parasite of two species of bats of the genus Peropteryx from the Mexican Neotropics (in the states of Chiapas and Yucatán). Morphological and molecular data (28s rDNA ribosomal gene sequences) were used to study Digeneans. Sagittatrema zutzi gen. nov. sp., nov., is diagnosed morphologically by having a sagittiform body, a genital pore in the midline of the body, posterior to the ventral sucker, and a cirrus sac running through much of the diameter of the ventral sucker. The nine sequences generated from the 28S rDNA gene were used to examine the phylogenetic affinities of this new taxon within the superfamily Microphalloidea Ward, 1901, using Maximum Likelihood and Bayesian Inference analyses. Both analyses resulted in trees with similar topologies and formed a well-supported clade (Bt = 100; pp = 1) with the Sagittatrema sequences. Because of the new genus's phylogenetic position and that some sister families to the proposed taxa, like Pleurogenidae and Prosthogonimidae, are polyphyletic, we prefer to consider Sagittatrema as a genus incertae sedis within Microphalloidea. A full systematic review of microphalloids is needed to confirm their phylogenetic position.

First molecular identification of the trematode Pulmonicola cochleotrema (Platyhelminthes: Opisthotrematidae) in West Indian manatees (Trichechus manatus, Sirenia: Trichechidae) from Puerto Rico and Florida.

West Indian manatees (Trichechus manatus) harbor a variety of endoparasites, including the nasal trematodePulmonicola cochleotrema, which infects the respiratory tract, especially the nasal passages. Previous studies have described and identified this digenean using morphological data only. This study presents the first molecular identification ofP. cochleotremain West Indian manatees from Puerto Rico and Florida. Samples of the trematode were collected from seven manatees found stranded dead at both locations. The small subunit ribosomal DNA (18S rDNA) was amplified from each sample using universal primers for different regions of the gene, resulting in a consensus sequence of 1871 base pairs. The phylogenetic reconstruction was carried out using DNA sequences of other species of digenean parasites from other hosts, including a trematode of the same taxonomic family from another sirenian species. Specimens collected from both locations show the same molecular identity using SSU rDNA sequence data. The identity ofP. cochleotremawas confirmed using the Basic Local Alignment Search Tool from the National Center for Biotechnology Information database, yielding a high similarity of 98.8 % withOpisthotrema dujonisand 98.2 % withLankatrema mannarenselocated in the same clade in our analysis. The latter two digeneans belong to the Opisthotrematidae as doesP. cochleotrema and previous studies reported them infecting the Eustachian tubes, esophagus, and digestive tract in dugongs (Dugong dugon). These findings evidence that the nasal trematode of manatees in Florida and Puerto Rico and the dugong, all inhabiting and feeding in marine environments, will have a marine mollusk as an intermediate host, probably a gastropod. The question remains, which species of nasal trematode are harbored by lotic-dwelling manatees in other parts of their distribution like South America.

Reproduction cycle, trematode parasitism and growth of freshwater mussel Anodonta anatina (Bivalvia: Unionidae)

Anodonta anatina, a widely distributed Eurasian freshwater mussel, has dramatically declined and listed as endangered species in IUCN Red List in some parts of the Europe. To better understand its basic biology and possible sex-dependent effects of parasitism on reproduction, we investigated the reproductive traits, trematode parasitism and growth between November 2020 and October 2021. Our data from a Finnish population indicates male-biased sex ratio and the gonadal development lasting throughout the year with a bradytictic brooding pattern. Gonadosomatic index of both sexes peaked in May and declined in June. Mature oocytes were smaller sized than those of previously studied unionids, fecundity was fairly low, and the maximum predicted lifespan was 14 years. Gonads were infected with digenean trematode parasites, Rhipidocotyle campanula being the dominant species. Interestingly, trematode infection rate was higher in females than in males. In July, when the water temperature reached its annual maximum, the trematode prevalence also peaked, which was accompanied with 16% of mussels being sterile. The trematode parasitism was thus negatively associated with reproduction, that might become even more affected if parasitism increases along with the predicted climate warming, which should be considered in possible future conservation and aquaculture efforts of this species.

