Genomics and molecular genetics of Clonorchis sinensis: current status and perspectives

MicroRNAs in opisthorchiids and their definitive hosts: Current Status and Perspectives

Opisthorchis felineus, Opisthorchis viverrini, and Clonorchis sinensis (family Opisthorchiidae) are parasitic flatworms that pose serious threats to humans in certain countries and cause opisthorchiasis/clonorchiasis. Opisthorchiid flukes parasitize the biliary tract of the host, causing cholangitis, cholecystitis, cholelithiasis and cholangiocarcinoma. In this review, we primarily focus on recent microRNAs (miRNAs) studies of opisthorchiid flukes and their definitive hosts. Many miRNAs are conserved and expressed in a developmentally stage specific manner in the three opisthorchiid flukes, which play important roles in the growth and development of Opisthorchiidae spp., as well as host-pathogen interactions. Some miRNAs might be potential biomarkers related to carcinogenesis of cholangiocarcinoma. Therefore, this review provides the basis for further investigating the roles of miRNAs in opisthorchiid flukes and their definitive hosts, as well as promoting the development of novel approaches to prevent and treat opisthorchiasis/clonorchiasis.

Liver Flukes: Clonorchis and Opisthorchis

Clonorchis sinensis, Opisthorchis viverrini and O. felineus are liver flukes of human and animal pathogens occurring across much of Europe and Asia. Nevertheless, they are often underestimated compared to other, better known neglected diseases in spite of the fact that many millions of people are infected and hundreds of millions are at risk. This is possibly because of the chronic nature of the infection and disease and that it takes several decades prior to a life-threatening pathology to develop. Several studies in the past decade have provided more information on the molecular biology of the liver flukes which clearly lead to better understanding of parasite biology, systematics and population genetics. Clonorchiasis and opisthorchiasis are characterized by a chronic infection that induces hepatobiliary inflammation, especially periductal fibrosis, which can be detected by ultrasonography. These chronic inflammations eventually lead to cholangiocarcinoma (CCA), a usually fatal bile duct cancer that develops in some infected individuals. In Thailand alone, opisthorchiasis-associated CCA kills up to 20,000 people every year and is therefore of substantial public health importance. Its socioeconomic impacts on impoverished families and communities are considerable. To reduce hepatobiliary morbidity and CCA, the primary intervention measures focus on control and elimination of the liver fluke. Accurate diagnosis of liver fluke infections in both human and other mammalian, snail and fish intermediate hosts is important for achieving these goals. While the short-term goal of liver fluke control can be achieved by praziquantel chemotherapy, a comprehensive health education package targeting school children is believed to be more beneficial for a long-term goal/solution. It is recommended that transdisciplinary research or multisectoral control approach including one health and/or eco health intervention strategy should be applied to combat the liver flukes and hence contribute to reduction of CCA in endemic areas.

Diagnosis of Human Trematode Infections

Digenetic trematodes form a major group of human parasites, affecting a large number of humans, especially in endemic foci. Over 100 species have been reported infecting humans, including blood, lung, liver and intestinal parasites. Traditionally, trematode infections have been diagnosed by parasitological methods based on the detection and the identification of eggs in different clinical samples. However, this is complicated due to the morphological similarity between eggs of different trematode species and other factors such as lack of sensitivity or ectopic locations of the parasites. Moreover, the problem is currently aggravated by migratory flows, international travel, international trade of foods and changes in alimentary habits. Although efforts have been made for the development of immunological and molecular techniques, the detection of eggs through parasitological techniques remains as the gold standard for the diagnosis of trematodiases. In the present chapter, we review the current status of knowledge on diagnostic techniques used when examining feces, urine, and sputum and also analyze the most relevant characteristics used to identify eggs with a quick key for the identification of eggs.

The NF-κB signalling pathway and TM7SF3 contribute to liver fibrosis caused by secreted phospholipase A2 of Clonorchis sinensis

Background

The NF-κB signalling pathway has been reported to be related to liver fibrosis, and we investigated whether the NF-κB signalling pathway is involved in liver fibrosis caused by secreted phospholipase A2 of Clonorchis sinensis (CssPLA2). Furthermore, expression of the receptor of CssPLA2 on the cell surface of hepatic stellate cells (HSCs) may greatly contribute to liver fibrosis.

