Molecular characterization of Fasciola gigantica from Mauritania based on mitochondrial and nuclear ribosomal DNA sequences

New perspectives for fascioliasis in Upper Egypt's new endemic region: Sociodemographic characteristics and phylogenetic analysis of Fasciola in humans, animals, and lymnaeid vectors

BACKGROUND

Fascioliasis is a significant vector-borne disease that has emerged in numerous tropical and subtropical countries causing severe health problems. Egypt is one of the fascioliasis endemic regions; however, the current situation in Upper Egypt is understudied, with only sporadic human cases or outbreaks. This study aims to highlight the sociodemographic characteristics of human fascioliasis in a newly emerged endemic area in Upper Egypt, along with risk factors analysis and the molecular characteristics of the fasciolid population in humans, animals, and lymnaeid snails.

METHODOLOGY/PRINCIPAL FINDINGS

The study reported Fasciola infection in patients and their close relatives by analyzing the risk of human infection. Morphological and molecular characterization was performed on lymnaeid snails. Multigene sequencing was also used to characterize fasciolids from human cases, cattle, and pooled snail samples. The study identified asymptomatic Fasciola infection among family members and identified the presence of peridomestic animals as a significant risk factor for infection. This is the first genetic evidence that Radix auricularia exists as the snail intermediate host in Egypt.

CONCLUSIONS/SIGNIFICANCE

This study revealed that Assiut Governorate in Upper Egypt is a high-risk area for human fascioliasis that requires additional control measures. Fasciola hepatica was the main causative agent infecting humans and snail vectors in this newly emerged endemic area. In addition, this is the first report of R. auricularia as the snail intermediate host transmitting fascioliasis in Upper Egypt. Further research is required to clarify the widespread distribution of Fasciola in Egypt's various animal hosts. This provides insight into the mode of transmission, epidemiological criteria, and genetic diversity of fasciolid populations in Upper Egypt.\.

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.

Potential Hybridization of Fasciola hepatica and F. gigantica in Africa-A Scoping Review

The occurrence of Fasciola gigantica and F. hepatica in Africa is well documented; however, unlike in Asia, there is a paucity of information on the existence of hybrids or parthenogenetic species on the continent. Nonetheless, these hybrid species may have beneficial characteristics, such as increased host range and pathogenicity. This study provides evidence of the potential existence of Fasciola hybrids in Africa. A literature search of articles published between 1980 and 2022 was conducted in PubMed, Google Scholar, and Science Direct using a combination of search terms and Boolean operators. Fasciola species were documented in 26 African countries with F. hepatica being restricted to 12 countries, whilst F. gigantica occurred in 24 countries, identified based on morphological features of adult Fasciola specimens or eggs and molecular techniques. The co-occurrence of both species was reported in 11 countries. However, the occurrence of potential Fasciola hybrids was only confirmed in Egypt and Chad but is suspected in South Africa and Zimbabwe. These were identified based on liver fluke morphometrics, assessment of the sperms in the seminal vesicle, and molecular techniques. The occurrence of intermediate host snails Galba truncatula and Radix natalensis was reported in Ethiopia, Egypt, South Africa, Tanzania, and Uganda, where F. hepatica and F. gigantica co-occurrences were reported. The invasive Pseudosuccinea columella snails naturally infected with F. gigantica were documented in South Africa and Egypt. In Zimbabwe, P. columella was infected with a presumed parthenogenetic Fasciola. This suggests that the invasive species might also be contributing to the overlapping distributions of the two Fasciola species since it can transmit both species. Notwithstanding the limited studies in Africa, the potential existence of Fasciola hybrids in Africa is real and might mimic scenarios in Asia, where parthenogenetic Fasciola exist in most Asian countries. In South Africa, aspermic F. hepatica and Fasciola sp. have been reported already, and Fasciola hybrids have been reported? in Chad and Egypt. Thus, the authors recommend future surveys using molecular markers recommended to identify Fasciola spp. and their snail intermediate hosts to demarcate areas of overlapping distribution where Fasciola hybrids and/or parthenogenetic Fasciola may occur. Further studies should also be conducted to determine the presence and role of P. columella in the transmission of Fasciola spp. in these geographical overlaps to help prevent parasite spillbacks.

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.

Molecular Identification of Fasciola Isolated from the Liver of Meat Animals in Fars Province, Iran

Background

Fasciola hepatica and Fasciola gigantica are flatworms that infect animals and humans. Fasciola is the parasite of the liver or bile ducts and intestines of mammals, where such animals are known as their “definite hosts.” The study aims to detect the genotype of Fasciola spp. from the livers of meat animals by using RFLP-PCR in samples collected from Fars province.

