Chapter 2 Fasciola, Lymnaeids and Human Fascioliasis, with a Global Overview on Disease Transmission, Epidemiology, Evolutionary Genetics, Molecular Epidemiology and Control

A mechanistic hydro-epidemiological model of liver fluke risk

The majority of existing models for predicting disease risk in response to climate change are empirical. These models exploit correlations between historical data, rather than explicitly describing relationships between cause and response variables. Therefore, they are unsuitable for capturing impacts beyond historically observed variability and have limited ability to guide interventions. In this study, we integrate environmental and epidemiological processes into a new mechanistic model, taking the widespread parasitic disease of fasciolosis as an example. The model simulates environmental suitability for disease transmission at a daily time step and 25 m resolution, explicitly linking the parasite life cycle to key weather–water–environment conditions. Using epidemiological data, we show that the model can reproduce observed infection levels in time and space for two case studies in the UK. To overcome data limitations, we propose a calibration approach combining Monte Carlo sampling and expert opinion, which allows constraint of the model in a process-based way, including a quantification of uncertainty. The simulated disease dynamics agree with information from the literature, and comparison with a widely used empirical risk index shows that the new model provides better insight into the time–space patterns of infection, which will be valuable for decision support.

Complex and dynamic transcriptional changes allow the helminth Fasciola gigantica to adjust to its intermediate snail and definitive mammalian hosts

BACKGROUND

The tropical liver fluke, Fasciola gigantica causes fasciolosis, an important disease of humans and livestock. We characterized dynamic transcriptional changes associated with the development of the parasite in its two hosts, the snail intermediate host and the mammalian definitive host.

RESULTS

Differential gene transcription analysis revealed 7445 unigenes transcribed by all F. gigantica lifecycle stages, while the majority (n = 50,977) exhibited stage-specific expression. Miracidia that hatch from eggs are highly transcriptionally active, expressing a myriad of genes involved in pheromone activity and metallopeptidase activity, consistent with snail host finding and invasion. Clonal expansion of rediae within the snail correlates with increased expression of genes associated with transcription, translation and repair. All intra-snail stages (miracidia, rediae and cercariae) require abundant cathepsin L peptidases for migration and feeding and, as indicated by their annotation, express genes putatively involved in the manipulation of snail innate immune responses. Cercariae emerge from the snail, settle on vegetation and become encysted metacercariae that are infectious to mammals; these remain metabolically active, transcribing genes involved in regulation of metabolism, synthesis of nucleotides, pH and endopeptidase activity to assure their longevity and survival on pasture. Dramatic growth and development following infection of the mammalian host are associated with high gene transcription of cell motility pathways, and transport and catabolism pathways. The intra-mammalian stages temporally regulate key families of genes including the cathepsin L and B proteases and their trans-activating peptidases, the legumains, during intense feeding and migration through the intestine, liver and bile ducts. While 70% of the F. gigantica transcripts share homology with genes expressed by the temperate liver fluke Fasciola hepatica, gene expression profiles of the most abundantly expressed transcripts within the comparable lifecycle stages implies significant species-specific gene regulation.

CONCLUSIONS

Transcriptional profiling of the F. gigantica lifecycle identified key metabolic, growth and developmental processes the parasite undergoes as it encounters vastly different environments within two very different hosts. Comparative analysis with F. hepatica provides insight into the similarities and differences of these parasites that diverged > 20 million years ago, crucial for the future development of novel control strategies against both species.