Methods

CssPLA2 was administered to BALB/c mice by abdominal injection. The levels of markers of NF-κB signalling pathway activation in mouse liver tissue were measured by quantitative RT-PCR, ELISA and western blot. Additionally, HSCs were incubated with CssPLA2, and an NF-κB signalling inhibitor (BAY 11-7082) was applied to test whether the NF-κB signalling pathway plays a role in the effect of CssPLA2. Then, the interaction between CssPLA2 and its receptor transmembrane 7 superfamily member 3 (TM7SF3) was confirmed by co-immunoprecipitation (co-IP) and GST pull-down. To determine how TM7SF3 influences the ability of CssPLA2 to cause liver fibrosis, a TM7SF3 antibody was used to block TM7SF3.

Results

The levels of the NF-ΚB signalling pathway activation markers TNF-α, IL-1β and phospho-p65 were increased by CssPLA2 in the context of liver fibrosis. In addition, the interaction between TM7SF3 and CssPLA2 was confirmed by co-IP and GST pull-down. When TM7SF3 was blocked by an antibody targeting 1–295 amino acids of TM7SF3, activation of HSCs caused by CssPLA2 was alleviated.

Conclusions

The NF-ΚB signalling pathway is involved in the activation of HSCs by CssPLA2. TM7SF3, the receptor of CssPLA2, plays important roles in liver fibrosis caused by CssPLA2.

Molecular characterization and immunodiagnostics of Dicrocoelium dendriticum species isolated from sheep of north-west Himalayan region

Despite its extensive presence among grazing ruminants, dicrocoeliosis, also known as 'small liver fluke' disease, is poorly known and often underestimated by researchers and practitioners in many countries. The accurate identification and prepatent diagnosis of Dicrocoelium dendriticum infection is an essential prerequisite for its prevention and control. In the present study, the morphologically identified specimens isolated from the bile ducts of sheep (Ovis aries) were validated through molecular data. The sequence analysis of the second internal transcribed spacer (ITS-2) of our isolates showed a high degree of similarity with D. dendriticum using the BLAST function of the National Center for Biotechnology Information (NCBI). The phylogenetic analysis of our isolates showed a close relationship with previously described D. dendriticum isolates from different countries. The antigenic profiles of somatic and excretory/secretory (E/S) antigens of D. dendriticum were revealed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting using sera from sheep naturally infected with D. dendriticum. By SDS-PAGE, 16 distinct bands were revealed from crude somatic fraction. Immunoblotting analysis of these proteins with positive sera exhibited six seroreactive bands ranging from 27 to 130 kDa. Among these, the 84 and 130 kDa bands were quite specific, with high diagnostic specificity and sensitivity. The E/S fraction comprised nine distinct bands, as revealed by SDS-PAGE analysis. Immunoblotting analysis of these proteins with positive sera exhibited five antigenic bands ranging from 27 to 130 kDa. Among these, the 130 kDa band was found to be quite specific, with high diagnostic specificity and sensitivity. The present study concludes that the protein bands of 84 and 130 kDa in somatic fraction and 130 kDa in E/S fraction can be used for the immunodiagnostic purpose for this economically important parasite, which may also encourage further studies regarding their vaccine potential.

Diagnosis of Human Trematode Infections

Digenetic trematodes form a major group of human parasites, affecting a large number of humans, especially in endemic foci. Over 100 species have been reported infecting humans, including blood, lung, liver, and intestinal parasites. Traditionally, trematode infections have been diagnosed by parasitological methods based on the detection and the identification of eggs in different clinical samples. However, this is complicated due to the morphological similarity between eggs of different trematode species and other factors such as lack of sensitivity or ectopic locations of the parasites. Moreover, the problem is currently aggravated by migratory flows, international travel, international trade of foods, and changes in alimentary habits. Although efforts have been made for the development of immunological and molecular techniques, the detection of eggs through parasitological techniques remains as the gold standard for the diagnosis of trematodiases. In this chapter, we review the current status of knowledge on diagnostic techniques used when examining feces, urine, and sputum and also analyze the most relevant characteristics used to identify eggs with a quick key for the identification of eggs.

