Trematode Research Articles

Trematode Parasite Infection Affects Temperature Selection in Aquatic Host Snails.

Animals infected by parasites or pathogens can exhibit altered behaviors that may reduce the costs of infection to the host or represent manipulations that benefit the parasite. Given that temperature affects many critical physiological processes, changes in thermoregulatory behaviors are an important consideration for infected hosts, especially ectotherms. Here we examined the temperature choices of freshwater snails (Helisoma trivolvis) that were or were not infected by a trematode (flatworm) parasite (Echinostoma trivolvis). Active snails that explored the experimental temperature gradient differed in their thermal preference based on their infection status, as parasitized snails chose to position themselves at a significantly higher temperature (mean: 25.4°C) compared to those that were uninfected (mean: 23.3°C). Given that snails rarely eliminate established trematode infections, we suggest that this altered thermal preference shown by infected hosts likely benefits the parasite by increasing the odds of successful transmission, either through enhanced production and emergence of infectious stages or by increasing spatial overlap with the next hosts of the complex life cycle. Further studies that employ experimental infections to examine temperature selection at different time points will be needed to understand the extent of altered host thermal preferences, as well as the possible benefits to both host and parasite.

Schistosomatoidea and Diplostomoidea.

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

MALDI-TOF mass spectrometry: a new tool for rapid identification of cercariae (Trematoda, Digenea).

Identification of cercariae was long based on morphological and morphometric features, but these approaches remain difficult to implement and require skills that have now become rare. Molecular tools have become the reference even though they remain relatively time-consuming and expensive. We propose a new approach for the identification of cercariae using MALDI-TOF mass spectrometry. Snails of different genera (Radix, Lymnaea, Stagnicola, Planorbis, and Anisus) were collected in the field to perform emitting tests in the laboratory. The cercariae they emitted (Trichobilharzia anseri, Diplostomum pseudospathaceum, Alaria alata, Echinostoma revolutum, Petasiger phalacrocoracis, Tylodelphys sp., Australapatemon sp., Cotylurus sp., Posthodiplostomum sp., Parastrigea sp., Echinoparyphium sp. and Plagiorchis sp.) were characterized by sequencing the D2, ITS2 and ITS1 domains of rDNA, and by amplification using specific Alaria alata primers. A sample of each specimen, either fresh or stored in ethanol, was subjected to a simple preparation protocol for MALDI-TOF analysis. The main spectral profiles were analyzed by Hierarchical Clustering Analysis. Likewise, the haplotypes were analyzed using the maximum likelihood method. Analytical performance and the log-score value (LSV) cut-off for species identification were then assessed by blind testing. The clusters obtained by both techniques were congruent, allowing identification at a species level. MALDI-TOF enables identification at an LSV cut-off of 1.7 without false-positives; however, it requires more data on closely related species. The development of a “high throughput” identification system for all types of cercariae would be of considerable interest in epidemiological surveys of trematode infections.

The Effect of Breeding Management on the Prevalence and Trematode infection Degree in calves

The Effect of Breeding Management on the Prevalence and Trematode infection Degree in calves

Suitability of Danish Bilharziasis Laboratory Technique (DBL) as Detection Test for Trematode Infection in Buffaloes

Trematodes are one of the devastating parasites in ruminants with significant public health and economic importance. Continued evaluation and development of novel detection methods for accurate diagnosis are highly warranted. This study aimed to assess the suitability of the Danish Bilharziasis Laboratory (DBL) technique as a detection test for Fasciola spp. and Paramphistomum spp. infection in buffaloes. Sensitivity and specificity were compared to post-mortem recovery of parasites from specific organs. A total of 246 buffaloes were examined in this study, of which 125 (50.81%) were infected with Fasciola spp. and 109 (44.31%) with Paramphistomum spp. by post-mortem detection. In contrast, 107 (43.50%) were positive for Fasciola spp. and 92 (37.40%) for Paramphistomum spp. by the DBL method. Sensitivity of DBL was high in detecting Fasciola spp. (85.6%) and Paramphistomum spp. (84.4%). The specificity was 100% for both parasites. Kappa coefficients (к) indicated an almost perfect agreement of the two tests in detecting Fasciola spp. (0.8539) and Paramphistomum spp. (0.8577). Based on these findings, DBL is a suitable technique for the detection of trematodes in buffaloes.