A socio-economic study of Fasciola infections in cattle and sheep at the Etoudi slaughterhouse, Yaoundé, Cameroon

A cross-sectional socio-economic study of fascioliasis in livestock was carried out at the Livestock Development Cooperation (SODEPA) slaughterhouse in Etoudi, Yaoundé during the periods covering the beginning and late dry season in the northern and eastern regions of Cameroon. A total of 768 cattle and 267 sheep were inspected for the presence of Fasciola species. The overall infection rate in cattle and sheep was 18% (n = 767) and 27% (n = 267), respectively. For the animals that were Fasciola positive, a total of 267.86 kg of liver in cattle was condemned, resulting in a loss of US$1124, while a total of 57 kg of liver was condemned from the sheep population, amounting to a loss of US$114. A total of US$76,097 was determined as losses incurred from condemnation of liver for both cattle and sheep per annum based on the total number slaughtered each year. The findings indicate that fascioliasis is present in cattle and sheep slaughtered in Cameroon and that it causes great economic losses due to condemnation of liver. The local climatic conditions, husbandry systems and the presence of snails (intermediate hosts) are probably the main factors influencing the incidence of the disease and may account for the epidemiological significance found in this study.

Prevalence of bovine fascioliasis in a new-emerging focus of human fascioliasis in BoyerAhmad district, southwest of Iran

BACKGROUND

The prevalence of fascioliasis in a population of cattle in a new-emerging focus of human fascioliasis in Boyer-Ahmad District, in the southwest of Iran, was investigated, using an ELISA system and coprological methods.

METHODS

Blood, as well as stool samples, were collected from 150 dairy cattle consisted of 82 (54.7%) males and 68 (45.3%) females, aged from 1 to 8 years, selected from different pastures. The stool samples were evaluated by direct wet mount microscopic examination as well as sedimentation methods. Moreover, modified Telemann was used for detecting of Fasciola eggs. Anti-Fasciola antibodies in the cattle sera samples were determined, using a Fasciola excretory-secretory antigen-specific ELISA.

RESULTS

Anti-Fasciola antibodies were detected in 64 (42.4%) of the subjects by ELISA. Out of 64 seropositive cases, 29 (45.3%) were female and 35 (54.6%) were male. No significant association was found between sex and seropositivity to fascioliasis. Considering the age of the cattle, the highest prevalence of fascioliasis (23%) was found in the 5-year old age group. However, the difference between the age of the cattle and seropositivity to fascioliasis was not statistically significant (P > 0.05). Fasciola eggs were not detected in fecal samples of any of the studied cattle, while Paramphistomide, as well as Dicrocoelium dendriticum eggs, were detected in 6 (4%) and 17 (11.3%) of the subjects, respectively.

CONCLUSION

Findings of the current study provide basic information about bovine fascioliasis in a new focus of human fascioliasis in Iran, which is needed for effective control of this parasitic infection in such 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 this 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.

Prevalence and risk factors of Fascioliasis in China

Fascioliasis has emerged as a significant public health problem among ruminants and humans. Human fascioliasis is a neglected food-borne parasitic disease, which has emerged or reemerged in more than 60 countries worldwide. In China, the first case of human fascioliasis was reported in 1921 in Fujian Province. The first major outbreak of this parasitic disease in 29 patients occurred in 2012 in Yunnan Province. Nonetheless, the prevalence of fascioliasis in China is probably underestimated due to the poor sensitivity of diagnostic tests, limited epidemiological data, and a poor understanding of the impact of subclinical illness. This study aimed to review the prevalence and risk factors of fascioliasis in China so as to improve the prevention and control of this disease.

Genetic Characterization of Cambodian Fasciola gigantica and Dispersal Direction of the Species in Asia

