Current status of fasciolosis in Vietnam: an update and perspectives

Effectiveness of health education in improving knowledge, attitude and practice related to foodborne zoonotic trematodes in Vietnam, with a particular focus on Clonorchis sinensis

OBJECTIVE

Foodborne zoonotic trematodes (FZT), which infect the liver, lungs and intestines of humans, are an emerging public health concern in tropical countries including Vietnam. In northern Vietnam, Clonorchis sinensis is recognised as the most important species of the FZT. Up to now, small-scale studies conducted in the country have indicated that health education could improve participants' knowledge and practices related to clonorchiasis, however strong evidence is still lacking. We conducted an intervention trial between 2020 and 2021 in four communes in Yen Bai and Thanh Hoa province, aiming to evaluate the impact of an extended educational package on knowledge, attitude and practices related to clonorchiasis, as well as on knowledge on the large liver fluke and minute intestinal flukes.

METHODS

To this end, baseline and post-intervention questionnaires were conducted. Generalised estimating equations models were run to analyse the impact of the intervention on knowledge, attitudes and practices over time in the intervention versus control group. Finally, 172 people in the intervention group and 162 in the control group were included for analysis.

RESULTS

Results demonstrated that the intervention significantly improved clonorchiasis knowledge, attitudes and practices, with higher odds for a correct knowledge response (odds ratio (OR) = 2.80, 95% confidence interval (CI) = 1.84-4.27, p-value < 0.001), increased average mean attitude score (mean = 0.363, 95%CI = 0.182-0.544, p-value < 0.001), and a reduced odds of consuming raw fish (OR = 0.15, 95%CI = 0.06-0.40, p = 0.002) in the intervention group compared to the control group post-intervention versus baseline. Additionally, participants in the intervention group exhibited enhanced basic knowledge of the large liver fluke and minute intestinal flukes post-intervention.

CONCLUSIONS

These findings demonstrate the potential of health education programs in preventing clonorchiasis in endemic areas, emphasising the importance of continued health education as a critical component of integrated control programs for clonorchiasis.

Environmental influence on abundance and infection patterns of snail intermediate hosts of liver and intestinal flukes in North and Central Vietnam

Liver and intestinal flukes (LIF) are important groups of foodborne zoonotic trematodes (FZTs) in Southeast Asia, including Vietnam. Their complex life cycles require specific freshwater snail species as the obligatory first intermediate hosts. In 2019, we conducted a longitudinal study in Yen Bai and Thanh Hoa provinces in North and Central Vietnam, respectively, to investigate the diversity of LIF and their infection prevalence in relation to snail host abundance and environmental factors. Using a combination of morphological and molecular identification techniques, we identified 10 LIF species infecting 11 snail host species. We observed significant seasonal variation in the mean abundance of several snail host species, with the majority of snails collected during the spring. We also detected seasonal changes in LIF species composition, with the highest species richness reported in the spring. Clonorchis sinensis and Fasciola gigantica, two medically important human liver flukes in Asia, were found only in the spring in Yen Bai. Our study revealed that not all snail host species have the same probability of becoming infected, and we recorded seasonal variations in the prevalence of LIF infection in different snail species in relation to water parameters.

Molecular Characterization of Fasciola hepatica in Sheep Based on DNA Sequences of Ribosomal ITS-1

Introduction

World Health Organization (WHO) considers Fascioliasis as a neglected tropical disease that requires global efforts for disease control. Data from the genetic characterization of Fasciola population shed light on the spread of infections among animals which could help in the development of effective parasite control. The aim of the present work was to genetically characterize Fasciola adult worms isolated from sheep in Saudi Arabia by sequence analysis of ITS-1 region.

Methods

A total of 12,653 slaughtered sheep in Jeddah city, Saudi Arabia were examined for the presence of Fasciola spp. adult worms. The ITS-1 region of all parasites was amplified and sequenced.

Results

Overall, 12 variants DNA sequences were obtained. The variance of isolates ranged from 0.00771 to 0.34405. BLAST search showed that all obtained sequences were Fasciola hepatica and had >99.3% similarity with F. hepatica isolates from Spain and USA (from different hosts other than sheep). Phylogenetic analysis showed that Fasciola isolates were closely related to isolates from different countries.

