Fascioliasis Due toFasciola hepaticaandFasciola giganticaInfection: An Update on This ‘Neglected’ Neglected Tropical Disease

Molecular and biochemical characterizations of a Fasciola gigantica retinoid X receptor-α isoform A (FgRXRα-A)

Fascioliasis is a parasitic infection in animals and humans caused by the parasitic flatworm genus Fasciola, which has two major species, F. hepatica and F. gigantica. A major concern regarding this disease is drug resistance, which is increasingly reported worldwide. Hence, the discovery of a novel drug as well as drug targets is crucially required. Therefore, this study aims to characterize the novel drug target in the adult F. gigantica. In the beginning, we hypothesized that the parasite might interact with some host molecules when it lives inside the liver parenchyma or bile ducts, specifically hormones and hormone-like molecules, through the specific receptors, primarily nuclear receptors (NRs), which are recognized as a major drug target in various diseases. The retinoid X receptor (RXR) is a member of subfamily 2 NRs that plays multitudinous roles in organisms by forming homodimers or heterodimers with other NRs. We obtained the full-length amino acid sequences of F. gigantica retinoid X receptor-alpha (FgRXRα-A) from the transcriptome of F. gigantica that existed in the NCBI database. The FgRXRα-A were computationally predicted for the basic properties, multiple aligned, phylogeny analyzed, and generated of 2D and 3D models. Moreover, FgRXRα-A was molecular cloned and expressed as a recombinant protein (rFgRXRα-A), then used for immunization for specific polyclonal antibodies. The native FgRXRα-A was detected in the parasite extracts and tissues, and the function was investigated by in vitro binding assay. The results demonstrated the conservation of FgRXRα-A to the other RXRs, especially RXRs from the trematodes. Interestingly, the native FgRXRα-A could be detected in the testes of the parasite, where the sex hormones are accumulated. Moreover, the binding assay revealed the interaction of 9-cis retinoic acid and FgRXRα-A, suggesting the function of FgRXRα-A. Our findings suggested that FgRXRα-A will be involved with the sexual reproduction of the parasite by forming heterodimers with other NRs, and it could be the potential target for further drug development of fascioliasis.

Fasciola gigantica Cathepsin L1H: High Sensitivity and Specificity of Immunochromatographic Strip Test for Antibody Detection

Fasciolosis is a zoonotic disease caused by Fasciola gigantica or F. hepatica infections, which are frequently occurring parasites in animals and humans. The present gold-standard diagnostic technique involves finding parasite eggs through microscopy. However, this method is also restricted due to low specificity and low sensitivity. An alternative to coprological diagnosis is the immunochromatographic strip (ICS) test, which is rapid, simple, convenient, and cost-effective, with high sensitivity and high specificity. Cathepsin L1H (CathL1H) is a cysteine protease secreted by F. gigantica, which is found in high amounts in newly excysted juvenile (NEJ) and juvenile stages. Cathepsin L1H plays an important role in both the immune response to invading pathogens and in the ability of some pathogens to evade the host immune system. The present study aims to develop an ICS test and detect antibodies against CathL1H in mice and cattle serum using the recombinant F. gigantica Cathepsin L1H (rFgCathL1H) and rabbit anti-rFgCathL1H antibody. The F. gigantica-infected serum and non-infected serum of mice and cattle were tested using the ICS test. Moreover, the strip results were confirmed with an indirect enzyme-linked immunosorbent assay (indirect ELISA). The relative sensitivity, specificity, and accuracy of the ICS strip were 97.5, 99.99, and 99.00%, respectively. Therefore, these data suggest that the ICS method could be used to detect F. gigantica antibodies to highly enhance throughput, reduce costs, and determine the best alternative on-site method.

Prevalence and risk factors associated with donkey gastrointestinal parasites in Shashemane and Suburbs, Oromia Region, Ethiopia

Background

Gastrointestinal parasites are the cause of morbidity and mortality in working donkeys and reduce their working performance.

Methods

A cross-sectional study was conducted from November 2020 to July 2021 to assess gastrointestinal parasite infection in working donkeys in Shashemane and the surrounding district. A total of 395 donkeys were randomly sampled for the study, and an examination was conducted using faecal egg count and the Baermann technique.