Molecular Identification and Phylogenetic Analysis of Nuclear rDNA Sequences of Clonorchis sinensis Isolates From Human Fecal Samples in Heilongjiang Province, China

Studying the genetic diversity of parasite is important for understanding their biogeography and molecular epidemiology, as well as for establishing disease prevention and control strategies. Clonorchis sinensis is an important foodborne parasite worldwide. However, despite its epidemiological significance, the genetic diversity of C. sinensis has not been well studied from human in northeastern China. In this study, a total of 342 fecal specimens were collected from residents living in five villages in Heilongjiang Province and analyzed for the presence of C. sinensis by PCR amplification and sequencing of the internal transcribed spacer 1 (ITS1) and ITS2 regions of nuclear ribosomal DNA. 21.64% (74/342) of fecal samples were found to be positive for C. sinensis by PCR. The sequences of the ITS1 region in 34 of the 74 samples (45.95%) matched that of MK179278, Genetic polymorphisms were observed at six nucleotide sites. The ITS2 gene sequence of 37 of the 74 samples (50%) matched that of MK179281. In conclusion, a low degree of genetic diversity between C. sinensis isolates from China and different geographical regions was found at ITS loci. Despite this conservation, sequencing of the rDNA region has provided important data that will be useful for future studies addressing the molecular evolution, biology, medical implications and ecology of C. sinensis.

Liver Flukes: Clonorchis and Opisthorchis

Clonorchis sinensis, Opisthorchis viverrini, and O. felineus are liver flukes of human and animal pathogens occurring across much of Europe and Asia. Nevertheless, they are often underestimated compared to other, better known neglected diseases in spite of the fact that many millions of people are infected and hundreds of millions are at risk. This is possibly because of the chronic nature of the infection and disease and that it takes several decades prior to a life-threatening pathology to develop. Several studies in the past decade have provided more information on the molecular biology of the liver flukes which clearly lead to better understanding of parasite biology, systematics, and population genetics. Clonorchiasis and opisthorchiasis are characterized by a chronic infection that induces hepatobiliary inflammation, especially periductal fibrosis, which can be detected by ultrasonography. These chronic inflammations eventually lead to cholangiocarcinoma (CCA), a usually fatal bile duct cancer that develops in some infected individuals. In Thailand alone, opisthorchiasis-associated CCA kills up to 20,000 people every year and is therefore of substantial public health importance. Its socioeconomic impacts on impoverished families and communities are considerable. To reduce hepatobiliary morbidity and CCA, the primary intervention measures focus on control and elimination of the liver fluke. Accurate diagnosis of liver fluke infections in both human and other mammalian, snail and fish intermediate hosts, are important for achieving these goals. While the short-term goal of liver fluke control can be achieved by praziquantel chemotherapy, a comprehensive health education package targeting school children is believed to be more beneficial for a long-term goal/solution. It is recommended that a transdisciplinary research or multisectoral control approach including one health and/or eco health intervention strategy should be applied to combat the liver flukes, and hence contribute to reduction of cholangiocarcinoma in endemic areas.

The Regulatory Roles of Toll-Like Receptor 4 in Secretions of Type 1/Type 2 Relative Cytokines by Splenocytes and Dendritic Cells Exposed to Clonorchis sinensis Excretory/Secretory Products

The roles of TLR4 in mediation of innate immune response and in regulation of adaptive immune responses triggered by Clonorchis sinensis remain unknown. In the present study, splenocytes derived from C3H/HeN (TLR4 ^wild ) and C3H/Hej mice (TLR4 ^mut ) that were infected with 45 metacercariae of C. sinensis were harvested, then stimulated by C. sinensis excretory/secretory products (ESP) or medium (control) for 48 h, respectively. Meanwhile, bone marrow-derived dendritic cells (BMDCs) from normal C3H/HeN and C3H/Hej mice were prepared and stimulated with medium, ESP, LPS, or ESP+LPS for 24 h, respectively. The supernatants were collected, and the concentrations of type 1 and type 2 relative cytokines were determined by ELISA. The maturation of BMDCs indicated by surface markers of CD80, CD86, and MHC II was evaluated by flow cytometry. The results showed that the levels of IFN-γ, IL-6, TNF-α, and IL-10 in the splenocytes from C. sinensis-infected TLR4 ^mut mice were significantly lower than those from TLR4 ^wild mice when they were further exposed to ESP. For BMDCs, the productions of the cytokines IL-12p70 and IL-10, but not IL-4, in the BMDCs from TLR4 mutation mice were predominantly decreased compared with those from TLR4 ^wild mice when the BMDCs were co-stimulated by ESP combined with LPS. Flow cytometry analysis showed that ESP could significantly decrease the high levels of CD80, CD86, and MHC II which were elevated by LPS. In conclusion, these data suggest that TLR4 may play a regulatory role in type 1 immune responses during C. sinensis infection.