Discussion

The current study showed that F. hepatica was the only spp. isolated from sheep in Jeddah. Further studies from different localities in Saudi Arabia are needed to help in the development of disease control.

Clinical characteristics of human fascioliasis in Egypt

There is a lack of epidemiological data on fascioliasis in Egypt regarding disease characteristics and treatment outcomes across different governorates. We aimed to identify the demographic, epidemiologic, clinical, laboratory, and radiological characteristics and treatment outcomes of patients diagnosed with fascioliasis in Egypt. Data on human fascioliasis were collected retrospectively from patients' medical records in the period between January 2018 and January 2020. The study included 261 patients. More than 40% of enrolled patients were in the age group of 21-40 years old. Geographically, 247 (94.6%) were from Assiut Governorate with 69.3% were from rural areas. The most frequent symptoms were right upper quadrant pain (96.9%), and fever (80.1%). Eosinophilia was found in 250 cases (95.8%). Hepatic focal lesions were detected in 131 (50.2%); out of them 64/131 (48.9%) had a single lesion. All patients received a single dose of 10 mg/kg of triclabendazole, 79.7% responded well to a single dose, while in 20.3% a second ± a third dose of treatment was requested. After therapy, there was a reduction in leucocytes, Fasciola antibodies titer, eosinophilic count, bilirubin, and liver enzymes with an increase in hemoglobin level. According to our findings, a high index of suspicion should be raised in cases with fever, right upper abdominal pain, and peripheral eosinophilia, and further imaging workup is mandated to detect hepatic focal lesions. Prompt treatment by triclabendazole can serve as a standard-of-care regimen even for suspected cases.

An overview of human helminthioses in Vietnam: Their prevention, control and lessons learnt

In Vietnam, helminthioses remain a major threat to public health and contribute to the maintenance of poverty in highly endemic regions. Through increased awareness of the damaging effects caused by helminthioses, the Vietnamese government has implemented many national programs over the past 30 years for the prevention and control of the most important helminthioses, such as, lymphatic filariasis, soil transmitted helminths, food borne zoonotic helminths, and others. Various control strategies have been applied to reduce or eliminate these worms, e.g. mass drug administration, economic development, control of vectors or intermediate hosts, public health interventions through education, proper composting procedures for excreta potentially containing helminth eggs, and the expansion of food supply chains and improved technologies for the production and inspection of food products. These control measures have resulted in a significant reduction in the distribution and transmission of helminth infections and have improved the overall living conditions and health outcomes of the Vietnamese citizens. However, the persistence of several helminth diseases continues in some endemic areas, especially where poverty is widespread and local traditions include the consumption of raw foods, especially fish and meats. This manuscript provides an overview of the helminth infection prevention and control programs conducted in Vietnam, their achieved results, learned lessons, and future works.

THE DIVERSITY OF CERCARIAE FROM FRESHWATER SNAILS IN LOWLAND AREAS OF BINH DINH AND PHU YEN PROVINCES, VIETNAM

A survey was conducted in the lowland areas of Binh Dinh and Phu Yen provinces in south central Vietnam to study the diversity of digenean cercariae within freshwater snails. These regions are known as highly endemic areas for the transmission of liver flukes, Fasciola spp. and Opisthorchis viverrini. In total, 13 snail species were found, and 3 of these were dominant, comprising 51.9% of all collected snails, i.e., Bithynia funiculata, Melanoides tuberculata, and Radix auriculata. Cercariae were found in 5 snail species, and among these, Indoplanorbis exustus had the highest overall prevalence of infection (38.5%). No cercarial infections were found in viviparid and ampullariid snails. Morphological identification resulted in 10 cercariae types that were illustrated and measured. Among them, xiphidiocercariae and echinostomata were the most common, causing 70.55% of all cercariae infections. Bithynia species had the most diverse digenean fauna. Molecular data revealed the presence of cercariae of 13 digenean species, including O. viverrini. The 18S rDNA sequences of echinostomata and xiphidiocercariae type 3, which were shed from different snail hosts, were similar to 2 and 3 digenean species, respectively. In conclusion, our findings highlight the diversity of digenean fauna in Binh Dinh and Phu Yen provinces.

