Emerging foodborne trematodiasis

The disease burden and its distribution characteristics of clonorchiasis in Guangdong Province, Southern China

BACKGROUND

Clonorchiasis has significant socioeconomic importance in endemic areas; however, studies investigating the disease burden in specific sub-regions are lacking. This study aims to address the gap by quantifying the current disease burden caused by clonorchiasis in Guangdong province and assessing its distribution characteristics.

METHODS

Comprehensive measures, including prevalence rates, disability-adjusted life years (DALYs), and direct medical costs, were used to assess the disease burden of clonorchiasis. To estimate the prevalence rate, the number of infections was divided by the examined population, based on the annual surveillance data on clonorchiasis cases during 2016-2021. The calculation of DALYs was based on the epidemiological parameters according to the definition issued by the World Health Organization. Cost data of clonorchiasis were utilized to quantify the direct medical costs. The distribution characteristics of disease burden were assessed through comparisons of groups of population defined by geographic area, time, and characteristics of people.

RESULTS

In 2021, clonorchiasis posed a significant disease burden in Guangdong Province. The prevalence rate was found to be 4.25% [95% CI (4.02%, 4.49%)], with an associated burden of DALYs of 406,802.29 [95% CI (329,275.33, 49,215,163.78)] person-years. The per-case direct medical costs of patients with clonorchiasis were estimated to be CNY 7907.2 (SD = 5154.4). Notably, while the prevalence rate and DALYs showed a steady decrease from 2016 to 2020, there was a rising trend in 2021. Spatial clustering of clonorchiasis cases and DALYs was also observed, particularly along the Pearl River and Han River. This suggests a concentration of the disease in these regions. Furthermore, significant differences in prevalence rates were found among various demographic groups, including sex, age, occupation, and education level. Additionally, patients with longer hospital stays were more likely to incur higher direct medical costs.

CONCLUSIONS

The burden of clonorchiasis in Guangdong Province remains high, despite significant progress achieved through the implementation of the prevention and control programs. It is suggested that measures should be taken based on the distribution characteristics to maximize the effectiveness of prevention and control, with a primary focus on key populations and areas.

Parasites of the liver: A global problem?

Parasitic liver diseases can be caused by trematodes, cestodes, nematodes, and protozoa. This pathology is significant because millions of people in different parts of the world have liver parasites, which can manifest themselves in the development of inflammation, liver cysts, cholecystitis, cholelithiasis, pancreatitis and liver cirrhosis that are often threatening their lives. The International Agency for Research on Cancer considers three species of trematodes, Schistosoma haematobium, Opisthorchis viverrini and Clonorchis sinensis, to be carcinogens. Complex modern examination methods, in some cases including extensive screening of large populations, are required for diagnosing liver parasites. Treatment of parasitic liver diseases is differentiated and can involve a combination of surgical and therapeutic measures. There is no doubt that the clinical and epidemiological scale allows one to regard parasitic liver diseases as a global healthcare problem.

Infection and biogeographical characteristics of Paragonimus westermani and P. skrjabini in humans and animal hosts in China: A systematic review and meta-analysis

BACKGROUND

Paragonimiasis, primarily caused by Paragonimus westermani and P. skrjabini in China, is a common food-borne parasitic zoonosis. However, the national distribution of Paragonimus spp. infection and its associated environmental determinants remain poorly understood. In this paper, we summarize the infection of P. westermani and P. skrjabini and describe key biogeographical characteristics of the endemic areas in China.

METHODS

Data on Paragonimus infection in humans and animal hosts were extracted from eight electronic databases, including CNKI, CWFD, Chongqing VIP, SinoMed, Medline, Embase, PubMed, and Web of Science. A random-effects meta-analysis model was used to estimate the pooled prevalence. All survey locations were georeferenced and plotted on China map, and scatter plots were used to illustrate the biogeographical characteristics of regions reporting Paragonimus infection.

RESULTS

A total of 28,948 cases of human paragonimiasis have been documented, with 2,401 cases reported after 2010. Among the 11,443 cases with reported ages, 88.05% were children or adolescents. The pooled prevalence of P. skrjabini is 0.45% (95% CI: 0.27-0.66%) in snails, 31.10% (95% CI: 24.77-37.80%) in the second intermediate host, and 20.31% (95% CI: 9.69-33.38%) in animal reservoirs. For P. westermani, the pooled prevalence is 0.06% (95% CI: 0.01-0.13%) in snails, 52.07% (95% CI: 43.56-60.52%) in the second intermediate host, and 21.40% (95% CI: 7.82-38.99%) in animal reservoirs. Paragonimus are primarily distributed in regions with low altitude, high temperature, and high precipitation. In northeastern China, only P. westermani infections have been documented, while in more southern areas, infections of both P. westermani and P. skrjabini have been reported.

CONCLUSIONS

Paragonimiasis remains prevalent in China, particularly among children and adolescents. Variations exist in the intermediate hosts and geographical distribution of P. westermani and P. skrjabini. Additionally, altitude, temperature, and precipitation may influence the distribution of Paragonimus.

Epidemiologic evaluation of pulmonary paragonimiasis in Japan using a Japanese nationwide administrative database

BACKGROUND

Paragonimiasis is a parasitic disease primarily contracted through consumption of undercooked freshwater crustaceans or wild boar meat. Large-scale nationwide epidemiological data on paragonimiasis are lacking. In this study, we aimed to investigate the nationwide epidemiology of hospitalized patients with paragonimiasis in Japan using a comprehensive nationwide Japanese administrative database.

METHODS

We evaluated the Japanese Diagnosis Procedure Combination (DPC) data of patients diagnosed with pulmonary paragonimiasis between April 1, 2012 and March 30, 2020. The patients' address and information, including age, sex, treatment (medication: praziquantel; surgery: open thoracotomy or intracranial mass extirpation), Japan coma scale, comorbidities, and length of hospital stay, were extracted.

RESULTS

Of the 49.6 million hospitalized patients, data were extracted on 73 patients with paragonimiasis, of whom 36 were male and 37 were female. The mean age was 49.7 years and the mean length of stay was 12.5 days. The most frequent comorbidity was pleural effusion (31.5 %), followed by pneumothorax (13.7 %). The sites of ectopic paragonimiasis in organs other than the lung included the liver (5.5 %), skin (4.1 %), and brain (2.7 %). Geographically, most patients were from the Kyushu region (54.8 %), followed by the Kanto region (22.0 %). Fukuoka Prefecture had the highest number of patients (22.0 %) by prefecture. During the study period, an average of 9.1 patients/year were hospitalized with lung paragonimiasis in Japan.

CONCLUSION

Paragonimiasis has not completely disappeared in Japan; thus, physicians should be aware of paragonimiasis in the Kyushu region, especially in the Fukuoka Prefecture.

Global distribution of zoonotic digenetic trematodes: a scoping review

BACKGROUND

Digenetic trematodes, including blood flukes, intestinal flukes, liver flukes, lung flukes, and pancreatic flukes, are highly diverse and distributed widely. They affect at least 200 million people worldwide, so better understanding of their global distribution and prevalence are crucial for controlling and preventing human trematodiosis. Hence, this scoping review aims to conduct a comprehensive investigation on the spatio-temporal distribution and epidemiology of some important zoonotic digenetic trematodes.

METHODS

We conducted a scoping review by searching PubMed, Web of Science, Google Scholar, China National Knowledge Infrastructure, and Wanfang databases for articles, reviews, and case reports of zoonotic digenetic trematodes, without any restrictions on the year of publication. We followed the inclusion and exclusion criteria to identify relevant studies. And relevant information of the identified studies were collected and summarized.

