Trematodes of the family Opisthorchiidae: a minireview

Automatic detection of Opisthorchis viverrini egg in stool examination using convolutional-based neural networks

Background

Human opisthorchiasis is a dangerous infectious chronic disease distributed in many Asian areas in the water-basins of large rivers, Siberia, and Europe. The gold standard for human opisthorchiasis laboratory diagnosis is the routine examination of Opisthorchis spp. eggs under a microscope. Manual detection is laborious, time-consuming, and dependent on the microscopist's abilities and expertise. Automatic screening of Opisthorchis spp. eggs with deep learning techniques is a useful diagnostic aid.

Methods

Herein, we propose a convolutional neural network (CNN) for classifying and automatically detecting O. viverrini eggs from digitized images. The image data acquisition was acquired from infected human feces and was processed using the gold standard formalin ethyl acetate concentration technique, and then captured under the microscope digital camera at 400x. Microscopic images containing artifacts and O.viverrini egg were augmented using image rotation, filtering, noising, and sharpening techniques. This augmentation increased the image dataset from 1 time to 36 times in preparation for the training and validation step. Furthermore, the overall dataset was subdivided into a training-validation and test set at an 80:20 ratio, trained with a five-fold cross-validation to test model stability. For model training, we customized a CNN for image classification. An object detection method was proposed using a patch search algorithm to detect eggs and their locations. A performance matrix was used to evaluate model efficiency after training and IoU analysis for object detection.

Results

The proposed model, initially trained on non-augmented data of artifacts (class 0) and O. viverrini eggs (class 1), showed limited performance with 50.0% accuracy, 25.0% precision, 50.0% recall, and a 33.0% F1-score. After implementing data augmentation, the model significantly improved, reaching 100% accuracy, precision, recall, and F1-score. Stability assessments using 5-fold cross-validation indicated better stability with augmented data, evidenced by an ROC-AUC metric improvement from 0.5 to 1.00. Compared to other models such as ResNet50, InceptionV3, VGG16, DenseNet121, and Xception, the proposed model, with a smaller file size of 2.7 MB, showed comparable perfect performance. In object detection, the augmented data-trained model achieved an IoU score over 0.5 in 139 out of 148 images, with an average IoU of 0.6947.

Conclusion

This study demonstrated the successful application of CNN in classifying and automating the detection of O. viverrini eggs in human stool samples. Our CNN model's performance metrics and true positive detection rates were outstanding. This innovative application of deep learning can automate and improve diagnostic precision, speed, and efficiency, particularly in regions where O. viverrini infections are prevalent, thereby possibly improving infection sustainable control and treatment program.

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.

The Occurrence of Freshwater Fish-Borne Zoonotic Helminths in Italy and Neighbouring Countries: A Systematic Review

In recent years, the consumption of fish products has surged in European countries, being an essential part of a healthy diet. Despite representing a small part of EU production, freshwater fisheries hold considerable significance for lake-dwelling populations and tourists seeking traditional dishes. This increased fish consumption has brought to light potential health risks associated with fish-borne zoonotic helminths (FBZHs), now acknowledged as global food-borne parasites. Fish-borne zoonotic helminths belong to various taxonomic groups, including nematodes (Anisakidae), trematodes (Opisthorchiidae and Heterophyidae), and cestodes (Diphyllobothriidae). More than 50 species of FBZH are known to cause human infections, derived from eating raw or undercooked aquatic foods containing viable parasites. Despite increased attention, FBZHs remain relatively neglected compared to other food-borne pathogens due to factors like chronic disease progression and under-diagnosis. This systematic review concentrates on the prevalence of six freshwater FBZHs (Clinostomum complanatum, Contracaecum rudolphii, Dibothriocephalus latus, Eustrongylides excisus, Opisthorchis felineus, and Pseudamphistomum truncatum) in Italy and neighbouring countries. The study explores the expansion of these parasites, analysing their biological and epidemiological aspects, and the factors that influence their proliferation, such as the increased cormorant population and the lake eutrophication phenomena. In summary, this research highlights the necessity for further research, the development of spatial databases, and the establishment of a unified European policy to effectively manage these multifaceted health concerns. It strongly advocates adopting a One-Health approach to address the growing incidence of parasitic zoonoses within the context of food safety in EU countries.