Research progress of cholangiocarcinoma induced by liver fluke infection

A liver fluke is a digenetic trematode parasitizing in the hepatic ducts of human beings or animals. Patients with liver fluke infection suffer from a series of hepatobiliary diseases. The prevalence of cholangiocarcinoma is significantly high in areas with a high incidence of clonorchiasis. A liver fluke is an important biocarcinogenic factor in the occurrence of cholangiocarcinoma. The secretory products of the body of this parasite and long-term mechanical stimulation induce continuous inflammation of the bile duct. Gene expression of the bile duct cells is imbalanced, leading to carcinogenesis of the bile duct. This article provides a summary of recent studies on the epidemiology, clinicopathology, and molecular biology of cholangiocarcinoma induced by liver fluke infection.

Expression of Clonorchis sinensis GIIIsPLA2 protein in baculovirus-infected insect cells and its overexpression facilitating epithelial-mesenchymal transition in Huh7 cells via AKT pathway

Although prior studies confirmed that group III secretory phospholipase A₂ of Clonorchis sinensis (CsGIIIsPLA₂) had stimulating effect on liver fibrosis by binding to LX-2 cells, large-scale expression of recombinant protein and its function in the progression of hepatoma are worth exploring. Because of high productivity and low lipopolysaccharides (LPS) in the Sf9-baculovirus expression system, we firstly used this system to express the coding region of CsGIIIsPLA₂. The molecular weight of recombinant CsGIIIsPLA₂ protein was about 34 kDa. Further investigation showed that most of the recombinant protein presented intracellular expression in Sf9 insect cell nucleus and could be detected only into cell debris, which made the protein purification and further functional study difficult. Therefore, to study the role of CsGIIIsPLA₂ in hepatocellular carcinoma (HCC) progression, CsGIIIsPLA₂ overexpression Huh7 cell model was applied. Cell proliferation, migration, and the expression level of epithelial-mesenchymal transition (EMT)-related molecules (E-cadherin, N-cadherin, α-catenin, Vimentin, p300, Snail, and Slug) along with possible mechanism were measured. The results indicated that CsGIIIsPLA₂ overexpression not only inhibited cell proliferation and promoted migration and EMT but also enhanced the phosphorylation of AKT in HCC cells. In conclusion, this study supported that CsGIIIsPLA₂ overexpression suppressed cell proliferation and induced EMT through the AKT pathway.

Clonorchis sinensis, an oriental liver fluke, as a human biological agent of cholangiocarcinoma: a brief review

Parasitic diseases remain an unarguable public health problem worldwide. Liver fluke Clonorchis sinensis is a high risk pathogenic parasitic helminth which is endemic predominantly in Asian countries, including Korea, China, Taiwan, Vietnam, and the far eastern parts of Russia, and is still actively transmitted. According to the earlier 8^th National Survey on the Prevalence of Intestinal Parasitic Infections in 2012, C. sinensis was revealed as the parasite with highest prevalence of 1.86% in general population among all parasite species surveyed in Korea. This fluke is now classified under one of the definite Group 1 human biological agents (carcinogens) by International Agency of Research on Cancer (IARC) along with two other parasites, Opisthorchis viverrini and Schistosoma haematobium. C. sinensis infestation is mainly linked to liver and biliary disorders, especially cholangiocarcinoma (CCA). For the purposes of this mini-review, we will only focus on C. sinensis and review pathogenesis and carcinogenesis of clonorchiasis, disease condition by C. sinensis infestation, and association between C. sinensis infestation and CCA. In this presentation, we briefly consider the current scientific status for progression of CCA by heavy C. sinensis infestation from the food-borne trematode and development of CCA.

Current status and perspectives of Clonorchis sinensis and clonorchiasis: epidemiology, pathogenesis, omics, prevention and control

Clonorchiasis, caused by Clonorchis sinensis (C. sinensis), is an important food-borne parasitic disease and one of the most common zoonoses. Currently, it is estimated that more than 200 million people are at risk of C. sinensis infection, and over 15 million are infected worldwide. C. sinensis infection is closely related to cholangiocarcinoma (CCA), fibrosis and other human hepatobiliary diseases; thus, clonorchiasis is a serious public health problem in endemic areas. This article reviews the current knowledge regarding the epidemiology, disease burden and treatment of clonorchiasis as well as summarizes the techniques for detecting C. sinensis infection in humans and intermediate hosts and vaccine development against clonorchiasis. Newer data regarding the pathogenesis of clonorchiasis and the genome, transcriptome and secretome of C. sinensis are collected, thus providing perspectives for future studies. These advances in research will aid the development of innovative strategies for the prevention and control of clonorchiasis.

