Enhanced detection of Opisthorchis viverrini infection: A comparative evaluation of modified one-step FECT and conventional diagnostic methods in low-intensity setting

The formalin-ethyl acetate concentration technique (FECT) is one of the most sensitive diagnostic method not only for all helminths, but also for Opisthorchis viverrini infections in stool examinations. However, it remains a diagnostic problem for light infections. We modified the one-step FECT to determine the low-intensity of O. viverrini infection and compared with various conventional detection methods. The study utilized 160 egg-positive and 160 randomly negative stool samples for O. viverrini eggs by conventional FECT (cFECT) to compare the methods, including the simple smear, the Kato-Katz method, the two commercial stool examination kits, and the one-step FECT. Our results showed that the one-step FECT method had the highest sensitivity (95.6 %), followed by cFECT (87.9 %), the Kato-Katz (55.5 %), Aquisfek SF-FIX® (48.3 %), simple smear (42.3 %), and Mini Parasep® SF (35.1 %). The ability of one-step FECT exhibited better ability to detect low parasite intensities compared to the cFECT (18 eggs per gram (e.p.g.) versus 34 e.p.g.) and the other conventional diagnostic methods. In addition, the investigation of O. viverrini infection in endemic regions in northeastern Thailand based on 3900 fecal samples revealed that the one-step FECT with an intensity of 66.8 e.p.g. (range 18-226) was significantly higher in sensitivity than cFECT, which had an intensity of 58.0 e.p.g. (range 34-214). Interestingly, fecal samples with less than 50 e.p.g. could not be detected by cFECT in 67 % of cases, and 69 out of 3900 samples were negative. In conclusion, one-step FECT improves the detection of low-intensity O. viverrini infection, which is suitable for parasites screening, especially for low-intensity infections in the community.

Re-evaluation of certain aspects of the EFSA Scientific Opinion of April 2010 on risk assessment of parasites in fishery products, based on new scientific data. Part 2

The objective of this opinion was to determine if any wild caught fish species, originating from specific fishing grounds and consumed in the EU/EFTA could be considered free of zoonotic parasites. In this Opinion the term 'fishery products' only refers to fresh finfish. As there are multiple fish species and numerous potential parasites, Anisakis sp. was used as an indicator of zoonotic parasites in marine areas. This parasite species is particularly suited as it is common in marine environments, capable of infecting multiple fish species and is the subject of the majority of published studies. On the rare occasion where Anisakis sp. data were not available, or all tests were negative, other parasites such as Contracaecum osculatum (s.l.) and/or Phocanema spp. were considered. In freshwater systems, all zoonotic parasites were investigated. Consumption, import and landing data were used to determine the most relevant fish species and, where possible, the source fishing areas were identified. The most commonly consumed wild caught fish species in the EU/EFTA include tuna, cod, Alaskan pollock, hake, herring, sardines, mackerel, trout and saithe. Although the majority of these fish are caught in the Atlantic Ocean, the Mediterranean and the Black Sea (37) as well as several areas in the Indian Ocean, imported fish may originate from any global fishing areas, with the exception of Antarctica. Based on the data, at least one zoonotic parasite has been reported in at least one fish species in each of the FAO marine fishing areas. Thus, due to relative low fish host specificity of the zoonotic parasites, the panel concluded that all wild caught fish species may be exposed to and infected with zoonotic parasites. The same applies to freshwater fishing areas, with many areas having multiple studies reporting the presence of zoonotic parasites in the wild caught fish species.