Fasciola gigantica and hybrid Fasciola are distributed throughout Asia. Herein, we investigated the species of the Fasciola fluke distributed in three hotspots of fascioliasis in Cambodia. A total of 92 flukes collected from 21 slaughtered cattle from Kandal (44), Battambang (41), and Kratie (7) Provinces were identified as F. gigantica using multiplex PCR for a nuclear phosphoenolpyruvate carboxykinase (PEPCK) gene. The overall prevalence of F. gigantica infestation was 7.14% (21/294). Phylogenetic as well as population genetics analyses were performed using the mitochondrial NADH dehydrogenase subunit 1 (ND1). The 19 ND1 haplotypes were identified from Cambodian F. gigantica (haplotype diversity, 0.83). All of the haplotypes were classified into F. gigantica haplogroup C, which includes ND1 haplotypes detected from Thailand, Vietnam, Indonesia, Myanmar, and China. Among haplogroup C, novel and unique haplotypes of Cambodia were found in the Battambang and Kandal Provinces, and the nucleotide diversity of the Cambodian population (0.00532) was the highest. Pairwise fixation indices among the F. gigantica populations from these countries indicated that the Cambodian and Thailand populations were related to each other. The highest genetic diversity in the Cambodian population suggests that F. gigantica in Cambodia may be the ancestor of the populations in Southeast Asian countries. Most likely, livestock movement, including Zebu cattle, played an important role in the transmission of F. gigantica. In this study, the hybrid Fasciola flukes that are commonly found in neighboring countries, were not found in Cambodia. Further comprehensive investigations of Fasciola prevalence should be conducted by analyzing a wider range of hosts throughout Cambodia to reach a more solid conclusion about the absence of hybrid flukes.

Fasciola species and their vertebrate and snail intermediate hosts in East and Southern Africa: a review

A systematic review was conducted focusing on the distribution of Fasciola species and their snail intermediate hosts (IHs) in East and Southern Africa. The reviewed literature showed that both Fasciola hepatica and F. gigantica are present in East and Southern Africa, and infect a wide range of domestic and wild ruminants. Fasciola gigantica was reported in six East African and five Southern African countries, where Radix natalensis (found in low altitudes) was reported to be the main IH. Fasciola hepatica was reported in Tanzania and Ethiopia (East Africa), and in South Africa and Zimbabwe (Southern Africa), where Galba truncatula (found in high altitudes) was documented as the IH in all countries except in Zimbabwe. Both Fasciola species were documented in Tanzania, Ethiopia, Zimbabwe and South Africa. An overlap of the two was observed in areas with an intermediate altitude in Ethiopia and South Africa, where Pseudosuccinea columella was widespread and assumed to transmit both species. Pseudosuccinea columella has been reported in South Africa and Namibia, and proven to transmit F. gigantica in South Africa; its role in Namibia in the transmission of Fasciola species has not been reported. Other lymnaeid species such as R. rubiginosa were reported in South Africa, and R. auricularia in South Africa and Botswana; their role in the transmission of Fasciola species has not been proven. Future studies should aim to determine the role of P. columella in the geographical spread of the two species in East and Southern African countries.

A Retrospective Study on Bovine Fascioliasis in Veterinary Regional Laboratories in Peninsular Malaysia

This is a retrospective study on bovine fascioliasis infection on cattle in Peninsular Malaysia, spanning from January 2007 to December 2017. Cattle were diagnosed with Fasciola based on the fecal examination and the results were reported to the Veterinary Regional Laboratories in Peninsular Malaysia. These records were analysed for the occurrence of bovine fascioliasis within that 11-year period. Records of annual diagnostic cases from five major Veterinary Regional Laboratories were examined: Bukit Tengah, Pulau Pinang (north); Kuantan, Pahang (east); Johor Bahru, Johor (south); Sepang, Selangor (west); and Kota Bharu, Kelantan (east). A positive fascioliasis infestation was calculated based on a number of positively infected cattle with Fasciola from a number of cattle examined. A total of 1988 cattle were examined during this period and 35 (1.76%) cattle were reported to be positive for bovine fascioliasis. Parasite infection was the highest at Bukit Tengah region (5.55%) where 19 cases were positive from 342 reported cases while, at Kuantan (4.96%), 15 positive cases were reported, unlike Johor Bahru (0.09%), with only 1 positive case from 1136 cattle examined. Sepang and Kelantan had no positive cases. These results showed that bovine fascioliasis was generally prevalent in the northern and southeast parts of the Peninsular Malaysia; however, there was no significant relationship between the region and the occurrence of fascioliasis.