Results

Out of the 395 sampled donkeys, different types of gastrointestinal parasites were identified. The parasites identified during the study were Strongyle spp. (100%), Oxyuris equi (10.1%), Parascaris equorum (23.8%), Fasciola spp. (0.3%), Gastrodiscus aegyptiacus (4.6%), Strongyloides westeri (47.8%) and Anoplocephala perfoliata (0.5%). Identification of L₃ larvae of GI parasites revealed that Cyathostomes spp. (96.2%), Strongylus vulgaris (92.9%), Trichostrongylus axei (90.4%), Strongylus edentatus (89.4%), and Dictyocaulus arnifieldi (49.6%) were the most prevalent. Infection with one species of helminth was more common (60.8%).

Conclusions

Thus, working donkeys in the present study area were infected with Strongyle spp. (100%), Strongyloides westeri (47.8%), Parascaris equorum (23.8%), Oxyuris equi (10.1%), Gastrodiscus aegyptiacus (4.6%), Anoplocephala perfoliata (0.5%) and Fasciola spp. (0.3%) parasites. Hence, comprehensive donkey health, management, and implementation of appropriate parasite control strategies should be implemented to alleviate these problems.

Transcriptomic analysis supports a role for the nervous system in regulating growth and development of Fasciola hepatica juveniles

Fasciola spp. liver flukes have significant impacts in veterinary and human medicine. The absence of a vaccine and increasing anthelmintic resistance threaten sustainable control and underscore the need for novel flukicides. Functional genomic approaches underpinned by in vitro culture of juvenile Fasciola hepatica facilitate control target validation in the most pathogenic life stage. Comparative transcriptomics of in vitro and in vivo maintained 21 day old F. hepatica finds that 86% of genes are expressed at similar levels across maintenance treatments suggesting commonality in core biological functioning within these juveniles. Phenotypic comparisons revealed higher cell proliferation and growth rates in the in vivo juveniles compared to their in vitro counterparts. These phenotypic differences were consistent with the upregulation of neoblast-like stem cell and cell-cycle associated genes in in vivo maintained worms. The more rapid growth/development of in vivo juveniles was further evidenced by a switch in cathepsin protease expression profiles, dominated by cathepsin B in in vitro juveniles and by cathepsin L in in vivo juveniles. Coincident with more rapid growth/development was the marked downregulation of both classical and peptidergic neuronal signalling components in in vivo maintained juveniles, supporting a role for the nervous system in regulating liver fluke growth and development. Differences in the miRNA complements of in vivo and in vitro juveniles identified 31 differentially expressed miRNAs, including fhe-let-7a-5p, fhe-mir-124-3p and miRNAs predicted to target Wnt-signalling, which supports a key role for miRNAs in driving the growth/developmental differences in the in vitro and in vivo maintained juvenile liver fluke. Widespread differences in the expression of neuronal genes in juvenile fluke grown in vitro and in vivo expose significant interplay between neuronal signalling and the rate of growth/development, encouraging consideration of neuronal targets in efforts to dysregulate growth/development for parasite control.

Molecular identification of cercaria Fasciola gigantica in lymnaeid snails in Kulon Progo, Yogyakarta

Lymnaeid snails play an essential role in transmitting fasciolosis as intermediate hosts. Therefore, this study aims to use the molecular method to identify liver fluke in lymnaeid snails. A total of 320 lymnaeid snails were collected from a rice field. The samples were dissected to collect cercaria and identified using polymerase chain reaction. Furthermore, the internal transcribed spacer 2 (ITS2) was used as the target gene to identify the species of cercaria. The result showed that 3.75% (12/320) of the snails were infected by Fasciola gigantica, while the phylogenetic tree based on ITS2 showed that the cercaria in this study was monophyletic and similar to species from several countries in Southeast Asia, including China. Furthermore, the haplotype network showed that all four cercaria samples were similar with sequences from several countries. This study suggests that the F. gigantica cercaria isolated from lymnaeid snails in Kulon Progo, Yogyakarta, Indonesia, has a sequence similar to that of other species in Southeast Asian countries, although no hybrid type was detected in these sequences. This is the first report on the molecular identification of cercaria F. gigantica isolated from lymnaeid snails in Yogyakarta, Indonesia.