Methods

Sixty Fasciola spp. samples were collected from infected slaughtered animals in three counties of Fars province, Iran (Jahrom, Nourabad Mamasani, and Kazeroun).Genomic DNA was extracted by the conventional phenol-chloroform method. For the study, PCR-RFLP and sequence analysis of the first nuclear ribosomal internal transcribed spacer (ITS1) region from Fasciola species were used to conduct the study.

Results

The fragment of about 700 bp in all the Fasciola samples was amplified. In total, 43 samples of Fasciola gigantica and 17 samples of Fasciola hepatica were identified.

Conclusion

The dominant Fasciola species in this region is Fasciola gigantica. Hence, it seems that hygienic policies should be developed to prevent and control fascioliasis because of the dominant species, Fasciola gigantica.

High-throughput sequencing of Fasciola spp. shows co-infection and intermediate forms in Balochistan, but only Fasciola gigantica in the Punjab province of Pakistan

Fasciola gigantica and Fasciola hepatica are digenetic trematodes causing fasciolosis in ruminants. The host and geographical distribution of both Fasciola species are influenced by environmental and climatic conditions favouring survival and development of free-living stages and intermediate hosts, and livestock management practices. The aim of the present study was to describe the host distribution of the two Fasciola species in buffalo, cattle, goats, and sheep in the Balochistan and Punjab provinces of Pakistan. 359 flukes were collected from a total of 32 livers from the four livestock species. Deep amplicon sequencing of the internal transcribed spacer region 2 of ribosomal DNA (rDNA ITS-2) and mitochondrial nicotinamide adenine dinucleotide dehydrogenase 1 (mtDNA ND-1) loci confirmed co-infection of F. hepatica and F. gigantica in Balochistan and single species F. gigantica infection in Punjab. In Balochistan, co-infections and hybrids of both Fasciola species were identified in cattle, with more F. hepatica detected than F. gigantica. However, F. hepatica was the only species identified in goats, and F. gigantica was the only species identified in buffalo. In Punjab, all flukes were confirmed as F. gigantica in each of the four livestock species. Overall, the results indicate differences in the host and geographical distribution of F. gigantica and F. hepatica, and provide useful knowledge for the development of control strategies for livestock and humans.

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.

Genetically 'pure' Fasciola gigantica discovered in Algeria: DNA multimarker characterization, trans-Saharan introduction from a Sahel origin and spreading risk into north-western Maghreb countries

Fascioliasis is a freshwater snail-borne zoonotic helminth disease caused by two species of trematodes: Fasciola hepatica of almost worldwide distribution and the more pathogenic F. gigantica restricted to parts of Asia and most of Africa. Of high pathological impact in ruminants, it underlies large livestock husbandry losses. Fascioliasis is moreover of high public health importance and accordingly included within the main neglected tropical diseases by WHO. Additionally, this is an emerging disease due to influences of climate and global changes. In Africa, F. gigantica is distributed throughout almost the whole continent except in the north-western Maghreb countries of Morocco, Algeria and Tunisia where only F. hepatica is present. The present study concerns the DNA multimarker characterization of the first finding of F. gigantica in sheep in Algeria by the complete sequences of rDNA ITS-1 and ITS-2 and mtDNA cox1 and nad1 genes. Sequence comparisons and network analyses show sequence identities and similarities suggesting a south-north trans-Saharan geographical origin, with introduction from Ghana, through the Sahel countries of Burkina Faso and Mali into Algeria. This way perfectly fits with nomadic pastoralism according to interconnecting intranational and transborder herd transhumance routes traditionally followed in this western part of Africa from very long ago. The risk for further spread throughout the three north-western Maghreb countries is multidisciplinarily analysed, mainly considering the present extensive motorization of the intranational transhumance system in Algeria, the lymnaeid snail vector species present throughout the north-western Maghreb, the increasing demand for animal products in the growing cities of northern Algeria and the continued human infection reports. Control measures should assure making anti-fasciolid drugs available and affordable for herders from the beginning and along their transhumant routes and include diffusion and rules within the regional regulatory framework about the need for herd treatments.

Molecular Confirmation of a Fasciola gigantica × Fasciola hepatica Hybrid in a Chadian Bovine

Fascioliasis is a zoonotic infection of humans and, more commonly, ruminants. It is caused by 2 liver fluke species, Fasciola hepatica and Fasciola gigantica, which differ in size. The traditional morphological methods used to distinguish the 2 species can be unreliable, particularly in the presence of hybrids between the 2 species. The development of advanced molecular methods has allowed for more definitive identification of Fasciola species, including their hybrids. Hybrids are of concern, as it is thought that they could acquire advantageous traits such as increased pathogenicity and host range. In 2013, we collected flukes from Fasciola-positive cattle, sheep, and goats slaughtered in 4 Chadian abattoirs. DNA from 27 flukes was extracted, amplified, and analyzed to identify species using the ITS1+2 locus. Twenty-six of the 27 flukes were identified as F. gigantica, while the remaining fluke showed heterozygosity at all variable sites that distinguish F. hepatica and F. gigantica. Cloning and sequencing of both alleles confirmed the presence of 1 F. hepatica and 1 F. gigantica allele. To our knowledge, this is the first unambiguous, molecular demonstration of the presence of such a hybrid in a bovine in sub-Saharan Africa.