Prevalence of fasciolosis in slaughtered dairy cattle from São Miguel Island, Azores, Portugal

Fasciolosis, caused by the trematode Fasciola hepatica, is considered one of the most important parasitosis in dairy cattle due to significant economic losses. The main objectives of this study were to determine the prevalence of fasciolosis in dairy cattle slaughtered at São Miguel Island (SMI) slaughterhouse and to ascertain areas (parishes and dairy herds), within the island, with highest risk for fasciolosis. The association among cattle age and weight with the occurrence of fasciolosis was also determined. From a sample of 24,389 cattle slaughtered in two years (2015-2016), a total of 1134 dairy cattle livers were inspected and, during this period, 531 were positive to fasciolosis and 603 presented no typical fasciolosis lesions. This study showed that fasciolosis has a broad geographical distribution on SMI and that is also found in cattle from other islands of the Azores archipelago, namely Flores Island. Although there were no significant differences in weight between healthy animals and parasitized ones, we observed that the older animals present a greater level of liver lesions and a higher level of parasitization, reflecting their longer period of exposure to the risk factor (ingestion of metacercariae in pastures infested by Galba truncatula).

Molecular characterization of liver fluke intermediate host lymnaeids (Gastropoda: Pulmonata) snails from selected regions of Okavango Delta of Botswana, KwaZulu-Natal and Mpumalanga provinces of South Africa

Lymnaeidae snail species are known to be intermediate hosts of human and livestock helminths parasites, especially Fasciola species. Identification of these species and their geographical distribution is important to better understand the epidemiology of the disease. Significant diversity has been observed in the shell morphology of snails from the Lymnaeidae family and the systematics within this family is still unclear, especially when the anatomical traits among various species have been found to be homogeneous. Although there are records of lymnaeid species of southern Africa based on shell morphology and controversial anatomical traits, there is paucity of information on the molecular identification and phylogenetic relationships of the different taxa. Therefore, this study aimed at identifying populations of Lymnaeidae snails from selected sites of the Okavango Delta (OKD) in Botswana, and sites located in the KwaZulu-Natal (KZN) and Mpumalanga (MP) provinces of South Africa using molecular techniques. Lymnaeidae snails were collected from 8 locations from the Okavango delta in Botswana, 9 from KZN and one from MP provinces and were identified based on phylogenetic analysis of the internal transcribed spacer (ITS-2). Analyses based on the ITS-2 marker identified the presence of a well-supported Radix clade containing Radix auricularia, R. natalensis and R. rubiginosa, which were not well resolved. Experimental samples from the OKD and KZN present in this clade were referable to these species. An unidentified experimental taxon from the OKD formed a well-supported sister clade to the Radix clade, although it was not possible to identify it. Galba truncatula was well supported in a sister relationship to a well-supported Pseudosuccinea columella clade which included samples from MP and KZN provinces of South Africa. We observed that P. columella shared the same habitats with R. natalensis and R. auricularia in KZN. Our study contributes new knowledge on the Lymnaeidae species present in Southern Africa and their phylogenetic relationships. The study further identifies the species which are likely to co-exist in the same environment and this information will be of use to those designing control programs for fasciolosis. This is the first study reporting the presence of R. auricularia in the OKD of Botswana and KZN province of South Africa.

Molecular characterization of Fasciola jacksoni from wild elephants (Elephas maximus maximus) of Sri Lanka: a taxonomic evaluation

Fasciola jacksoni is a significant contributor to the health and mortality of Asian elephants, particularly those in Sri Lanka. Despite the impact of fascioliasis on elephant populations, it is a neglected veterinary disease with limited taxonomic understanding. Molecular characterization and phylogenetic analysis of F. jacksoni were carried out to evaluate its suggested basal position in the Fasciolidae. Adult worms were collected during post-mortem of elephants, and eggs were collected from living elephants in National parks across Sri Lanka. Using the mitochondrial genes nicotinamide dehydrogenase subunit 1 (nad1) and cytochrome oxidase subunit 1 (cox1), and a partial 28S ribosomal DNA (28S rDNA), DNA sequences were generated from the F. jacksoni adult and egg material. Maximum likelihood (ML) phylogenetic analyses did not resolve F. jacksoni to be basal to the Fasciolidae. Furthermore, the ML analyses showed that the genus Fasciola was not monophyletic and that F. jacksoni was a sister species to the deer liver fluke Fascioloides magna. A clear framework is required to determine the taxonomic status of F. jacksoni and this current study provides the first detailed application of molecular techniques from multiple hosts across Sri Lanka with the production of reference DNA sequences for this important parasite.