An annotated checklist of the eukaryotic parasites of humans, exclusive of fungi and algae

The classification of "parasites" in the medical field is a challenging notion, a group which historically has included all eukaryotes exclusive of fungi that invade and derive resources from the human host. Since antiquity, humans have been identifying and documenting parasitic infections, and this collective catalog of parasitic agents has expanded considerably with technology. As our understanding of species boundaries and the use of molecular tools has evolved, so has our concept of the taxonomy of human parasites. Consequently, new species have been recognized while others have been relegated to synonyms. On the other hand, the decline of expertise in classical parasitology and limited curricula have led to a loss of awareness of many rarely encountered species. Here, we provide a comprehensive checklist of all reported eukaryotic organisms (excluding fungi and allied taxa) parasitizing humans resulting in 274 genus-group taxa and 848 species-group taxa. For each species, or genus where indicated, a concise summary of geographic distribution, natural hosts, route of transmission and site within human host, and vectored pathogens are presented. Ubiquitous, human-adapted species as well as very rare, incidental zoonotic organisms are discussed in this annotated checklist. We also provide a list of 79 excluded genera and species that have been previously reported as human parasites but are not believed to be true human parasites or represent misidentifications or taxonomic changes.

Pathogenicity and virulence of the liver flukes Fasciola hepatica and Fasciola Gigantica that cause the zoonosis Fasciolosis

Fasciolosis caused by the liver flukes Fasciola hepatica and Fasciola gigantica is one of the most important neglected parasitic diseases of humans and animals. The ability of the parasites to infect and multiply in their intermediate snail hosts, and their adaptation to a wide variety of mammalian definitive hosts contribute to their high transmissibility and distribution. Within the mammalian host, the trauma caused by the immature flukes burrowing through the liver parenchyma is associated with most of the pathogenesis. Similarly, the feeding activity and the physical presence of large flukes in the bile ducts can lead to anemia, inflammation, obstruction and cholangitis. The high frequency of non-synonymous polymorphisms found in Fasciola spp. genes allows for adaptation and invasion of a broad range of hosts. This is also facilitated by parasite’s excretory-secretory (ES) molecules that mediate physiological changes that allows their establishment within the host. ES contains cathepsin peptidases that aid parasite invasion by degrading collagen and fibronectin. In the bile ducts, cathepsin-L is critical to hemoglobin digestion during feeding activities. Other molecules (peroxiredoxin, cathepsin-L and Kunitz-type inhibitor) stimulate a strong immune response polarized toward a Treg/Th2 phenotype that favors fluke’s survival. Helminth defense molecule, fatty acid binding proteins, Fasciola-specific glycans and miRNAs modulate host pro-inflammatory responses, while antioxidant scavenger enzymes work in an orchestrated way to deter host oxidant-mediated damage. Combining these strategies Fasciola spp. survive for decades within their mammalian host, where they reproduce and spread to become one of the most widespread zoonotic worm parasites in the world.

Human Fascioliasis (Liver Fluke Disease) in Hawai'i: Case Report and Review of Human Fascioliasis Acquired in the United States

Fascioliasis is a foodborne zoonotic infection caused by the trematode liver flukes: Fasciola hepatica and Fasciola gigantica (F. gigantica). Infections may cause acute and chronic hepatobiliary tract diseases in herbivore animals and humans. Fascioliasis is present worldwide, particularly in regions where sheep and cattle are raised. The global burden of human fascioliasis is estimated to be 2.7 million. Human infections are rare in the United States, and most infections were acquired abroad. In the 1950s, several human cases of F. gigantica infection were reported from Hawai'i, but no subsequent cases have been reported until the case described here. This case report describes a man from Hawai'i Island who ate raw wild watercress, and 22 days later, developed acute phase fascioliasis with fever, acute hepatitis, peripheral eosinophilia, and hypodense lesions seen on liver diagnostic imaging. Immunodiagnostic tests were positive for Fasciola species. Based on earlier reports from Hawai'i, F. gigantica infection was likely. Clinical abnormalities resolved after treatment with triclabendazole. Physicians should consider fascioliasis in immigrants and travelers from endemic areas with acute hepatitis and eosinophilia after eating raw wild watercress or chronic hepatobiliary disease. Hepatobiliary imaging and serological testing are useful for diagnosis. Oral triclabendazole is the preferred treatment. Animal fascioliasis appears to be spreading in the United States, and the popularly perceived health benefits of eating raw wild watercress and other aquatic plants may lead to more human infections. The rarity of human infections in Hawai'i suggests that it is safe to eat commercially grown watercress cultivated in Hawai'i.