Genetic diversity and multiplicity of infection in Fasciola gigantica isolates of Pakistani livestock

Fasciola spp. are responsible for over 3 billion US dollars of production loss annually in livestock and cause widespread zoonotic disease. Nevertheless, understating of the emergence and spread of the trematode species is poor. The multiplicity of F. gigantica infection and its spread is potentially influenced by multiple factors, including the abundance of suitable intermediate hosts, climatic conditions favouring the completion of the parasite's lifecycle, and translocation of infected animals, or free-living parasite stages between regions. Here we describe the development of a 'tremabiome' metabarcoding sequencing method to explore the numbers of F. gigantica genotypes per infection and patterns of parasite spread, based on genetic characteristics of the mitochondrial NADH dehydrogenase 1 (mt-ND-1) locus. We collected F. gigantica from three abattoirs in the Punjab and Balochistan provinces of Pakistan, and our results show a high level of genetic diversity in 20 F. gigantica populations derived from small and large ruminants consigned to slaughter in both provinces. This implies that F. gigantica can reproduce in its definitive hosts through meiosis involving cross- and self-breeding, as described in the closely related species, Fasciola hepatica. The genetic diversity between the 20 populations derived from different locations also illustrates the impact of animal movements on gene flow. Our results demonstrate the predominance of single haplotypes, consistent with a single introduction of F. gigantica infection in 85% of the hosts from which the parasite populations were derived. This is consistent with clonal reproduction in the intermediate snail hosts.

Genetic characterisation of Fasciola gigantica from Ghana

Fasciola hepatica and Fasciola gigantica are the causal agents of the zoonotic food-born disease fascioliasis. Africa is primarily endemic to F. gigantica, although sympatric presence of F. hepatica is known for some countries. The present situation of fascioliasis in western Africa, and Ghana in particular, is still poorly understood, and studies including molecular identification of species and variants are lacking. In this explorative study we genotyped 19 Fasciola isolates obtained by opportunistic sampling in the Upper East and Upper West Regions of Ghana. All isolates were identified as F. gigantica based on a partial sequence of the 28S rRNA (548 bp) gene. In addition, the complete mtDNA nad1 (903 bp) gene was employed to infer intraspecific microvariation among isolates. Six nad1 haplotypes were identified that clustered into two West African haplogroups when compared with previous records from Nigeria. These preliminary data suggest that fascioliasis in Ghana is (at least) mainly caused by F. gigantica, and that transmission may be principally autochthonous. However, the small number of isolates prevents firm conclusions, and this study is intended to stimulate molecular surveys on this neglected disease in a neglected region.

First genetic characterization of Fasciola hepatica in Argentina by nuclear and mitochondrial gene markers

Fasciola hepatica is a trematode showing genetic variation among isolates from different regions of the world. The objective of this work was to characterize for the first time F. hepatica isolates circulating in different regions of Argentina. Twenty-two adult flukes were collected from naturally infected bovine livers in different areas from Argentina and used for DNA extraction. We carried out PCR amplification and sequence analysis of the ribosomal internal transcribed spacer 1 (ITS1), mitochondrial nicotinamide adenine dinucleotide dehydrogenase subunits 4 and 5 (nad4 and nad5) and mitochondrial cytochrome c oxidase subunit I (cox1) genes as genetic markers. Phylogenies were reconstructed using maximum parsimony algorithm. A total of 6 haplotypes were found for cox1, 4 haplotypes for nad4 and 3 haplotypes for nad5. The sequenced ITS1 fragment was identical in all samples. The analyzed cox1 gene fragment is the most variable marker and is recommended for future analyses. No geographic association was found in the Argentinean samples.

A review of bovine fasciolosis and other trematode infections in Nigeria

Trematode infections cause serious economic losses to livestock worldwide. Global production losses due to fasciolosis alone exceed US$3 billion annually. Many trematode infections are also zoonotic and thus a public health concern. The World Health Organization has estimated that about 56 million people worldwide are infected by at least one zoonotic trematode species, and up to 750 million people are at risk of infection. Fasciolosis caused by the fluke Fasciola gigantica is endemic in Nigeria and is one of the most common causes of liver condemnation in abattoirs. Total cattle losses from Fasciola infection in Nigeria have been estimated to cost £32.5 million. Other trematode infections of cattle, including paramphistomosis, dicrocoeliasis and schistosomiasis, have all been reported in various parts of Nigeria, with varying prevalence. Most publications on trematode infections are limited to Nigerian local and national journals, with very few international reports. This paper therefore summarized the current data on distribution, control and zoonotic trematode infections in Nigeria and other African countries. We also identified research gaps and made recommendations for future research and areas for funding for policy/planning.