Diagnosing Human Fascioliasis Using ELISA Immunoassays at a Tertiary Referral Hospital in Hanoi: A Cross-Sectional Study

Infections with the zoonotic liver flukes Fasciola gigantica and Fasciola hepatica may result in severe disease in humans. In Vietnam, an emergence of fascioliasis cases has been observed from the late 1990s onwards. Various diagnostic tools are used in the country, but the agreement between these tools has not been critically evaluated. We aimed to describe the clinical presentation and diagnostic outcomes in fascioliasis patients in Vietnam. A retrospective, cross-sectional study was conducted on the medical records of a group of 145 patients diagnosed with fascioliasis at a tertiary referral hospital in Hanoi. Based on the review, sociodemographic background and clinical presentation were recorded. These patients all received standard routine serologic tests, including internal antibody (Ab)-ELISA, an enzyme-linked immunosorbent assay (ELISA), and commercial coproantigen (cAg)-ELISA. The majority of cases were between 30 and 59 years old (68.3%), and about half of them were male (51.0%). Upper quadrant and epigastric pain were the most commonly reported symptoms (61.4% and 35.2%, respectively). All but one patient had liver lesions upon ultrasound examination (99.3%), and eosinophilia was present in most of the patients (89.7%). A high number of patients were positive in the in-house and the commercial Ab-ELISA (95.9% and 87.4%, respectively), yet only a slight agreement was observed between the two tests (kappa coefficient, 0.06). A further 47.4% of cases were positive for the commercial cAg-ELISA, whereas stool microscopy indicated the presence of Fasciola spp. eggs in 25.7% of patients. The current study emphasizes the challenges related to the diagnosis of human fascioliasis in Vietnam.

Development of a loop-mediated isothermal amplification assay for detection of Austropeplea tomentosa from environmental water samples

Lymnaeid snails are key intermediate hosts for the development and survival of Fasciola spp., the causative agent of Fascioliasis which are economically important parasites infecting humans and livestock globally. The current control method for treating Fascioliasis is heavily reliant on anthelmintic drugs, particularly Triclabendazole (TCBZ) which has resulted in drug-resistant parasites and poses significant risk as there are no long-term efficacious alternatives available. Sustainable control measures at the farm level could include both parasite and snail control will play an important role in Fasciola spp. control and reduce the reliance on anthelmintic drugs. Implementation of such sustainable control measures requires effective identification of snails on the property however Lymnaeid snails are small and difficult to physically locate. Snail identification using an environmental DNA approach is a recent approach in which physically locating snails are not required. Austropeplea tomentosa, is the primary intermediate snail host for F. hepatica transmission in South-East Australia and we present an in-field loop-mediated isothermal amplification and water filtering method for the detection of A. tomentosa eDNA from water samples to improve current surveillance methods. This methodology is highly sensitive with a detection limit of 5 × 10^− 6 ng/μL, detected in < 20 minutes, with cumulative sample preparation and amplification time under 1 hour. This proposed workflow could assist in monitoring areas to determine the risk of Fascioliasis infection and implement strategies to manage snail populations to ultimately reduce the risk of infection for humans and livestock.

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.

Insights on foodborne zoonotic trematodes in freshwater snails in North and Central Vietnam