Molecular testing for clinical diagnosis and epidemiological investigations of intestinal parasitic infections

Over the past few decades, nucleic acid-based methods have been developed for the diagnosis of intestinal parasitic infections. Advantages of nucleic acid-based methods are numerous; typically, these include increased sensitivity and specificity and simpler standardization of diagnostic procedures. DNA samples can also be stored and used for genetic characterization and molecular typing, providing a valuable tool for surveys and surveillance studies. A variety of technologies have been applied, and some specific and general pitfalls and limitations have been identified. This review provides an overview of the multitude of methods that have been reported for the detection of intestinal parasites and offers some guidance in applying these methods in the clinical laboratory and in epidemiological studies.

Genetic variation between and within Triodontophorus brevicauda and Triodontophorus nipponicus revealed by analyses of mtDNA and rDNA gene sequences

Triodontophorus spp. parasitizes the large intestine of equine, causing strongylid diseases. The present study assessed genetic variation in five gene regions within and between Triodontophorus brevicauda and Triodontophorus nipponicus from Heilongjiang Province and the Inner Mongolia Autonomous region. The five gene markers were three mitochondrial (mt) genes, cytochrome c oxidase subunit I (cox1), NADH dehydrogenase subunit 5 (nad5), cytochrome b (cytb); and two ribosomal RNA genes, the internal transcribed spacer 1 (ITS1) and the internal transcribed spacer 2 (ITS2). Partial (p) sequences of cox1, nad5, cytb and the complete ITS rDNA region were PCR amplified from individual nematodes, and the amplicons were subjected to sequencing in both directions. The size of the three mt genes is identical in both species: 761 bp (p cox1), 505 bp (pnad5) and 562 bp (pcytb); the length of the two ribosomal genes is different: 376 bp and 370 bp (ITS1), and 333 bp and 322 bp (ITS2), respectively. Intraspecific variation between T. brevicauda and T. nipponicus was 0-1.5% and 0-1.1% for pcox1, 0-2.0% and 0-2.0% for pnad5, 0-1.4% and 0-2.2% for pcytb, 0-0.8% and 0-1.1% for ITS1 and 0-0.9% and 0-2.2% for ITS2. Interspecific variation within the nematodes was 13.5-14.3% for pcox1, 15.5-18.7% for pnad5, 16.7-18.6% for pcytb, 11.5-13.1% for ITS1 and 16.0-18.4% for ITS2. Phylogenetic analyses based on the combined mt gene sequences, as well as with the ITS sequences, show each species forming a monophyletic group of individuals. However, samples of different species from the same geographical origin did not always cluster together. These results provide valuable information for further studies of systematics and population genetics of the genus Triodontophorus.

Gastropod-Borne Helminths: A Look at the Snail-Parasite Interplay

More than 300 million people suffer from a range of diseases caused by gastropod-borne helminths, predominantly flatworms and roundworms, whose life cycles are characterized by a diversified ecology and epidemiology. Despite the plethora of data on these parasites, very little is known of the fundamental biology of their gastropod intermediate hosts, or of the interactions occurring at the snail-helminth interface. In this article, we focus on schistosomes and metastrongylids of human and animal significance, and review current knowledge of snail-parasite interplay. Future efforts aimed at elucidating key elements of the biology and ecology of the snail intermediate hosts, together with an improved understanding of snail-parasite interactions, will aid to identify, plan, and develop new strategies for disease control focused on gastropod intermediate hosts.

Identification and characterization of Clonorchis sinensis cathepsin B proteases in the pathogenesis of clonorchiasis

BACKGROUND

Human clonorchiasis is a prevailing food-borne disease caused by Clonorchis sinensis infection. Functional characterizations of key molecules from C. sinensis could facilitate the intervention of C. sinensis associated diseases.

METHODS

In this study, immunolocalization of C. sinensis cathepsin B proteases (CsCBs) in C. sinensis worms was investigated. Four CsCBs were expressed in Pichia pastoris yeast cells. Purified yCsCBs were measured for enzymatic and hydrolase activities in the presence of various host proteins. Cell proliferation, wound-healing and transwell assays were performed to show the effect of CsCBs on human cells.