Trace elements assessment in Cerastoderma glaucum from port areas in the Tunisian Mediterranean coast: The influence of parasites on bioaccumulation

In the present study, the seasonal concentration of seven trace elements was investigated in sediment and the cockle Cerastoderma glaucum tissues from two port areas in the North-East and South of Tunisia comparing cockles non-parasitized (NP) and parasitized (P) with digenean parasites. Elements concentration in sediments analyzed in both sites revealed that Zinc (Zn), Chromium (Cr), and Lead (Pb) were the most abundant ones, while Cadmium (Cd) and Mercury (Hg) were less abundant. The bioaccumulation of trace metals and Arsenic (As) in the tissues of cockles seems to be modulated by both the infection state and the parasite species. The relationship between bioaccumulation of metals and As, trematode species and abiotic parameters showed that the availability of certain metals for uptake by P cockles of both sites was influenced by the salinity and temperature of the water. Our results corroborate the possibility of using digenean infecting bivalves in biomonitoring aquatic ecosystems.

The phylogenetic position and analysis of Renicola and Apharyngostrigea species isolated from Cattle Egret (Bubulcus ibis)

Cattle Egret (Bubulcus ibis) is one of the most well-known herons in Egypt. It is called the friend of the farmer because it benefits farmers and helps them get rid of insects and worms. It acts as a reservoir for many diseases. Few researchers have discussed the significance of parasitic diseases that affect this wild bird and may lead to mortalities among the population especially the importance of vital organs such as kidneys. Therefore, this study aimed to spotlight parasitic infection-affected herons in Egypt and consider the risks to this beneficial bird. During this study, 23 Bubulcus ibis were captured after their death from Abou Rewash Giza Governorate, Egypt, during the period from February to September (2022). Renicola species (spp.) and Apharyngostrigea spp. are two important digenean parasites that were recovered from the kidneys, and small intestine of the heron Cattle Egret (Bubulcus ibis) with an infection rate of (17.2%) and (11.8%) respectively. Histopathological techniques were used to assess tissue alterations while light microscopy and molecular assays were used to assess the parasites. The parasites’ morphological and morphometrical characteristics, as well as polymerase chain reaction and sequencing assays (mitochondrial sections), were investigated for the first time in Egypt. These parasites were given in-depth illustrations and drawings. The distinctive qualities of the two species were discussed. As the first record from Egypt, the nucleotide sequences discovered in this work have been uploaded into the GenBank database (accession numbers: OR021986 and OQ955829). Microscopically, the renal blood vessels had vasculitis, necrosis, and other degenerative alterations. Further research analyzing the health of various heron spp. and environmental deterioration can help to close information gaps about the interactions between parasites, their hosts, and environmental health.

Redox-active metals and oxidative stress-mediated myopathies in Callinectes amnicola, blue crab populations from impacted sites of the Lagos Lagoon: inferences for adverse ecological outcomes.

While oxidative stress pathways are associated with a wide variety of tissue pathologies, its applications for evaluating and discerning ecological risks are limited. This study seeks to associate trends of lipid peroxidation and oxidative stress to risks of muscle pathologies in blue crabs inhabiting regions of the Lagos Lagoon. Crab samples (n = 520) were selected from pollution-impacted sites of the lagoon at Iddo, Ajah, Okobaba, Makoko, and the mid-lagoon area (control site). Antioxidant enzyme capacity, i.e., superoxide dismutase, catalase, glutathione peroxidase (GPx), and glutathione-S-transferase, and lipid peroxidation were evaluated in the muscle tissue of the blue crabs. The study findings showed distinct patterns of metal uptake in muscle, with redox-active metals (Cu and Zn) and redox-inactive metals (Pb and Cd) exhibiting site-specific differences. Additionally, there were changes in antioxidant modulation, lipid peroxidation, and the presence of associated myopathies. Blue crabs from sites (Makoko and Ajah) with greater uptake of redox-active metals (Cu and Zn) in muscle tissue showed higher trends of lipid peroxidation and the most prevalence of severe regression-type myopathies. Sites with lower uptake of redox-active metals showed the predominance of circulatory-type myopathies. This study also provides evidence of severe necrosis and myositis associated with digenean parasite cysts in crab muscle. Pathological evidence of severe skeletal muscle deterioration in the presence of greater lipid peroxidation could have implications for motor-neuron activity and reduced force-generating capacity necessary for adaptive responses in the wild. We conclude that elevated uptake of redox metals could aggravate the onset of myopathies in wild populations.

