Genetic diversity of Fasciola hepatica in Spain and Peru

Variations in Genetic Diversity of Invasive Species Lithobates catesbeianus in China

The introduction and subsequent range expansion of the American bullfrog (Lithobates catesbeianus) is part of a rising trend of troublesome biological invasions happening in China. This detrimental amphibious invasive species has strong adaptability. After its introduction and spread, it established its own ecological niche in many provinces of China, and its range has continued to expand to more areas. Previous studies recorded the introduction time of bullfrogs and calculated the changes in their genetic diversity in China using mitochondria, but the specific introduction route in China is still unknown. Expanding upon previous research, we employed whole-genome scans (utilizing 2b-RAD genomic sequencing) to examine single nucleotide polymorphisms (SNPs) and microsatellites within Lithobates catesbeianus to screen the genomes of these invasive amphibian species from eight Chinese provinces and two U.S. states, including Kansas, where bullfrogs originate. A total of 1,336,475 single nucleotide polymorphic loci and 17 microsatellite loci were used to calculate the genetic diversity of bullfrogs and their migration pathways. Our results suggest that the population in Hunan was the first to be introduced and to spread, and there may have been multiple introductions of subpopulations. Additionally, the genetic diversity of both the SNP and microsatellite loci in the Chinese bullfrog population was lower than that of the US population due to bottleneck effects, but the bullfrogs can adapt and spread rapidly. This study will offer crucial insights for preventing and controlling future introductions into the natural habitats in China. Additionally, it will assist in devising more precise strategies to manage the existing populations and curtail their continued expansion, as well as aim to improve clarity and originality while mitigating plagiarism risk.

Molecular characterization of Fasciola hepatica in endemic regions of Colombia

Fasciola hepatica is a zoonotic trematode that affects a wide range of hosts, including cattle, sheep, and goats. The economic impact of the parasite on the cattle industry is significant, with high losses reported worldwide. While its impact on human health was previously underestimated, recent years have seen a rise in fascioliasis cases, leading to increased interest among researchers globally. To characterize the genetic diversity and intraspecific variation of this parasite in South America, specifically in Colombia, we collected 105 adult parasites from cattle bile ducts in seven Colombian departments (Antioquia, Boyacá, Santander, Cauca, Cundinamarca, Nariño, Norte de Santander, and Santander) to assess the parasite's phenotypic analyses, genetic diversity, and population structure. A computer image analysis system (CIAS) was applied based on standardized morphological measurements. Liver-fluke size was studied by principal component analysis (PCA). DNA sequences were obtained for nuclear markers such as the 28S, β-tubulin 3, ITS1, ITS2, and the mitochondrial marker Cytochrome Oxidase I (COI). Multiple statistical tests were performed, and the parasite's population structure was analyzed. Maximum Likelihood (ML) phylogenetic reconstructions were carried out using the sequences obtained herein and sequences available in GenBank. Morphological results revealed that all the obtained individuals matched F. hepatica's morphology. There was no evidence of high genetic diversity, and the absence of genetic structure at the country-level was notable, possibly caused by a demographic expansion of this trematode in Colombia or the low resolution of the molecular markers employed. Future studies are still needed to unveil the genetic population structure of F. hepatica across the country.

Assessment of genetic markers for multilocus sequence typing (MLST) of Fasciola isolates from Iran

BACKGROUND

Several markers have been described to characterise the population structure and genetic diversity of Fasciola species (Fasciola hepatica (F. hepatica) and Fasciola gigantica (F. gigantica). However, sequence analysis of a single genomic locus cannot provide sufficient resolution for the genetic diversity of the Fasciola parasite whose genomes are ∼1.3 GB in size.

OBJECTIVES

To gain a better understanding of the gene diversity of Fasciola isolates from western Iran and to identify the most informative markers as candidates for epidemiological studies, five housekeeping genes were evaluated using a multilocus sequence typing (MLST) approach.

METHODS

MLST analysis was developed based on five genes (ND1, Pepck, Pold, Cyt b and HSP70) after genomic DNA extraction, amplification and sequencing. Nucleotide diversity and phylogeny analysis were conducted on both concatenated MLST loci and each individual locus. A median joining haplotype network was created to examine the haplotypes relationship among Fasciola isolates.

