Trematode Research Articles

STUDIES ON NEW DIGENEAN TREMATODE OF THE GENUS ORIENTOCREADIUM TUBANGI, 1931 PARASITIZING FRESH WATER FISH, CHANNA PUNCTATA (BLOCH.)

Trematode infections occur worldwide. Trematodes, also called flukes, cause various clinical infections in humans. The parasites are so named because of their conspicuous suckers, the organs of attachment (trematos means "pierced with holes"). The present research deals with the detailed description and study of new species Orientocreadium punctatum Sp. Nov. found in the stomach and intestine of Channa punctata (Bloch) from Aurangabad, Osmanabad, Ahmednagar district of M.S. India during Feb., 2005 - Jan., 2007. The present species is comes closer to all the known species of the genus 3 Orientocreadium in having general topography of organs but differs due to elongated, and non-spinose body, sub terminal and spherical oral sucker, Ventral sucker rounded, Pre- pharynx absent, Pharynx muscular, oval, Oesophagus short, genital pore pre-acetabular, testes unequal, post-ovarian, cirrus pouch crescent shaped, ovary oval, pre-testicular, large, behind oral sucker, receptaculum seminis absent, eggs elongated, oval and non-operculated.

Identification of Adult Fasciola spp. Using Matrix-Assisted Laser/Desorption Ionization Time-of-Flight (MALDI-TOF) Mass Spectrometry

Fascioliasis is a neglected trematode infection caused by Fasciola gigantica and Fasciola hepatica. Routine diagnosis of fascioliasis relies on macroscopic identification of adult worms in liver tissue of slaughtered animals, and microscopic detection of eggs in fecal samples of animals and humans. However, the diagnostic accuracy of morphological techniques and stool microscopy is low. Molecular diagnostics (e.g., polymerase chain reaction (PCR)) are more reliable, but these techniques are not routinely available in clinical microbiology laboratories. Matrix-assisted laser/desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) is a widely-used technique for identification of bacteria and fungi; yet, standardized protocols and databases for parasite detection need to be developed. The purpose of this study was to develop and validate an in-house database for Fasciola species-specific identification. To achieve this goal, the posterior parts of seven adult F. gigantica and one adult F. hepatica were processed and subjected to MALDI-TOF MS to create main spectra profiles (MSPs). Repeatability and reproducibility tests were performed to develop the database. A principal component analysis revealed significant differences between the spectra of F. gigantica and F. hepatica. Subsequently, 78 Fasciola samples were analyzed by MALDI-TOF MS using the previously developed database, out of which 98.7% (n = 74) and 100% (n = 3) were correctly identified as F. gigantica and F. hepatica, respectively. Log score values ranged between 1.73 and 2.23, thus indicating a reliable identification. We conclude that MALDI-TOF MS can provide species-specific identification of medically relevant liver flukes.

MicroRNAs expression profiles in Schistosoma japonicum of different sex 14 and 28 days post-infection.

Different miRNAs are involved in the life cycles of Schistosoma japonicum. The aim of this study was to examine the expression profile of miRNAs in individual S. japonicum of different sex before and after pairing (18 and 24 dpi). The majority of differential expressed miRNAs were highly abundant at 14 dpi, except for sja-miR-125b and sja-miR-3505, in both male and female. Moreover, it was estimated that sja-miR-125b and sja-miR-3505 might be related to laying eggs. sja-miR-2a-5p and sja-miR-3484-5p were expressed at 14 dpi in males and were significantly clustered in DNA topoisomerase III, Rap guanine nucleotide exchange factor 1 and L-serine/L-threonine ammonia-lyase. Target genes of sja-miR-2d-5p, sja-miR-31- 5p and sja-miR-125a, which were expressed at 14 dpi in males but particularly females, were clustered in kelch-like protein 12, fructose-bisphosphate aldolase, class I, and heat shock protein 90 kDa beta. Predicted target genes of sja-miR-3483-3p (expressed at 28 dpi in females but not in males) were clustered in 26S proteasome regulatory subunit N1, ATPdependent RNA helicase DDX17. Predicted target genes of sja-miR-219-5p, which were differentially expressed at 28 dpi in females but particularly males, were clustered in DNA excision repair protein ERCC-6, protein phosphatase 1D, and ATPase family AAA domaincontaining protein 3A/B. Moreover, at 28 dpi, eight miRNAs were significantly up-regulated in females compared to males. The predicted target genes of these miRNAs were significantly clustered in heat shock protein 90 kDa beta, 26S proteasome regulatory subunit N1, and protein arginine N-methyltransferase 1. To sum up, differentially expressed miRNAs may have an essential role and provide necessary information on clarifying this trematode's growth, development, maturation, and infection ability to mammalian hosts in its complex life cycle, and may be helpful for developing new drug targets and vaccine candidates for schistosomiasis.