The complete mitochondrial genome of Morishitium polonicum (Trematoda, Cyclocoelidae) and its phylogenetic implications.

Trematodes can adversely impact the health and survival of wild animals. The trematode family Cyclocoelidae, which includes large digenean bird parasites, lacks molecular analysis, and reclassifications have not been supported. This study produced the first fully assembled and annotated mitochondrial genome sequence for the trematode Morishitium polonicum. The whole length of the M. polonicum (GenBank accession number: OP930879) mitogenome is 14083 bp, containing 22 transfer ribonucleic acids (tRNAs), 2 ribosomal RNAs (rRNAs, rrnL and rrnS), and a noncoding control section (D-loop) 13777 to 13854 bp in length. The 12 PCG areas have 3269 codons and a total length of 10053 bp, which makes up 71.38% of the mitochondrial genome's overall sequence. Most (10/12) of the PCGs that code for proteins begin with ATG, while the nad4L and nad1 genes have a GTG start codon. Phylogenetic analysis using the concatenated nucleotide sequences of 12 PCGs, and the ML tree analysis results showed that M. polonicum is more closely related to with Echinostomatidae and Fasciolidae, which indicates that the family Cyclocoelidae is more closely associated with Echinochasmidae. This study provides mtDNA information, and analysis of mitogenomic structure and evolution. Moreover, we aimed to understand the phylogenetic relationships of this fluke.

Occurrence of digenean parasites in freshwater snails in the Murrumbidgee catchment area, Australia

Freshwater snails are important hosts in the life cycles of many medically important parasites, particularly for digenetic trematodes such as liver flukes and schistosomes. The current study was conducted to determine the infection of freshwater snails with parasites that can potentially be transmitted to humans within the Murrumbidgee catchment area which is an area of widespread intensive aquaculture in Australia. A total of 116 freshwater snails, belonging to three species (Isidorella hainesii, Glyptophysa novaehollandica and Bullastra lessoni), were examined for the presence of parasites in both man-made and natural environments. The analysis of sequence data, including the internal transcribed spacers (ITS) of nuclear ribosomal DNA, small subunit (18S) ribosomal DNA, and large subunit (28S) ribosomal DNA, indicated that the collected parasites belonged to two distinct genera, namely Clinostomum and Echinostoma. It is noteworthy that species of both of these digenean parasites have the potential to be zoonotic. Cercariae of both Clinostomum and Echinostoma were observed in snails collected from aquaculture settings. It is important to highlight that infectious stages of Clinostomum has been previously detected in edible fish within Australia. This information raises concerns regarding the potential transmission of these parasites to humans through the consumption of contaminated fish. These findings emphasize the importance of monitoring and controlling the presence of Clinostomum and Echinostoma in aquaculture environments to minimise the risk of zoonotic infections and ensure food safety. Further research and surveillance are needed to better understand the prevalence, transmission dynamics, and potential public health implications associated with these parasites in the context of aquaculture in Australia.

Deepest digenean parasite: Molecular evidence of infection in a lower abyssal gastropod at 6,200 m

Little is known about the diversity and ecology of digenean parasites in the abyssal ocean (3500–6500 m deep) with previous occurrence records down only to 4877 m. Here, we report a 28S rDNA sequence of the fish digenean genus Lepidapedon (Lepidapedidae), amplified from DNA extract of a velutinid gastropod collected at 6185–6221 m in the Kuril–Kamchatka Trench, Northwest Pacific. This represents the deepest record for the platyhelminth class Digenea and, to our knowledge, for any group of fish parasites. Our finding also verifies for the first time that abyssal lepidapedids exploit benthic snails as intermediate hosts. The present species of Lepidapedon presumably accomplishes its life cycle in the lowermost abyssal zone with macrourid fish as the definitive host.