RESULTS

We identified a total of 470 articles that met the inclusion criteria and were included in the review finally. Our analysis revealed the prevalence and global distribution of species in Schistosoma, Echinostoma, Isthmiophora, Echinochasmus, Paragonimus, Opisthorchiidae, Fasciolidae, Heterophyidae, and Eurytrema. Although some flukes are distributed worldwide, developing countries in Asia and Africa are still the most prevalent areas. Furthermore, there were some overlaps between the distribution of zoonotic digenetic trematodes from the same genus, and the prevalence of some zoonotic digenetic trematodes was not entirely consistent with their global distribution. The temporal disparities in zoonotic digenetic trematodes may attribute to the environmental changes. The gaps in our knowledge of the epidemiology and control of zoonotic digenetic trematodes indicate the need for large cohort studies in most countries.

CONCLUSIONS

This review provides important insights into the prevalence and global distribution of some zoonotic digenetic trematodes, firstly reveals spatio-temporal disparities in these digenetic trematodes. Countries with higher prevalence rate could be potential sources of transmitting diseases to other areas and are threat for possible outbreaks in the future. Therefore, continued global efforts to control and prevent human trematodiosis, and more international collaborations are necessary in the future.

Idiopyrgus souleyetianus (Gastropoda: Tomichiidae) as an intermediate host of the liver fluke Amphimerus sp. (Trematoda: Opisthorchiidae) in Brazil

Despite the importance of fish-borne trematodes of the family Opisthorchiidae as causative agents of human liver fluke disease, studies on these parasites outside Asia are relativally scarce. In South America, human focus of amphimerosis is known in Ecuador since the mid-20th century, and Amphimerus spp. have also been reported in wild and domestic mammals. Nevertheless, the knowledge on the snails that act as the first intermediate host of these potentially zoonotic parasites are scarce. Herein, a new cercaria of the pleurolophocercous morphotype found in the freshwater snail Idiopyrgus souleyetianus from Brazil was subjected to morphological and molecular studies. Multigene phylogenetic analyses based on 28S, 5.8S-ITS-2 and Cox-1 sequences enabled the identification of Amphimerus sp., a species distinct from that reported in humans from Ecuador. This cercariae was morphologically compared with other opisthorchiid cercariae known. The possible occurrence of human amphimerosis in Brazil is discussed.

Trematode infection in ruminants and diversity of snail hosts across three agro-ecological zones in Ethiopia

The occurrence of trematodes among ruminants and their snail vectors is a major concern across various agro-ecological regions of Ethiopia. Trematodes pose significant threats to animals, causing considerable economic losses and impacting public health. In this study, we have investigated 784 ruminant fecal samples, and 520 abattoir samples, alongside the collection and identification of snail vectors from various agro-ecological regions. Fecal examinations revealed Fasciola, Paramphistomum and Schistosoma species infected 20.5% (95% CI: 17.6, 23.8), 11.7% (95% CI: 9.6, 14.2), and 6.3% (95% CI: 4.1, 9.1) of the animals, respectively. The overall prevalence of trematodes among ruminants was 28.8% (95% CI: 25.7, 32.1%), with 6.0% (95% CI: 4.3, 7.7) showing mixed infections. Fasciola was more prevalent in Asela (26%) compared to Batu (19%) and Hawassa (11.5%), while a higher proportion of animals in Batu were infected with Paramphistomum. Schistosoma eggs were detected only in Batu (12.5%), but not in other areas. Sheep and cattle exhibited higher infection rates with Fasciola, Paramphistoma, and Schistosoma compared to goats. Significant associations were observed between trematode infections and risk factors including agro-ecology, animal species, body condition score, and deworming practices. About 20.8% and 22.7% of the slaughtered animals harbored Fasciola and Paramphistomum flukes, respectively, with a higher prevalence in Asela and Hawassa abattoirs compared to Batu abattoir. Additionally, a total of 278 snails were collected from the study areas and identified as lymnae natalensis, lymnae trancatula, Biomphalaria pffiferi, Biomphlaria sudanica, and Bulinus globosus. In conclusion, the study highlights the widespread occurrence of trematode infections, emphasizing the need for feasible control measures to mitigate their economic and public health impacts.

Diagnosis of fasciolosis antibodies in Brazilian cattle through ELISA employing both native and recombinant antigens

Bovine fasciolosis is a parasitic disease with a global reach. Coprological based on egg detection in fecal samples and liver inspection to evaluate the presence of the parasite is currently the gold standard for diagnosing chronic fasciolosis in cattle. However, these techniques are labor-intensive and ineffective during the acute phase of the disease. Serodiagnosis using native and recombinant antigens has become an interesting alternative in efforts to identify cattle fasciolosis. We evaluated cattle from abattoir (n = 139) and farms (n = 500) through liver inspection and coprological examination, respectively. Our laboratory team optimized and validated enzyme-linked immunosorbent assay tests based on somatic antigen, excretory/secretory proteins, and the recombinant antigen cathepsin L-1 to detect serum antibodies against fasciolosis in cattle. For animals from abattoir, 10 were positive for fasciolosis according to liver inspection. Both FhES and FhrCL-1 presented an area under the receiver operating characteristic (AUROC) curve of 0.80, with a sensitivity of 0.80 (95% CI: 0.46-0.95) and 0.70 (95% CI: 0.38-0.90) and specificity of 0.81 (95% CI: 0.73-0.87) and 0.87 (95% CI: 0.80-0.92), respectively. For those cattle from farms, 28 were positive only for fasciolosis according to coprological examination. In this scenario, FhES gave the best performance, with an AUROC of 0.84, sensitivity of 0.79 (95% CI: 0.60-0.90), and specificity of 0.86 (95% CI: 0.82-0.89). In conclusion, our study highlights the potential of serodiagnosis for accurately screening cattle fasciolosis. The promising sensitivity and specificity values of FhES when compared to liver inspection or coprological examination enhance its importance for cattle fasciolosis diagnosis.

IMPORTANCE

The aim of this article was to identify antibodies against fasciolosis in cattle in Brazil. The methodology was reproduced in our laboratory and applied for the first time to the Brazilian cattle herd. The antigens tested can be used as a screening test and thus speed up the diagnosis of bovine fascioliasis.

Digenean infections in snails (cercariae stage) in Can Gio Mangrove Biosphere Reserve, Ho Chi Minh City, Vietnam

Foodborne zoonotic trematodiasis is a public health problem in many countries. A study on digenean larvae (cercariae stage) obtained from snails in all ten main small canals and two rice fields was carried out in Can Gio Mangrove Biosphere Reserve, Ho Chi Minh city, Vietnam to identify the snail composition and digenean prevalence in snails. The snails were sampled in the dry season (January 2022) and the wet season (June 2022). In the ten canals, 23 snail species belonging to 16 genera, 10 families from the samplings were found; however, there were no cercariae in these 23 snail species. In the two rice fields, 11 snail species in 11 genera and 7 families were collected. In which, Bithynia siamensis in Ly Nhon rice field and Thiara scabra in Binh Khanh rice field infected xiphidio cercariae. For Bithynia siamensis, the prevalence in the dry season (5.6%) was higher than in the wet season (4.6%) (P > 0.05). In Binh Khanh rice field, only one Thiara scabra infected cercariae in the wet season. Further research on digenean infection in different months and in other water bodies in Can Gio Mangrove Biosphere Reserve should be done to contribute to the control of digeneans and reserve the biodiversity.

A systematic review of the effects of hepatitis B and C virus on the progression of liver fluke infection to liver cancer

Hepatitis B and C virus, Opisthorchis viverrini and Clonorchis sinensis, are all individually known to put a person at increased risk for cholangiocarcinoma and hepatocellular carcinoma. This paper seeks to determine if there is any interaction between liver flukes and hepatitis virus infection that are known to put a person at an increased risk for cholangiocarcinoma and hepatocellular carcinoma collectively. This paper seeks to determine whether there is any publicly available articles in English that determine if having a hepatitis viral co-infection along with liver flukes would influence the risk of developing liver cancer. We followed PRISMA systematic review guidelines to conduct a literature review. Three manuscripts fit the search criteria. Two presented evidence in support of a synergistic relationship between liver fluke and viral hepatitis infection while the other found no relationship. One manuscript determined that the interaction between hepatitis B and C. sinensis did not have any significant risk of liver cancer. Studies found that HBV affected progression of co-infection to liver cancer but may have its own disease state worsened by presence of liver flukes. Only one paper was found that presented data on HCV, therefore no conclusion can be drawn due to the lack of evidence discovered. Of the studies, the conclusions and strength of the data were mixed. However, the stronger studies suggested a synergistic relationship between liver flukes and HBV to increase the risk of progressing to liver cancer.