Targeting Kinases in Fasciola hepatica: Anthelminthic Effects and Tissue Distribution of Selected Kinase Inhibitors.

Protein kinases have been discussed as promising druggable targets in various parasitic helminths. New drugs are also needed for control of fascioliasis, a food-borne trematode infection and worldwide spread zoonosis, caused by the liver fluke Fasciola hepatica and related species. In this study, we intended to move protein kinases more into the spotlight of Fasciola drug research and characterized the fasciolicidal activity of two small-molecule inhibitors from human cancer research: the Abelson tyrosine kinase (ABL-TK) inhibitor imatinib and the polo-like 1 (PLK1) inhibitor BI2536. BI2536 reduced viability of 4-week-old immature flukes in vitro, while adult worms showed a blockade of egg production. Together with a significantly higher transcriptional expression of PLK1 in adult compared to immature worms, this argues for a role of PLK1 in fluke reproduction. Both fluke stages expressed ABL1-TK transcripts at similar high levels and were affected by imatinib. To study the uptake kinetic and tissue distribution of imatinib in F. hepatica, we applied matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) for the first time in this parasite. Drug imaging revealed the accumulation of imatinib in different fluke tissues from 20 min to 12 h of exposure. Furthermore, we show that imatinib is metabolized to N-desmethyl imatinib by F. hepatica, a bioactive metabolite also found in humans. Besides the vitellarium, gastrodermal tissue showed strong signal intensities. In situ hybridization demonstrated the gastrodermal presence of abl1 transcripts. Finally, we assessed transcriptional changes of physiologically important genes in imatinib-treated flukes. Moderately increased transcript levels of a gene encoding a multidrug resistance protein were detected, which may reflect an attempt to defend against imatinib. Increased expression levels of the cell cycle dependently expressed histone h2b and of two genes encoding superoxide dismutases (SODs) were also observed. In summary, our pilot study demonstrated cross-stage activity of imatinib but not BI2536 against immature and adult F. hepatica in vitro; a fast incorporation of imatinib within minutes, probably via the oral route; and imatinib-induced expression changes of physiologically relevant genes. We conclude that kinases are worth analyzing in more detail to evaluate the potential as therapeutic targets in F. hepatica.

Exposing the Barcoding Void: An Integrative Approach to Study Snail-Borne Parasites in a One Health Context.

Trematodes are snail-borne parasites of major zoonotic importance that infect millions of people and animals worldwide and frequently hybridize with closely related species. Therefore, it is desirable to study trematodiases in a One Health framework, where human and animal trematodes are considered equally important. It is within this framework that we set out to study the snail and trematode communities in four artificial lakes and an abattoir in Zimbabwe. Trematode infections in snails were detected through multiplex PCR protocols. Subsequently, we identified snails by sequencing a partial mitochondrial cytochrome c oxidase subunit I (COI) fragment, and trematodes (adults from the abattoir and larval stages detected in snails) using COI and nuclear rDNA markers. Of the 1,674 collected snails, 699 were molecularly analyzed, in which we identified 12 snail and 19 trematode species. Additionally, three parasite species were sampled from the abattoir. Merely four trematode species were identified to species level through COI-based barcoding. Moreover, identification of members of the superfamilies Opisthorchioidea and Plagiorchioidea required a phylogenetic inference using the highly conserved 18S rDNA marker, as no related COI reference sequences were present in public databases. These barcoding challenges demonstrate a severe barcoding void in the available databases, which can be attributed to the neglected status of trematodiases. Adding to this, many available sequences cannot be used as different studies use different markers. To fill this gap, more studies on African trematodes, using a standardized COI barcoding region, are desperately needed.