Phylogenetic analysis of Fasciola spp. isolated from slaughtered cattle in KwaZulu-Natal and Mpumalanga provinces of South Africa based on the cytochrome c oxidase subunit I mitochondrial marker

Fasciola spp. are the causative agents of fascioliasis in humans and livestock. Before the development of control and management measures, the geographical distribution of the species and patterns of infection must be considered. Because of difficulties in the phenotypic differentiation and morphometric classification of Fasciola spp., DNA molecular markers have become more useful for fluke differentiation and description of phylogenetic patterns. This study aimed to differentiate and describe the phylogenetic background of Fasciola spp. isolated from cattle slaughtered at three abattoirs in the Mpumalanga and KwaZulu-Natal provinces of South Africa. The cytochrome c oxidase I (COI) - FHCO1 (forward: 5'-TTGGTTTTTTGGGCATCCT-3') and FHCO1 (reverse: 5' -AGGCCACCACCAAATAAAAGA3') - marker was sequenced from 55 Fasciola flukes that were collected from abattoirs in catchment areas of the KwaZulu-Natal and Mpumalanga provinces. Fasciola hepatica was demonstrated to have 100% prevalence in KwaZulu-Natal and Mpumalanga (highveld), respectively, and 76% prevalence in the lowveld (Belfast area) of Mpumalanga. Two animals from the Belfast metapopulation were co-infected with both Fasciola gigantica and F. hepatica. DNA sequence analysis of all the isolates demonstrated a sequence conservation of 0.472, nucleotide diversity of 0.082 and Tajima's D of -1.100; however, it was not statistically significant (p > 0.05). Twenty-two haplotypes were identified, with 18 novel haplotypes being unique to the isolates from South Africa. Within the study samples, 12 haplotypes were isolated to a few individuals, with a haplotype diversity of 0.8957 indicating high genetic diversity. Principal coordinate analysis supported the clustering and distribution of the haplotypes, with 11.38% of the variation being attributed to coordinate 2 and 55.52% to coordinate 1. The distribution of Fasciola spp. has been demonstrated to be related to the distribution of the freshwater intermediate host snails, Lymnaea spp., as well as the relative altitude of the localities in South Africa. Information provided by this study serves as preliminary evidence for further studies on the mapping of the distribution of F. gigantica and F. hepatica in South Africa, which is key in designing control programmes for fascioliasis in humans and livestock.

Global serum proteomic changes in water buffaloes infected with Fasciola gigantica

BACKGROUND

The liver fluke Fasciola gigantica modulates several signaling pathways in infected buffaloes to facilitate its survival and establishment of persistent infection. In response to the parasite invasion, buffaloes activate innate and adaptive immune responses to counter the parasite infection. To detect new proteins that might be involved in the interaction between F. gigantica and the buffaloes, and that also might serve as biomarkers for fasciolosis, we used proteomic techniques to study the serum proteome of buffaloes during F. gigantica infection. Here, we used an isobaric tags for relative and absolute quantitation (iTRAQ)-based quantitative proteomic approach to identify serum proteins that are differentially expressed in infected buffaloes compared to uninfected control buffaloes. Additionally, we applied a parallel reaction monitoring (PRM) assay to validate specific proteins identified by the iTRAQ method.