Imaging findings of human hepatic fascioliasis: a case report and review of the literature

Background

Fascioliasis is a food-borne hepatobiliary zoonosis caused by Fasciola hepatica and Fasciola gigantica. Human infestations are predominantly seen in developing countries where the disease is endemic, but, due to the increase in international travel rates, hepatic fascioliasis is also appearing in nonendemic areas including Europe and the USA. The clinical and laboratory findings are usually nonspecific. Cross-sectional imaging can be very helpful in the diagnosis of fascioliasis as well as to differentiate it from other liver diseases with a very similar clinical picture. The objectives of this case report are to discuss imaging findings of hepatic fascioliasis and to review the literature.

Case presentation

We report the case of a 35-year-old Iranian patient who presented with right upper quadrant pain, low-grade fever, fatigue, and anorexia. The patient had a history of recent travel to the Gilan Province of Iran, almost a month before the onset of symptoms, which is an endemic area of fascioliasis in the country. Laboratory examinations revealed eosinophilia, elevated hepatic enzymes, and slightly raised C-reactive protein. Contrast-enhanced computed tomography of the patient shows clusters of focal ill-defined hypodense lesions with mild peripheral enhancement in the right liver lobe and subcapsular regions. Magnetic resonance imaging of the liver revealed multiple ill-defined lesions of low signal intensity on the T1-weighted image and high signal intensity on the T2-weighted image, extending from the liver capsule into deeper parenchyma toward periportal regions, which shows mild peripheral enhancement on post-contrast images. Imaging-based diagnosis of fascioliasis was made depending on the characteristic distribution of subcapsular tracts/lesions on the above-mentioned imaging, which was then confirmed by serologic tests using enzyme-linked immunosorbent assay. The patient was treated with triclabendazole, showing great clinical improvement, and was eventually discharged in good health condition.

Conclusion

The imaging findings in this case report highlight the importance of cross-sectional imaging for further evaluation of suspected cases of fluke-induced liver disease. The hypothesis of hepatic fascioliasis should be always considered when consistent radiological findings are observed. Clusters of tortuous subcapsular lesions with peripheral contrast enhancement extending into deeper liver parenchyma are characteristic imaging findings that strongly suggest hepatic fascioliasis.

Identification and characterization of cytosolic malate dehydrogenase from the liver fluke Fasciola gigantica

The liver fluke zoonoses, Fasciola spp. are parasitic helminths infecting humans and animals globally. Recent sequencing of the genome of Fasciola gigantica has provided a basis to understand the biochemistry of this parasite. Here, we identified the cytosolic malate dehydrogenase in F. gigantica (FgMDH) and characterized the enzyme biochemically and structurally. F. gigantica encodes a single cytosolic MDH, a key enzyme of the citric acid cycle. It catalyzes the reversible oxidation of malate to oxaloacetate using NAD⁺. The Fgmdh gene was amplified and cloned for expression of the recombinant protein. The purified protein showed a molecular weight of ~ 36 kDa that existed in a dimeric form in solution. The recombinant enzyme was catalytically active as it catalyzed both forward and reverse reactions efficiently. The kinetic parameters were determined for both directions. The structure of FgMDH and human MDH were modeled and validated. The superimposition of both the model structures showed overall structural similarity in the active site loop region, however, the conformation of the residues was different. Molecular docking elucidated the binding sites and affinities of the substrates and cofactors to the enzyme. Simulation of molecular dynamics and principal component analysis indicated the stability of the systems and collective motions, respectively. Understanding the structural and functional properties of MDH is important to better understand the roles of this enzyme in the biochemistry of the parasite.

Designing a vaccine for fascioliasis using immunogenic 24 kDa mu-class glutathione s-transferase

Fascioliasis, caused by the liver fluke Fasciola gigantica, is a significant zoonotic disease of the livestock and human, causing substantial economic loss worldwide. Triclabendazole (TCBZ) is the only drug available for the management of the disease against which there is an alarming increase in drug resistance. No vaccine is available commercially for the protection against this disease. Increasing resistance to TCBZ and the lack of a successful vaccine against fascioliasis demands the development of vaccines. In the present study, a structural immunoinformatics approach was used to design a multi-epitope subunit vaccine using the glutathione S-transferase (GST) protein of Fasciola gigantica. The GST antigen is a safe, non-allergic, highly antigenic, and effective vaccine candidate against various parasitic flukes and worms. The cytotoxic T lymphocytes, helper T lymphocytes, and B-cell epitopes were selected for constructing the vaccine based on their immunogenic behavior and binding affinity. The physicochemical properties, allergenicity, and antigenicity of the designed vaccine were analyzed. To elucidate the tertiary structure of the vaccine, homology modeling was performed, followed by structure refinement and docking against the TLR2 immune receptor. Molecular dynamics simulations showed a stable interaction between the vaccine and the receptor complex. Finally, in silico cloning was performed to evaluate the expression and translation of the vaccine construct in the E. coli expression system. Further studies require experimental validation for the safety and immunogenic behavior of the designed vaccine.