Foodborne zoonotic trematode (FZT) infections are common neglected tropical diseases in Southeast Asia. Their complicated life cycles involve freshwater snails as intermediate hosts. A cross-sectional study was conducted in Yen Bai and Thanh Hoa provinces in North and Central Vietnam, to investigate the diversity of cercariae of potential FZT and to construct the phylogenetic relationship of trematode cercariae based on the Internal Transcribed Spacer 2 (ITS2) region. Among 17 snail species collected from various habitats, 13 were infected by 10 cercarial groups among which parapleurolophocercous, pleurolophocercous, and echinostome cercariae were of zoonotic importance. The monophyletic tree separated cercarial sequences into different groups following the description of the cercariae families in which Haplorchidae, Opisthorchiidae, Echinochasmidae, and Echinostomatidae are important families of FZT. The overall prevalence was different among snail species and habitats and showed a seasonal trend. Parapleurolophocercous and echinostome cercariae emerged as the most common cercariae in snails in Yen Bai, while monostome, echinostome, and megalura cercariae were most common in Thanh Hoa. Using a molecular approach, we identified Parafossarulus striatulus as the first intermediate snail host of Clonorchis sinensis in Thac Ba Lake. Melanoides tuberculata and Bithynia fuchsiana were we identified preferred intermediate snail hosts of a diverse range of trematode species including intestinal flukes (i.e., Haplorchis pumilio and Echinochasmus japonicus) in Yen Bai and Thanh Hoa, respectively.

Fasciola Species Introgression: Just a Fluke or Something More?

The threats posed by a range of viral and bacterial zoonotic diseases inevitably receive renewed attention in the wake of global pandemic events due to their overt and devastating impacts on human health and the economy. Parasitic zoonoses, however, many of which affect millions of people each day, are frequently ignored. In the case of fasciolosis, caused by infection with Fasciola hepatica or Fasciola gigantica, this oversight has allowed for the expansion of areas of parasite sympatry and thus increased the incidence of hybridization and possible introgression between the two species. Here we highlight how an increased demand for animal-derived protein, combined with a lack of appropriate tools for detection of these events, is changing the status quo of these zoonotic parasites.

Increased demand for animal-derived protein from Fasciola hepatica-endemic countries has led to a growing number of reports of hybridization between F. hepatica and Fasciola gigantica in Southeast Asia.

Hybridization and eventual introgression have been reported in a range of protozoan, helminth, and arthropod parasites and act as important drivers of evolutionary change and adaptation.

Introgression between Fasciola spp. remains unproven but has potentially serious human and animal health consequences as seen in other parasites.

New tools for the characterization of hybridization and introgression events between Fasciola spp. are needed.

Fascioliasis and fasciolopsiasis: Current knowledge and future trends

Food-borne zoonotic trematodiases are classified as neglected diseases by the World Health Organization. Among them, fascioliasis is caused worldwide by Fasciola hepatica and F. gigantica, and represent a huge problem in livestock production and human health in endemic areas. Fasciolopsis buski, restricted to specific regions of Asia, causes fasciolopsiasis. The incidence of these trematodiases is underestimated due to under-reporting and to the lack of sensitive and widely accepted tool for their diagnosis. This, together with a rising trend in reporting of drug resistance and the need for an effective vaccine against these parasites, pose a challenge in the effective control of these diseases. Here, the latest reports on fascioliasis outbreaks between 2000 and 2020 and the most recent advances in their epidemiology, diagnosis, treatment and control are revised. Finally, future needs in the field of fascioliasis and fasciolopsiasis are presented, which could be addressed based on current knowledge and by means of new emerging technologies.

Establishment of an Experimental Procedure for Preparing Trial Serum Samples for the Specific Serodiagnosis of Toxocara canis for External Quality Assessment Schemes

Background

External quality assessment (EQA) provides evidence of reliable, accurate, and precise results for customers using the diagnostic test for Toxocara canis. Objective. To establish a procedure for producing standard Toxocara canis serum samples for serodiagnostic testing in EQA.

Methods

The collected serum samples to contain anti-Toxocara canis serum samples for serodiagnostic testing in EQA. F-test and a T-test were applied to evaluate their homogeneity and stability.

Results

Among eleven samples positive by ELISA, ten of them were confirmed via Western blotting by positive reaction with 5 specific Toxocara canis serum samples for serodiagnostic testing in EQA. Toxocara canis serum samples for serodiagnostic testing in EQA. p > 0.05). Samples produced by both methods were stable for 7 days at 30°C (p > 0.05). Samples produced by both methods were stable for 7 days at 30°C (

Conclusion

Specific serodiagnosis samples of anti-Toxocara canis antibodies for EQA could be produced that possessed homogeneity and stability lasting for 3 months and 6 months by the freeze-drying and freezing methods, respectively. At 30°C, the samples produced by both methods were stable for 7 days, suitable for delivery to remote laboratories.Toxocara canis serum samples for serodiagnostic testing in EQA.