Therapeutic efficacy of praziquantel against trematode infection in one-stripe spiny eel Macrognathus aral

Therapeutic efficacy of praziquantel against trematode infection in one-stripe spiny eel Macrognathus aral

Survey of Stenomelania Fisher, 1885 (Cerithioidea, Thiaridae): The potential of trematode infections in a newly-recorded snail genus at the coast of Andaman Sea, South Thailand

Stenomelania snails (Fisher 1885) have been reported from the coastal regions of the Indian Ocean and the Pacific Ocean, spanning India to Australia. Here, the species diversity and distribution of these snails in the south of Thailand are recorded. The snails were also examined for trematode infections in 13 locations in three Provinces, viz. Krabi, Trang and Satun, along the coast of the Andaman Sea. A total of 1,551 snails were in five morphs tentatively identified as Stenomelania aspirans, S. crenulata, S. punctata, S. torulosa and the closely-related Neoradina prasongi. With 10 infected snails, the trematode infection rate was 0.64%. The cercariae were categorised into three species from two morphologically-distinguishable types, viz. parapleurolophocercous cercariae (Haplorchis taichui and Procerovum cheni) and xiphidiocercariae (Loxogenoides bicolor), through the morphological characterisation of the larval stage. These trematodes were also analysed using the internal transcribed spacer subunit II region to confirm the species identity at generic and infrageneric levels.

Effects of first intermediate host density, host size and salinity on trematode infections in mussels of the south-western Baltic Sea.

Trematode prevalence and abundance in hosts are known to be affected by biotic drivers as well as by abiotic drivers. In this study, we used the unique salinity gradient found in the south-western Baltic Sea to: (i) investigate patterns of trematode infections in the first intermediate host, the periwinkle Littorina littorea and in the downstream host, the mussel Mytilus edulis, along a regional salinity gradient (from 13 to 22) and (ii) evaluate the effects of first intermediate host (periwinkle) density, host size and salinity on trematode infections in mussels. Two species dominated the trematode community, Renicola roscovita and Himasthla elongata. Salinity, mussel size and density of infected periwinkles were significantly correlated with R. roscovita, and salinity and density correlated with H. elongata abundance. These results suggest that salinity, first intermediate host density and host size play an important role in determining infection levels in mussels, with salinity being the main major driver. Under expected global change scenarios, the predicted freshening of the Baltic Sea might lead to reduced trematode transmission, which may be further enhanced by a potential decrease in periwinkle density and mussel size.

Комплексний вплив нітратів і біотичних чинників на активність in vitro війок фронтального миготливого епітелію зябрового апарату Sinanodonta woodiana (Mollusca, Bivalvia, Unionidae)