RESULTS

Thirty-three Fasciola isolates (19 F. hepatica and 14 F. gigantica) were included in the study. A total of 2971 bp was analysed for each isolate and 31 sequence types (STs) were identified among the 33 isolates (19 for F. hepatica and 14 for F. gigantica isolates). The STs produced 44 and 42 polymorphic sites and 17 and 14 haplotypes for F. hepatica and F. gigantica, respectively. Haplotype diversity was 0.982 ± 0.026 and 1.000 ± 0.027 and nucleotide diversity was 0.00200 and 0.00353 ± 0.00088 for F. hepatica and F. gigantica, respectively. There was a high degree of genetic diversity with a Simpson's index of diversity of 0.98 and 1 for F. hepatica and F. gigantica, respectively. While HSP70 and Pold haplotypes from Fasciola species were separated by one to three mutational steps, the haplotype networks of ND1 and Cyt b were more complex and numerous mutational steps were found, likely due to recombination.

CONCLUSIONS

Although HSP70 and Pold genes from F. gigantica were invariant over the entire region of sequence coverage, MLST was useful for investigating the phylogenetic relationship of Fasciola species. The present study also provided insight into markers more suitable for phylogenetic studies and the genetic structure of Fasciola parasites.

Human and Animal Fascioliasis: Origins and Worldwide Evolving Scenario

Fascioliasis is a plant- and waterborne zoonotic parasitic disease caused by two trematode species: (i) Fasciola hepatica in Europe, Asia, Africa, the Americas, and Oceania and (ii) F. gigantica, which is restricted to Africa and Asia. Fasciolid liver flukes infect mainly herbivores as ruminants, equids, and camelids but also omnivore mammals as humans and swine and are transmitted by freshwater Lymnaeidae snail vectors. Two phases may be distinguished in fasciolid evolution. The long predomestication period includes the F. gigantica origin in east-southern Africa around the mid-Miocene, the F. hepatica origin in the Near-Middle East of Asia around the latest Miocene to Early Pliocene, and their subsequent local spread. The short postdomestication period includes the worldwide spread by human-guided movements of animals in the last 12,000 years and the more recent transoceanic anthropogenic introductions of F. hepatica into the Americas and Oceania and of F. gigantica into several large islands of the Pacific with ships transporting livestock in the last 500 years. The routes and chronology of the spreading waves followed by both fasciolids into the five continents are redefined on the basis of recently generated knowledge of human-guided movements of domesticated hosts. No local, zonal, or regional situation showing disagreement with historical records was found, although in a few world zones the available knowledge is still insufficient. The anthropogenically accelerated evolution of fasciolids allows us to call them "peridomestic endoparasites." The multidisciplinary implications for crucial aspects of the disease should therefore lead the present baseline update to be taken into account in future research studies.

Multiplex PCR and Sequence Analysis to Investigate Genetic Diversity of Fasciola Isolates from Cattle and Sheep in Turkey

Fasciolosis is a highly prevalent helminthic infection caused by Fasciola hepatica and F. gigantica. With the aim of identifying hybrid Fasciola flukes, multiplex PCR was performed to amplify the pepck gene. Furthermore, to determine Fasciola haplotypes, mitochondrial nad1 gene was amplified and sequenced, and phylogenetic analyses were performed. Adult Fasciola isolates were collected from 51 cattle and 51 sheep, genomic DNA was isolated, and one-step multiplex PCR was subsequently performed to amplify pepck. Isolates that generated a 510 bp band were identified as F. gigantica, those that generated a 241 bp band were identified as F. hepatica, and those that generated both bands were identified as hybrid (aspermic) flukes. Multiplex PCR data identified four isolates as F. gigantica and 84 as F. hepatica. Fourteen hybrid isolates (five cattle and nine sheep) were identified. On unidirectional DNA sequence analysis of nad1 PCR products, three sequences were identified as F. gigantica and 99 as F. hepatica. In addition, only 4 of 87 haplotypes detected for F. hepatica nad1 sequences were found to be previously reported, while the remaining 83 are unique to this study. To summarize, this study is the first to report the existence of hybrid Fasciola flukes and 83 unique haplotypes of F. hepatica in Turkey.

Development of novel DNA marker for species discrimination of Fasciola flukes based on the fatty acid binding protein type I gene

Background

Multiplex polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism (RFLP) for nuclear phosphoenolpyruvate carboxykinase (pepck) and polymerase delta (pold), respectively, have been used to differentiate Fasciola hepatica, F. gigantica, and hybrid Fasciola flukes. However, discrimination errors have been reported in both methods. This study aimed to develop a multiplex PCR based on a novel nuclear marker, the fatty acid binding protein type I (FABP) type I gene.