Which species is in the faeces at a time of global livestock movements: single nucleotide polymorphism genotyping assays for the differentiation of Fasciola spp

Fasciolosis, caused by Fasciola hepatica and Fasciola gigantica, is a globally distributed zoonotic disease of livestock. While F. hepatica and F. gigantica have temperate and tropical distributions, respectively, parasite sympatry occurs in parts of Asia and Africa. A growing protein demand has the potential to facilitate the translocation of parasites from endemic to non-endemic areas, via associated international livestock movements. Such is the case in Southeast Asia, where livestock trade from F. hepatica-endemic countries into China and Vietnam may account for detection of F. hepatica hybrid/introgressed forms. Of particular importance is Lao People's Democratic Republic, which acts as a major livestock thoroughfare for the region. Our ability to understand the impacts of livestock-associated Fasciola spp. movements on local animal and human health is hindered by a lack of ante-mortem diagnostic tools allowing species differentiation. Molecular tools have been developed for Fasciola spp. differentiation, however those rely on access to pure DNA from adult specimens, limiting their application to post-mortem use. Our aim was to detect and differentiate F. hepatica from the endemic F. gigantica in local smallholder cattle in a region of Southeast Asia with frequent livestock trafficking. To do this we designed and validated ante-mortem molecular assays for Fasciola spp. differentiation targeting single-nucleotide polymorphisms (SNPs) within ITS1 and lsrRNA. We then deployed these SNP genotyping assays to diagnose Fasciola spp. infection in 153 local cattle from 27 villages in Northern Laos. We demonstrate the presence of F. hepatica DNA, confirmed by qualitative Sanger and quantitative Illumina amplicon sequencing of ITS1 and lsrRNA, and highlight the shortfalls of Sanger sequencing for Fasciola spp. identification due to the preferential amplification of F. gigantica nucleotides in mixed DNA samples. The outlined protocol enables rapid surveillance of faecal samples for the presence of Fasciola species eggs, their co-infection and/or infection with F. hepatica/F. gigantica hybrids.

Case Report: First Molecular Diagnosis of Liver Abscesses Due to Fasciola hepatica Acute Infection Imported from Vietnam

We report a case of Fasciola hepatica liver abscesses in a 67-year-old female returning from a trip to Vietnam. She has been suffering from a fever, right abdominal pain for 4 days, and major eosinophilia. Radiologic investigations showed multiple hypodense confluent abscesses in the right lobe of the liver, complicated by occlusive thrombosis of the right branch of the portal vein. The serological investigation of helminth-elicited eosinophilia showed only a positive serology for F. hepatica. Despite repeated negative stool examinations for any intestinal pathogen, the diagnosis was established by the detection of F. hepatica DNA in stool and pus aspirate samples.

Zoonotic transmission of intestinal helminths in southeast Asia: Implications for control and elimination

Intestinal helminths are extremely widespread and highly prevalent infections of humans, particularly in rural and poor urban areas of low and middle-income countries. These parasites have chronic and often insidious effects on human health and child development including abdominal problems, anaemia, stunting and wasting. Certain animals play a fundamental role in the transmission of many intestinal helminths to humans. However, the contribution of zoonotic transmission to the overall burden of human intestinal helminth infection and the relative importance of different animal reservoirs remains incomplete. Moreover, control programmes and transmission models for intestinal helminths often do not consider the role of zoonotic reservoirs of infection. Such reservoirs will become increasingly important as control is scaled up and there is a move towards interruption and even elimination of parasite transmission. With a focus on southeast Asia, and the Philippines in particular, this review summarises the major zoonotic intestinal helminths, risk factors for infection and highlights knowledge gaps related to their epidemiology and transmission. Various methodologies are discussed, including parasite genomics, mathematical modelling and socio-economic analysis, that could be employed to improve understanding of intestinal helminth spread, reservoir attribution and the burden associated with infection, as well as assess effectiveness of interventions. For sustainable control and ultimately elimination of intestinal helminths, there is a need to move beyond scheduled mass deworming and to consider animal and environmental reservoirs. A One Health approach to control of intestinal helminths is proposed, integrating interventions targeting humans, animals and the environment, including improved access to water, hygiene and sanitation. This will require coordination and collaboration across different sectors to achieve best health outcomes for all.