Effects of MPC, 2 MPC, and 3MPC water solutions of potassium nitrate and biotic factors (trematode infection and “gill pregnancy”) were studied on the duration of locomotion and beat frequency of epithelial cilia of outer demibranchs of Sinanodonta woodiаna (Lea, 1834). The species has recently invaded the system of water bodies of Ukraine. It has occupied numerous water bodies in the Kiliya distributary of Danube Delta, establishing populations of density and biomass. Statistically significant differences by the studied parameters of ciliary epithelium (duration of locomotion and beat frequency of cilia) were not observed in the control group of non-infected males and latent females of S. woodiana. In females with “gill pregnancy”, the duration of ciliary locomotion decreased by 1.5 times, and beat frequency by 1.4 times (P>99.9 %). It should be noted that the outer surface of demibranchs of female mollusks was completely covered by the filled to the brim marsupial pockets. Thus, the functional load of gills is high, leading to the development of compensatory processes in experimental animals. The processes induce increased effectiveness of protective factors that counteract them. Another biotic factor negatively affecting the experimental pond mussels was the high rates of trematode infection in the hosts’ reproductive glands which contained sporocysts and cercariae of Rhipidocotyle campanula Dujardin, 1845. Prevalence of that infection ranged from 50 to 100 %. These rates of infection were associated with sharply declining functions of cilia of the gill epithelium in studied animals. The compound pathogenic influence of parasite and “gill pregnancy” factors even more affected the functional parameters of outer gill ciliary epithelium. The MPC levels of toxicant in the water medium were accompanied with the first symptom of intoxication of the Chinese pond mussel, the stage of stimulation. At that point, the functional parameters of epithelial cilia of “pregnant” females and in moderately and weakly infected mollusks of both sexes increased in response to exposure to the toxic factor. With the growing concentrations of toxicant to 2 MPC and 3 MPC, the experimental pond mussels developed the pathological process of intoxication, which progressed from the stage of depression to sublethal and lethal stages. Accordingly, the locomotion activity of ciliary epithelium increasingly declined and, in the end, stopped. The “gill pregnancy” and high rates of trematode infection exacerbated the consequences of the process.

Parasite Assemblages in a Bivalve Host Associated with Changes in Hydrodynamics

Studies on marine community structure and their modulation by horizontal and vertical abiotic gradients have focused on free-living species, neglecting parasites despite their important role in ecosystems. Field observations, a laboratory flume experiment and modelling were used to examine parasite infection patterns related to host tidal and spatial position along a Portuguese coastal lagoon (Ria de Aveiro). Cockles (Cerastoderma edule) and trematodes were used as a host-parasite model to test the hypotheses: (1) higher infection levels in subtidal cockles, positioned downstream and (2) higher current velocity in downstream areas with consequent higher cockle infection. Cockles were collected from two spatial and tidal positions in two seasons. The relationship between current velocity and cockle infection was examined experimentally by exposing cockles to cercariae of Himasthla elongata at two current velocities. Intertidal cockles displayed higher infection, highlighting vertical position as an important driver of infection possibly due to first host proximity and/or trematode life cycle facilitation (higher cockle exposure to final host predation). The hydrodynamic model showed that the Ria de Aveiro was abiotically heterogenous with cockles displaying higher infection levels in the downstream area. Multiple regression analysis demonstrated a positive correlation between salinity, dissolved oxygen, current velocity and trematode abundance. The influence of current velocity on infection success was corroborated experimentally. The present study demonstrated the importance of host vertical and horizontal position on trematode infection, highlighting the positive influence of current velocity by supporting settlement and promoting favourable abiotic conditions.

Adult Trematodes (Platyhelminthes) of freshwater fishes from Argentina: a checklist

This work provides information on the occurrence of adult trematodes (Aspidogastrea and Digenea) in freshwater fishes from Argentina. To date, a total of 77 trematode species belonging to 21 families have been recorded. Haploporidae, Allocreadiidae and Cryptogonimidae (15, nine and nine species, respectively) showed the highest species richness, whereas the number of species ranged from one to seven species for the other 18 families. Of these, five new species have been recently described in Argentina; nine were cited for the first time; 17 had new host records, and 28 were reported from new localities. The orders Characiformes, Perciformes and Siluriformes harboured the highest richness of trematode species.