Massive hepatic trematodosis in 5 juvenile bald eagles

Hepatic trematodosis by opisthorchiid flukes has been reported sporadically in North American fish-eating raptors. Bald eagles (Haliaeetus leucocephalus) infected by these flukes often have various degrees of granulomatous cholangitis, pericholangitis, necrosis of adjacent hepatocytes, and subsequent hepatic fibrosis. Species identification has been complicated by the inability to dissect intact specimens from liver tissue. Between 2007 and 2018, 5 juvenile bald eagles with massive hepatic trematodosis were identified at autopsy. Histologically, flukes were non-spinous. Parasitologic identification revealed ventral suckers (80-93 µm diameter), and uteri containing golden, operculated eggs (~25.0 × 12.0 µm). An unfixed frozen liver sample of one eagle was analyzed by PCR and DNA sequencing targeting the large subunit rRNA, ITS region, and cox1 genes of the parasite. The fluke DNA sequences shared 99.6%, 98.4%, and 87.0% similarity, respectively, with Erschoviorchis anuiensis, a newly described opisthorchiid species infecting the liver and pancreas of fish-eating birds in Europe and Asia. Infection by E. anuiensis is highly pathogenic in several piscivorous bird species. The clinical significance of trematodosis in our 5 cases is uncertain because all birds had comorbidities.

Foodborne Parasites and Their Complex Life Cycles Challenging Food Safety in Different Food Chains

Zoonotic foodborne parasites often represent complex, multi host life cycles with parasite stages in the hosts, but also in the environment. This manuscript aims to provide an overview of important zoonotic foodborne parasites, with a focus on the different food chains in which parasite stages may occur. We have chosen some examples of meat-borne parasites occurring in livestock (Taenia spp., Trichinella spp. and Toxoplasma gondii), as well as Fasciola spp., an example of a zoonotic parasite of livestock, but transmitted to humans via contaminated vegetables or water, covering the 'farm to fork' food chain; and meat-borne parasites occurring in wildlife (Trichinella spp., Toxoplasma gondii), covering the 'forest to fork' food chain. Moreover, fish-borne parasites (Clonorchis spp., Opisthorchis spp. and Anisakidae) covering the 'pond/ocean/freshwater to fork' food chain are reviewed. The increased popularity of consumption of raw and ready-to-eat meat, fish and vegetables may pose a risk for consumers, since most post-harvest processing measures do not always guarantee the complete removal of parasite stages or their effective inactivation. We also highlight the impact of increasing contact between wildlife, livestock and humans on food safety. Risk based approaches, and diagnostics and control/prevention tackled from an integrated, multipathogen and multidisciplinary point of view should be considered as well.

Gastrointestinal parasites of cats in Egypt: high prevalence high zoonotic risk

BACKGROUND

Several gastrointestinal parasites that infect cats pose potential health threats for humans and animals. The present study is the first to report gastrointestinal (GIT) parasites in feces of stray cats from Gharbia governorate, Egypt. Findings were combined with those published in the earlier surveys from various Egyptian governorates, and various meta-analyses were conducted to underline the parasitic zoonoses from cats in Egypt.

RESULTS

Out of 143 samples tested in Gharbia, 75 (52.4%) were found infected with 13 different parasites. Co-infections were observed in 49.3% of positives. Several parasites were detected, e.g., Toxocara cati (30.0%), Toxascaris leonina (22.4%), hookworms (8.4%), taeniids (4.2%), Strongyloides spp. (2.1%), Physaloptera spp. (2.1%), Alaria spp. (1.4%) and Dipylidium caninum (0.7%). Opisthorchis-like eggs were found in a single sample being the first report from cats in Africa. Oocysts of 4 coccidian parasites were identified, and a few Toxoplasma gondii-like oocysts were detected in 2 samples (1.4%). Results of the meta-analysis illustrated that occurrence of T. gondii oocysts in feces of cats from Egypt may have been overestimated in earlier studies; 1432 cats have been tested and displayed a 5 times higher pooled prevalence (11.9%) than the published global pooled prevalence for T. gondii oocysts in cats. This overestimation might have occurred because some small-sized oocysts that belong to other coccidian parasites were mis-identified as T. gondii. Toxocara cati had a high pooled prevalence (22.5%) in cats from Egypt, which is even greater than the published pooled prevalence in cats globally; however, several reports from Egypt have neglected the role of T. cati in human toxocarosis. Dipylidium caninum displayed also a high prevalence (26.7%).

CONCLUSION

Several zoonotic parasite species have been found in stray cats from Egypt, raising concerns about the risks to the Egyptian human population as well as environmental contamination. Prompt surveillance supervised by the government and accompanied by data dissemination will be helpful for developing effective control strategies.

Parasites of the liver - epidemiology, diagnosis and clinical management in the European context

Parasites in the liver cause significant global morbidity and mortality, as they can lead to recurrent cholangitis, cirrhosis, liver failure and cancer. Due to climate change and globalisation, their incidence is increasing, especially in Europe. The correct diagnosis of a hepatic parasite is often delayed because clinicians are unfamiliar with respective entities. Therefore, in this review, we aim to provide clinicians with a comprehensive clinical picture of hepatic parasites and to bring these neglected parasitic liver diseases to the wider attention of hepatology stakeholders in Europe and around the world.