Clonorchiasis and opisthorchiasis: epidemiology, transmission, clinical features, morbidity, diagnosis, treatment, and control

Clonorchis sinensis, Opisthorchis viverrini, and Opisthorchis felineus are important liver flukes that cause a considerable public health burden in eastern Asia, southeastern Asia, and eastern Europe, respectively. The life cycles are complex, involving humans, animal reservoirs, and two kinds of intermediate hosts. An interplay of biological, cultural, ecological, economic, and social factors drives transmission. Chronic infections are associated with liver and biliary complications, most importantly cholangiocarcinoma. With regard to diagnosis, stool microscopy is widely used in epidemiologic surveys and for individual diagnosis. Immunologic techniques are employed for screening purposes, and molecular techniques facilitate species differentiation in reference laboratories. The mainstay of control is preventive chemotherapy with praziquantel, usually combined with behavioral change through information, education and communication, and environmental control. Tribendimidine, a drug registered in the People's Republic of China for soil-transmitted helminth infections, shows potential against both C. sinensis and O. viverrini and, hence, warrants further clinical development. Novel control approaches include fish vaccine and biological control. Considerable advances have been made using multi-omics which may trigger the development of new interventions. Pressing research needs include mapping the current distribution, disentangling the transmission, accurately estimating the disease burden, and developing new diagnostic and treatment tools, which would aid to optimize control and elimination measures.

Liver Flukes: Clonorchis and Opisthorchis

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

Diagnosis of Human Trematode Infections

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

Fasciola hepatica soluble antigens (FhAg) induce ovine PMN innate immune reactions and NET formation in vitro and in vivo

Fasciola hepatica causes liver fluke disease, a worldwide neglected and re-emerging zoonotic disease, leading to hepatitis in humans and livestock. In the pathogenesis, flukes actively migrate through liver parenchyma provoking tissue damage. Here, parasites must confront leukocytes of the innate immune system in vivo. Polymorphonuclear neutrophils (PMN) are the most abundant granulocytes and first ones arriving at infection sites. PMN may display neutrophil extracellular traps (NETs), consisting of nuclear DNA, decorated with histones, enzymes, and antimicrobial peptides. We investigated for the first time whether F. hepatica soluble antigens (FhAg) can also trigger NETosis and innate immune reactions in exposed ovine PMN. Thus, isolated PMN were co-cultured with FhAg and NET formation was visualized by immunofluorescence and scanning electron microscopy analyses resulting in various phenotypes with spread NETs being the most detected in vitro. In line, NETs quantification via Picogreen®-fluorometric measurements revealed induction of anchored- and cell free NETs phenotypes. Live cell 3D-holotomographic microscopy revealed degranulation of stimulated PMN at 30 min exposure to FhAg. Functional PMN chemotaxis assays showed a significant increase of PMN migration (p = 0.010) and intracellular ROS production significantly increased throughout time (p = 0.028). Contrary, metabolic activities profiles of FhAg-exposed PMN did not significantly increase. Finally, in vivo histopathological analysis on F. hepatica-parasitized liver tissue sections of sheep showed multifocal infiltration of inflammatory cells within liver parenchyma, and further fluorescence microscopy analyses confirmed NETs formation in vivo. Overall, we hypothesized that NET-formation is a relevant host defence mechanism that might have a role in the pathogenesis of fasciolosis in vivo.

Intron Regions as Genetic Markers for Population Genetic Investigations of Opisthorchis viverrini sensu lato and Clonorchis sinensis

Opisthorchiasis and clonorchiasis are prevalent in Southeast and Far-East Asia, which are caused by the group 1 carcinogenic liver flukes Opisthorchis viverrini sensu lato and Clonorchis sinensis infection. There have been comprehensive investigations of systematics and genetic variation of these liver flukes. Previous studies have shown that O. viverrini is a species complex, called "O. viverrini sensu lato". More comprehensive investigations of molecular systematics and population genetics of each of the species that make up the species complex are required. Thus, other polymorphic genetic markers need to be developed. Therefore, this study aimed to characterize the intron regions of taurocyamine kinase gene (TK) to examine the genetic variation and population genetics of O. viverrini and C. sinensis collected from different geographical isolates and from a range of animal hosts. We screened seven intron regions embedded in TK. Of these, we selected an intron 5 of domain 1 (TkD1Int5) region to investigate the genetic variation and population genetics of theses liver flukes. The high nucleotide and haplotype diversity of TkD1Int5 was detected in O. viverrine. Heterozygosity with several insertion/deletion (indel) regions were detected in TkD1Int5 of the O. viverrine samples, whereas only an indel nucleotide was detected in one C. sinensis sample. Several O. viverrine samples contained three different haplotypes within a particular heterozygous sample. There were no genetic differences between C. sinensis isolated from various animal host. Heterozygous patterns specifically detected in humans was observed in C. sinensis. Thus, TkD1Int5 is a high polymorphic genetic marker, which could be an alternative marker for further population genetic investigations of these carcinogenic liver flukes and other related species from a wide geographical distribution and variety of animal hosts.

Incidence of fish-borne trematode infections and associated factors: results from a cohort study in highly endemic communities in northern Vietnam

Fish-borne trematodes (FiBT) are an important group of zoonotic parasites negatively affecting human health, mainly in Asia. Most studies on FiBT have applied a cross-sectional design, which provides weaker evidence on potential risk factors for transmission than a cohort study. This cohort study aimed to estimate the incidence and identify associated risk factors for FiBT infection in Vietnam. Between April 2018 and May 2019, two communes in Yen Bai province, a highly endemic area for FiBT, were visited for sampling. Participants with a negative stool result for FiBT at baseline, were invited for follow-up and data collection, at months 4, 9, and 13. Stools were examined using Kato-Katz and formalin-ethyl acetate concentration techniques to detect FiBT eggs, whereas a questionnaire was used for interviewing participants to determine the risk factors for FiBT infection during each follow-up period. The incidence risk and the incidence rate were calculated, and univariate and multivariable models were run to identify the risk factors for FiBT. A total of 194 people, negative for FiBT eggs at the baseline survey, were invited to participate in the study, and 111 people agreed to enroll in the follow-up. The incidence risk at months 4, 9, and 13 was 9.0%, 6.4%, and 5.1%, respectively. We finally used data from 95 participants for the risk factor analysis, excluding 16 people lost for the follow-up. Overall, 20 people became infected with FiBT (IR = 21.1%). The incidence rate of FiBT infection was 21.4/100 person-year. In the univariate analysis, consumption of raw fish was the main risk factor (RR = 4.59, 95%CI = 1.95-10.82), followed by being male (RR = 3.41, 95%CI = 1.56-7.45) and drinking alcohol (RR = 3.25, 95%CI = 1.49-7.11). In the multivariable analysis, only consumption of raw-fish dishes was significantly associated with FiBT infection. The people who consumed raw fish were 3.44 (95%CI = 1.11-10.70) times more at risk of infection with FiBT as compared to individuals who did not consume raw fish. It can be concluded that the FiBT incidence is high in the study area. More awareness campaigns are needed to stop eating raw fish in these areas to reduce FBT infection.