A cascade of biological invasions and parasite spillback in man-made Lake Kariba

Parasite spillback, the infection of a non-indigenous organism by a native parasite, is a highly important although understudied component of ecological invasion dynamics. Here, through the first analysis of the parasite fauna of lymnaeid gastropods of Lake Kariba (Zimbabwe). We illustrate how the creation of an artificial lake may lead to a cascade of biological invasions in which an invasive aquatic plant promotes the proliferation of invasive gastropods, which in turn alters the epidemiology of trematodiases of potential medical and veterinary importance. Using a new multiplex Rapid Diagnostic PCR assay, we assessed the prevalence of Fasciola sp. infections in the gastropod populations. Both gastropod hosts and trematode parasites were identified using DNA barcoding. We provide the first record of the invasive North-American gastropod Pseudosuccinea columella in Lake Kariba. This species was found at 14 out of 16 sampled sites and its abundance was strongly positively correlated with the abundance of the invasive South-American water hyacinth (Eichhornia crassipes). About 65% of the P. columella specimens analysed were infected with a hitherto unknown Fasciola species. Phylogenetic analyses indicate close affinity to Fasciola hepatica and F. gigantica, which cause fasciolosis, an important liver disease affecting both ruminants and humans. In addition, another non-native Lymnaeid species was found: a Radix sp. that clustered closely with a Vietnamese Radix species. Radix sp. hosted both amphistome and Fasciola trematodes. By linking an invasion cascade and parasite spillback, this study shows how both processes can act in combination to lead to potentially important epidemiological changes.

Evaluation of a Commercial Enzyme-Linked Immunosorbent Assay Kit and In-House Fasciola gigantica Cysteine Proteinases-Based Enzyme-Linked Immunosorbent Assays for Diagnosis of Human Fascioliasis

Fascioliasis, caused by Fasciola hepatica and Fasciola gigantica infection, is a major food-borne trematodiasis in many places of the world, with the central region of Vietnam being reported as a highly endemic area. Stool examination for Fasciola eggs is not a sensitive method, and immunodiagnostic methods are preferable. We investigated various enzyme-linked immunosorbent assays (ELISAs) to evaluate their efficacy for fascioliasis diagnosis. Test sera used are primarily screened using an ELISA kit produced in Vietnam (VN kit; Viet Sinh Chemical Producing & Trading Co. Ltd., Ho Chi Minh City, Vietnam): Seropositive individuals having symptoms compatible with fascioliasis were regarded as clinically diagnosed fascioliasis cases. A commercial Fasciola IgG ELISA kit from Diagnostic Automation/Cortez Diagnostics, Inc. (USA kit; Woodland Hills, CA), which has been commonly used in Vietnam, was assessed and compared with in-house ELISA systems, including a cystatin-capture (CC) ELISA using crude worm extract (CWE) and an indirect ELISA using a synthetic peptide Ac-TPTCHWECQVGYNKTYDEE-NHMe designed from the F. gigantica cathepsin B (FgCB5) molecule. The USA kit was suitable for routine diagnosis after recalibration of the manufacturer's suggested cutoff point. Cystatin-capture ELISA with CWE provided good sensitivity and specificity with perfect agreement to the results of the USA kit. In dot-blot ELISA, recombinant FgCB5 reacted more strongly with human antisera than did other F. gigantica antigens tested. Enzyme-linked immunosorbent assay using the synthetic peptide fragment of the FgCB5 exhibited nearly 80% sensitivity and specificity, but the test results showed low agreement with CC-ELISA or the USA kit. In conclusion, the commercially available Fasciola IgG ELISA kit from the United States and the in-house CC ELISA using CWE are suitable for practical diagnosis for fascioliasis.