A review of molecular identification tools for the opisthorchioidea

The superfamily Opisthorchioidea encompasses the families Cryptogonimidae, Opisthorchiidae and Heterophyidae. These parasites depend on the aquatic environment and include marine and freshwater species. Some species, such as Clonorchis sinensis and Opisthorchis viverrini, have a high impact on public health with millions of infected people worldwide and have thus been the object of many studies and tool developments. However, for many species, tools for identification and detection are scarce. Although morphological descriptions have been used and are still important, they are often not efficient on the immature stages of these parasites. Thus, during the past few decades, molecular approaches for parasite identification have become commonplace. These approaches are efficient, quick and reliable. Nonetheless, for some parasites of the superfamily Opisthorchioidea, reference genomic data are limited. This study reviews available genetic data and molecular tools for the identification and/or the detection of this superfamily. Molecular data on this superfamily are mostly based on mitochondrial and ribosomal gene sequence analyses, especially on the cytochrome c oxidase subunit 1 gene and internal transcribed spacer regions respectively.

Insight into One Health Approach: Endoparasite Infections in Captive Wildlife in Bangladesh

Introduction: Endoparasites in captive wildlife might pose a threat to public health; however, very few studies have been conducted on this issue, and much remains to be learned, especially in limited-resource settings. This study aimed to investigate endoparasites of captive wildlife in Bangladesh. Perception and understanding of veterinarians regarding one health and zoonoses were also assessed. Materials and Methods: A cross-sectional study was conducted from October 2019 to August 2020. A total of 45 fecal samples from 18 different species of wild animals (i.e., 11 species of mammals: herbivores, carnivores, and omnivores, six birds, and a single reptile species) were collected randomly. Parasitological assessments were done by modified formalin ether sedimentation technique and rechecked by Sheather's sugar floatation technique. Molecular identification of Spirometra spp. was conducted by amplifying the cytochrome c oxidase 1 (cox1) gene. Questionnaire surveys among 15 veterinarians and an in-depth interview (IDI) with a zoo officer were conducted. Results: Helminths (Spirometra sp., Capillaria sp., Ascaridia/Heterakis, opisthorchiid, strongyles, acuariid, hookworms, roundworms, and unidentified nematode larvae) and protozoa (coccidian oocyst) were identified, and the overall prevalence was 48.9% (22/45). The cox1 sequences (341 bp) of the Bangladesh-origin Spirometra species from lion showed 99.3-99.7% similarity to the reference sequences of Spirometra decipiens (GenBank No: KJ599679.1; MT122766). The majority of study participants (86.6%) agreed about the importance of endoparasite control in zoo animals, and 73.3% expressed that the one health concept should be promoted in Bangladesh. Only 6.7% of veterinarians perceived confidence in diagnosing parasitic diseases and preventing antiparasiticidal resistance. Conclusions: In the present survey, we found a considerable prevalence of endoparasites in captive wildlife. For the first time, zoonotically important S. decipiens from lion was molecularly characterized in Bangladesh. Veterinarian training is required to improve parasite control knowledge and practice. This study highlights the need for routine parasitological assessment, promotion of one health, and improvement of the implementation of current parasite control strategies in zoo animals.

Helminth eggs from early cretaceous faeces

The exceptional fossil site of Las Hoyas (upper Barremian, Cuenca, Spain) yields abundant small to medium vertebrate coprolites, hindering the search for parasites. We studied the contents of 29 coprolites that were previously classified into distinct morphotypes. Several parasitic eggs were retrieved from two of these coprolites, confirming the second record of digenea trematode eggs and nematode (ascaridid) eggs from an Early Cretaceous locality. The cylindrical coprolite containing anisakid eggs was likely produced by a crocodylomorph as the parasite host, whereas the bump-headed lace coprolite indicates the role of a fish as an intermediary or definitive host of the trematodes and ascaridids. These trace and body fossils show that the Las Hoyas 126-129 Ma lacustrine ecosystem documents the early connection between basal Gonorynchiformes fish and digenetic trematodes.

Liver fluke infections by Amphimerus sp. (Digenea: Opisthorchiidae) in definitive and fish intermediate hosts in Manabí province, Ecuador