Morphological and molecular identification of Explanatum explanatum in domestic water buffalo in Pakistan

More than 70 species of the family Paramphistomatidae, have been identified in ruminants in different parts of the world. Most are pathogenic, causing amphistomosis. Adult flukes of this Family have a predilection for the rumen, liver or bile duct of ruminants where they may cause damage to the epithelium. Identification of adult paramphistomes to the species level based on morphology alone requires specialized knowledge, whereas, molecular genetic marker analysis is more precise and transferable. In the present study, we performed both morphological and molecular characterization of fifteen adult flukes collected from the liver of domesticated buffalo in the Punjab province of Pakistan. The morphology of five of these flukes was examined in detail and on this basis these were identified as either Explanatum explanatum or Explanatum bathycotyle. PCR and sequencing of the ITS-2 rDNA region from these 5 flukes, plus 10 others, revealed a single haplotype in all cases. This differed by just a single nucleotide polymorphism from a previously described E. explanatum ITS-2 rDNA sequence. Phylogenetic comparison of these E. explanatum ITS2-rDNA sequences with those from other Paramphistomatidae, Fasciola and Dicrocoelium species was performed to assess within and between species variation and validate the use of ITS-2 rDNA as a robust species-specific marker for E. explanatum. This work provides a validated species-specific marker of E. explanatum and the first report of this parasite species from Pakistan.

Molecular evidence shows that the liver fluke Fasciola gigantica is the predominant Fasciola species in ruminants from Pakistan

Fascioliasis is an important disease affecting livestock, with great costs to producers worldwide. It has also become a serious issue for human populations in some endemic areas as an emerging zoonotic infection. There are two Fasciola species of liver fluke responsible for this disease, which occur worldwide, Fasciola hepatica and Fasciola gigantica. Identifying these two species on the basis of adult or egg morphology requires specialist knowledge due to the similarity of characters, and may misidentify putative intermediate or hybrid forms. In this study we sequenced the internal transcribed spacer 2 (ITS-2) rDNA of liver flukes collected from multiple species of hosts from seven localities in the Punjab and Baluchistan provinces of Pakistan, to determine the distribution of these two species. All 46 flukes processed in this study, collected from seven sites, showed the rDNA ITS-2 genotype corresponding to F. gigantica, contradicting previous reports, based on adult and egg morphology, that both species are present in Pakistan, with F. hepatica being the more common.

Prevalence of Fasciola gigantica infection in slaughtered animals in south-eastern Lake Chad area in relation to husbandry practices and seasonal water levels

Background

Fasciolosis has been described in sub-Saharan Africa in many accounts, but the latest reports from Chad are from the 1970s. Mobile pastoralists perceive liver parasites as a significant problem and think that proximity to Lake Chad can lead to infection. This study aimed to assess the importance of liver fluke infections in mobile pastoralists’ livestock in the south-eastern Lake Chad region.

In 2011, all animals presented at three slaughter slabs near Gredaya in the south-eastern Lake Chad area were examined for infection with Fasciola spp. during routine meat inspections.

Results

This study included 616 goats, 132 sheep and 130 cattle. The prevalence of adult Fasciola gigantica was 68% (CI 60-76%) in cattle, 12% (CI 10-16%) in goats and 23% (CI 16-30%) in sheep. From all infected animals (n = 200), 53% (n = 106) were classified as lightly infected with 1-10 parasites, 18% (n =36) as moderately infected with 11-100 parasites and 29% (n = 58) as heavily infected with more than 100 parasites per animal.

Animals grazing close to the shores of Lake Chad had a much higher risk of infection (prevalence =38%; n = 329) than animals not feeding at the lake (n = 353), with only one goat being positive (prevalence = 0.28%).

The ethnic group of the owner was a strong determinant for the risk of infection. Ethnic group likely served as a proxy for husbandry practices. Geospatial distribution showed that animals originating from areas close to the lake were more likely to be infected with F. gigantica than those from more distant areas.

Conclusions

Livestock belonging to ethnic groups which traditionally stay near surface water, and which were reported to feed near Lake Chad, have a high risk of infection with F. gigantica. Pastoralist perception of fasciolosis as a priority health problem was confirmed.

Regular preventive and post-exposure treatment is recommended for animals grazing near the lake. However, further economic analysis is needed.