Food- and vector-borne parasitic zoonoses: Global burden and impacts

Around 25% of the global population suffer from one or more parasitic infections, of which food- and vector-borne parasitic zoonotic diseases are a major concern. Additionally, zoonoses and communicable diseases, common to man and animals, are drawing increased attention worldwide. Significant changes in climatic conditions, cropping pattern, demography, food habits, increasing international travel, marketing and trade, deforestation, and urbanization play vital roles in the emergence and re-emergence of parasitic zoonoses. Although it is likely to be underestimated, the collective burden of food- and vector-borne parasitic diseases accounts for ∼60 million disability-adjusted life years (DALYs). Out of 20 neglected tropical diseases (NTDs) listed by the World Health Organization (WHO) and the Centres for Disease Control and Prevention (CDC), 13 diseases are of parasitic origin. There are about 200 zoonotic diseases of which the WHO listed eight as neglected zoonotic diseases (NZDs) in the year 2013. Out of these eight NZDs, four diseases, namely cysticercosis, hydatidosis, leishmaniasis, and trypanosomiasis, are caused by parasites. In this review, we discuss the global burden and impacts of food- and vector-borne zoonotic parasitic diseases.

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.

Serum metabolic profiling of rats infected with Clonorchis sinensis using LC-MS/MS method

Background

Clonorchiasis is an important foodborne parasitic disease. The omics-based-techniques could illuminate parasite biology and further make innovations in the research for parasitic diseases. However, knowledge about the serum metabolic profiles and related metabolic pathways in clonorchiasis is very limited.

Methods

A untargeted ultra-high performance liquid tandem chromatography quadrupole time of flight mass spectrometry (UHPLC-QTOF-MS) was used to profile the serum metabolites of rats at both 4 and 8 weeks post infection (wpi) with Clonorchis sinensis (C. sinensis). Additionally, multivariate statistical analysis methods were employed to identify differential metabolites. Next, serum amino acids and phosphatidylcholines (PCs) levels were determined by targeted metabolomics analysis.

Result

A total of 10530 and 6560 ions were identified in ESI+ and ESI- modes. The levels of phosphatidylcholines, glycerophosphocholine and choline were significantly changed, with the shift in lipid metabolism. Significant changes were also observed in amino acids (isoleucine, valine, leucine, threonine, glutamate and glutamine). Targeted analysis showed that BCAAs (isoleucine, valine, leucine) levels significantly increased at 4 wpi and decreased at 8 wpi; threonine was increased at 8 wpi, whereas glutamate and glutamine showed a decreasing trend at 8 wpi. Additionally, the level of 17 PCs were significantly changed in infected rats. Marked metabolic pathways were involved in clonorchiasis, including glycerophospholipid metabolism, alanine, aspartate and glutamate metabolism, histidine metabolism and pyrimidine metabolism.

Conclusion

These results show that C. sinensis infection can cause significant changes in the rat serum metabolism, especially in amino acids and lipids. The metabolic signature together with perturbations in metabolic pathways could provide more in depth understanding of clonorchiasis and further make potential therapeutic interventions.

Co-infection of hepatitis E virus, Clonorchis sinensis, and Escherichia coli: A case report

Hepatitis E virus (HEV) is a common cause of acute hepatitis that threatens human health worldwide. With the popularization of detection technology, the reports of hepatitis E have gradually increased. Here, we present a rare case of co-infection with hepatitis E viruses, Clonorchis sinensis and Escherichia coli. A 52-year-old man was hospitalized because of fatigue, jaundice, and nausea for more than 2 weeks. Laboratory tests showed elevated bilirubin, aminotransferase (ALT), and aspartate aminotransferase (AST); HEV-IgM was positive, and HEV-RNA could be detected. Moreover, parasites were found in the biliary drainage and the biliary culture, which suggested Escherichia coli. The patient was effectively treated with praziquantel, imipenem, and hepatoprotective drugs and his clinical symptoms were relieved after 2 months; total bilirubin decreased to 85.1 μmol/L, ALT decreased to 92.4 U/L, and AST decreased to 102 U/L.

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.

Essential Oils as Novel Anthelmintic Drug Candidates

Helminths, with an estimated 1.5 billion annual global infections, are one of the major health challenges worldwide. The current strategy of the World Health Organization to prevent helminth infection includes increasing hygienic awareness, providing better sanitation and preventative anthelmintic drug therapy in vulnerable populations. Nowadays, anthelmintic drugs are used heavily in livestock, both in case of infection and as a preventative measure. However, this has led to the development of resistance against several of the most common drugs, such as levamisole, ivermectin and thiabendazole. As many as 70% of the livestock in developed countries now has helminths that are drug resistant, and multiple resistance is common. Because of this, novel anthelmintics are urgently needed to help combat large-scale production losses. Prior to this review, no comprehensive review of the anthelmintic effects of essential oils and their components existed. Multiple review articles have been published on the uses of a single plant and its extracts that only briefly touch upon their anthelmintic activity. This review aims to provide a detailed overview of essential oils and their components as anthelmintic treatment against a wider variety of helminths.

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.

Pharmacokinetics of Ascending Doses of Praziquantel in Adults Infected with Opisthorchis felineus in Western Siberia, Russian Federation

Opisthorchiasis due to the liver fluke Opisthorchis felineus is highly prevalent in rural regions of Western Siberia, causing severe liver and bile duct maladies. Praziquantel administered as a three-dose regimen is the only drug used to treat O. felineus-infected individuals. A simpler single-dose treatment might serve as an alternative. The aim of this study was to compare the pharmacokinetic (PK) properties of single, ascending doses of praziquantel compared to multiple dosing in patients infected with O. felineus to contribute to updated treatment guidelines. Dried blood spots (DBSs) of 110 adults were collected at 11 time points post-drug administration at single oral doses of 20, 40, and 60 mg/kg, as well as 3× 20 mg/kg (4 h dosing interval). DBS samples were analyzed using a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method, and PK parameters were obtained for R-, S-, and R-trans-4-OH-praziquantel employing noncompartmental analysis. We observed the highest drug exposure for all analytes when the triple-dose scheme was used; area under the concentration-time curve from 0 to 24 h (AUC_0-24) values of 8.04, 27.75, and 36.38 μg/mL·h were obtained, respectively. Maximal plasma concentrations (C_max) values of 1.72, 4.89, and 2.69 μg/mL were calculated for R-, S-, and R-trans-4-OH-praziquantel, respectively, when patients were given a single 60-mg/kg dose, and they peaked at 1.5 and 2 h for the enantiomers and at 3 h for the metabolite. The herein-generated PK data, together with results that will be obtained from the integrated efficacy study, lay the groundwork for a possibly optimized treatment scheme for O. felineus-infected patients.

Two Distinct Superoxidase Dismutases (SOD) Secreted by the Helminth Parasite Fasciola hepatica Play Roles in Defence against Metabolic and Host Immune Cell-Derived Reactive Oxygen Species (ROS) during Growth and Development

The antioxidant superoxide dismutase (SOD) catalyses the dismutation of superoxide, a dangerous oxygen free radical, into hydrogen peroxide and molecular oxygen. Superoxide generation during the oxidative burst of the innate immune system is considered a key component of the host defence against invading pathogens. We demonstrate the presence and differential expression of two SODs in Fasciola hepatica, a leaderless cytosolic (FhSOD1) and an extracellular (FhSOD3) form containing a secretory signal peptide, suggesting that the parasites exploit these enzymes in distinct ways to counteract reactive oxygen species (ROS) produced by cellular metabolism and immune defences. Both enzymes are highly expressed by the infective newly excysted juvenile (NEJ) stages and are found in abundance in their excretory–secretory products (ES), but only FhSOD1 is present in adult ES, suggesting that the antioxidants have different functions and pathways of secretion, and are under separate temporal expression control during the migration, growth, and development of the parasite. Functionally, the recombinant FhSOD1 and FhSOD3 exhibit similar activity against superoxide to their mammalian counterparts. Confocal immuno-localisation studies demonstrated the presence of FhSOD1 and FhSOD3 on the NEJ tegument and parenchyma, supporting our suggestion that these enzymes are secreted during host invasion to protect the parasites from the harmful oxidative bursts produced by the activated innate immune response. By producing superoxide enzymatically in vitro, we were able to demonstrate robust killing of F. hepatica NEJ within 24 h post-excystment, and that the lethal effect of ROS was nullified with the addition of SOD and catalase (the antioxidant enzyme responsible for the dismutation of hydrogen peroxide, a by-product of the SOD reaction). This study further elucidates the mechanism by which F. hepatica protects against ROS derived from cellular metabolism and how the parasite could mitigate damage caused by the host’s immune response to benefit its survival.