Methods

Nucleotide sequence variations of FABP type I were analyzed using DNA samples of F. hepatica, F. gigantica, and hybrid Fasciola flukes obtained from 11 countries in Europe, Latin America, Africa, and Asia. A common forward primer for F. hepatica and F. gigantica and two specific reverse primers for F. hepatica and F. gigantica were designed for multiplex PCR.

Results

Specific fragments of F. hepatica (290 bp) and F. gigantica (190 bp) were successfully amplified using multiplex PCR. However, the hybrid flukes contained fragments of both species. The multiplex PCR for FABP type I could precisely discriminate the 1312 Fasciola samples used in this study. Notably, no discrimination errors were observed with this novel method.

Conclusions

Multiplex PCR for FABP type I can be used as a species discrimination marker in place of pepck and pold. The robustness of the species-specific primer should be continuously examined using a larger number of Fasciola flukes worldwide in the future since nucleotide substitutions in the primer regions may cause amplification errors.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05538-7.

Population structure, molecular characterization, and phylogenetic analysis of Fasciola gigantica from two locations in Uganda

Fasciola gigantica is a major pathogen that causes fasciolosis in Africa. A recent study in Uganda demonstrated that Fasciola flukes were present in 65.7% of slaughtered cattle. However, molecular identification of Fasciola species has not yet been performed in the country. In the present study, 292 Fasciola flukes were collected from Kampala and Gulu, Uganda. The samples were identified as F. gigantica using a multiplex polymerase chain reaction (PCR) assay for phosphoenolpyruvate carboxykinase (pepck) and a PCR-restriction fragment length polymorphism (RFLP) assay for DNA polymerase delta (pold). A significant genetic difference between F. gigantica obtained from cattle slaughtered at Kampala and Gulu was observed by analyzing the mitochondrial markers NADH dehydrogenase subunit 1 (nad1) and cytochrome C oxidase subunit 1 (cox1). Fasciola collected from Gulu had a more diversified population than that collected from Kampala, probably because of differences in livestock management systems. One of the possible reasons for this observation is that cattle slaughtered in Gulu were reared under an extensive communal grazing system, which is suitable for maintaining parasite diversity, whereas cattle slaughtered in Kampala mainly originated from fenced/closed farms, which limits parasite diversity. However, the cause of the difference between these two locations was not clearly defined by the results of this study. The F. gigantica population from Uganda was related to that obtained from Zambia. A star-like phylogeny was detected in a median-joining network analysis, which indicated rapid population expansion and suggested that the F. gigantica populations from both countries are maintained by domestic ruminants in eastern Africa. Interestingly, the F. gigantica population from Uganda was not related to those from Egypt and Nigeria. The results of the present study suggest that F. gigantica populations in African countries are indigenous to each country or region.

New Insights Into the Genetic Variability of Fasciola Hepatica (Trematoda) in Algeria and Relationships with Other Geographic Regions Revealed By Mitochondrial DNA

This study aims to investigate the level of genetic variability of Fasciola hepatica flukes isolated from cattle in Algeria and to determine the phylogenetic and phylogeographic relationships with sequences isolated worldwide. Mitochondrial (Cytochrome c Oxidase subunit I gene - COI) and nuclear markers (Internal Transcribed Spacers of nuclear ribosomal DNA - ITS) for 24 F. hepatica flukes isolated from 12 cattle in North Algeria were characterised. Only two haplotypes were obtained for the COI gene, resulting in a low level of genetic variation. The analysis of variation among the COI sequences isolated from around the world did not show high levels of genetic divergence, and the phylogenetic analysis revealed a genetic similarity among F. hepatica isolates from different areas of the world. The analysis of the ITS region showed a low level of variability, which prevented obtaining informative phylogenetic and phylogeographic results. The present study also revealed that specimens of F. hepatica are genetically similar in different hosts, indicating that the genetic structure among populations of this parasite is not influenced by the host species. The low levels of genetic variation for COI and ITS regions among fluke isolates from all continents are consistent with a common origin for the flukes’ worldwide distribution.

Molecular characteristics and genetic diversity of Fasciola hepatica from sheep in Xinjiang, China

Introduction

Fasciola hepatica is a trematode infecting ruminants worldwide and occasionally affecting other animal species, including humans. It causes significant economic losses. Geographic distribution and patterns of infection must be considered before control and management measures are developed for this parasite. DNA molecular markers are useful for the identification of flukes and elucidation of their genetic evolution. Therefore, the population structure of F. hepatica was studied using this method in sheep in Xinjiang, China.

Material and Methods

The molecular characteristics, genetic relationships within the population and dispersal patterns of F. hepatica isolates were analysed based on the cox1 and nad1 genes. The population structure of F. hepatica from three regions of Xinjiang was explored and a neutrality test was conducted.