Trematode infections in frogs: Do all cercarial morphotypes infect and induce effects on the common hourglass tree frog, <i>Polypedates</i> <i>cruciger</i>?

Trematode infections are known to induce malformations and increase mortality in amphibians. However, not all the larval trematodes induce effects on the host. Nine types of cercariae (A-I) belonging to five morphotypes (oculopleurolophocercous, distome, gymnocephalous, xiphidiocercariae and pleurolophocercous) shed by the freshwater snail, Melanoides sp. were tested. Tadpoles of the common hourglass tree frog Polypedates cruciger at 10 days post-hatch (Gosner stage 27/28) were exposed to the cercariae in a mesocosm experiment. First exposure was carried out to identify which morphotypes induce effects on the host and later the exposures were repeated using selected cercariae, who induced effects on the host. Survival, growth and development of malformations were recorded in 15 and 30 days post-hatch tadpoles and metamorphs. Of the nine cercariae types, only three types., gymnocephalous (Type C) and two pleurolophocercous types (H and I), induced effects on the host with a single exposure. The repeated exposures showed that the cercariae type H significantly reduced the survival of tadpoles (4 replicates; Chi square test, X2 = 15.172, p<0.001) but not the cercariae type I (7 replicates; X2 =2.105, p= 0.147). Both cercariae types induced axial malformations such as kyphosis and scoliosis. The exposures incurred no changes to the size of tadpoles, but types H and I prolonged their growth period. Cercariae type C caused open wounds in the belly area of the host. This type of malformations has not been recorded in frogs before. However, cercariae type C was not shed by any of the snails collected later and therefore replicates were not carried out to confirm its effect. The results show that only some cercariae types induce effects on the frog host, possibly the cercariae types that use the tadpoles as the intermediate host to enter the definitive host and to complete its life cycle. Previous studies have reported two cercariae types induce frog malformations, hence collectively four cercariae types have demonstrated trematode induced effects on P. cruciger.

Parasitic infections in relation to practices and knowledge in a rural village in Northern Thailand with emphasis on fish-borne trematode infection.

The present study integrates several aspects of a parasitological survey in a rural community village combining community knowledge of parasites, their potential transmission routes and health risk factors. A rural community located in Northern Thailand was surveyed for intestinal parasites, and an overall prevalence of 45.2% for helminths and 4.8% for protozoan infections was identified. Socio-demographic characteristics, customs and perceptions were compiled using individual questionnaires and interviews for participants surveyed for parasitic screening. The results allowed us to determine the knowledge and perception of local people concerning helminthic infection and transmission. Despite the fact that the participants in this community were aware of parasitic transmission routes, their widespread custom of eating raw fish and meat render the reduction of helminthiasis difficult. A detailed study on the infection of fish-borne parasitic trematodes, the most prevalent helminth, allowed us to determine that the distance from a given household to the river is a determinant of infection intensity. Health education activities organised in the local community resulted in a change in perception of risks associated with parasite transmission.

Exploring the evolutionary potential of parasites: Larval stages of pathogen digenic trematodes in their thiarid snail host Tarebia granifera in Thailand