Liver fluke eggs in bile duct brush cytology: An unexpected diagnosis during evaluation of a biliary stricture

Clonorchis sinensis, a liver fluke parasite, infects humans through ingestion of raw or undercooked fish, crabs, or crayfish in endemic areas where the parasite is found. Clonorchis sinensis infects the liver, gallbladder, and bile duct in humans, causing Clonorichiasis. Although the majority of patients are asymptomatic, long-lasting infections may cause severe disease. Without treatment, human infection may persist for the parasite's lifespan (25-30 years). Pathologic diagnosis can be challenging as sampling may demonstrate limited cellularity with minuscule eggs that may be overlooked. Here, we report a rare case of liver fluke eggs diagnosed in bile duct brush cytology.

Metabolome alterations in Clonorchis sinensis after treatment with tribendimidine and praziquante in vivo

Tribendimidine (TBD) is a broad-spectrum anthelmintic drug that is also significantly effective in treating clonorchiasis. In this study, the altered metabolomes of Clonorchis sinensis (C. sinensis) in rats after TBD administration were quantified by using ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) and gas chromatography-mass spectrometry (GC-MS) to explore the possible active sites of TBD against clonorchiasis through altered metabolites and metabolic pathway analysis, and the results are expected to provide a target for the future design of anti-Clonorchis sinensis drugs. The worm burden reduction rate and scanning electron microscopy demonstrated that praziquantel (PZQ, positive control drug) and TBD had significant effects on C. sinensis in rats after treatment at a single dose of 200 mg/kg for 24 h. For the MS-based metabolomic analysis, a total of 173 standard metabolites (126 amino acids, 10 phospholipids and 37 fatty acids) were utilized as a reference metabolite database for metabolome identification. In total, 32 amino acids, 71 phospholipids and 27 fatty acids were detected in the C. sinensis of each group. Among these metabolites, 10 amino acids were significantly decreased in both drug-treated groups. Four lysophosphatidyl cholines (LPCs), six lysophosphatidyl ethanolamines (LPEs) and one phosphatidyl inositol (PI) were significantly increased after treatment with TBD. There were no significant changes in fatty acids among the control group and the two drug-treated groups. The results indicated that TBD administration caused a decrease in amino acids involved in the metabolic pathways of energy consumption and an increase in lysophospholipids, which are the hydrolysis products of phospholipase2 (PLA2) in the phospholipid metabolic pathways. The increased lysophospholipid content can destroy the cell membrane, increase membrane permeability, and even cause exposure to internal antigens that can be attacked by host antibodies. Perhaps the destroyed membrane, the exposed internal antigens and the consumed energy are the cause of the damage and death of C. sinensis after TBD administration. This is an interesting problem that can be examined in future research.

Inflammatory pathways and cholangiocarcinoma risk mechanisms and prevention

Cholangiocarcinoma (CCA), a neoplasm burdened by a poor prognosis and currently lacking adequate therapeutic treatments, can originate at different levels of the biliary tree, in the intrahepatic, hilar, or extrahepatic area. The main risk factors for the development of CCA are the presence of chronic cholangiopathies of various etiology. To date, the most studied prodromal diseases of CCA are primary sclerosing cholangitis, Caroli's disease and fluke infestations, but other conditions, such as metabolic syndrome, nonalcoholic fatty liver disease and obesity, are emerging as associated with an increased risk of CCA development. In this review, we focused on the analysis of the pro-inflammatory mechanisms that induce the development of CCA and on the role of cells of the immune response in cholangiocarcinogenesis. In very recent times, these cellular mechanisms have been the subject of emerging studies aimed at verifying how the modulation of the inflammatory and immunological responses can have a therapeutic significance and how these can be used as therapeutic targets.

Population dynamics and diversity of trematode infections in Bithynia siamensis goniomphalos in an irrigated area in northeast Thailand

Several trematodes including Opisthorchis viverrini utilize Bithynia siamensis goniomphalos as a snail intermediate host in their life cycles. In order to capture a comprehensive range of host–parasite interactions and their transmission dynamic patterns, B. s. goniomphalos were sampled monthly over 4 consecutive years in an irrigated paddy-field habitat in northeast Thailand. Using a standard cercarial shedding method, a high diversity of trematodes (17 types) was recovered. Virgulate xiphidiocercariae were the most prevalent (7.84%) followed by O. viverrini (0.71%). In addition to seasonal and environmental factors, the quantity of irrigation water for rice cultivation correlated with transmission dynamics of trematodes in B. s. goniomphalos. The peak prevalence of all trematode infections combined in the snails shifted from the cool-dry season in 2010–2012 to the hot-dry season in 2013 associated with an increasing quantity of water irrigation. A low frequency of mixed trematode infections was found, indicating that the emergence of virgulate cercariae, but not of O. viverrini, was negatively impacted by the presence of other trematodes in the same snail. Taken together, the observed results suggest that interactions between host and parasite, and hence transmission dynamics, depend on specific characteristics of the parasite and environmental factors including irrigated water for rice cultivation.

Long Non-Coding RNA and mRNA Expression Analysis in Liver of Mice With Clonorchis sinensis Infection

Clonorchiasis is recognized as an important zoonotic parasitic disease worldwide. However, the roles of host long non-coding RNAs (lncRNAs) and messenger RNAs (mRNAs) in the response to Clonorchis sinensis (C. sinensis) infection remain unknown. Here we compared the expression of lncRNAs and mRNAs in the liver tissue of mice infected with C. sinensis, in order to further understand the molecular mechanisms of clonorchiasis. A total of 388 lncRNAs and 1,172 mRNAs were found to be differentially expressed with absolute value of fold change (FC) ≥ 2.0 and p < 0.05 by microarray. Compared with controls, Gm6135 and 4930581F22Rik were the most over- and under-expressed lncRNAs; flavin-containing monooxygenase 3 (Fmo3) and deleted in malignant brain tumors 1 (Dmbt1) were the most over- and under-expressed mRNAs. Moreover, functional annotation showed that the significantly different mRNAs were related with “FOXO signaling pathway”, “Wnt signaling pathway”, and “AMPK signaling pathway”. Remarkably, lncRNA Gm8801 were significantly correlated with mRNA glycerol-3-phosphate acyltransferase mitochondrial (Gpam), insulin receptor substrate 2 (Irs2), and tumor necrosis factor receptor superfamily member 19 (Tnfrsf19) in ceRNA networks. These results showed that the expression profiles of lncRNAs and mRNAs in the liver changed after C. sinensis infection. Our results provided valuable insights into the lncRNAs and mRNAs involved in clonorchiasis pathogenesis, which may be useful for future control strategies.