How costly are metacercarial infections in a bivalve host? Effects of two trematode species on biochemical performance of cockles

Bivalve stocks have been decreasing in the last decades largely due to emergent diseases and consequent mass mortality episodes. Cerastoderma edule (the edible cockle) is one of the most exploited bivalves in Europe and is among the most common hosts for trematodes, the most prevalent macroparasites in coastal waters but yet poorly studied. Therefore, in the present study, this bivalve species was used as host model to determine if trematode infection exerts a negative effect on bivalve energy metabolism and balance and if the tissues targeted by different trematodes influence the metabolic cost, with physiological and biochemical consequences. Cockles were experimentally infected with two trematode species, Himasthla elongata and Renicola roscovitus, that infect the foot and palps, respectively. Trematode infection exerted a negative effect on the metabolism of C. edule, the second intermediate host, by reduction of oxygen consumption. A different host biochemical response was found depending on trematode species, especially in regard to the level of oxygen consumption decrease and the preferential accumulation of lipids and glycogen. This study represents a step towards the understanding of host-trematode relationships that can be used to better predict potential conservation threats to bivalve populations and to maximize the success of stock and disease management.

Prevalence of Gastrointestinal Helminth Parasites in Gallus gallus domesticus in Lucknow, U. P, India

Poultry industry occupies an important position in the provision of animal protein and plays a vital role in the national economy. Helminthiasis caused by helminth parasites is one of the most common infections affecting health of poultry and indirectly leading to great economic loss among small livestock holders. The prevalence of gastrointestinal helminth parasites in Gallus gallus domesticus was studied from January 2017 to December 2019 in the parasitology laboratory of Zoology Department, Babasaheb Bhimrao Ambedkar University, Lucknow, India. In this study, a total of 557 domestic fowls were examined to identify the different types of gastrointestinal helminth infections. During regular examination of helminth parasites, the highest prevalence was observed for Ascaridia galli (41.7%), followed by Cotugnia diagnopora (17.6%), Raillietina tetragona (11%), Heterakis gallinarum (7.4%) and Raillietina cesticillus (6.64%). In the monsoon season, prevalence was found to be higher than the summer and winter. Females were found to be more infected than the males. There was no trematode infection detected during the study period. The gross pathological lesions were observed in case of Heterakis gallinarum infection. The results of this study suggest that both nematodes and cestodes are prevalent in domestic fowls in the studied area.

No evidence for a dilution effect of the non-native snail, Potamopyrgus antipodarum, on native snails.

The dilution effect can occur by a range of mechanisms and results in reduced parasite prevalence in host taxa. In invaded ecosystems, the dilution effect can benefit native species if non-native species, acting as resistant or less competent hosts, reduce rates of parasitic infections in native species. In field experiments, we assessed whether manipulating biomass of the non-native snail, Potamopyrgus antipodarum, caused a dilution effect by reducing trematode infections in three taxa of native snails. In contrast to many studies showing resistant or less competent non-native hosts can “dilute” or reduce infection rates, we found no evidence for a dilution effect reducing infection rates of any of the native snails. We suggest that a dilution effect may not have occurred because most trematode taxa are highly host specific, and thus the trematode transmission stages did not recognize the invasive snail as a possible host. In this case, community composition appears to be important in influencing the dilution effect.

Rapid detection of Galba truncatula in water sources on pasture-land using loop-mediated isothermal amplification for control of trematode infections

BackgroundFascioliasis caused by the trematodes Fasciola hepatica and F. gigantica, is a global neglected zoonotic disease estimated to cost the livestock industry over €2.5 billion annually. Farm management measures and sustainable use of anthelmintics can, in principle, effectively control trematode infection in livestock and reduce the rate of developing anthelmintic resistance. Previously, we designed an environmental DNA (eDNA) assay to identify a common trematode intermediate host, the freshwater snail Galba truncatula, in water sources to measure specific trematode infection risk areas on pasture-land. To improve this procedure, we now report a loop-mediated isothermal amplification (LAMP) assay to identify G. truncatula eDNA.MethodsA LAMP assay was designed and optimised (e.g. temperature, time duration and primer concentration) to identify G. truncatula DNA. The ability of the LAMP assay to target G. truncatula DNA was identified, and LAMP assay limit of detection was investigated in comparison to conventional PCR. In the field, 48 water samples were collected from stream, ditch and water pool habitats in four locations at two Aberystwyth University farms over a seven week period to investigate the applicability of the LAMP assay for use on eDNA samples, in comparison to conventional PCR.ResultsThe LAMP assay delivered detectable results in 30 min at 63 °C. The assay discriminated between G. truncatula DNA and non-target DNA, presenting a level of DNA detection comparable to conventional PCR. No significant difference was found between the ability of the LAMP and PCR assay to identify G. truncatula eDNA in water samples. Kappa coefficient analysis revealed a moderate level of agreement between LAMP and PCR assays.ConclusionsThis study demonstrated that the LAMP assay can detect G. truncatula eDNA in a simple and rapid manner. The LAMP assay may become a valuable tool to determine optimum pasture management for trematode parasite control.