Minute intestinal flukes from several distinct families of endoparasitic platyhelminths are a medically important group of foodborne trematodes prevalent throughout Southeast Asia and Australasia. Their lifecycle is complex, with freshwater snails as primary intermediate hosts, with infecting multiple species of arthropods and fish as second intermediate hosts, and with birds and mammals including humans as definitive hosts. In Southeast Asian countries, the diversity of snail species of the Thiaridae which are frequently parasitized by trematode species is extremely high. Here, the thiarid Tarebiagranifera in Thailand was studied for variation of trematode infections, by collecting the snails every two months for one year from each locality during the years 2004–2009, and during 2014–2016 when snails from the same localities were collected and new localities found. From ninety locations a total of 15,076 T.granifera were collected and examined for trematode infections. With 1,577 infected snails the infection rate was found to be 10.46 %. The cercariae were categorized into fifteen species from eight morphologically distinguishable types representing several distinct families, viz. (i) virgulate xiphidiocercariae (Loxogenoidesbicolor, Loxogenesliberum and Acanthatriumhistaense), (ii) armatae xiphidiocercariae cercariae (Maritreminoidescaridinae and M.obstipus); (iii) parapleurophocercous cercariae (Haplorchispumilio, H.taichui and Stictodoratridactyla); (iv) pleurophocercous cercariae (Centrocestusformosanus); (v) megarulous cercariae (Philophthalmusgralli); (vi) furcocercous cercariae (Cardicolaalseae, Alariamustelae and Transversotremalaruei); as well as (vii) echinostome-type cercariae, and (viii) gymnocephalous-type cercariae. In addition, a phylogenetic marker (internal transcribed spacers 2, ITS2) was employed in generic and infrageneric level classifications of these trematodes, using sequences obtained from shed cercariae isolated from T.granifera specimens of the second study period collected in various regions in Thailand. We obtained ITS2 sequences of cercariae from nine species (of seven types): Loxogenoidesbicolor, Loxogenesliberum, Maritreminoidesobstipus, Haplorchistaichui, Stictodoratridactyla, Centrocestusformosanus, Philophthalmusgralli, as well as from one species each of echinostome cercariae and gymnocephalous cercariae. Thus, this analysis combines the parasites’ data on morphology and geographical occurrence with molecular phylogeny, aiming to provide the groundwork for future studies looking into more details of the parasite-snail evolutionary relationships.

Molecular phylogeography and reproductive biology of the freshwater snail Tarebia granifera in Thailand and Timor (Cerithioidea, Thiaridae): morphological disparity versus genetic diversity

The freshwater thiarid gastropod Tarebiagranifera (Lamarck, 1816), including taxa considered either congeneric or conspecific by earlier authors, is widespread and abundant in various lentic and lotic water bodies in mainland and insular Southeast Asia, with its range extending onto islands in the Indo-West-Pacific. This snail is, as one of the most frequent and major first intermediate host, an important vector for digenic trematodes causing several human diseases. As a typical thiarid T.granifera is viviparous and parthenogenetic, with various embryonic stages up to larger shelled juveniles developing within the female’s subhemocoelic (i.e non-uterine) brood pouch. Despite the known conchological disparity in other thiarids as well as this taxon, in Thailand Tarebia has been reported with the occurrence of one species only. In light of the polytypic variations found in shell morphology of freshwater snails in general and this taxon in particular, the lack of a modern taxonomic-systematic revision, using molecular genetics, has hampered more detailed insights to date, for example, into the locally varying trematode infection rates found in populations of Tarebia from across its range in Thailand as well as neighboring countries and areas. Here, we integrate evidence from phylogeographical analyses based on phenotypic variation (shell morphology, using biometry and geometric morphometrics) with highly informative and heterogeneous mtDNA sequence data (from the gene fragments cytochrome c oxidase subunit 1 and 16 S rRNA). We evaluate both the morphological and molecular genetic variation (using several phylogenetic analyses, including haplotype networks and a dated molecular tree), in correlation with differences in the reproductive biology among populations of Tarebia from various water bodies in the north, northwest, central, and south of Thailand, supplementing our respective analyses of parasite infections of this thiarid by cercaria of 15 trematode species, reported in a parallel study. Based on the comparison of topotypical material from the island of Timor, with specimens from 12 locations as reference, we found significant, albeit not congruent variation of both phenotype and genotype in Tarebiagranifera, based on 1,154 specimens from 95 Thai samples, representing a geographically wide-ranging, river-based cross-section of this country. Our analyses indicate the existence of two genetically distinct clades and hint at possible species differentiation within what has been traditionally considered as T.granifera. These two lineages started to split about 5 mya, possibly related to marine transgressions forming what became known as biogeographical barrier north of the Isthmus of Kra. Grounded on the site-by-site analysis of individual Tarebia populations, our country-wide chorological approach focussing on the conchologically distinct and genetically diverse lineages of Tarebia allows to discuss questions of this either reflecting subspecific forms versus being distinct species within a narrowly delimited species complex. Our results, therefore, provide the ground for new perspectives on the phylogeography, evolution and parasitology of Thai freshwater gastropods, exemplified here by these highly important thiarids.