Development of analytical methods GC-MS vs LC-UV for the serum monitoring of an inflammatory glycotoxin (methylglyoxal): A new biomarker of bovine hepatobiliary distomatosis

Two analytical methods; high performance liquid chromatography and gas chromatography were used to determine the content of 2-methylquinoxaline, a methylglyoxal-derived agent in sera from cattle with fascioliasis. Methylglyoxal is a highly mutagenic and cytotoxic reactive dicarbonyl compound formed by non-enzymatic fragmentation of triose phosphate GAP and DHAP during glycolysis which regularly contributes to repositioning the energetic balance between physiological and pathological situations. The aim of this study was to propose the MGO as a new biomarker in the bovine fasciolosis. Strongly infected animals showed a correlation between the relatively high levels of Fasciola hepatica anti-f2 antibody and methylglyoxal compared to unharmed animals. Also, an acute hyperglycemia was recorded and closely related to hepatic parenchyma hyperplasia, inflammation, bile ducts obstruction and scléro-fibrous foci formation.Unlike HPLC, which has shown analytical flaws and irregularities, GC-MS remains an excellent diagnostic tool for detecting and quantifying methylglyoxal in biological fluids. The developed method has been validated under FDA guidelines. A full scan-range was set from m/z 39 to 144/999 and the molecular weight of the 2-methylquinoxaline was identified according to NIST Database and ES. Methylglyoxal was the only analyte successfully quantified in a relatively short run time. It was linear over a concentration range of 0.057-5.7  μg.ml-1with mean recoveries and RSD of 118% and 3.63% respectively. The intra and inter-day assays were satisfying and not exceed 3.00%. Results reflect the degree of precision of our method and indicate that MGO was an important contributor to understand the hepatic failure independently of other serum markers.

Detecting Fasciola hepatica and Fasciola gigantica microRNAs with loop-mediated isothermal amplification (LAMP)

Fascioliasis is a parasitic infection typically caused by two common parasites of class Trematodo, genus Fasciola, namely Fasciola hepatica and Fasciola gigantica. The widespread of these species in water and food makes fascioliasis become a global zoonotic disease that affects 2.4 million people in more than 75 countries worldwide. Typically, F. hepatica and F. gigantica can be recognized by parasitological techniques to detect Fasciola spp. eggs, immunological techniques to detect worm-specific antibodies, or by molecular techniques such as PCR to detect parasitic genomic DNA. Recently, miRNAs have been raised as a key regulator and potential diagnostic biomarkers of diseases, including parasitic infection. An isothermal PCR called loop-mediated isothermal amplification (LAMP) is rapid, sensitive, and its amplification process is so extensive that making LAMP well-suited for field diagnostics. LAMP reactions for miRNA detection have been introduced and were able to detect the target miRNA amounts in the wide range of 1.0 amol to 1.0 pmol, exhibiting high selectivity to differentiate one-base between miRNA sequences. Here, we introduced a modified LAMP to detect a species-specific miRNA of F. hepatica and F. gigantica. Our method did not demand an initial heating step and the reactions had a high sensitivity that greater than 1000 times in comparison to that reported in previous studies. Most importantly, the technique could perform well with parasitic miRNA presenting in bovine serum samples without sophisticated equipment required. These results create a promising technique basis for some novel and simple device to diagnose fascioliasis and other parasitic infection diseases at point-of-care.

Highlights of human ectopic fascioliasis: a systematic review

Fascioliasis is a tropical zoonotic disease caused by the Fasciola parasite. The adult parasite usually resides in the liver and biliary ducts; however, several cases of ectopic fascioliasis (EF) have been reported. This study is a highlight on EF according to the confirmed case reports. In a setting of systematic review, we found 25 eligible articles containing 26 confirmed cases of EF (any date until 30 November 2018), including abdominal and intestinal EF in six cases, skin and subcutaneous tissues in five cases, eye in four cases, brain and pancreas in three cases, neck and lymph node in two cases, and lung, dorsal spine, and peritoneal cavity in one case, respectively. The result indicates that fascioliasis can have diverse ectopic forms and should be more attended in the endemic regions of fascioliasis in order to distinguish from other endemic diseases.