Parasitic Fauna of Captive Snakes (Serpentes, Colubridae) from Northeastern Argentina

This study aimed to evaluate the status of parasitic infections of colubrid snakes living in serpentariums in northeastern Argentina. Specimens were analyzed through clinical examination and coproparasitological surveys. In cases of death, specimens were necropsied, and histopathological exams were performed to determine its cause(s). Out of 30 specimens examined from 12 different species, parasites were found in 25 of them (83%). Nematodes were most common, with rhabdiasid and ascaridid helminths accounting for 57% and 40% of all infections, respectively. Further, the ascarid Hexametra boddaertii was identified in a specimen of Erythrolamprus aesculapii. Coccidian, digenean, and pentastomid parasites were also found less frequently. We identified the pentastomids Raillietiella furcocerca and Cephalobaena tetrapoda in specimens of Pseudablabes patagoniensis. We revealed systemic lesions induced by endoparasites, including enteritis and detachment of the gut mucosa by ascarids, tissue granulomas by rhabdiasids, and pulmonary microhemorrhages by pentastomids. Additionally, rhabdiasid-induced lesions in Duvernoy's gland were shown for the first time. Regarding ectoparasites, we identified the tick Amblyomma dissimile in a specimen of P. patagoniensis. On the whole, this study provides relevant information about the prevalence and pathophysiological effects of parasites on captive colubrids and paves the way for treatment strategies of such infections.

Light and scanning electron microscope observations of the digenean intestinal parasite Acanthostomum spiniceps Looss 1896 (Cryptogonimidae) from the catfish Bagrus bajad and B. docmak

Fishes of the River Nile are a promising source of animal protein. The catfishes Bagrus bajad Fabricius 1775 and Bagrus docmak Fabricius 1775 are economically important with well-marketable size and use in fish farming. Digenean parasites cause severe damage to the gut tissue of their fish hosts. There are still some questions regarding the taxonomical features of the genus Acanthostomum Looss 1899. The present study has revealed new morphological features that confirmed the identity of the collected worms as Acanthostomum spiniceps Looss 1896 and aided in elucidating the possible functions of different internal organs and surface features. A long-stemmed excretory bladder was detected but there was no evidence of gonotyl. The circumoral spines (28–30) were detected in the early juvenile stage and adult. The ventral sucker has no tegumental folds in juveniles or crescent-shaped tegumental folds in adults but possesses two overlapping lips. In both juveniles and adults, the oral sucker with the associated circumoral spines assumed retracted, and protracted positions reflecting its highest movement activity. Elongation of the anterior region and partial emergence of the oral cavity in living juveniles and adults were described. The possible functions of the forebody glands and the posterior body openings near the anal pores were discussed. Large, non-ciliated, dome-shaped, and small ciliated, button-like papillae were concentrated on the body surface, particularly the oral and ventral suckers. The tegument possesses densely arranged single-pointed and scale-like spines that gradually decrease in size and number as they proceed posteriorly.

First Report of <i>Aphanurus stossichii</i> (Digenea: Hemiuridae) from <i>Engraulis encrasicolus</i> on the Turkish Coast of the Black Sea, with Light and Scanning Electron Microscopic Observations

The aim of this study is to investigate in detail the morphological features of the digenean parasite Aphanurus stossichii isolated from the European anchovy Engraulis encrasicolus using light and scanning electron microscopy (SEM). The specimens of A. stossichii were obtained from the pharynx and stomach of the European E. encrasicolus caught by commercial fishing vessels in the Black Sea. Parasites were killed in a hot normal saline solution, preserved in to 70% ethanol for light microscopic (LM) studies, and in 2.5% glutaraldehyde for SEM. The morphological diagnostic features of A. stossichii were studied in detail under both LM and SEM. The morphological characteristics of the examined adult A. stossichii specimens were found to be similar to the original descriptions describing the basic characteristics of forebody and hindbody shape, the position and shape of the vitellarium, ovary, and and testes, and the shapes of oral and ventral sucker. The measurement data for all morphological diagnostics were provided; photomicrographs of each part of the parasite were presented. Infection prevalence, mean intensity and mean abundance values were 8.89%, 4.5 and 0.4, respectively. All available records of A. stossichii morphology are based on light microscope, this is the first study to identification the morphological features of the parasite with SEM. This research is the first on A. stossichii presence in E. encrasicolus on the Turkish Black Sea coast.

Diversity of digeneans parasitizing Mullus barbatus and Mullus surmuletus (Teleostean, Mullidae) off the coast of Algerian.