RESULTS

A total of 313, 459 and 399 proteins were identified at 3, 42 and 70 days post-infection, respectively; of these 92, 93 and 138 were differentially abundant proteins. Some of the identified differentially abundant proteins, including complement factor H related 5, complement component C6, complement component C7, amine oxidase, plasma serine protease inhibitor and lysozyme, are known to be involved in complement system activation, blood coagulation, platelet activation, lymphocyte's adhesion and lysozyme hydrolysis. Analysis of data for all three time points after infection identified six significantly upregulated proteins in infected serum that separated infected and uninfected buffaloes into distinct clusters. Further PRM analysis confirmed the expression of five proteins, namely MHC class I antigen, Beta-2-microglobulin, NID2 protein, Fetuin-B and Fibrinogen gamma-B chain.

CONCLUSIONS

These findings provide novel insights into the serum proteomics signature of buffaloes during F. gigantica infection.

Molecular analysis reveals expansion of Fasciola hepatica distribution from Afghanistan to China

Recently, phosphoenol pyruvate carboxykinase (pepck) and DNA polymerase delta (pold) were established as reliable nuclear markers for species identification of Fasciola spp. in multiplex polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism-based assays, respectively. Currently, little is known about Fasciola species distribution in Central Asia. Therefore, the objective of the present study was to perform precise molecular species identification of liver flukes from Afghanistan and to reveal their dispersal route(s) via phylogenetic analysis based on mitochondrial nad1 haplotypes. Ninety-two Fasciolaflukes collected from sheep in Kabul, Afghanistan, were identified as F. hepatica based on pepck and pold screening. Although the pepck fragment pattern obtained via multiplex PCR analysis could not distinguish the species of the seven Fasciola flukes, the pepck nucleotide sequence data confirmed that they were F. hepatica.The 20 nad1 haplotypes detected among the Afghani liver flukes were closely related to those from China and Egypt, with the F_STvalue (-0.003, P = .41) between the F. hepatica populations from Afghanistan and China confirming a very close relationship. Nucleotide diversity was greater in the population from Afghanistan compared with that from China, indicating that the Afghani population was older, and that the dispersal direction of F. hepatica was from Afghanistan to China. The results of the present study contribute to our understanding of the dispersal of F. hepatica from its predicted origin, the Fertile Crescent.

Prevalence of fasciolosis in livestock and humans: A systematic review and meta-analysis in Iran

Fasciolosis is a re-emerging disease of livestock and rarely human, being endemic in Iran. Herein, we aimed to quantitatively assess the human seropositivity and prevalence of animal fasciolosis in our country. English and Persian databases were searched for online literature. In total, 10 human seroprevalence studies and 49 animal investigations were obtained from January 1999 to March 2019. Only animal studies were included in meta-analysis. The highest human seroprevalence was detected in Guilan province (326/452; 50%). The pooled prevalence of the animal infections was calculated as 6.2% (95% CI = 5.8%-6.5%). In detail, the prevalence ranges in three hosts included as 4.2% (95% CI = 3.8%-4.5%) in sheep, 9% (95% CI = 8.0%-9.9%) in cattle and 3.1% (95% CI = 2.4%-3.7%) in goat. The highest prevalence rate was observed in the north, 11.8% (95% CI = 8.4%-15.1%), while the lowest prevalence was detected in the central Iran with 1.8% (95% CI = 1.3%-2.3%). Egger's regression test revealed no significant publication bias (P = 0.307). Also, there was no remarkable correlation between weighted prevalence and sample size (P = 0.249) as well as year of study (P = 0.172). These findings would be necessary for better preventive strategies in case of human and animal Fasciola infections as well as snail intermediate hosts.

Genome-wide association study of endo-parasite phenotypes using imputed whole-genome sequence data in dairy and beef cattle

BACKGROUND

Quantitative genetic studies suggest the existence of variation at the genome level that affects the ability of cattle to resist to parasitic diseases. The objective of the current study was to identify regions of the bovine genome that are associated with resistance to endo-parasites.