Human fascioliasis in Africa: A systematic review

Fascioliasis is a globally distributed, parasitic zoonosis, caused by Fasciola hepatica and F. gigantica. A comprehensive overview of the epidemiology of human fascioliasis in Africa is missing up to now. Therefore, our objective was to conduct a systematic review aiming to summarize recent knowledge on the distribution, prevalence, and risk factors of human fascioliasis in Africa. A key word search was performed in PubMed, Web of Science and Africa Wide, to gather relevant literature, published between the 1st of January 2000 and 31st of December 2020. A total of 472 records were initially retrieved, with 40 full text articles retained for the qualitative synthesis. Human fascioliasis was reported in 12 African countries, namely Algeria, Angola, Cape Verde, Egypt, Ethiopia, Ghana, Morocco, Nigeria, Senegal, South-Africa, Tanzania and Tunisia. The majority of the studies was conducted in Egypt. A total of 28 records were population surveys. Coproscopy was the most commonly used tool for fascioliasis diagnosis in these surveys. Gender (being female), consumption of raw vegetables/seeds, age, owning livestock, and use of unsafe drinking water sources, were identified as risk factors in 7 studies. Furthermore, 43 case reports were retrieved, described in 12 studies. Eosinophilia was present in 39 of these cases, while 11 had positive coproscopy results. Eight cases described having eaten raw wild vegetables. Overall, the low number and quality of records retrieved indicates that human fascioliasis remains a truly neglected disease in Africa, and more epidemiological studies are urgently needed to both establish the actual distribution as well as risk factors on the continent.

Current status of human liver fluke infections in the Greater Mekong Subregion

The Greater Mekong Subregion (GMS) is a trans-national region of the Mekong River basin in Southeast Asia comprising Cambodia, the People's Republic of China (specifically Yunnan Province and Guangxi Zhuang Autonomous Region), Lao People's Democratic Republic (Lao PDR), Myanmar, Thailand, and Vietnam home to more than 340 million people or almost 4.5% of the global population. Human liver fluke infections caused by Opisthorchis viverrini and Clonorchis sinensis have been major public health problems in this region for decades. Opisthorchiasis caused by O. viverrini is prevalent in Thailand, Lao PDR, Cambodia and central-southern Vietnam with more than 12 million people infected. Clonorchiasis caused by C. sinensis is endemic in northern Vietnam and Guangxi with estimated 3.5 -5 million infected. The infections can cause several liver and biliary diseases such as cholangitis, periductal fibrosis, gallstones, and cholangiocarcinoma (CCA), a fatal bile duct cancer. Key determinants of the geographical distribution differences of the two liver fluke species are snail species and geographic barriers. Main risk behaviour of the infections is the culture of eating raw fish "the raw attitude" of people in the GMS, especially the Tai/Dai/Thai/Laos ethnic groups, the major population in the GMS. Over the past 20 years, there is a big change in prevalence of the infections. Opisthorchiasis has long been endemic, particularly in northern and northeastern Thailand and Lao PDR with over 8-10 million cases estimated. However, after several rounds of national campaign against opisthorchiasis using integrated control approach in Thailand over the past three decades, the prevalence of O. viverrini infection has reduced from over 15% in 1996 to 2.2% in 2019. High prevalence of O. viverrini infection continues in Lao PDR and central Vietnam. Emerging high prevalence, up to a maximum of 47.5%, has been noted in Cambodia during the past 10 years possibly due to more studies being conducted rather than increasing prevalence. O. viverrini infection has now also been reported in Lower Myanmar in recent years. Clonorchiasis has been known in northern Vietnam and southern China for a long time. Several surveys have reported infections in Guangxi in the last 10 years, and until now liver fluke infected cases have not been reported in Yunnan. Overall, nowadays, there is a shift in high risk areas for GMS liver fluke infection from northeastern Thailand to Lao PDR, Cambodia, Vietnam, Myanmar, and Guangxi P.R. China. Urgent systematic disease mapping and integrated liver fluke control using One Health approaches should be implemented nationwide in GMS countries.

Extracellular vesicles from Fasciola gigantica induce cellular response to stress of host cells

Extracellular vesicles (EVs) from parasitic helminths play an important role in immunomodulation. However, EVs are little studied in the important parasite Fasciola gigantica. Here the ability of EVs from F. gigantica to induce cellular response to stress (reactive oxygen species generation, autophage and DNA damage response) in human intrahepatic biliary epithelial cells (HIBEC) was investigated. F. gigantica-derived EVs were isolated by ultracentrifugation, and identified with transmission electron microscopy, nanoparticle size analysis and parasite-derived EV markers. Internalization of EVs by HIBEC was determined by confocal immunofluorescence microscopy and flow cytometry. ROS levels in HIBEC were detected by molecular probing. EVs-induced autophagy and DNA-damaging effects were determined by evaluating expression levels of light chain 3B protein (LC3B), phosphor- H2A.X and phosphor-Chk1, respectively. Results revealed that EVs with sizes predominately ranging from 39 to 110 nm in diameter were abundant in adult F. gigantica and contained the parasite-derived marker proteins enolase and 14-3-3, and EVs were internalized by HIBEC. Further, uptake of EVs into HIBEC was associated with increased levels of reactive oxygen species, LC3Ⅱ, phosphor-H2A.X and phosphor-Chk1, suggesting EVs are likely to induce autophagy and DNA damage & repair processes. These results indicate F. gigantica EVs are associated with modulations of host cell responses and have a potential important role in the host-parasite interactions.

Paragonimus and its hosts in China: An update

Paragonimiasis is an important foodborne parasitic disease. Over 50 species of Paragonimus have been reported worldwide, and China has the widest distribution and largest number of species. The detection of Paragonimus metacercariae from second intermediate hosts has been reported in 22 provinces and municipalities. The most frequently reported species are P. westermani, P. skrjabini, P. heterotremus and Euparagonimus cenocopiosus. In this review, we collected and reviewed relevant reports on the detection of Paragonimus metacercariae in second intermediate hosts from 1937 to 2020 from all areas of China. We provide an updated and current summary of Paragonimus species and their hosts in China. Data on the geographical range, species distribution, and second intermediate host species of Paragonimus were extracted. ArcGIS10.2 software was used to generate distribution maps of Paragonimus for four time periods: 1937-1990, 1991-2005, 2006-2020 and 1937-2020. We analyzed the geographic and spatiotemporal dynamics of Paragonimus prevalence in natural foci and provided a basis for further research and paragonimiasis prevention strategies in China.

Invasive snails, parasite spillback, and potential parasite spillover drive parasitic diseases of Hippopotamus amphibius in artificial lakes of Zimbabwe

Background

Humans impose a significant pressure on large herbivore populations, such as hippopotami, through hunting, poaching, and habitat destruction. Anthropogenic pressures can also occur indirectly, such as artificial lake creation and the subsequent introduction of invasive species that alter the ecosystem. These events can lead to drastic changes in parasite diversity and transmission, but generally receive little scientific attention.

Results

In order to document and identify trematode parasites of the common hippopotamus (Hippopotamus amphibius) in artificial water systems of Zimbabwe, we applied an integrative taxonomic approach, combining molecular diagnostics and morphometrics on archived and new samples. In doing so, we provide DNA reference sequences of the hippopotamus liver fluke Fasciola nyanzae, enabling us to construct the first complete Fasciola phylogeny. We describe parasite spillback of F. nyanzae by the invasive freshwater snail Pseudosuccinea columella, as a consequence of a cascade of biological invasions in Lake Kariba, one of the biggest artificial lakes in the world. Additionally, we report an unknown stomach fluke of the hippopotamus transmitted by the non-endemic snail Radix aff. plicatula, an Asian snail species that has not been found in Africa before, and the stomach fluke Carmyerius cruciformis transmitted by the native snail Bulinus truncatus. Finally, Biomphalaria pfeifferi and two Bulinus species were found as new snail hosts for the poorly documented hippopotamus blood fluke Schistosoma edwardiense.

Conclusions

Our findings indicate that artificial lakes are breeding grounds for endemic and non-endemic snails that transmit trematode parasites of the common hippopotamus. This has important implications, as existing research links trematode parasite infections combined with other stressors to declining wild herbivore populations. Therefore, we argue that monitoring the anthropogenic impact on parasite transmission should become an integral part of wildlife conservation efforts.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-021-01093-2.