Amphimerus sp. is a fluke that dwells in the biliary tracts of vertebrate definitive hosts including humans, domestic, and wild mammals in Latin America. Opisthorchiid liver infections are rarely studied in the Americas confirming its status as a neglected tropical disease. In Ecuador, small trematode eggs were reported in human cases from the province of Manabí in 1949, and recently, Amphimerus sp. adults were recovered from human and reservoir hosts in the province of Esmeraldas. Due to the lack of research on the infectious sources of Amphimerus sp. in the continent, we have developed a series of epidemiological studies with parasitological and molecular techniques to elucidate the endemicity of opisthorchiid fluke infections. We developed a cross-sectional study in three communities at Pedro Pablo Gómez parish in the province of Manabí, Ecuador. We examined a total of 176 fecal samples to detect opisthorchiid eggs, and four fish species to find opisthorchiid metacercariae. To study adult worms, we treated and purged seven patients in a family and dissected the livers of a dog and a cat infected. We observed morphological features of adults and metacercariae and used polymerase chain reaction with restricted fragment length polymorphism (PCR-RFLP) and DNA sequencing of a section of the ITS2 gene for identification. Small trematode eggs were detected in 63 (35.8%) out of 176 fecal samples of residents in the three study sites. Adult opisthorchiid flukes were recovered from human patients, a dog and a cat, and they were morphologically and molecularly identified as Amphimerus sp. Opisthorchiid metacercariae were also identified molecularly as Amphimerus sp. in four fish species, i.e., Rhoadsia altipinna, Bryconamericus bucay, Andinoacara rivulatus, and Piabucina aureoguttata. Metacercariae of the heterophyid Haplorchis pumilio were also found in the four fish species examined. This is the first study to confirm the current endemicity of Amphimerus sp. in Pedro Pablo Gómez, Manabí, Ecuador. The adult worms isolated here shared morphological characteristics with previous Amphimerus sp. descriptions and were molecularly similar to Amphimerus sp. described in the province of Esmeraldas. Moreover, this study is the first to document four fish species as infection sources of Amphimerus sp. detected via a molecular protocol targeting the metacercariae of the parasite. Fish species identified here should be targeted for public health campaigns to avoid further human liver-fluke infections by Amphimerus sp. or potential intestinal-fluke infections by H. pumilio or others.

Among neglected tropical diseases, foodborne trematodiases rank among the least studied, especially in the Americas. In Ecuador, a parasite of the genus Amphimerus, family Opisthorchiidae, has been found in the biliary ducts of humans, cats, and dogs, in the northern province of Esmeraldas. Reports as old as 1949 document opisthorchiid infections in the coastal province of Manabí. Given a lack of studies elucidating the infective larval stage of these flukes in Ecuador, we decided to conduct parasitological and molecular experiments to characterize the presence of these human liver infections in the area. We found adult Amphimerus sp. flukes in humans and other domestic animals, and its metacercariae in four edible freshwater fish species: Rhoadsia altipinna, Bryconamericus bucay, Andinoacara rivulatus, and Piabucina aureoguttata. Moreover, we found a prevalence of 35.8% of small trematode eggs in humans. Finally, we also found the metacercariae of the intestinal fluke Haplorchis pumilio in all fish species examined. Our findings confirm the area of Pedro Pablo Gómez as an endemic region for opisthorchiid liver infections due to Amphimerus sp., and expand the human differential diagnosis of small trematode eggs to liver and intestinal flukes. Consumption of undercooked freshwater fish of the species identified here could lead to Amphimerus sp. infections. Surveillance in other areas known for raw fish consumption would likely unveil new cases of foodborne trematodiases in Ecuador and other regions.

Multiplex PCR for simultaneous identification of the most common European Opisthorchiid and Heterophyid in fish or fish products

Among others, the families Opisthorchiidae and Heterophyidae includes several genera causing fish-borne zoonoses and distributed also in European Countries and that are included in the ParaFishControl (Advanced Tools and Research Strategies for Parasite Control in European farmed fish) H2020 EU project. Due to the small size of the metacercariae, the infective stage for human, these parasites cannot be detected visually in fish and monitoring requires expert application of time-consuming techniques. The aim of this was to develop a rapid and affordable molecular method based on multiplex PCR for simultaneous identification of metacercariae of the most common European Opisthorchiid and Heterophyid in fish or fish products.

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.

Paropisthorchis caninus Stephens, 1912: Synopsis of identity and pathological findings due to spontaneous infection in the liver of a street dog in Assam, India

The present study describes a small liver fluke recovered at post-mortem and the pathological alteration produced by the parasite in the liver of a street dog from Assam, India. The spatulate parasite measured 3-4 mm in length and 1.0-1.25 mm in width with spiny body surface and showed a grossly visible peduncle projecting from the ventral surface at the anterior portion. The eggs of the parasite contained well developed miracidia. The parasite was identified as Paropisthorchis caninus. Identity of the parasite is discussed in the light of available literature and found to be morphologically different from other reported species of dog Opisthorchis. Pathological lesions observed in the liver included degeneration of hepatic parenchyma, hyperplasia of bile duct epithelium, fibrous tissue proliferation and formation of pseudo lobule which were the characteristics of chronic proliferative inflammation.

Opisthorchis felineus and Metorchis bilis Metacercariae in Cyprinid Fish Leuciscus idus in Nura-Sarysu River, Kazakhstan

Aim of the present study was to provide presence of opisthorchiid metacercariae in cyprinid fish Leuciscus idus in Nura-Sarysu river, Kazakhstan. Infection rate of the ides by the metacercariae was 42%. The metacercariae, similar morphologically to those of the liver flukes, were found: elliptical in shape, 0.19–0.25×0.15–0.22 mm, oral and ventral suckers nearly equal size, and excretory bladder O-shape with black content, occupying posterior part of the body. The metacercariae were divided into 2 groups with differences in size and thickness of cyst wall. Adult flukes were recovered from the Syrian hamsters infected with the opisthorch metacercariae and identified with morphological characters to Opisthorchis felineus and Metorchis bilis. DNA sequences of ITS1, ITS2, and cox1 supported the taxonomic assignment.