Tissue-specific transcriptome analyses provide new insights into GPCR signalling in adult Schistosoma mansoni

Schistosomes are blood-dwelling trematodes with global impact on human and animal health. Because medical treatment is currently based on a single drug, praziquantel, there is urgent need for the development of alternative control strategies. The Schistosoma mansoni genome project provides a platform to study and connect the genetic repertoire of schistosomes to specific biological functions essential for successful parasitism. G protein-coupled receptors (GPCRs) form the largest superfamily of transmembrane receptors throughout the Eumetazoan phyla, including platyhelminths. Due to their involvement in diverse biological processes, their pharmacological importance, and proven druggability, GPCRs are promising targets for new anthelmintics. However, to identify candidate receptors, a more detailed understanding of the roles of GPCR signalling in schistosome biology is essential. An updated phylogenetic analysis of the S. mansoni GPCR genome (GPCRome) is presented, facilitated by updated genome data that allowed a more precise annotation of GPCRs. Additionally, we review the current knowledge on GPCR signalling in this parasite and provide new insights into the potential roles of GPCRs in schistosome reproduction based on the findings of a recent tissue-specific transcriptomic study in paired and unpaired S. mansoni. According to the current analysis, GPCRs contribute to gonad-specific functions but also to nongonad, pairing-dependent processes. The latter may regulate gonad-unrelated functions during the multifaceted male-female interaction. Finally, we compare the schistosome GPCRome to that of another parasitic trematode, Fasciola, and discuss the importance of GPCRs to basic and applied research. Phylogenetic analyses display GPCR diversity in free-living and parasitic platyhelminths and suggest diverse functions in schistosomes. Although their roles need to be substantiated by functional studies in the future, the data support the selection of GPCR candidates for basic and applied studies, invigorating the exploitation of this important receptor class for drug discovery against schistosomes but also other trematodes.

Soluble expression and purification of a full-length asparaginyl tRNA synthetase from Fasciola gigantica

We report the molecular cloning, expression, and single-step homogeneous purification of a full-length asparaginyl tRNA synthetase (NRS) from Fasciola gigantica (FgNRS). Fasciola gigantica is a parasitic liver fluke of the class Trematoda. It causes fascioliasis that infects the liver of various mammals, including humans. Aminoacyl tRNA synthetases (AARS) catalyze the first step of protein synthesis. They attach an amino acid to its cognate tRNA, forming an amino acid-tRNA complex. The gene that codes for FgNRS was generated by amplification by polymerase chain reaction. It was then inserted in the expression vector pQE30 under the transcriptional control of the bacteriophage T5 promoter and lac operator. M15 Escherichia coli strain transformed with the FgNRS expression vector pQE30-NRS accumulates large amounts of a soluble protein of about 61 kDa. The protein was purified to homogeneity using immobilized metal affinity chromatography. The recombinant protein was further confirmed by immunoblotting with anti-His antibody. Following size exclusion chromatography, the FgNRS was stable and observed to be a dimeric protein. In this study, the expression and purification procedures have provided a simple and efficient method to obtain full-length FgNRS in large quantities. This will provide an opportunity to study the structure, dynamics and function of NRS.

Photomediated Larvicidal Activity of Pheophorbide a against Cercaria Larvae of Fasciola gigantica

Fasciolosis is a parasitic disease caused by Fasciola gigantica. The freshwater snail Lymnaea acuminata is the intermediate host of F. gigantica which cause endemic fasciolosis in the northern part of India. To investigate larvicidal activity of pure and laboratory extracted pheophorbide a (Pa) against cercaria larvae of F. gigantica, data were analyzed in different spectra of visible light, sunlight, and laboratory conditions. Photostimulation of chlorophyll derivative pheophorbide a (Pa) caused time and concentration dependent larvicidal activity against cercaria larvae of F. gigantica. Larvicidal activity of pure Pa under 650 nm and 400-650 nm (8 h LC₅₀ 0.006 mg/10 mL) was more pronounced than extracted Pa under same irradiations (650 nm LC₅₀ 0.12 mg/10 mL, 400-650 nm LC₅₀ 0.14 mg/10 mL). Lowest toxicity of pure (8 h LC₅₀ 0.14 mg/10 mL) and extracted Pa (8 h LC₅₀ 1.25 mg/10 mL) was noted under 400 nm. Pa was found to be toxic in laboratory conditions also. The results presented in this paper indicate that pheophorbide a possess potential larvicidal activity against Fasciola gigantica larvae in different wavelengths of visible light, sunlight, and laboratory conditions.