Coprological study of trematode infections and associated host risk factors in cattle during the dry season in and around Bahir Dar, northwest Ethiopia

This study was conducted to estimate the prevalence and identify risk factors associated with trematode infections in cattle in and around Bahir Dar, northwest Ethiopia. Fecal samples collected from randomly selected 369 cattle were examined using simple sedimentation technique for differential trematode eggs count. The animals were found shedding eggs of three groups of trematodes, namely Fasciola spp., paramphistomes and Schistosoma spp. The overall prevalence of trematodes was 61.0%, and specific prevalence for Fasciola, paramphistomes and Schistosoma was 20.1%, 48.5% and 16.5%, respectively. A substantial overlap was observed in the occurrence of Fasciola and paramphistomes. The prevalence of all the three trematodes identified in this study was significantly (P < 0.05) associated with body condition and breed, while the prevalence of Fasciola and paramphistomes was also associated with age. The mean (± SE) fecal egg count per gram of feces (EPG) for Fasciola, paramphistomes and Schistosoma was 4.3 (± 0.55), 25.7 (± 2.11) and 3.1 (± 0.42), respectively. EPG of Fasciola was significantly correlated with EPG of paramphistomes (P < 0.001). The EPG for all the three trematodes was associated with body condition and breed of animals (P < 0.05), while EPG for paramphistomes was also affected by age of the animals (P < 0.05). The prevalence of all the three major trematodes of animal health importance with high rate of mixed infection along with poor body condition, suggests substantial economic loss incurred due to reduced productivity in cattle in the study area.

Infections with Digenean Trematode Metacercariae in Two Invasive Alien Fish, Micropterus salmoides and Lepomis macrochirus, in Two Rivers in Chungcheongbuk-do, Republic of Korea.

Present study was performed to survey infection status of digenetic trematode metacercariae in 2 alien fish species, Micropterus salmoides (largemouth bass) and Lepomis macrochirus (bluegill), in 2 rivers draining Chungcheongbuk-do, Republic of Korea. A total of 107 largemouth bass and 244 bluegills were caught in Daecheong-ho (ho=lake) and Musim-cheon (a branch of Geum-gang), in Chungcheongbuk-do April–July 2015. Additionally, 68 native fish of 5 species, i.e., Zacco platypus, Hemibarbus longirostris, Carassius auratus, Pseudogobio esocinus and Puntungia herzi, were caught from the same water bodies. All of the fish collected were examined by artificial digestion method. The metacercariae of Centrocestus armatus, Clinostomum complanatum, Metagonimus sp. and Diplostomum spp. were detected from 4 out of 5 native fish species in Daecheong-ho. However, any metacercariae were not found from 87 M. salmoides and 177 L. macrochirus in Daecheong-ho. In Musim-cheon, metacercariae of Exorchis oviformis and Metacercaria hasegawai were detected from 78% Z. platypus and 34% L. macrochirus, but any metacercariae not found in M. salmoides. We report here that the 2 alien fish species were less infected with the metacercariae than the native ones. Surveys on the metacercariae in the alien fish species in geographically various rivers should be undertaken for better understanding on the role of alien fish species in the trematode infections in Republic of Korea.