A duplex PCR for the simultaneous detection of Fasciola hepatica and Clonorchis sinensis

Both Fasciola hepatica and Clonorchis sinensis are endemic in China, South Korea, Japan and other Southeast Asian countries. Reliable and sensitive diagnostic methods are needed for detecting their infections in humans and animals. Differential simplex and duplex polymerase chain reaction (PCR) methods were developed. The PCRs targeted the second internal transcribed spacer (its2) (408 bp) of F. hepatica, and NADH dehydrogenase subunit 2 gene (nad2) (527 bp) of C. sinensis. Both simplex PCRs detected as little as 2 pg genomic DNA in one microliter in a 25 μL PCR reaction system. The duplex PCR had similar detection limit as well, and detected as low as one egg in 200 mg feces. These methods were analytical specific with no amplification being observed from the gemonic DNA of Fasciolopsis buski, Haemonchus contortus, Ascaris ovis or Eimeri ahsata. Of 158 sheep fecal samples collected from various farms, four and one samples were PCR-positive for F. hepatica and C. sinensis, respectively. The duplex PCR method described here is time-saving and convenient, and may prove to be an invaluable tool for molecular detection and epidemiological investigation of F. hepatica and C. sinensis in endemic area.

Freshwater mussels (Anodonta anatina) reduce transmission of a common fish trematode (eye fluke, Diplostomum pseudospathaceum)

Recent results suggest that bivalves can play an important role in restraining the spread of various aquatic infections. However, the ability of mussels to remove free-living stages of macroparasites and reduce their transmission is still understudied, especially for freshwater ecosystems. We investigated the influence of the common freshwater mussel (Anodonta anatina) on the transmission of a trematode (eye fluke, Diplostomum pseudospathaceum), which frequently infects fish in farms and natural habitats. In our experiments, mussels caused a significant decrease (P < 0·001) in the abundance of trematode free-living stages, from 6520 to 1770 cercariae L-1 on average (about 4-fold in 2 h). Individual clearance rates of mussels were 0·6‒3·7 L per hour (mean 1·9). These tests were followed by experimental infections of rainbow trout (Oncorhynchus mykiss) with different doses of D. pseudospathaceum cercariae in the presence or absence of mussels. Exposure of fish to cercariae in the presence of mussels significantly (P < 0·05) reduced the infection intensities in fish (by 30-40%) at all exposure doses. Our results indicate that freshwater bivalves can markedly reduce local cercariae densities and could be useful in mitigation of trematodoses harmful to fish farming.

Unexpected hosts: imaging parasitic diseases

Radiologists seldom encounter parasitic diseases in their daily practice in most of Europe, although the incidence of these diseases is increasing due to migration and tourism from/to endemic areas. Moreover, some parasitic diseases are still endemic in certain European regions, and immunocompromised individuals also pose a higher risk of developing these conditions. This article reviews and summarises the imaging findings of some of the most important and frequent human parasitic diseases, including information about the parasite's life cycle, pathophysiology, clinical findings, diagnosis, and treatment. We include malaria, amoebiasis, toxoplasmosis, trypanosomiasis, leishmaniasis, echinococcosis, cysticercosis, clonorchiasis, schistosomiasis, fascioliasis, ascariasis, anisakiasis, dracunculiasis, and strongyloidiasis. The aim of this review is to help radiologists when dealing with these diseases or in cases where they are suspected. Teaching Points • Incidence of parasitic diseases is increasing due to migratory movements and travelling. • Some parasitic diseases are still endemic in certain regions in Europe. • Parasitic diseases can have complex life cycles often involving different hosts. • Prompt diagnosis and treatment is essential for patient management in parasitic diseases. • Radiologists should be able to recognise and suspect the most relevant parasitic diseases.

Helminth infections in domestic dogs from Russia

Dogs are the hosts for a wide helminth spectrum including tapeworms, flatworms, and nematodes. These parasites affect the dog health and cause morbidity and mortality, especially in young and old animals. Some species, as Toxocara canis, Ancylostoma caninum, Dipylidium caninum, and Echinococcus spp. are well-known zoonotic parasites worldwide, resulting in high public health risks. Poor data about canine helminth species and prevalence are available in Russia, mainly due to the absence of official guidelines for the control of dog parasites. Moreover, the consequent low quality of veterinary monitoring and use of preventive measures, the high rate of environmental contamination by dog feces and the increase of stray dog populations, make the control of the environmental contamination by dog helminths very difficult in this country. This paper reviews the knowledge on canine helminth fauna and prevalence in Russia. Practical aspects related to diagnosis, treatment, and control of parasitic diseases of dogs in Russia are discussed.