Identification of Fasciola Species Isolates from Nghe An Province, Vietnam, Based on ITS1 Sequence of Ribosomal DNA Using a Simple PCR-RFLP Method

Fascioliasis—a disease caused by Fasciola spp. (Platyhelminthes: Trematoda: Digenea)—is considered as the most important helminthic infection of bovine, sheep, and buffalo in Vietnam. The aim of this study is to detect the genotype of Fasciola spp. isolated from bovine and buffalo in the Nghe An province, central Vietnam, using PCR-RFLP and sequence analysis of the first nuclear ribosomal internal transcribed spacer (ITS1). Adult Fasciola spp. were isolated from bile ducts of bovine and buffalo in Nghe An province, Vietnam. Overall, 96 adult flukes from livers of slaughtered animals were collected from abattoirs of different areas. They included 7 samples from infected bovine and 89 samples from infected buffalo. 96/96 samples were identified as Fasciola species by ITS1 of rDNA. In this study, a PCR-RFLP method was used to distinguish between F. hepatica and F. gigantica in ITS1 of rDNA (680 bp) with RsaI restriction enzyme. RFLP pattern with RsaI produced a consistent pattern of 360, 100, and 60 bp fragments in F. hepatica, whereas F. gigantica worms had a profile of 360, 170, and 60 bp in size, respectively. The results showed that using PCR-RFLP based on the first internal transcribed spacers (ITS1) of the ribosomal RNA revealed that 93 out of 96 isolates were of Fasciola gigantica type, whereas three isolates presented an intermediate Fasciola. In the present study, F. gigantica and intermediate form were coexisting in bovine and buffalo in the Nghe An province of central Vietnam, whereas F. hepatica was not detected.

Distribution Status of Hybrid Types in Large Liver Flukes, Fasciola Species (Digenea: Fasciolidae), from Ruminants and Humans in Vietnam

The aim of this study is to delineate ‘admixed hybrid’ and ‘introgressive’ Fasciola genotypes present in the Fasciola population in Vietnam. Adult liver flukes collected from ruminants in 18 Provinces were morphologically sorted out by naked eyes for small (S), medium (M) and large (L) body shapes; and human samples (n=14) from patients. Nuclear ribosomal (rDNA) ITS1 and ITS2, and mitochondrial (mtDNA) nad1 markers were used for determination of their genetic status. Total 4,725 worm samples of ruminants were tentatively classified by their size: 6% (n=284) small (S)-, 13% (n=614) medium (M)-, and 81% (n=3,827) large (L)-forms. All the representative (n=120, as 40 each group) and 14 human specimens, possessed maternal mtDNA of only F. gigantica and none of F. hepatica. Paternally, all (100%) of the L-(n=40) and 77.5% (n=31) of the M-flukes had single F. gigantica rDNA indicating ‘pure’ F. gigantica. A majority (90%, n=36) of the S- and 15% (n=6) of the M-worms had single F. hepatica rDNA, indicating their introgressive; the rest (10%, n=4) of the S- and 7.5% (n=3) of the M-flukes had mixture of both F. gigantica and F. hepatica rDNAs, confirming their admixed hybrid genetic status. Fourteen human samples revealed 9 (64%) of pure F. gigantica, 3 (22%) of introgressive and 2 (14%) of admixed hybrid Fasciola spp. By the present study, it was confirmed that the small worms, which are morphologically identical with F. hepatica, are admixed and/or introgressive hybrids of Fasciola spp., and able to be the pathogens of human fascioliasis.

Identity of Fasciola spp. in sheep in Egypt

Background

In Egypt, liver flukes, Fasciola spp. (Digenea: Fasciolidae), have a serious impact on the farming industry and public health. Both Fasciola hepatica and Fasciola gigantica are known to occur in cattle, providing the opportunity for genetic recombination. Little is known on the identity and genetic variability of Fasciola populations in sheep.