Interactions between two parasites of brown trout (Salmo trutta): Consequences of preinfection.

Preinfection by one parasitic species may facilitate or by contrast hamper the subsequent penetration and/or establishment of other parasites in a host. The biology of interacting species, timing of preinfection, and dosage of subsequent parasite exposure are likely important variables in this multiparasite dynamic infection process. The increased vulnerability to subsequent infection can be an important and often overlooked factor influencing parasite virulence. We investigated how the preinfection by freshwater pearl mussel Margaritifera margaritifera glochidia could influence the success of subsequent infection by the common trematode Diplostomum pseudospathaceum in brown trout Salmo trutta and vice versa whether preinfection by the trematode made fish more susceptible to glochidia infection. The first experiment was repeated twice with different (low and high) exposure doses to initiate the subsequent trematode infection, while in the second experiment we varied the timing of the preinfection with trematodes. The preinfection with glochidia made fish more vulnerable to subsequent infection with trematodes. Since the trematodes penetrate through the gills, we suggest that increased host vulnerability was most likely the result of increased respiration caused by the freshwater pearl mussel glochidia encysted on gills. In turn, brown trout preinfected with trematodes were more vulnerable to the subsequent glochidial infection, but only if they were preinfected shortly before the subsequent infection (20 hr). Fish preinfected with trematodes earlier (2 weeks before the subsequent infection) did not differ in their vulnerability to glochidia. These effects were observed at moderate intensities of infections similar to those that occur in nature. Our study demonstrates how the timing and sequence of exposure to parasitic species can influence infection success in a host–multiparasite system. It indicates that the negative influence of glochidia on host fitness is likely to be underestimated and that this should be taken into consideration when organizing freshwater pearl mussel restoration procedures.

Seroprevalence of bovine intestinal schistosomosis in different agro- ecological zones of south India using excretory-secretory antigen based ELISA

Intestinal schistosmosis caused by Schistosoma spindale and S. indicum is an important snail borne trematode infection that adversely affects the production and productivity of bovines in India. The present communication reports the high seroprevalence of infection among dairy cattle and buffaloes, under field conditions, utilizing a sensitive and specific excretory-secretory antigen based ELISA. Comparison of ELISA with copro-PCR, microscopy and post-mortem mesentery examination revealed the diagnostic superiority of ELISA. Seroprevalence of infection was mapped for the first time in India with special emphasis to agro- ecological zones. Anti-schistosome antibodies were detected in 34.96% of dairy cattle and buffaloes in the state with the evidence of significant influence of topography on the prevalence of infection. The study also highlighted the need to trace endemic pockets of infection in the country through efficient ante-mortem surveillance and to initiate anti-schistosome therapy prior to animal transport.

Interactive effects of contamination and trematode infection in cockles biochemical performance

Anthropogenic activities, especially those involving substances that pollute the environment can interfere with bivalve populations, as well as parasitism, a fundamental ecological interaction often neglected. In marine environments, organisms are concomitantly exposed to pollutants and parasites, a combination with synergistic, antagonistic or additive effects representing a potential threat to aquatic communities sustainability. In the present study, Cerastoderma edule (the edible cockle)–Himasthla elongata (trematode) was used as host–parasite model. Cockles are worldwide recognized as good sentinel and bioindicator species and can be infected by several trematodes, the most abundant macroparasites in coastal waters. Tested hypotheses were: 1) cockles exposed to increasing parasite pressure will present greater stress response; 2) cockles exposure to arsenic (single concentration test: 5.2 μg L−1) will change parasite infection success and cockles stress response to infection. Arsenic was used for being one of the most common pollutants in the world and stress response assessed using biochemical markers of glycogen content, metabolism, antioxidant activity and cellular damage. Results showed that intensity of parasite pressure was positively correlated to biochemical response, mainly represented by higher metabolic requirements. Contamination did not affect parasite infection success. Compared to arsenic, trematode infection alone exerted a stronger impact: higher glycogen storage, metabolism and cellular damage and antioxidant activity inhibition. In interaction, parasitism and arsenic reduced hosts metabolism and cellular damage. Therefore, to a certain extent and in a contamination scenario, cockles may benefit from trematode infection, working as a protection for the pollutant accumulation in the organisms, reducing overall ROS production, which can consequently led to less toxic effects. These findings highlighted the deleterious effects of trematode infection in their hosts and showed the importance of including parasitology in ecotoxicological studies.