Cryptosporidium in fish: Implications for aquaculture and beyond

Aquaculture industries are expanding worldwide and control of Cryptosporidium is of great importance. Cryptosporidiosis is a serious waterborne/foodborne disease, responsible for infectious outbreaks globally. Current knowledge on the Cryptosporidium species in the aquatic environment and their occurrence in piscine hosts is steadily increasing since the Cryptosporidium species have been detected in marine, freshwater, cultured, captive and ornamental fish in a wide range of geographical regions. The zoonotic potential of these parasites and their pathological impact on piscine hosts have been increasingly reported and the fishborne zoonotic risk from Cryptosporidium spp. is of major importance from a public health point of view. Zoonotic subtypes in fish have been described in various studies and are probably related to water contamination from animal and human wastes. This review critically evaluated existing scientific data, related to Cryptosporidium species in piscine hosts, emphasizing transmission routes and the potential impact of piscine cryptosporidiosis in aquaculture. This knowledge will facilitate consumers, authorities and water industries such as fisheries and aquaculture, the prevention and control of waterborne and fishborne cryptosporidiosis in fish products.

Prevalence and spatial distribution of heterophyidiasis in Southern Philippines

Heterophyidiasis is a fish-borne zoonotic disease that is considered to be an emerging public health problem in the Philippines. This study was carried out to determine the spatial distribution and risk factors of heterophyidiasis in five selected villages in New Corella, Davao del Norte in Southern Mindanao. Of the 1,101 individuals examined, 26 (2.36% overall prevalence rate, 95% CI 1.46-3.25) were positive for heterophyid eggs. Higher infection rate was observed in males (3.85%, 95% CI 2.27-5.43) than females (0.76%, 95% CI 0.02-1.5). Mapping of cases was done to show the spatial distribution of heterophyidiasis in New Corella. Multiple logistic regression analysis showed that gender, raw freshwater fish consumption, undercooked grilled fish consumption and proximity to rivers or creeks are the risk factors significantly associated with heterophyid infection. This study confirmed the presence of heterophyid infection in humans in the surveyed villages in New Corella in Southern Philippines.

Recognition Pattern of the Fasciola hepatica Excretome/Secretome during the Course of an Experimental Infection in Sheep by 2D Immunoproteomics

Excretory/secretory products released by helminth parasites have been widely studied for their diagnostic utility, immunomodulatory properties, as well as for their use as vaccines. Due to their location at the host/parasite interface, the characterization of parasite secretions is important to unravel the molecular interactions governing the relationships between helminth parasites and their hosts. In this study, the excretory/secretory products from adult worms of the trematode Fasciola hepatica (FhES) were employed in a combination of two-dimensional electrophoresis, immunoblot and mass spectrometry, to analyze the immune response elicited in sheep during the course of an experimental infection. Ten different immunogenic proteins from FhES recognized by serum samples from infected sheep at 4, 8, and/or 12 weeks post-infection were identified. Among these, different isoforms of cathepsin L and B, peroxiredoxin, calmodulin, or glutathione S-transferase were recognized from the beginning to the end of the experimental infection, suggesting their potential role as immunomodulatory antigens. Furthermore, four FhES proteins (C2H2-type domain-containing protein, ferritin, superoxide dismutase, and globin-3) were identified for the first time as non-immunogenic proteins. These results may help to further understand host/parasite relationships in fasciolosis, and to identify potential diagnostic molecules and drug target candidates of F. hepatica.

A fluorescence AuNPs-LISA: A new approach for Opisthorchis viverrini (Ov) antigen detection with a simple fluorescent enhancement strategy by surfactant micelle in urine samples

The colorimetric AuNPs-LISA is a new, powerful technique for the detection of Opisthorchis viverrini antigen (OvAg) in urine samples. However, the diagnostic sensitivity of the colorimetric AuNPs-LISA is powerless to screen ultralow concentrations of OvAg in urine samples in cases of early stage liver fluke infection. This work, we aimed to improve the diagnostic sensitivity of the colorimetric AuNPs-LISA by developing a new fluorescence AuNPs-LISA. O-phenylenediamine (OPD) was used as the chromogenic substrate instead of the tetramethylbenzidine (TMB) of the colorimetric AuNPs-LISA. Interestingly, the fluorescence of the OPD oxidation product by the peroxidase-like activity of labelled AuNPs can be extremely enhanced by a non-ionic surfactant, especially the Triton X-100. The proposed assay exhibited a dynamic linear detection of OvAg concentration in the range of 34.18 ng mL^-1 to 273.44 ng mL^-1 with the limit of detection at 36.97 ng mL^-1 which the detection sensitivity enhancement around 1200-fold when comparing with the colorimetric AuNPs-LISA. This model exhibits high diagnosis sensitivity, specificity and accuracy, 91.28%, 91.75%, and 91.59%, respectively, compared to the traditional ELISA. The fluorescence AuNPs-LISA showed excellent potential for the diagnosis of OvAg in urine samples from endemic areas. This will provide an effective tool for the detection, control and elimination of human opisthorchiasis.

Masculinity and misinformation: Social dynamics of liver fluke infection risk in Thailand

Liver fluke infection through the consumption of raw or undercooked freshwater fish is a major public health problem in the Mekong Region. Despite the extensive efforts of liver fluke health campaigns, Northeast Thailand still reports high human infection prevalence as consumption of raw fish dishes has diminished but not ceased. This study examines the roles of social-cultural factors, particularly the influences of masculinity and misinformation, on liver fluke infection risk. Participant observation, questionnaire surveys and semi-structured interviews were conducted in four villages in Kalasin Province, Thailand, to scrutinize reasons for raw fish consumption, gender differences in raw fish culture, processes of liver fluke information dissemination, and the extent of information mismatch. Our results show that one of the key reasons (76.9%) underlying continued raw fish consumption are deeply embedded cultural practices associated with ways of rural life. About 30% of the participants indicated that they would not avoid eating raw fish, regardless of knowing the health consequences. Gender difference is evident, with 75.6% of males consuming raw fish salad (koi pla), compared to 42.7% of females. Some male participants associate raw meat consumption with virility and strength. Such beliefs underscore the cultural linkage of koi pla consumption with masculinity. Misconceptions of liver fluke life cycle and risk of infection remain, as only 15.3% of the participants correctly selected raw fish as the food source for liver fluke infection while 84.2% misunderstood that other raw foods could lead to infection. The multi-layered and hierarchical structure of public health information dissemination from medical professionals to health officers and village health volunteers to villagers has contributed to information mismatch between different layers. Our study builds on others which call for multi-pronged scientific and social strategies, as well as culturally attuned approaches to public health messaging. The study raises masculinity and misinformation as relevant considerations in disease prevention. Incorporating grounded research and gendered perspectives are part of appreciating the cultural roots of raw fish consumption. Realizing the significant role of village health volunteers in information dissemination and in supplying coherent public health messages is vital for effective health campaigns.

Metabolic Homeostasis in Chronic Helminth Infection Is Sustained by Organ-Specific Metabolic Rewiring

Opisthorchiasis, is a hepatobiliary disease caused by flukes of the trematode family Opisthorchiidae. A chronic form of the disease implies a prolonged coexistence of a host and the parasite. The pathological changes inflicted by the worm to the host's hepatobiliary system are well documented. Yet, the response to the infection also triggers a deep remodeling of the host systemic metabolism reaching a new homeostasis and affecting the organs beyond the worm location. Understanding the metabolic alternation in chronic opisthorchiasis, could help us to pinpoint pathways that underlie infection opening possibilities for the development of more selective treatment strategies. Here, with this report we apply an integrative, multicompartment metabolomics analysis, using multiple biofluids, stool samples and tissue extracts to describe metabolic changes in Opisthorchis felineus infected animals at the chronic stage. We show that the shift in lipid metabolism in the serum, a depletion of the amino acids pool, an alteration of the ketogenic pathways in the jejunum and a suppressed metabolic activity of the spleen are the key features of the metabolic host adaptation at the chronic stage of O. felineus infection. We describe this combination of the metabolic changes as a "metabolically mediated immunosuppressive status of organism" which develops during a chronic infection. This status in combination with other factors (e.g., parasite-derived immunomodulators) might increase risk of infection-related malignancy.