Results

The cox1 and nad1 genes have 21 and 42 variable sites, respectively, which can be classified into 34 and 33 haplotypes. Median-joining network and phylogenetic tree analyses showed that there was no significant variation in F. hepatica isolates between the three geographical regions. Analysis of variance revealed that the genetic variation of F. hepatica was mainly present within the populations. The neutrality test indicated that the populations were relatively stable but the Hami population may have undergone short-term expansion.

Conclusion

This study revealed for the first time the molecular characteristics, genetic diversity and dispersal patterns of F. hepatica isolates from sheep in Xinjiang, thus providing new insights into the genetic variation and haplotype diversity of F. hepatica from indigenous sheep.

The causative agents of fascioliasis in animals and humans: Parthenogenetic Fasciola in Asia and other regions

Parthenogenetic Fasciola is the causative agent of fascioliasis in animals and humans and is widely distributed in Asian countries, such as Japan, South Korea, China, Vietnam, Thailand, the Philippines, Myanmar, Bangladesh, Nepal, and India. Parthenogenetic Fasciola geographically originated from central and eastern China, where it exists between the habitats of Fasciola hepatica and Fasciola gigantica; it likely appeared thousands of years ago following hybridization between F. hepatica and F. gigantica. Parthenogenetic Fasciola consists of diploids and triploids that possess nuclear genome of both F. hepatica and F. gigantica and mitochondrial genome of either F. hepatica or F. gigantica. Maternal parents of parthenogenetic Fasciola are either F. hepatica having Fh-C4 haplotype or F. gigantica having Fg-C2 haplotype in mitochondrial NADH dehydrogenase subunit 1 (ND1) nucleotide sequences. Parthenogenetic Fasciola flukes with the Fh-C4 haplotype have spread from China to South Korea and Japan, whereas the flukes with the Fg-C2 haplotype have not only spread to Korea and Japan but also southward to Vietnam, Thailand, the Philippines, Myanmar, Bangladesh, Nepal, and India. Parthenogenetic Fasciola can be distinguished from F. hepatica and F. gigantica using combinational DNA sequence analysis of nuclear phosphoenolpyruvate carboxykinase (pepck) and DNA polymerase delta (pold) along with mitochondrial ND1 markers. The establishment of parthenogenetic Fasciola is expected as follows: parthenogenetic diploids with the Fh-C4 and Fg-C2 haplotypes first appeared based on single or multiple interspecific hybridization events; subsequently, parthenogenetic triploids emerged via backcross events between the maternal parthenogenetic diploid and either paternal bisexual F. hepatica or F. gigantica. Parthenogenetic Fasciola diploids and triploids then survived for thousands of years by clonal parthenogenetic reproduction, and generated descendants with ND1 haplotypes, which were derived from the Fh-C4 and Fg-C2 due to nucleotide substitution. Thus, the emergence of parthenogenetic Fasciola may be due to extremely uncommon and accidental events. Parthenogenetic Fasciola should be treated as a new asexual hybrid species.

On the arrival of fasciolosis in the Americas

Fasciola hepatica is a worldwide emerging and re-emerging parasite heavily affecting several regions in South America. Some lymnaeid snail species of American origin are among the major hosts of F. hepatica worldwide. Recent paleoparasitological findings detected its DNA in a 2300-year-old sample in Patagonia, countering the common hypothesis of the recent arrival of F. hepatica in the Americas during European colonization. Thus, the theory of an initial introduction in the 1500s can no longer be sustained. This article discusses how it was possible for F. hepatica to reach and spread in the Americas in relation to the availability and compatibility of hosts through natural and incidental introductions. Our study will serve to better understand the ongoing Neotropical scenario of fasciolosis.

High prevalence and risk factors of fascioliasis in cattle in Amazonas, Peru

Fascioliasis is a zoonotic disease caused by parasites of the genus Fasciola spp. which cause an important loss to the livestock industry. The objectives of this study were: to estimate the prevalence of fascioliasis in three provinces of Amazonas, to evaluate possible risk factors of infection in cattle and to genetically characterize the Fasciola haplotypes circulating in this area. According to the results the prevalence of fascioliasis in cattle was 90.13% (712/790). Odds ratio results showed a significant association between fascioliasis and the Brown Swiss breed (OR = 2.62; 95% CI: 1.57-4.35; p < 0.001), and with female cattle older than 30 months (OR = 1.71; 95% CI: 1.05-2.79; p < 0.031). According to the molecular genetic studies using the gene marker NAD1, six haplotypes of Fasciola hepatica were found in the 35 infected livers collected. The results obtained in this study are concerning due to the high prevalence presented and it reveals the necessity of a continuing monitoring because of the high risk of transmission to humans.