RESULTS

CsCBs were localized in the excretory vesicle, oral sucker and intestinal tract of C. sinensis. Recombinant yCsCBs from yeast showed active enzymatic activity at pH 5.0-5.5 and at 37-42 °C. yCsCBs can degrade various host proteins including human serum albumin, human fibronectin, human hemoglobin and human IgG. CsCBs were detected in liver tissues of mice and cancer patients afflicted with clonorchiasis. Various bioassays collectively demonstrated that CsCBs could promote cell proliferation, migration and invasion of human cancer cells.

CONCLUSION

Our results demonstrated that CsCBs can degrade various human proteins and we proved that the secreted CsCBs are involved in the pathogenesis of clonorchiasis.

Identification of microRNA genes in three opisthorchiids

Background

Opisthorchis felineus, O. viverrini, and Clonorchis sinensis (family Opisthorchiidae) are parasitic flatworms that pose a serious threat to humans in some countries and cause opisthorchiasis/clonorchiasis. Chronic disease may lead to a risk of carcinogenesis in the biliary ducts. MicroRNAs (miRNAs) are small noncoding RNAs that control gene expression at post-transcriptional level and are implicated in the regulation of various cellular processes during the parasite- host interplay. However, to date, the miRNAs of opisthorchiid flukes, in particular those essential for maintaining their complex biology and parasitic mode of existence, have not been satisfactorily described.

Methodology/Principal Findings

Using a SOLiD deep sequencing-bioinformatic approach, we identified 43 novel and 18 conserved miRNAs for O. felineus (miracidia, metacercariae and adult worms), 20 novel and 16 conserved miRNAs for O. viverrini (adult worms), and 33 novel and 18 conserved miRNAs for C. sinensis (adult worms). The analysis of the data revealed differences in the expression level of conserved miRNAs among the three species and among three the developmental stages of O. felineus. Analysis of miRNA genes revealed two gene clusters, one cluster-like region and one intronic miRNA in the genome. The presence and structure of the two gene clusters were validated using a PCR-based approach in the three flukes.

Conclusions

This study represents a comprehensive description of miRNAs in three members of the family Opistorchiidae, significantly expands our knowledge of miRNAs in multicellular parasites and provides a basis for understanding the structural and functional evolution of miRNAs in these metazoan parasites. Results of this study also provides novel resources for deeper understanding the complex parasite biology, for further research on the pathogenesis and molecular events of disease induced by the liver flukes. The present data may also facilitate the development of novel approaches for the prevention and treatment of opisthorchiasis/clonorchiasis.

Liver flukes of the family Opisthorchiidae cause diseases of the hepatobiliary system, known as opisthorchiasis/clonorchiasis. The chronic forms of these diseases greatly increase the risk of cancer developing in the biliary ducts. Much has been elucidated regarding the developmental biology of opisthorchiid flukes and the molecular pathological effects on the definitive host; however, the role of microRNAs (short non-coding RNAs) capable of influencing the pathogenic process and host-parasite interactions have not yet been comprehensively studied. The aim of the present work was to identify the miRNA genes of the liver flukes and provide a basis for further investigating the roles of these miRNAs in the complex opisthorchiidae life cycle and the pathogenesis of disease.

Clonorcis sinensis eggs are associated with calcium carbonate gallbladder stones

Calcium carbonate gallbladder stones were easily neglected because they were previously reported as a rare stone type in adults. The aim of this study was to investigate the relationship between calcium carbonate stones and Clonorchis sinensis infection. A total of 598 gallbladder stones were studied. The stone types were identified by FTIR spectroscopy. The C. sinensis eggs and DNA were detected by microscopic examination and real-time fluorescent PCR respectively. And then, some egg-positive stones were randomly selected for further SEM examination. Corresponding clinical characteristics of patients with different types of stones were also statistically analyzed. The detection rate of C. sinensis eggs in calcium carbonate stone, pigment stone, mixed stone and cholesterol stone types, as well as other stone types was 60%, 44%, 36%, 6% and 30%, respectively, which was highest in calcium carbonate stone yet lowest in cholesterol stone. A total of 182 stones were egg-positive, 67 (37%) of which were calcium carbonate stones. The C. sinensis eggs were found adherent to calcium carbonate crystals by both light microscopy and scanning electron microscopy. Patients with calcium carbonate stones were mainly male between the ages of 30 and 60, the CO2 combining power of patients with calcium carbonate stones were higher than those with cholesterol stones. Calcium carbonate gallbladder stones are not rare, the formation of which may be associated with C. sinensis infection.