Emergence of the Zoonotic Biliary Trematode Pseudamphistomum truncatum in Grey Seals (Halichoerus grypus) in the Baltic Sea

The biliary trematode Pseudamphistomum truncatum parasitizes a wide range of fish-eating mammals, including humans. Here we report the emergence of this parasite in grey seals (Halichoerus grypus) in the Baltic Sea. One hundred eighty-three of 1 554 grey seals (11.9%) examined from 2002-2013 had detectable hepatobiliary trematode infection. Parasite identification was confirmed as P. truncatum by sequencing the ITS2 region of a pool of five to 10 trematodes from each of ten seals collected off the coast of seven different Swedish counties. The proportion of seals parasitized by P. truncatum increased significantly over time and with increasing age of seals. Males were 3.1 times more likely to be parasitized than females and animals killed in fishery interactions were less likely to be parasitized than animals found dead or hunted. There was no significant difference in parasitism of seals examined from the Gulf of Bothnia versus those examined from the Baltic Proper. Although the majority of infections were mild, P. truncatum can cause severe hepatobiliary disease and resulted in liver failure in at least one seal. Because cyprinid fish are the second intermediate host for opisthorchiid trematodes, diets of grey seals from the Baltic Sea were analysed regarding presence of cyprinids. The proportion of gastrointestinal tracts containing cyprinid remains was ten times higher in seals examined from 2008 to 2013 (12.2%) than those examined from 2002 to 2007 (1.2%) and coincided with a general increase of trematode parasitism in the host population. The emergence and relatively common occurrence of P. truncatum in grey seals signals the presence of this parasite in the Baltic Sea ecosystem and demonstrates how aquatic mammals can serve as excellent sentinels of marine ecosystem change. Investigation of drivers behind P. truncatum emergence and infection risk for other mammals, including humans, is highly warranted.

Clonorchis sinensis and Opisthorchis spp. in Vietnam: current status and prospects

Clonorchis sinensis and Opisthorchis viverrini are clinically important small liver flukes because of their known association with development of cholangiocarcinoma. In Vietnam, high prevalence of C. sinensis infection in humans was previously reported in northern provinces, and O. viverrini infection has been detected in several central provinces. However, diagnosis of C. sinensis and O. viverrini infections in the past was merely based on faecal egg examination. This method alone can lead to misidentification at the species level because of morphological similarity between the eggs of these liver flukes and minute intestinal trematodes of the family Heterophyidae. In fact, recent surveys in Vietnam revealed that infection with several minute intestinal flukes, such as Haplorchis pumilio and H. taichui, are much more common than infection with C. sinensis or O. viverrini, and they often co-infect humans. Thus, previously reported prevalence of small liver fluke infection in Vietnam was likely over-estimated due to mis identification of parasites in copro-parasitological examinations. In addition, there is some confusion about identification of cercariae, metacercariae and also adults of C. sinensis and O. viverrini in intermediate and definitive hosts. The aim of this review is, therefore, to draw realistic pictures of the past and present scientific reports on the epidemiology and biology of C. sinensis and Opisthorchis spp. infection in Vietnam.

Review and Current Status of Opisthorchis viverrini Infection at the Community Level in Thailand

Opisthorchis viverrini is remains a public health problem in Thailand, particularly in the northeast and north regions which have the highest incidences of chonalgiocarcinoma (CCA). O. viverrini causes the disease opithorchiasis, and its has been classified as a group 1 biological carcinogen. Humans, dogs, and cats become infected with O. viverrini by ingesting raw or undercooked fish containing infective metacercariae. The first human cases of O. viverrini infection were reported in Thailand 100 years ago, and it's still a problem at the community level. Based on data for the year 2009, more than 6 million people were infected with O. viverrini. Associated medical care and loss of wages in Thailand costs about $120 million annually. This review highlights the current status of O. viverrini infection in communities of Thailand through active surveillance for the five years period from 2010 and 2015. A total of 17 community-based surveys were conducted, most in the northeast region. Some 7 surveys demonstrated a high prevalence over 20%, and the highest was 45.7%. Most commonly infection was found in age group of 35 years and older, males, and agricultural workers. Although, the national prevalence may be decreasing but the results show that the O. viverrini infection is still high in communities of the northeast region. Therefore, the focus in populations living in northeast Thailand should be screening of infection and changing their eating behavior.