Stimulating Neoblast-Like Cell Proliferation in Juvenile Fasciola hepatica Supports Growth and Progression towards the Adult Phenotype In Vitro

Fascioliasis (or fasciolosis) is a socioeconomically important parasitic disease caused by liver flukes of the genus Fasciola. Flukicide resistance has exposed the need for new drugs and/or a vaccine for liver fluke control. A rapidly improving ‘molecular toolbox’ for liver fluke encompasses quality genomic/transcriptomic datasets and an RNA interference platform that facilitates functional genomics approaches to drug/vaccine target validation. The exploitation of these resources is undermined by the absence of effective culture/maintenance systems that would support in vitro studies on juvenile fluke development/biology. Here we report markedly improved in vitro maintenance methods for Fasciola hepatica that achieved 65% survival of juvenile fluke after 6 months in standard cell culture medium supplemented with 50% chicken serum. We discovered that this long-term maintenance was dependent upon fluke growth, which was supported by increased proliferation of cells resembling the “neoblast” stem cells described in other flatworms. Growth led to dramatic morphological changes in juveniles, including the development of the digestive tract, reproductive organs and the tegument, towards more adult-like forms. The inhibition of DNA synthesis prevented neoblast-like cell proliferation and inhibited growth/development. Supporting our assertion that we have triggered the development of juveniles towards adult-like fluke, mass spectrometric analyses showed that growing fluke have an excretory/secretory protein profile that is distinct from that of newly-excysted juveniles and more closely resembles that of ex vivo immature and adult fluke. Further, in vitro maintained fluke displayed a transition in their movement from the probing behaviour associated with migrating stage worms to a slower wave-like motility seen in adults. Our ability to stimulate neoblast-like cell proliferation and growth in F. hepatica underpins the first simple platform for their long-term in vitro study, complementing the recent expansion in liver fluke resources and facilitating in vitro target validation studies of the developmental biology of liver fluke.

Parasitic worms require a host organism in order to survive and reproduce. As such, it is difficult to study them outside of a host. Some parasites can be maintained in vitro using cell culture methods; in the case of F. hepatica, previously-reported methods are unsatisfactory because they are difficult to reproduce and unable to support long term growth and development. Here we have developed a new set of methods for maintaining F. hepatica juveniles in vitro. These methods use simple, commonly available reagents and techniques, enabling us to keep fluke alive in vitro for at least 6 months, as well as stimulating the development of characteristics that resemble adult parasites. Over time, our in vitro fluke show changes in the structure and complexity of individual tissues, and the proteins they produce, such that they are more reminiscent of adult, than juvenile fluke. Additionally, we demonstrate that fluke growth is supported by the division of cells resembling stem cells, which have not been reported previously for F. hepatica. This work will support the study of liver fluke, enabling the development of new drugs and vaccines for the treatment of liver fluke infections of humans and animals.

Genotoxic potential of Fasciolagigantica infection in experimentally infected rabbits

A number of parasitic platyhelminthes are known to cause genotoxicity in humans and animals. However no such information is available on tropical liver fluke, Fasciola gigantica, which incurs huge economic losses worldwide. In the present study the genotoxic potential of F. gigantica infection in rabbits, experimentally infected with the metacercarial cysts of this parasite, has been investigated using the standard comet assay and micronucleus (MNi) test on the isolated hepatocytes and the whole blood from the infected rabbits. The tail length of the comet in both hepatocytes and reticulocytes from the infected animals was significantly prominent (p < 0.05) as compared to the controls. About 61.17 % of the hepatocytes from the infected rabbits were positive for MNi formation. A number of blood cells also showed cellular deformities, which were recognised as spicule type, schistocytes, tear drop type, acanthocytes and dumbbell type. It is possible that during the establishment of host-parasite relationship the worms might have released some products which could have contributed to the induction of cellular and DNA damage. However, long term studies are required to understand the serious implications of such an effect caused by F. gigantica, though hepatic carcinoma has not been reported so far due to fasciolosis, however, considering the present results the possibility may not be rule out for the disease progression in this direction.