Characteristics of SARS-CoV-2 and Opisthorchis viverrini coinfections: insights into immune responses and clinical outcomes

The effects of co-infections with SARS-CoV-2 and parasitic diseases have been little investigated in terms of immune response, disease dynamics, and clinical outcomes. This study aimed to explore the impact of co-infection with Opisthorchis viverrini and SARS-CoV-2 on the immune response concerning clinical symptoms and the severity of pulmonary abnormalities. A cross-sectional study was conducted, including healthy participants as controls, participants with opisthorchiasis, SARS-CoV-2 infection, and a co-infection group with both diseases. Characteristics of SARS-CoV-2 infection were assessed based on clinical parameters and severity of pulmonary abnormalities, whereas opisthorchiasis burden was evaluated by eggs-per-gram (EPG) counts. Immune responses were assessed by measuring levels of interferon-γ (IFN-γ), SARS-CoV-2 anti-spike receptor binding domain (RBD) IgG, and neutralizing antibody against SARS-CoV-2. In the co-infected group, clinical parameters and hospitalization rates were lower than in the SARS-CoV-2 group. Pulmonary abnormalities, such as bronchial fibrosis, were commonly observed in the SARS-CoV-2 group, leading to hospitalization in some cases. Participants with opisthorchiasis had higher IFN-γ levels than healthy individuals. IFN-γ levels were significantly lower in the co-infection group compared with the SARS-CoV-2 group (P = 0.002). There was a significant (P = 0.044) positive correlation between RBD-specific IgG and percent neutralization levels in the SARS-CoV-2 group. Levels of both were somewhat lower (not statistically significant) in the co-infection group. A negative correlation was observed between opisthorchiasis burden (EPG counts) and IFN-γ and RBD-specific IgG levels in the co-infected group. Following vaccination, the increase in IgG levels against the RBD protein was significantly lower in the co-infected group than in the SARS-CoV-2 group. These results suggest that O. viverrini infection suppresses immune responses and may lead to a reduction in severity in cases of SARS-CoV-2 co-infection.

Zoonotic human liver flukes, a type 1 biocarcinogen, in freshwater fishes: genetic analysis and confirmation of molluscan vectors and reservoir hosts in Bangladesh

BACKGROUND

Opisthorchiid flukes, particularly Opisthorchis viverrini, Opisthorchis felineus, Clonorchis sinensis, and Metorchis spp. are the most common fish-borne zoonotic human liver flukes (hLFs). Liver fluke infections are more prevalent in resource-deprived and underprivileged areas. We herein estimated the prevalence of the metacercariae (MC) of major hLFs in common large freshwater fishes (lFWF) marketed for human consumption from some selected areas of Bangladesh along with detection of their molluscan vectors and reservoirs.

METHODS

The current status of fish-borne zoonotic hLF infections in lFWF was investigated along with their molluscan vectors and mammalian reservoir hosts in Mymensingh and Kishoreganj in Bangladesh from July 2018-June 2022 using conventional and multiple molecular techniques, such as PCR, PCR-restriction fragment length polymorphism (RFLP), sequencing, and bioinformatic analyses. The infection rate of fishes was analyzed using the Z-test and the loads of MC were compared using the chi-squared (χ2) test.

RESULTS

The MC of C. sinensis, Opisthorchis spp., and Metorchis spp. were detected in 11 species of common and popular lFWF. In lFWF, the estimated prevalence was 18.7% and the mean load was 137.4 ± 149.8 MC per 100 g of fish. The prevalence was the highest (P < 0.05) in spotted snakehead fishes (Channa punctata, 63.6%). The highest rate of infection (P < 0.05) was observed with the MC of C. sinensis (11.8%). Metacercariae were almost equally (P > 0.05) distributed between the head and body of fishes. The infection rate was slightly higher in cultured (19.6%) fishes. The MC of C. sinensis, O. felineus, O. viverrini, and Metorchis orientalis in fishes were confirmed using PCR, PCR-RFLP and bioinformatics. The cercariae of opisthorchiid (Pleurolophocercus cercariae) flukes were only recovered from Bithynia spp. (3.9%, 42 out of 1089). The ova of hLFs from dogs (4.3%, 5 out of 116) and cats (6.0%, 6 out of 100), and adult flukes (M. orientalis) from ducks (41.1% 113 out of 275) were detected.

CONCLUSIONS

The MC of hLFs are highly prevalent in fresh water fishes in Bangladesh. Reservoir hosts, such as street dogs, cats, and ducks carried the patent infection, and residents of Bangladesh are at risk.