Dynamic transcriptome landscape of Paragonimus proliferus developmental stages in the rat lungs

Paragonimus proliferus, a lung fluke of the genus Paragonimus, was first reported in Yunnan province, China. P. proliferus can infect Sprague-Dawley (SD) rats and cause lung damage, but there is still no direct evidence of human infection. Until now, there has been a lack of studies on P. proliferus parasitism and development in mammalian lung tissue. The aim of this study was to perform transcriptomic profiling of P. proliferus at different developmental stages. SD rats were infected with P. proliferus metacercariae obtained from crabs; worms isolated from the lungs at different time points as well as metacercariae were subjected to whole transcriptome sequencing. Overall, 34,403 transcripts with the total length of 33,223,828 bp, average length of 965 bp, and N50 of 1833 bp were assembled. Comparative analysis indicated that P. proliferus, similar to other Paragonimus spp., expressed genes related to catabolism, whereas P. proliferus-specific transcripts were related to the maintenance of cellular redox homeostasis, sensitivity to bacteria, and immune response. Transcriptional dynamics analysis revealed that genes involved in the regulation of catabolism and apoptosis had stable expression over the P. proliferus life cycle, whereas those involved in development and immune response showed time-dependent changes. High expression of genes associated with immune response corresponded to that of genes regulating the sensitivity to bacteria and immune protection. We constructed a P. proliferus developmental model, including the development of the body, suckers, blood cells, reproductive and tracheal systems, lymph, skin, cartilage, and other tissues and organs, and an immune response model, which mainly involved T cells and macrophages. Our study provides a foundation for further research into the molecular biology and infection mechanism of P. proliferus.

MicroRNA Interference in Hepatic Host-Pathogen Interactions

The liver is well recognized as a non-immunological visceral organ that is involved in various metabolic activities, nutrient storage, and detoxification. Recently, many studies have demonstrated that resident immune cells in the liver drive various immunological reactions by means of several molecular modulators. Understanding the mechanistic details of interactions between hepatic host immune cells, including Kupffer cells and lymphocytes, and various hepatic pathogens, especially viruses, bacteria, and parasites, is necessary. MicroRNAs (miRNAs), over 2600 of which have been discovered, are small, endogenous, interfering, noncoding RNAs that are predicted to regulate more than 15,000 genes by degrading specific messenger RNAs. Several recent studies have demonstrated that some miRNAs are associated with the immune response to pathogens in the liver. However, the details of the underlying mechanisms of miRNA interference in hepatic host-pathogen interactions still remain elusive. In this review, we summarize the relationship between the immunological interactions of various pathogens and hepatic resident immune cells, as well as the role of miRNAs in the maintenance of liver immunity against pathogens.

The occurrence and abundance of infective stages of zoonotic nematodes in selected edible fish sold in Australian fish markets

Seafood is nutritious and a healthy source of proteins and its regular consumption is highly recommended by medical professionals and dieticians. Owing to this, the global consumption of seafood per capita has been significantly increasing since the 1960s. Consequently, seafood-borne pathogens, including parasites, have also become more widely known and recognised. In Australia, a vast island country, information about such parasites is extremely limited. This study aimed to determine the prevalence and abundance of zoonotic parasites, including anisakid nematodes, in selected Australian edible fish. Four species of fish, namely tiger flathead, Platycephalus richardsoni (n = 43), blue mackerel, Scomber australasicus (n = 117), snapper, Pagrus auratus (n = 11) and school whiting, Sillago flindersi (n = 90) were purchased from a fish market. Although a range of parasites was found, due to their significance for human health, the focus of this study was on nematodes whose infectious stage was found in these fish. The prevalence of nematodes in these fish species was 86.05%, 64.10%, 45.45% and 56.67%, respectively. Among the parasites found, Anisakis spp., Contracaecum spp. and Hysterothylacium spp. in tiger flathead, blue mackerel and school whiting, might be of zoonotic importance. Our findings suggest there is a need to revise current seafood safety protocols and develop educational campaigns for seafood industries stakeholders.

Abundance of Opisthorchis felineus Metacercariae in cyprinid fish in the middle Ob River basin (Tomsk region, Russia)

Infection with the liver fluke, Opisthorchis felineus, caused by the consumption of infected raw or undercooked cyprinid fish is common in humans and carnivores in the middle Ob River basin (Tomsk region, Russia) and can lead to diseases in humans. The goal of this study was the status of fish infection with O. felineus metacercariae in order to assess the role of fish in the infection of the human population in the middle Ob River basin.

Of the 14 Cyprinidae species recorded in the middle Ob River basin, we examined 6 cyprinid species for prevalence and intensity of infection with O. felineus metacercariae. Five of these species (Leuciscus idus, Leuciscus leuciscus, Rutilus rutilus, Abramis brama, and Carassius gibelio) are of commercial value, while the common bleak is an object of amateur fishing. In addition, we conducted a survey of the fish consumption habits as part of a community-based cross-sectional study in the rural Shegarsky district, Tomsk region, Russian Federation.

O. felineus metacercariae were observed in muscles of all examined species except for the Prussian carp. The ide is the main infection source in the Ob River (prevalence of infection, 100%, and intensity, 50.5 metacercariae per fish) and the common dace in the Tom River (91.1% and 12.7 metacercariae). Although the two alien species (bream and common bleak) are susceptible to infection with O. felineus metacercariae, the prevalence of infection in these fish and in the roach did not exceed 3%. The prevalence and intensity of infection in fish increased with age and size. The infection characteristics of fish in different water flows were different. The cyprinid species account on average for 69.8% of the commercial fish harvested in the Tomsk region. According to epidemiological survey, among 600 participants, 87.5% (n = 525) of respondents consumed river fish, with the most popular fish being cyprinids including Prussian carp, dace, ide and bream, followed by pike and perch.

Thus, the epizootological state of the water flows in the middle Ob River basin is adverse with respect to opisthorchiasis, as indicated by high infection rates of liver fluke metacercariae in ide and common dace, which are abundant species of high commercial value. An extremely high prevalence of infection suggests a strong transmission cycle with a high rate of infection from infected humans and/or animal reservoir hosts to snails and fish. In addition to treating humans, there should be a strong focus on identifying these potential reservoir hosts to reduce subsequent infection in humans. Furthermore, since the intensity of infection in humans is determined by the presence of fish species such as ide and dace in the diet, they should be included in a dietary change campaign by eliminating the consumption of raw fish.

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Commercial cyprinid species play the key role in maintaining opisthorchiasis foci.

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The ide and common dace are the main source of human and animal infection.

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Measures to control Opisthorchis felineus should target these two species of fish.

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The invasion of fish increases with their age and size.

Model-based spatial-temporal mapping of opisthorchiasis in endemic countries of Southeast Asia

Opisthorchiasis is an overlooked danger to Southeast Asia. High-resolution disease risk maps are critical but have not been available for Southeast Asia. Georeferenced disease data and potential influencing factor data were collected through a systematic review of literatures and open-access databases, respectively. Bayesian spatial-temporal joint models were developed to analyze both point- and area-level disease data, within a logit regression in combination of potential influencing factors and spatial-temporal random effects. The model-based risk mapping identified areas of low, moderate, and high prevalence across the study region. Even though the overall population-adjusted estimated prevalence presented a trend down, a total of 12.39 million (95% Bayesian credible intervals [BCI]: 10.10–15.06) people were estimated to be infected with O. viverrini in 2018 in four major endemic countries (i.e., Thailand, Laos, Cambodia, and Vietnam), highlighting the public health importance of the disease in the study region. The high-resolution risk maps provide valuable information for spatial targeting of opisthorchiasis control interventions.

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.