Structural basis of urea‐induced unfolding of Fasciola gigantica glutathione S‐transferase

Glutathione S-transferases (GSTs) are enzymes that are involved in the detoxification of harmful electrophilic endogenous and exogenous compounds by conjugating with glutathione (GSH). The liver fluke GSTs have multifunctional roles in the host-parasite interaction, such as general detoxification and bile acid sequestration to synthase activity. The GSTs have been highlighted as vaccine candidates towards parasitic flukes. In this study, we have thoroughly examined the urea-induced unfolding of a mu-class Fasciola gigantica GST1 (FgGST1) using spectroscopic techniques and molecular dynamic simulations. FgGST1 is a highly cooperative molecule, because during urea-induced equilibrium unfolding, a concurrent unfolding of the protein without stabilization of any folded intermediate was observed. The protein was stabilized with conformational free energy of about ~12.36 kcal/mol. The protein loses its activity with increasing urea concentration, as the GSH molecule is not able to bind to the protein. We also studied the fluorescence quenching of Trp residues and the obtained K SV data that provided additional information on the unfolding of FgGST1. Molecular dynamic trajectories simulated in different urea concentrations and temperatures indicated that urea destabilizes FgGST1 structure by weakening hydrophobic interactions and the hydrogen bond network. We observed a precise correlation between the in vitro and in silico studies.

The molecular structure of Schistosoma mansoni PNP isoform 2 provides insights into the nucleoside selectivity of PNPs.

Purine nucleoside phosphorylases (PNPs) play an important role in the blood fluke parasite Schistosoma mansoni as a key enzyme of the purine salvage pathway. Here we present the structural and kinetic characterization of a new PNP isoform from S. mansoni, SmPNP2. Thermofluorescence screening of different ligands suggested cytidine and cytosine are potential ligands. The binding of cytosine and cytidine were confirmed by isothermal titration calorimetry, with a KD of 27 μM for cytosine, and a KM of 76.3 μM for cytidine. SmPNP2 also displays catalytic activity against inosine and adenosine, making it the first described PNP with robust catalytic activity towards both pyrimidines and purines. Crystal structures of SmPNP2 with different ligands were obtained and comparison of these structures with the previously described S. mansoni PNP (SmPNP1) provided clues for the unique capacity of SmPNP2 to bind pyrimidines. When compared with the structure of SmPNP1, substitutions in the vicinity of SmPNP2 active site alter the architecture of the nucleoside base binding site thus permitting an alternative binding mode for nucleosides, with a 180° rotation from the canonical binding mode. The remarkable plasticity of this binding site enhances our understanding of the correlation between structure and nucleotide selectivity, thus suggesting new ways to analyse PNP activity.

Impact of trematode infections on periphyton grazing rates of freshwater snails.

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

Trematodosis pada Sapi dan Kerbau di Wilayah Endemik Schistosomiasis di Provinsi Sulawesi Tengah, Indonesia