Characterization ofDicrocoelium dendriticumisolates from small ruminants in Shaanxi Province, north-western China, using internal transcribed spacers of nuclear ribosomal DNA

The genetic variations in internal transcribed spacers (ITS) spanning ITS-1, 5.8S and ITS-2 rDNA ofDicrocoelium dendriticum, isolated from sheep and goats in four geographical regions in Shaanxi province, were examined. The lengths of ITS-1, 5.8S and ITS-2 rDNA sequences forD. dendriticumwere 749 bp, 161 bp and 234 bp, respectively. Intra-specific sequence variations ofD. dendriticumwere 0–0.5% for ITS-1 and 0–1.3% for ITS-2 rDNA, while the inter-specific variations among species in genusDicrocoeliumin ITS-2 rDNA were 3.4–12.3%. Phylogenetic analysis based on sequences of ITS-2 rDNA showed that allD. dendriticumisolates in the present study were grouped with referenceD. dendriticumisolates from sheep and goats, andD. dendriticumisolates from cattle and Japanese serow were clustered in a sister clade. However, the phylogenetic tree could not reveal geographically genetic relationships ofD. dendriticumisolates in different origins and hosts. These findings provided basic information for further study of molecular epidemiology and control ofD. dendriticuminfection in Shaanxi province as well as in the world.

Phylogenetic analysis of Pomacea canaliculata isolates collected from rice fields in different origins of China by combined mitochondrial 12S and 16S genes

To study the genetic relationships of Pomacea canaliculata collected from rice fields in China, the mitochondrial (mt) 12S and 16S of 9 P. canaliculata isolates from 5 southern provinces in China were sequenced and analyzed. The intra-specific sequence variations of P. canaliculata were 0-1.1% for 12S and 0--0.6% for 16S, while the inter-specific variations among common Pomacea species in mt 12S and 16S were 3.0-11.7% and 2.3-10.1%, respectively. Phylogenetic analysis based on combined sequences of mt 12S and 16S revealed complex genetic structure of P. canaliculata in China. Two phylogenetic groups of P. canaliculata were indicated in China with one group sistered to P. canaliculata isolates from USA, and two groups were even found in the same province. The phylogenetic relationships of Pomacea spp. also could be effectively inferred by combined sequences of mt 12S and 16S. These findings provided basic information for further study of population genetics and diffusion pattern of P. canaliculata in China as well as in the world.

Genetic variability of Baylisascaris schroederi from the Qinling subspecies of the giant panda in China revealed by sequences of three mitochondrial genes

The present study examined the variations in three mitochondrial (mt) DNA sequences, namely cytochrome b (cytb), cytochrome c oxidase subunit 3 (cox3) and NADH dehydrogenase subunit 5 (nad5), among Baylisascaris schroederi isolates from the Qinling subspecies of the giant panda in Shaanxi province, northwestern China. No differences in length were detected in the three mt fragments from different isolates. The intra-specific sequence variations within all B. schroederi samples were 0-2.6% for pcytb, 0-1.8% for pcox3 and 0-2.1% for pnad5, while the inter-specific sequence differences among members of the genus Baylisascaris were 8.2-15.2%, 6.2-15.9% and 8.4-16.0% for pcytb, pcox3, pnad5, respectively. A phylogenetic analysis of the combined sequences of pcytb, pcox3 and pnad 5 showed that all B. schroederi samples in the present study were located in two large clusters, with one cluster containing samples from giant pandas in Sichuan province. These findings provide basic information for further study of molecular epidemiology and control of B. schroederi infection in the Qinling subspecies of the giant panda and throughout China.

A combination of the Kato-Katz methods and ELISA to improve the diagnosis of clonorchiasis in an endemic area, China

Background

Examination of feces by light microscopy is widely used for specific parasitological diagnosis of clonorchiasis. However, the true incidence of infection is underestimated owing to the high missing diagnosis rate of this method. The enzyme-linked immunosorbent assay (ELISA) is widely used for the detection and control of clonorchiasis but the practicality of this method is unclear. The purpose of this study was to evaluate the effect of ELISA as a supplementary method for the diagnosis of clonorchiasis.