Mullus barbatus and Mullus surmuletus (Perciformes, Mullidae) are a common marine teleost of great commercial importance in many coastal areas. We studied the communities of Digenea species in two congeneric Mullidae hosts collected on the Algerian coast in the southern Mediterranean. Five hundred and seven M. barbatus and one hundred and twenty-three M. surmuletus were examined. During this work, we collected six species of parasitic Digenea which are related to five different families: Hemiuridae represented by Lecithocladium excisum, Fellodistomidae by Proctoeces maculatus and which is reported only from M. surmuletus, Derogenidae by Derogenes latus, Monorchiidae by Proctotrema bacilliovatum and finally Opecoelidae represented by two species Opecoeloides furcatus and Poracanthium furcatum. A critical systematic study revealed an apparent overlap in morphometric data of the six Digenean species from two host fishes. Therefore, the two mullet species are likely to share the same parasite community, and the stenoxenic specificity of Digenean parasites is briefly argued. Prevalence values showed that in the midst of six hundred and thirty Mullidae, one hundred and ninety-six are parasitized (31.11 %). Statistical tests showed that the most parasitized fish hosts are M. surmuletus with a high prevalence value (47.15 %), and on the other hand, they proved that small fish are more parasitized than others. Also, the lack of homogeneity between the different parasites is reported. We also note that the use of factorial correspondence analysis (FCA) allowed us, for the first time to highlight the distribution of the parasite species identified in the two mullets according to the seasons.

Consumption of trematode parasite infectious stages: from conceptual synthesis to future research agenda.

Given their sheer cumulative biomass and ubiquitous presence, parasites are increasingly recognized as essential components of most food webs. Beyond their influence as consumers of host tissue, many parasites also have free-living infectious stages that may be ingested by non-host organisms, with implications for energy and nutrient transfer, as well as for pathogen transmission and infectious disease dynamics. This has been particularly well-documented for the cercaria free-living stage of digenean trematode parasites within the Phylum Platyhelminthes. Here, we aim to synthesize the current state of knowledge regarding cercariae consumption by examining: (a) approaches for studying cercariae consumption; (b) the range of consumers and trematode prey documented thus far; (c) factors influencing the likelihood of cercariae consumption; (d) consequences of cercariae consumption for individual predators (e.g. their viability as a food source); and (e) implications of cercariae consumption for entire communities and ecosystems (e.g. transmission, nutrient cycling and influences on other prey). We detected 121 unique consumer-by-cercaria combinations that spanned 60 species of consumer and 35 trematode species. Meaningful reductions in transmission were seen for 31 of 36 combinations that considered this; however, separate studies with the same cercaria and consumer sometimes showed different results. Along with addressing knowledge gaps and suggesting future research directions, we highlight how the conceptual and empirical approaches discussed here for consumption of cercariae are relevant for the infectious stages of other parasites and pathogens, illustrating the use of cercariae as a model system to help advance our knowledge regarding the general importance of parasite consumption.

A first record of digenean parasites of the dwarf sperm whale Kogia sima with morphological and molecular information.

Two species of digenean trematodes of the family Brachycladiidae were obtained from two male dwarf sperm whales Kogia sima that stranded along the island of Kyushu, southern Japan in 2017. From the liver of the first animal, a single, large gravid specimen of a digenean species was collected. The morphological features were consistent with those of the genus Brachycladium. The worm had a large body and was characterized by anterior caeca without lateral diverticula, the shape of testes, ovary, and eggs. Molecular analyses using gene sequences of the 28S rRNA and the mitochondrial NADH dehydrogenase subunit 3 also supported the inclusion of this specimen into the genus Brachycladium. The identity of this worm is undetermined due to the lack of information on the genus and is reported as Brachycladium sp. From the cranial sinuses of the second animal, 33 specimens of digeneans were collected that were morphologically identified as Nasitrema gondo. This report documents a new host record for N. gondo, and the sequence information is provided for this digenean for the first time. This is the second record of digenean parasites for the family Kogiidae, and the first record with morphological and molecular information. The possibility of digenean infection in the liver and cranial sinus should be kept in mind during the necropsy of stranded kogiids.