Global prevalence of 4 neglected foodborne trematodes targeted for control by WHO: A scoping review to highlight the gaps

BACKGROUND

Foodborne trematodiases (FBTs) are a group of trematodes targeted for control as part of the World Health Organization (WHO) road map for neglected tropical diseases from 2021 to 2030. Disease mapping; surveillance; and capacity, awareness, and advocacy building are critical to reach the 2030 targets. This review aims to synthesise available data on FBT prevalence, risk factors, prevention, testing, and treatment.

METHODS

We searched the scientific literature and extracted prevalence data as well as qualitative data on the geographical and sociocultural risk factors associated with infection, preventive/protective factors, and methods and challenges of diagnostics and treatment. We also extracted WHO Global Health Observatory data representing the countries that reported FBTs during 2010 to 2019.

RESULTS

One hundred and fifteen studies reporting data on any of the 4 FBTs of focus (Fasciola spp., Paragonimus spp., Clonorchis sp., and Opisthorchis spp.) were included in the final selection. Opisthorchiasis was the most commonly reported and researched FBT, with recorded study prevalence ranging from 0.66% to 88.7% in Asia, and this was the highest FBT prevalence overall. The highest recorded study prevalence for clonorchiasis was 59.6%, reported in Asia. Fascioliasis was reported in all regions, with the highest prevalence of 24.77% reported in the Americas. The least data was available on paragonimiasis, with the highest reported study prevalence of 14.9% in Africa. WHO Global Health Observatory data indicated 93/224 (42%) countries reported at least 1 FBT and 26 countries are likely co-endemic to 2 or more FBTs. However, only 3 countries had conducted prevalence estimates for multiple FBTs in the published literature between 2010 to 2020. Despite differing epidemiology, there were overlapping risk factors for all FBTs in all geographical areas, including proximity to rural and agricultural environments; consumption of raw contaminated food; and limited water, hygiene, and sanitation. Mass drug administration and increased awareness and health education were commonly reported preventive factors for all FBTs. FBTs were primarily diagnosed using faecal parasitological testing. Triclabendazole was the most reported treatment for fascioliasis, while praziquantel was the primary treatment for paragonimiasis, clonorchiasis, and opisthorchiasis. Low sensitivity of diagnostic tests as well as reinfection due to continued high-risk food consumption habits were common factors.

CONCLUSION

This review presents an up-to-date synthesis on the quantitative and qualitative evidence available for the 4 FBTs. The data show a large gap between what is being estimated and what is being reported. Although progress has been made with control programmes in several endemic areas, sustained effort is needed to improve surveillance data on FBTs and identify endemic and high-risk areas for environmental exposures, through a One Health approach, to achieve the 2030 goals of FBT prevention.

Prevalence and Associated Risk Factors of Intestinal Parasitic Infections: A Population-Based Study in Phra Lap Sub-District, Mueang Khon Kaen District, Khon Kaen Province, Northeastern Thailand

Intestinal parasitic infections are still a crucial problem among communities in Northeast Thailand. Misuse of antiparasitic drugs and unhealthy food behaviors are known. This study aimed to explore the prevalence, behavioral health factors, and motivation for self-treatment of anti-parasitic drugs in this area. A community-based cross-sectional study was conducted in Phra Lap sub-district, Mu Khon Kaen district, Khon Kaen province, Northeast Thailand, in 2016. A total of 419 participants were recruited to complete a self-administered questionnaire and stool examination. Binary logistic regression was used to assess the association between the risk factor and parasitic infection. Forty-two participants (10%; 95%CI 7.5-13.3) were positive for at least one parasite species. In this community, the most detected intestinal parasite was Opisthorchis viverrini (5.3%), followed by Strongyloides stercoralis (3.1%). A total of 67.5% of the participants had the experience of anti-parasitic drug treatment within previous 1 year, and "Often eat raw food" was the most common reason for the use of anti-parasitic drugs. On multivariate analysis, parasitic infections were significantly associated with male gender (ORadj. 2.42; 95%CI 1.00-5.85), age ≥ 60 years (ORadj. 7.55; 95%CI 1.60-35.76), and often consuming raw food of at least one type (ORadj. 2.37; 95%CI 1.03-5.44). Given these findings, correction of the dietary habit of eating raw fish/meat, which is the most important measure, and limitation of the use of anthelmintic treatment for individuals with stools positive for ova as well as emphasis on sanitary toilets will be implemented for the prevention and control of parasitic infection in endemic communities.