Methods

This study was performed to determine the prevalence of liver flukes in sheep in Menofia Province as a representative area of the delta region in Egypt, as measured by postmortem examination of slaughtered animals at three abattoirs. The identity and genetic variability of Fasciola spp. in slaughtered animals were determined by PCR-sequence analysis of the nuclear ribosomal internal transcribed spacer 1 (ITS1) and the mitochondrial NADH dehydrogenase subunit 1 (nad1) genes.

Results

Physical inspection of the liver indicated that 302 of 2058 (14.7%) slaughtered sheep were infected with Fasciola spp. Sequence analysis of the ITS1 and nad1 genes of liver flukes from 17 animals revealed that 11 animals were infected with F. hepatica, four with F. gigantica, and two with both species. Seventy eight of 103 flukes genetically characterized from these animals were F. hepatica, 23 were F. gigantica, and two had ITS1 sequences identical to F. hepatica but nad1 sequences identical to F. gigantica. nad1 sequences of Egyptian isolates of F. gigantica showed pronounced differences from those in the GenBank database. Egyptian F. gigantica haplotypes formed haplogroup D, which clustered in a sister clade with haplogroups A, B and C circulating in Asia, indicating the existence of geographic isolation in the species.

Conclusions

Both F. hepatica and F. gigantica are prevalent in sheep in Egypt and an introgressed form of the two occurs as the result of genetic recombination. In addition, a geographically isolated F. gigantica population is present in the country. The importance of these observations in epidemiology of fascioliasis needs to be examined in future studies.

Seroprevalence of fascioliasis, toxocariasis, strongyloidiasis and cysticercosis in blood samples diagnosed in Medic Medical Center Laboratory, Ho Chi Minh City, Vietnam in 2012

Background

Despite the global effort against neglected tropical diseases (NTDs), developing countries with middle to low income are still burdened by them. Vietnam has been undergoing substantial economic growth and urbanization, but underprivileged people living in rural and suburban areas are still having little access to public health infrastructure and proper sanitation. Hitherto, limited information is available for seroprevalence and risk factors of several parasitic diseases in Vietnam.

Methods

A retrospective study was performed on diagnostic results of Fasciola spp., Toxocara spp., Strongyloides stercoralis and Taenia solium IgG ELISA tests from Medic Medical Center Laboratory, Ho Chi Minh City in 2012. The data were first stratified before statistical analyses were performed. Seroprevalence of fascioliasis, toxocariasis, strongyloidiasis and cysticercosis was determined and the age and gender risk factors were evaluated.

Results

Seroprevalence of fascioliasis, toxocariasis, strongyloidiasis and cysticercosis was 5.9 % (590/10,084; 95 % CI: 5.44–6.36), 45.2 % (34,995/77,356; 95 % CI: 44.85–45.55), 7.4 % (3,174/42,920; 95 % CI: 7.15–7.65) and 4.9 % (713/14,601; 95 % CI: 4.55–5.25), respectively. Co-exposure to multiple parasites was detected in 890 males (45.7 %; 95 % CI: 43.49–47.91) and 1,059 females (54.3 %; 95 % CI: 52.09–56.51). Social structure and differences in behavioural factors caused the gender factor to have a significant effect on the prevalence of all the diseases, while the seropositivity for fascioliasis and strongyloidiasis were age group-related.

Conclusions

The seroprevalence of fascioliasis, toxocariasis, strongyloidiasis and cysticercosis in the blood samples diagnosed in Medic Medical Center Laboratory, Ho Chi Minh City, in year 2012 were comparatively high. The Vietnamese customs and cultures, dietary habits and agricultural practices exposed them to high risk of contracting NTDs. Despite the possibility of false positive results due to antigenic cross-reactions, detection of IgG antibodies remains as a reliable method in sero-epidemiological study as it is non-invasive and demonstrates previous exposure of individuals to the parasites. Besides the implementation of strategies to control these diseases, epidemiological analysis and surveillance of diseases should also be continually strengthened to monitor the effectiveness of regimens and interventions.