Chromosome morphometry in opisthorchiid species (Platyhelminthes, Trematoda)

Few existing studies have dealt with cytogenetics in trematodes, largely due to the attendant technical difficulty of chromosome preparation. We performed a comparative analysis of chromosomes in five opistorchiid species, including Opisthorchis felineus Rivolta, 1884, Opisthorchis viverrini Poirier, 1886, Clonorchis sinensis Cobbold, 1875, Metorchis xanthosomus Creplin 1846, and Metorchis bilis (Braun, 1790) Odening, 1962. For some of these species, no detailed morphometric description of their karyotypes has yet been published; for the karyotype of Metorchis bilis this is the first-ever description. We found that opisthorchiids, like other trematodes, are characterized by karyotypic conservatism (N=6-7) and karyotype asymmetry, although comparison of chromosome morphometric traits did reveal differences between the karyotypes of the species. Moreover, to address certain a methodological issue in trematode chromosome preparation, we analyzed how the source of chromosomal material (partenitae or mature flukes) and the chromosome preparation techniques used (air-drying and cell suspension methods) affected chromosome spreading and size, concluding that the most reliable comparative method involves comparing relative parameters (relative length, arm ratio, centromeric index) of chromosomes prepared using the same technique.

Integrative taxonomy of European parasitic flatworms of the genus Metorchis Looss, 1899 (Trematoda: Opisthorchiidae)

Metorchis spp. are flukes (Platyhelminthes: Digenea) that infect vertebrates, including humans, dogs, cats, poultry and wild game, with cyprinid freshwater fish serving as typical second intermediate hosts. In their definitive hosts, the Metorchis spp. are difficult to identify to species. We provide and analyze sequences of two nuclear (18S rDNA and ITS2) and two mitochondrial (CO1 and ND1) DNA loci of four morphologically identified European species of the Metorchis, namely Metorchis albidus, Metorchis bilis, Metorchis crassiusculus and Metorchis xanthosomus, and of another opisthorchiid, Euamphimerus pancreaticus. DNA analysis suggests that the Metorchis specimens identified morphologically as M. albidus (from Lutra lutra), M. bilis (from Phalacrocorax carbo) and M. crassiusculus (from Aquila heliaca and Buteo rufinus) represent a single species. Thus, M. albidus (Braun, 1893) Loos, 1899 and M. crassiusculus (Rudolphi, 1809) Looss, 1899 are recognized as junior subjective synonyms of M. bilis (Braun, 1790) Odening, 1962. We also provide comparative measurements of the Central European Metorchis spp., and address their tissue specificity and prevalence based on the examination of extensive bird cohort from 1962 to 2015. M. bilis and M. xanthosomus can be morphologically diagnosed by measuring the extent of genitalia relative to body length and by the size ratio of their suckers. They also differ in their core definitive hosts, with ducks (Anas, Aythya) and coots (Fulica) hosting M. xanthosomus, and cormorants (Phalacrocorax), the birds of prey (Buteo, Aquila, etc.), piscivorous mammals (Lutra, Vulpes, Ursus, etc.) and humans hosting M. bilis. Previous reports on the Metorchis spp. contain numerous suspected misidentifications.

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.

Adult Opisthorchis felineus major protein fractions deduced from transcripts: comparison with liver flukes Opisthorchis viverrini and Clonorchis sinensis

The epidemiologically important liver flukes Opisthorchis felineus, Opisthorchis viverrini, and Clonorchis sinensis are of interest to health professionals, epidemiologists, pharmacologists, and molecular biologists. Recently the transcriptomes of the latter two species were intensively investigated. However our knowledge on molecular biology of O. felineus is scarce. We report the first results of the O. felineus transcriptome analysis. We isolated and annotated a total of 2560 expressed sequence tag (EST) sequences from adult O. felineus (deposited within the database of expressed sequence tags (dbEST), under accession numbers GenBank: JK624271-JK626790, JK006511-JK006547, JK649790-JK649792). Clustering and analysis resulted in the detection of 267 contigs. Of the protein sequences deduced from these, 82% had homologs in the NCBI (nr) protein database and 63% contained conserved domains, allowing the functions to be interpreted using the Gene Ontology terms. Comprehensive analysis of Opisthorchiidae- and Trematoda-specific substitutions within amino acid sequences deduced for the proteins myoglobin, vitelline precursor protein, cathepsin F, and 28kDa glutathione transferase was carried out. The gene set of the 32 ribosomal proteins for the three Opisthorchiidae species with the addition of available Schistosoma and Fasciola orthologs was created and is provided in the supplementary. The orthologous gene set created was used for inferring phylogeny within the Trematoda with special attention to interrelations within the Opisthorchiidae. The phylogenetic analysis revealed a closer relationship between C. sinensis and O. viverrini and some divergence of O. felineus from either O. viverrini or C. sinensis.

Opisthorchis felineus and Metorchis bilis are the main agents of liver fluke infection of humans in Russia

Liver fluke infections are gradually transforming from a local problem of individual geographic regions to a widespread problem. The observed expansion is likely to be connected with the ever-increasing intensity of traffic flow and migration of the infected carriers between cities, regions, and countries. Opisthorchis felineus, the trematode belonging to the family Opisthorchiidae, is a well known causative agent of the infection called opisthorchiasis. Metorchis bilis, also a member of the family Opisthorchiidae, causes metorchiasis, a disease very close to opisthorchiasis in symptomatology. Genetic markers can be used to develop methods for differential diagnostics of these diseases. However, the questions connected with epidemiology of these trematode infections, their clinical characteristics, prognosis and therapy remain open. This review briefs the general biological characteristics of O. felineus and M. bilis persisting in various countries of Eurasia, their geographical range, epidemiology and molecular diagnostics of these liver flukes.