Infection rate of Opisthorchis viverrini metacercariae in cyprinoid fish from the markets and its association to human opisthorchiasis in the local community in the Northeast Thailand

The prevalence of Opisthorchis viverrini, a fish-borne zoonotic trematode that can provoke cholangiocarcinoma, is high in the Northeast Thailand. The aim of this study was to determine the prevalence of O. viverrini metacercariae in the cyprinid fish and determine its association of O. viverrini infection among the consumers who regularly buy fish in the markets. A cross-sectional study was conducted in nine provinces covering 20 districts of Thailand, and we examined 778 cyprinoid fish specimens belonging to five species purchased from local markets. Pepsin-HCl digestion method was used to recover O. viverrini metacercariae from fish. In all districts surveyed, O. viverrini metacercariae-positive fish were found with the infection rates ranging from 3.9 to 21.1%. All five fish species studied were positive for O. viverrini metacercariae: Henicorhynchus siamensis (13.7%), Cyclocheilichtys spp. (12.7%), Hampala spp. (8.1%), Systomus spp. (6.9%) and Barbonymus goniatus (5.0%). An average prevalence of O. viverrini infection was 7.1% in the fish consumers surveyed in the markets. The source of fish was determined and our results showed that parasitized fish are sold in markets up to 100 km away from the point of capture, which contributes to the dispersion and maintenance of this helminthiasis. Our results point to the transmission of liver flukes via markets, in spite of many active programs of health education, elimination, prevention and control aimed to reduce O. viverrini infection and subsequent cholangiocarcinoma in the endemic areas of Thailand.

Reduction of Reinfection Rates with Opisthorchis viverrini through a Three-Year Management Program in Endemic Areas of Northeastern Thailand

To clarify the reinfection profile associated with risk factors of opisthorchiasis, we conducted an epidemiological study on the chemotherapeutic effects on reinfection with O. viverrini in the endemic areas of Northeastern Thailand for 3 years. A total of 3,674 fecal samples were collected from participants in villages of 5 provinces. They were examined microscopically using a modified technique of formalin ethyl-acetate concentration. Egg-positive residents were reexamined year (2018) by year (2019) after treatment with a single dose (40 mg/kg) of praziquantel. Health education was provided to the participants yearly. The egg-positive rate of O. viverrini was 14.3%, and was highest (22.2%) in the 20–30 year-old group in 2017. The egg positive rate was 15.3% in dogs and 11.4% cats. Human reinfection rate was 15.5% and 6.3% in next 2 years, and was highest (23.2%) among the fishermen. Relative risk factors of reinfection were significantly higher for males, over 40-year-old age, or working as fishermen or farmers, and eating uncooked fish within the preceding year. A significant difference resulting from a health education program was observed in the third year. Therefore, health education and sustainable surveillance for opisthorchiasis should be maintained to decrease the risk of reinfection.

Discovery of Carcinogenic Liver Fluke Metacercariae in Second Intermediate Hosts and Surveillance on Fish-Borne Trematode Metacercariae Infections in Mekong Region of Myanmar