Cattle and buffaloes have economic value as a source of protein and draught power. The people of Sulawesi also use buffalo in various custom and religious activities. Infections by Trematodes may disrupt livestock productivity. In Indonesia, endemic Schistosomiasis can only be found in Central Sulawesi, Indonesia (Lindu, Napu, and Bada Valleys). There is no data on the status of Trematode infection in cattle and buffalo animals in the area. The study was conducted using a cross-sectional design to measure the prevalence of Trematodosis in cattle and buffalo around the endemic areas of Schistosomiasis in July-November 2016. A total of 261 stool samples consisting of 173 cattle and 88 buffaloes from 7 villages (Anca, Bewa, Mount Gintu, Sedoa, Wangga, Watumaeta, and Wuasa Villages) were collected and stored at 2-8 °C until further analysis. The Danish Bilharziasis Laboratory method was chosen to quantify the infection by trematodes. The prevalence of the overall trematodosis of this study was 85.06%. The prevalence of Trematodosis in buffalo was higher than in cattle and differed statistically (P<0.05). The highest prevalence was Paramphistomiasis (75.48%), followed by Fascioliasis (67.05%) and Schistosomiasis japonica (30.27%). The trematodosis prevalence of each village also varied and differed statistically (P<0.05). Intensites of infection of mild, moderate, and severe infections were reported in this study. Mixed infections by two even three species of trematodes were reported in this study. Two newly endemic Schistosomiasis villages are reported, namely Bewa Village and Gunung Gintu. The results of this study are used as a basis for controlling Trematodosis in large ruminants in endemic areas especially with zoonotic potential.

Behavioural impacts of trematodes on their snail host: Species‐specific effects or generalised response?

AbstractBehavioural changes induced by parasites are extremely common, but their ultimate causes are often difficult to determine: they may represent adaptive manipulation by the parasite, adaptive responses by the host, or non‐adaptive side‐effects of infection. Contrasting the impacts of different parasites on the same host species offers an opportunity to test for species‐specific changes in host behaviour, which are less likely to be general side‐effects. Here, we tested the impacts of three trematode species (Apatemon sp. I, Plagiorchioid sp. I, and Maritrema poulini) on movement, microhabitat choice and responses to predator cues of their common intermediate host, the freshwater snail Potamopyrgus antipodarum. All three trematodes cause the castration of their host, and thus adaptive host responses to infection can be ruled out. In laboratory trials, snails infected with Apatemon sp. I moved a shorter total distance during the experimental period than uninfected control snails. However, all three trematode species similarly neutralised the attraction to lighted areas shown by uninfected snails, and none of the trematodes affected the time spent moving by their host or its responses to predator cues. Overall, there was little evidence for species‐specific effects on host behaviour by the three different trematode species in the same snail host. The single difference in induced behavioural change, involving one trematode species and one specific behavioural measure, is insufficient to reject the hypothesis that the behavioural impacts on the snail host are general and non‐adaptive by‐products of trematode infection.

Relative importance of chemical attractiveness to parasites for susceptibility to trematode infection.

While the host immune system is often considered the most important physiological mechanism against parasites, precontact mechanisms determining exposure to parasites may also affect infection dynamics. For instance, chemical cues released by hosts can attract parasite transmission stages. We used the freshwater snail Lymnaea stagnalis and its trematode parasite Echinoparyphium aconiatum to examine the role of host chemical attractiveness, physiological condition, and immune function in determining its susceptibility to infection. We assessed host attractiveness through parasite chemo‐orientation behavior; physiological condition through host body size, food consumption, and respiration rate; and immune function through two immune parameters (phenoloxidase‐like and antibacterial activity of hemolymph) at an individual level. We found that, although snails showed high variation in chemical attractiveness to E. aconiatum cercariae, this did not determine their overall susceptibility to infection. This was because large body size increased attractiveness, but also increased metabolic activity that reduced overall susceptibility. High metabolic rate indicates fast physiological processes, including immune activity. The examined immune traits, however, showed no association with susceptibility to infection. Our results indicate that postcontact mechanisms were more likely to determine snail susceptibility to infection than variation in attractiveness to parasites. These may include localized immune responses in the target tissue of the parasite. The lack of a relationship between food consumption and attractiveness to parasites contradicts earlier findings that show food deprivation reducing snail attractiveness. This suggests that, although variation in resource level over space and time can alter infection dynamics, variation in chemical attractiveness may not contribute to parasite‐induced fitness variation within populations when individuals experience similar environmental conditions.