Ecological studies on the helminth parasites of catfishes Bagrus spp. (Bagridae) and Chrysichthys auratus (Claroteidae) inhabiting Damietta branch, River Nile, Egypt

ABSTRACT The results of a survey on the helminth parasites of the catfishes Bagrus spp. Forsskål, 1775 and Chrysichthys auratus Geoffroy,1809 inhabiting Damietta branch of the River Nile at Mansoura city, Dakahlia Governorate, Egypt, have been demonstrated. During the period of March 2020 to February 2021, five species were detected from Bagrus spp. and represented by one monogenean Quadriacanthus bagrae from the gills, three digeneans Acanthostomum absconditum, Acanthostomum spiniceps and Haplorchoides cahirinus and a single nematode species Capillostrongyloides fritschi from the intestine. Only one monogenean species Protoancylodiscoides mansourensis was detected from the gills of Chrysichthys auratus. Except for a few months, most monogeneans, digeneans and nematodes of Bagrus spp. and C. auratus were recorded in all months of the year. The digeneans A. absconditum, A. spinicips, and H. cahirinus are eudominant and A. absconditum was the most dominant while the nematode C. fritschi is subrecedent. In Bagrus spp., the digenean parasites attained the highest prevalence over the monogeneans and nematode parasites throughout the year (77.7%). There was a definite seasonal change in the studied helminths, but no general common trend or pattern was observed. Most helminth parasites showed a higher prevalence in male fishes than females while they attained a higher abundance in females than males. There was a significant difference in the mean prevalence as well as in the mean intensity of most examined parasite species in male fishes and females but a significant difference in the mean abundance of males and females was only recorded for the digenean parasites. Most parasites showed a higher prevalence as the condition factor of the host increased.

Morphological and molecular characterization of Calicophoron raja (Näsmark, 1937) collected from wild Bovidae in South Africa

Paramphistomes, commonly known as rumen flukes, are digenean parasites that infect ruminants. Accurate morphological identification of paramphistome species is challenging and often neglected. For instance, it requires sagittal midline sections of adult flukes, which are difficult to prepare. Therefore, the majority of the genetic information on paramphistomes found in the International Nucleotide Sequence Database is not supported by morphological descriptions, and the DNA barcodes of paramphistome species remain unreliable. In the present study, both morphological and molecular characterizations were simultaneously performed to ensure the reliability of the DNA information for the paramphistome species Calichophoron raja (Näsmark, 1937). The morphological characteristics of the sagittal and horizontal sections of adult flukes from a black wildebeest (Connochaetes gnou) and a waterbuck (Kobus ellipsiprymnus) in South Africa were identical to those previously described for Ca. raja. Additionally, this study represents a new host record of the species from Co. gnou. All sequences of the internal transcribed spacer 2 region of ribosomal DNA were 100% identical among the 18 flukes analyzed in the present study. A single nucleotide mutation was observed between Ca. raja in this study and Ca. raja detected in domestic ruminants in Kenya.

A Brief Review of Parasitic Castration in Aquatic Snails and Its Contribution in Control of Diverse Vector Snail Populations and Trematodiases in Man and Animals

Snails are invertebrate gastropod molluscs inhabited both the terrestrial and aquatic habitats. Most of these animals are dioeciously and their sexes are separated. In many monoecious (hermaphrodite) snail species, individuals have both male and female gonads. But in pulmonate monoecious snail species individuals have only single gonad called “ovotestis” which contains both testicular and ovarian tissues. In general, aquatic snail species are intermediate hosts of digenean trematode parasites of vertebrates including man and animals. In addition, aquatic snails are also act as vector of diverse trematodiases, such as schistosomiasis, clonorchiasis, opisthorchiasis, fascioliasis, amphistomiasis, etc. The prevalence of these digenetic trematode parasitic diseases in diverse geographical provinces is depending on the population of vector or intermediate host snail species. In fact, the various larval stages of digenean trematode parasites, such as sporocysts, rediae and cercariae are developed and multiplied asexually in the organ of hepatopancreas and/or gonads of host snails. These parasitic trematode larvae also act as castrators for snails and potential to prevent or block partially or completely their reproduction called “parasitic castration”. In this biological process, trematode larvae destroy the gonads in two ways, one is mechanically and the other physiologically. Parasitic castration is also induces sex conversion, gigantism and alteration the gene expression in brain of snails. In present communication, the most common vector snail species, different forms of trematode larvae and their basic biology and mode of parasitic castration in aquatic snails and its contribution in control of diverse vector snail populations and spreading of trematodiases are considered and brief and critically reviewed. Simultaneously, research gaps have also been highlighted for further advance research work. This review is helpful in understanding of biology or mechanism of parasitic castration and its contributory role the balancing of aquatic ecosystem.