Countries of lower Mekong regions are highly alarmed by the spread of fish-borne trematode infections, i.e., small liver flukes and minute intestinal flukes especially in Thailand, Lao People’s Democratic Republic (Lao PDR), Vietnam, Cambodia and Myanmar. Moreover; the incidence of cholangiocarcinoma has also been increasing in the endemic area of liver fluke infections. Only a few reports have been published concerning the fish-borne trematodes infections in the central region of Myanmar. However; there is still a lack of information regarding the status of trematodes infections in second intermediate hosts in the Mekong region of Myanmar. Therefore, we conducted surveillance on the distribution of trematode metacercariae in small cyprinoid fishes collected from the Mekong region of Myanmar. A total of 689 fishes (12 different species of cyprinoid fishes) have been collected and examined by pepsin digestion methods. We discovered four species of fish-borne trematode metacercariae infections, i.e., carcinogenic liver fluke, Opisthorchis viverrini; minute intestinal flukes, Haplorchis taichui; Haplorchis pumilio and Haplorchoides sp. in Tachileik, the Mekong Region of Myanmar. The outcome of this study could be a useful index for the fish-borne zoonotic trematode epidemiology in the Mekong area. Besides, the results of our study contribute to filling the gap of information necessary for the control and prevention of fish-borne trematode zoonotic infections in the Mekong region.

Repeated praziquantel treatment and Opisthorchis viverrini infection: a population-based cross-sectional study in northeast Thailand

Background

Opisthorchis viverrini infection is highly prevalent in northeast Thailand. This liver fluke is classified as a carcinogen due to its causal links with cholangiocarcinoma (CCA) development. Although treatment with praziquantel (PZQ) effectively cures O. viverrini infection, the prevalence remains high due to the traditional consumption of raw fish. Therefore, re-infection is common in the endemic community, leading to severe hepato-biliary morbidities including the fatal CCA. In this study, we evaluate the association between the frequency of previous PZQ treatment and current O. viverrini infections among Thai adults living in the endemic area of northeast Thailand.

Methods

This study includes all participants who were screened for O. viverrini infection in the Cholangiocarcinoma Screening and Care Program (CASCAP), northeast Thailand. History of PZQ treatment was recorded using a health questionnaire. O. viverrini infections were diagnosed using urine antigen detection. Associations between PZQ and O. viverrini were determined by adjusted odds ratio (aOR) and 95% confidence interval (CI) using multiple logistic regression.

Results

Among participants, 27.7% had previously been treated once with PZQ, 8.2% twice, 2.8% three times, and 3.5% more than three times. Current O. viverrini prevalence was 17% (n = 524). Compared with participants who never used PZQ, the aOR for infection among those who used the drug once was 1.09 (95% CI: 0.88–1.37), twice was 1.19 (95% CI: 0.85–1.68), three times was 1.28 (95% CI: 0.74–2.21), and more than three times was 1.86 (95% CI: 1.18–2.93; P = 0.007).

Conclusions

The population with a frequent history of PZQ use and still continued raw fish consumption showed high levels of repeated reinfection with O. viverrini. They were infected, treated and re-infected repeatedly. These findings suggest that certain participants continue raw fish consumption even after previous infection. This is a particular problem in highly endemic areas for O. viverrini and increases the risk of CCA.

Electronic supplementary material

The online version of this article (10.1186/s40249-019-0529-5) contains supplementary material, which is available to authorized users.

Parasitic infections in relation to practices and knowledge in a rural village in Northern Thailand with emphasis on fish-borne trematode infection

The present study integrates several aspects of a parasitological survey in a rural community village combining community knowledge of parasites, their potential transmission routes and health risk factors. A rural community located in Northern Thailand was surveyed for intestinal parasites, and an overall prevalence of 45.2% for helminths and 4.8% for protozoan infections was identified. Socio-demographic characteristics, customs and perceptions were compiled using individual questionnaires and interviews for participants surveyed for parasitic screening. The results allowed us to determine the knowledge and perception of local people concerning helminthic infection and transmission. Despite the fact that the participants in this community were aware of parasitic transmission routes, their widespread custom of eating raw fish and meat render the reduction of helminthiasis difficult. A detailed study on the infection of fish-borne parasitic trematodes, the most prevalent helminth, allowed us to determine that the distance from a given household to the river is a determinant of infection intensity. Health education activities organised in the local community resulted in a change in perception of risks associated with parasite transmission.