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

Clonorchiasis caused by Clonorchis sinensis is an important foodborne parasitosis of humans and animals, and is predominantly a hepatobiliary disease. Globally, nearly 35 million people were infected with C. sinensis, with approximately 15 million being in China. Patients would chronically present fatigue, jaundice, abdominal discomfort, along with the increased risk of developing into a form of cholangiocarcinoma that is fatal to humans. Treatment of clonorchiasis by praziquantel has been very successful, but this is dependent on early accurate diagnosis and correct species identification. The present article reviews the current status of knowledge in genomics and functional genomics of C. sinensis, and summarizes the main DNA-based techniques for the specific diagnosis of C. sinensis infection and studies of genetic variation in C. sinensis, and provides perspectives for future studies. The advances in genomics and molecular genetics of C. sinensis shed new sight on our understanding of population structure of C. sinensis as well as the prevention and control of clonorchiasis.

A novel nuclear marker, Pm-int9, for phylogenetic studies of Opisthorchis felineus, Opisthorchis viverrini, and Clonorchis sinensis (Opisthorchiidae, Trematoda)

Opisthorchis felineus, O. viverrini, and Clonorchis sinensis, the trematodes of the family Opisthorchiidae, are important human parasites. Two previous studies (Kang et al. Parasitol Int 57:191-197, 2008; Katokhin et al. Dokl Biochem Biophys 421:214-217, 2008) have provided evidence using ribosomal and mitochondrial sequences that O. viverrini, O. felineus, and C. sinensis are closely related. We developed a novel nuclear marker, Pm-int9, which included the ninth intron of the paramyosin gene and flanking exon sequences. Samples of O. felineus from four localities of West Siberia, C. sinensis from the Russian Far East, and O. viverrini from Thailand were genotyped by Pm-int9. Little variation was detected in exon sequences, however, intron sequences turned out to be more variable than ribosomal internal transcribed spacers. We can conclude that Pm-int9 is valuable for interspecific variation studies. Phylogenetic analysis based on Pm-int9 revealed that O. viverrini and C. sinensis were closer to each other than either of them to O. felineus, supporting the opinion that C. sinensis should be considered the sister species of Opisthorchis spp.

Opisthorchiasis mimicking primary biliary cirrhosis as an indication for liver transplantation

BACKGROUND/AIMS

Opisthorchiasis, a helminthic infection occurring endemically in certain areas of Europe and Asia is caused by parasites of the class trematoda. Failure to treat or a significant delay in the institution of an adequate therapy can lead to considerable complications in the further course of the disease.

CASE

A 56-year-old patient diagnosed with primary biliary cirrhosis (PBC) with Child-Pugh stage B was referred to our surgical department from a peripheral hospital for liver transplantation. She had spent 50 years of her life in Kazakhstan.

RESULTS

As the treatment of choice, orthotopic liver transplantation was carried out. The routine postoperative pathological analysis of the explanted liver showed the histological picture of opisthorchiasis. Further work-up in an effort to confirm the histological diagnosis was repeatedly negative.

CONCLUSIONS

Opisthorchiasis should always be a diagnostic consideration in an unclear case of chronic liver disease especially in patients living in endemic areas.

Clonorchis sinensis and Opisthorchis viverrini: development of a mitochondrial-based multiplex PCR for their identification and discrimination

We report a single, one-step PCR approach for detection and discrimination of Clonorchis sinensis and Opisthorchis viverrini in different life-stage forms (adults, metacercariae, and eggs) from fish intermediate hosts and from infected patients. Primers designed for species-specific PCR, amplifying portions of the mitochondrial (mt) genome, were also suitable for a multiplex PCR. The latter was a single, one-step reaction under high stringency conditions, using simultaneously 2 pairs of primers (1 pair for C. sinensis--product size 612 bp, and 1 pair for O. viverrini--product size 1357 bp). Assays using serially diluted templates demonstrated that as little as 0.78 ng of genomic DNA of either species could yield amplicons. Genomic DNA extracted from different life-stage forms including adult worms (of both species), eggs (of O. viverrini), eggs possibly of several trematode species (collected from patients infected with C. sinensis in Vietnam) and mixed metacercariae of common trematodes (collected from fishes in the C. sinensis endemic areas), yielded specific bands of the correct size and their identity was confirmed by sequence analysis. The multiplex PCR approach described here proved to be a species-specific, sensitive and fast tool for accurate diagnosis of clonorchiasis and/or opisthorchiasis, permitting the detection of their metacercariae in infected fishes or adult/eggs from patients in endemic areas.