Towards the comprehension of fasciolosis (re-)emergence: an integrative overview

The increasing distribution and prevalence of fasciolosis in both human and livestock are concerning. Here, we examine the various types of factors influencing fasciolosis transmission and burden and the interrelations that may exist between them. We present the arsenal of molecules, 'adjusting' capabilities and parasitic strategies of Fasciola to infect. Such features define the high adaptability of Fasciola species for parasitism that facilitate their transmission. We discuss current environmental perturbations (increase of livestock and land use, climate change, introduction of alien species and biodiversity loss) in relation to fasciolosis dynamics. As Fasciola infection is directly and ultimately linked to livestock management, living conditions and cultural habits, which are also changing under the pressure of globalization and climate change, the social component of transmission is also discussed. Lastly, we examine the implication of increasing scientific and political awareness in highlighting the current circulation of fasciolosis and boosting epidemiological surveys and novel diagnostic techniques. From a joint perspective, it becomes clear that factors weight differently at each place and moment, depending on the biological, environmental, social and political interrelating contexts. Therefore, the analyses of a disease as complex as fasciolosis should be as integrative as possible to dissect the realities featuring each epidemiological scenario. Such a comprehensive appraisal is presented in this review and constitutes its main asset to serve as a fresh integrative understanding of fasciolosis.

Evidence of population structuring following population genetic analyses of Fasciola hepatica from Argentina

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320 Argentinian Fasciola hepatica were genotyped using a panel of microsatellites.

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Overall there was high genotypic richness: 263 distinct genotypes were identified.

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Population structuring of F. hepatica was evident across Argentina.

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Within these sub-populations there is largely random mating.

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Transmission of clonemates occurs: clonal parasites accounted for 26.6% of all parasites.

Fasciola hepatica, the liver fluke, is a trematode parasite that causes disease of economic importance in livestock. As a zoonosis this parasite also poses a risk to human health in areas where it is endemic. Population genetic studies can reveal the mechanisms responsible for genetic structuring (non-panmixia) within parasite populations and provide valuable insights into population dynamics, which in turn enables theoretical predictions of evolutionary dynamics such as the evolution of drug resistance. Here we genotyped 320 F. hepatica collected from 14 definitive hosts from four provinces in Argentina. STRUCTURE analysis indicated three population clusters, and principal coordinate analysis confirmed this, showing population clustering across provinces. Similarly, pairwise F_ST values amongst all four provinces were significant, with standardised pairwise F_ST (F′_ST) ranging from 0.0754 to 0.6327. Therefore, population genetic structure was evident across these four provinces in Argentina. However, there was no evidence of deviation from Hardy–Weinberg equilibrium, so it appears that within these sub-populations there is largely random mating. We identified 263 unique genotypes, which gave a clonal diversity of 82%. Parasites with identical genotypes, clones, accounted for 26.6% of the parasites studied and were found in 12 of the 14 hosts studied, suggesting some clonemate transmission.

Molecular characterization and phylogenetic analysis of Fasciola hepatica from high- plateau and steppe areas in Algeria

A previous study based on mitochondrial DNA markers reported the presence of Fasciola hepatica in Algeria. However, a precise species identification is still required. In this report, a total of 68 Fasciola isolates, collected from high-plateau (Bordj-Bou-Arreridj) and steppe (Djelfa) areas of Algeria, were identified at the species level by multiplex PCR and PCR-restriction fragment length polymorphism (RFLP) for nuclear phosphoenolpyruvate carboxykinase (pepck) and DNA polymerase delta (pold), respectively. The result of the multiplex PCR conflicted with that of the PCR-RFLP; however, subsequent nucleotide sequencing of pepck clearly showed that all isolates should be classified as F. hepatica. The two mitochondrial markers, NADH dehydrogenase subunit I (nad1) and cytochrome c oxidase subunit 1 (cox1), revealed a close relationship between the parasite populations from the plateau and those from the steppe. A dispersal direction from the high plateau to the steppe was indicated because the former population was more diversified than the latter. Moreover, these populations were more closely related to populations from Spain than those from Egypt or Afghanistan. Given the population characteristic of F. hepatica in Spain and the history of cattle trade, it seems likely that the parasite was introduced to Algeria from Europe through a route across the Mediterranean Sea.