Methodology/Principal Findings

The present study recruited 2,359 clinically suspected patients from Heilongjiang Province, China. In all, 954 cases were identified as antibody-positive by immunoglobulin (IgG)-ELISA and 495 individuals were diagnosed as egg-positive by the Kato-Katz (KK) method. The seropositive and egg-negative individuals were re-examined by repeated egg counts and/or the number of KK slides and 18 (18.18%) cases were confirmed as clonorchiasis. The 40.44%, antibody-positive rate determined by IgG-ELISA was significantly higher (P<0.05) than the 21.75% egg-positive rate found by examination of feces. A Bayesian approach indicated that the prevalence of clonorchiasis in this region was 22.27% and that the sensitivity, specificity, positive predictive value and negative predictive value of IgG-ELISA were 98.7%, 76.53%, 54.66% and 99.52%, respectively. The agreement between the two methods was moderate (kappa value = 0.564). The clonorchiasis patients lived mainly along the Songhua River. The risk factors, except for ethnic factors, were estimated effectively by both methods.

Conclusions/Significance

The present study suggested that clonorchiasis was widely distributed in Heilongjiang Province, China. The missing diagnosis rate was high using the KK technique alone. The combination of immunological methods and parasitological techniques could improve diagnostic accuracy and reduce the missing diagnosis rate. ELISA used as an auxiliary diagnostic method was realistic and practical for a large-scale screening test, monitoring the prevalence and assessing the risk factors of clonorchiasis.

Canine and feline parasitic zoonoses in China

Canine and feline parasitic zoonoses have not been given high priority in China, although the role of companion animals as reservoirs for zoonotic parasitic diseases has been recognized worldwide. With an increasing number of dogs and cats under unregulated conditions in China, the canine and feline parasitic zoonoses are showing a trend towards being gradually uncontrolled. Currently, canine and feline parasitic zoonoses threaten human health, and cause death and serious diseases in China. This article comprehensively reviews the current status of major canine and feline parasitic zoonoses in mainland China, discusses the risks dogs and cats pose with regard to zoonotic transmission of canine and feline parasites, and proposes control strategies and measures.

Current status of food-borne trematode infections

Food-borne trematodiases constitute an important group of the most neglected tropical diseases, not only in terms of research funding, but also in the public media. The Trematoda class contains a great number of species that infect humans and are recognized as the causative agents of disease. The biological cycle, geographical distribution, and epidemiology of most of these trematode species have been well characterized. Traditionally, these infections were limited, for the most part, in populations living in low-income countries, particularly in Southeast Asia, and were associated with poverty. However, the geographical limits and the population at risk are currently expanding and changing in relation to factors such as growing international markets, improved transportation systems, and demographic changes. The diagnosis of these diseases is based on parasitological techniques and only a limited number of drugs are currently available for treatment, most of which are unspecific. Therefore, in-depth studies are urgently needed in order to clarify the current epidemiology of these helminth infections and to identify new and specific targets for both effective diagnosis and treatment. In this review, we describe the biology, medical and epidemiological features, and current treatment and diagnostic tools of the main groups of flukes and the corresponding diseases.

Characterization of Baylisascaris schroederi from Qinling subspecies of giant panda in China by the first internal transcribed spacer (ITS-1) of nuclear ribosomal DNA

In the present study, a total of 20 nematode isolates, (including 10 male and 10 female worms) representing Baylisascaris schroederi from 5 Qinling subspecies of giant pandas (Ailuropoda melanoleuca) in Shaanxi Province of China, were characterized and grouped genetically by the first internal transcribed spacer (ITS-1) of nuclear ribosomal DNA (rDNA). The rDNA fragment spanning 3' end of 18S rDNA, complete ITS-1 rDNA, and 5' end of 5.8S rDNA were amplified and sequenced. The sequence variability in ITS-1 rDNA was examined within B. schroederi and among parasites in order Ascaridata available in GenBank™, and their phylogenetic relationships were also reconstructed. The sequences of ITS-1 rDNA for all the B. schroederi isolates were 427 bp in length, with no genetic variation detected among these isolates. Phylogenetic analyses based on the ITS-1 rDNA sequences revealed that all the male and female B. schroederi isolates sequenced in the present study were posited into the clade of genus Baylisascaris, sistered to zoonotic nematodes in genus Ascaris, and the ITS-1 rDNA sequence could distinguish different species in order Ascaridata. These results showed that the ITS-1 rDNA provides a suitable molecular marker for the inter-species phylogenetic analysis and differential identification of nematodes in order Ascaridata.