Disease's hidden death toll: Using parasite aggregation patterns to quantify landscape-level host mortality in a wildlife system.

World-wide, infectious diseases represent a major source of mortality in humans and livestock. For wildlife populations, disease-induced mortality is likely even greater, but remains notoriously difficult to estimate-especially for endemic infections. Approaches for quantifying wildlife mortality due to endemic infections have historically been limited by an inability to directly observe wildlife mortality in nature. Here we address a question that can rarely be answered for endemic pathogens of wildlife: what are the population- and landscape-level effects of infection on host mortality? We combined laboratory experiments, extensive field data and novel mathematical models to indirectly estimate the magnitude of mortality induced by an endemic, virulent trematode parasite (Ribeiroia ondatrae) on hundreds of amphibian populations spanning four native species. We developed a flexible statistical model that uses patterns of aggregation in parasite abundance to infer host mortality. Our model improves on previous approaches for inferring host mortality from parasite abundance data by (i) relaxing restrictive assumptions on the timing of host mortality and sampling, (ii) placing all mortality inference within a Bayesian framework to better quantify uncertainty and (iii) accommodating data from laboratory experiments and field sampling to allow for estimates and comparisons of mortality within and among host populations. Applying our approach to 301 amphibian populations, we found that trematode infection was associated with an average of between 13% and 40% population-level mortality. For three of the four amphibian species, our models predicted that some populations experienced >90% mortality due to infection, leading to mortality of thousands of amphibian larvae within a pond. At the landscape scale, the total number of amphibians predicted to succumb to infection was driven by a few high mortality sites, with fewer than 20% of sites contributing to greater than 80% of amphibian mortality on the landscape. The mortality estimates in this study provide a rare glimpse into the magnitude of effects that endemic parasites can have on wildlife populations and our theoretical framework for indirectly inferring parasite-induced mortality can be applied to other host-parasite systems to help reveal the hidden death toll of pathogens on wildlife hosts.

Production and characterization of monoclonal antibodies against highly immunogenic Opisthorchis viverrini proteins and development of coproantigen detection

Opisthorchis viverrini and other foodborne trematode infections are major health concerns in the Greater Mekong Subregion. Currently, the gold-standard diagnostic method for opisthorchiasis is conventional stool examination for the presence of parasite eggs. This method lacks sensitivity and needs an experienced technician. We therefore produced monoclonal antibodies to highly immunogenic O. viverrini proteins aiming at detecting specific antigens in the feces. In this study, BALB/C mice were immunized using semi-purified somatic antigens and spleen cells were fused with a Sp2/0 myeloma cell line. Four hybridomas (1A2, 1E12, 2C7 and 8D6) were selected and cloned due to their strong reaction against O. viverrini somatic protein, resulting in three IgM clones and one IgG2 clone. Immunohistochemistry showed that 1A2, 1E12, 2C7 and 8D6 stained the parenchyma cells, gut, tegument and muscles, respectively. Western-blot analysis revealed that only antibody 1A2 could detect coproantigen (approx. 73 kDa protein) in feces of hamsters infected with O. viverrini. The 1A2 monoclonal antibody may be of value in the diagnosis of opisthorchiasis by coproantigen detection.

Prevalence of Liver Trematode Infections in Cattle in the Province of Ağrı in Turkey

This study was conducted to determine the prevalence of distomatosis in cattle in the Ağrı province in Turkey. The livers and bile ducts of 200 slaughtered cattle were examined macroscopically, and the gall bladders were examined by sedimentation. The presence of Fasciola hepatica eggs and antigens in 188 cattle were investigated using sedimentation and coproantigen ELISA, respectively. Egg counts per gram of faeces (EPG) was determined using the modified McMaster sedimentation method. Adult Fasciola hepatica and Dicrocoelium dendriticum were found in the bile ducts of 47 and 25 cattle, respectively. Examination of the gall bladders of cattle revealed the presence of eggs of Fasciola hepatica and D. dendriticum in 63 and 48 cattle, respectively. The coproantigens of Fasciola hepatica were found in 148 (78.7%) cattle using ELISA. Additionally, the eggs of F. hepatica were found in 63 (33.5%) cattle by sedimentation, with the value of EPG between 17 and 83. The prevalence of D. dendriticum was determined as 25.5%, with the value of EPG between 17 and 67. In this study, distomatosis was detected in cattle in Ağrı province using coproantigen ELISA and sedimentation methods along with macroscopic examination. The findings necessitate an urgent implementation of an effective prevention and control program, which can increase the awareness of cattle breeders regarding these diseases. Furthermore, there is also a need for more detailed studies on these diseases.

Zoonotic Transmission and Infection from Bovine Feces in Selected Ricefields of Lake Mainit, Philippines

Ricefields are suitable nidus of active parasite transmission via bovines due to often unprotected exposure by humans and livestock that utilize the habitat for farming and foraging. This study was conducted to assess infection of protozoans, trematodes and nematodes from bovine feces from ricefields of Brgy Magpayang, San Isidro and Matin-ao surrounding Lake Mainit, Philippines. Bovine fecal samples collected from these ricefields were processed using the Formalin Ethyl Acetate Sedimentation (FEA-SD) technique. A total of five species from three major parasite groups (protozoans, trematodes and nematodes) were observed. Bovines from ricefields of Brgy San Isidro harbored the highest number of fecal parasites. The liver fluke Fasciola sp. was the most predominant species observed with the highest prevalence (69%) across study areas. In contrast, multiple parasite burden of Fasciola sp., hookworms, coccidian oocysts and Ascaris sp. eggs were observed from bovines from Brgy San Isidro and Matin-ao. This study is the first report of parasites from bovine feces in selected ricefields of Lake Mainit. The high prevalence of Fasciola eggs in bovines calls for an extensive assessment of possible widespread bovine fascioliasis in the area.

Temperature–parasite interaction: do trematode infections protect against heat stress?

Blue mussels (Mytilus edulis) are important ecosystem engineers along Atlantic coastlines, where they are regularly subjected to rapid changes in temperature during the transition between tides. Global climate change and more frequent extreme weather events are expected to intensify this thermal stress even further. These increases in temperatures will not only affect intertidal mussels directly but also increase transmission dynamics of their parasites. Together, the effects of rises in temperature and parasitism will likely result in higher pressure on M. edulis and their ability to perform vital ecosystem services. In a set of experiments, we tested the effects of infections with the trematode Himasthla elongata and high temperatures during low tide air-exposure. Overall, we hypothesised that temperature and parasite infection intensity would each have significant negative effects on M. edulis survival, and that both stressors together would have a synergistic detrimental impact. Overall, high temperature levels had a strong negative effect on mussel survival. However, our results revealed a surprisingly more complex picture in infected individuals. While moderate parasite loads and increased temperature showed additive negative effects on mussel survival, high parasite infection intensities appeared to nullify the detrimental effects of temperature stress on mussels. Under climate warming, these benefits of parasites might actually outweigh the costs of infection and prove beneficial. Overall, these results suggest that the interactions between host–parasite systems and their changing environment are much more complex than a simple additive effect of multiple stressors.