METHODS

Individual cattle records were available for Fasciola hepatica-damaged liver from 18 abattoirs. Deregressed estimated breeding values (EBV) for F. hepatica-damaged liver were generated for genotyped animals with a record for F. hepatica-damaged liver and for genotyped sires with a least one progeny record for F. hepatica-damaged liver; 3702 animals were available. In addition, individual cow records for antibody response to F. hepatica on 6388 genotyped dairy cows, antibody response to Ostertagia ostertagi on 8334 genotyped dairy cows and antibody response to Neospora caninum on 4597 genotyped dairy cows were adjusted for non-genetic effects. Genotypes were imputed to whole-sequence; after edits, 14,190,141 single nucleotide polymorphisms (SNPs) and 16,603,644 SNPs were available for cattle with deregressed EBV for F. hepatica-damaged liver and cows with an antibody response to a parasitic disease, respectively. Association analyses were undertaken using linear regression on one SNP at a time, in which a genomic relationship matrix accounted for the relationships between animals.

RESULTS

Genomic regions for F. hepatica-damaged liver were located on Bos taurus autosomes (BTA) 1, 8, 11, 16, 17 and 18; each region included at least one SNP with a p value lower than 10^-6. Five SNPs were identified as significant (q value < 0.05) for antibody response to N. caninum and were located on BTA21 or 25. For antibody response to F. hepatica and O. ostertagi, six and nine quantitative trait loci (QTL) regions that included at least one SNP with a p value lower than 10^-6 were identified, respectively. Gene set enrichment analysis revealed a significant association between functional annotations related to the olfactory system and QTL that were suggestively associated with endo-parasite phenotypes.

CONCLUSIONS

A number of novel genomic regions were suggestively associated with endo-parasite phenotypes across the bovine genome and two genomic regions on BTA21 and 25 were associated with antibody response to N. caninum.

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

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

New insight into genetic variation and haplotype diversity of Fasciola hepatica from Algeria

The liver fluke Fasciola hepatica is the main cause of fasciolosis in North Africa leading to significant economic losses and public health problems. In this study, the ribosomal internal transcribed spacer (ITS), cytochrome c oxidase I (COI), the mitochondrial region spanning the COI-trnT-rrnL, and the NADH dehydrogenase subunit I (NADI) markers were used to characterize Fasciola flukes from Algeria. Fasciola appeared widespread from the east to the west of Algeria. Among 1701 sampled cattle from 8 Algerian provinces, 5% were infected. Using morphological and morphometric analysis, one morphotype of Fasciola was observed. Nuclear ITS marker indicated that all collected flukes belong to F. hepatica. Multiple alignments of ITS dataset revealed two haplotypes, one described here for the first time. Analysis of molecular variance (AMOVA) of mitochondrial markers revealed weak population structure in Algeria. Mismatch distributions, neutrality tests, and median-joining network analysis all were compatible with a recent expansion of Algerian F. hepatica population. Fasciolosis appeared common in Algerian cattle, it seems that the absence of control strategy coupled to the favorable Mediterranean climate may lead to a reconstruction and dispersion of its populations. This study provides important results concerning the genetic characterization and variability of F. hepatica in Algeria as well as the significant role of cattle importation in shaping its dispersal route worldwide.

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

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

Numerous Fasciola plasminogen-binding proteins may underlie blood-brain barrier leakage and explain neurological disorder complexity and heterogeneity in the acute and chronic phases of human fascioliasis

Human fascioliasis is a worldwide, pathogenic food-borne trematodiasis. Impressive clinical pictures comprising puzzling polymorphisms, manifestation multifocality, disease evolution changes, sequelae and mortality, have been reported in patients presenting with neurological, meningeal, neuropsychic and ocular disorders caused at distance by flukes infecting the liver. Proteomic and mass spectrometry analyses of the Fasciola hepatica excretome/secretome identified numerous, several new, plasminogen-binding proteins enhancing plasmin generation. This may underlie blood-brain barrier leakage whether by many simultaneously migrating, small-sized juvenile flukes in the acute phase, or by breakage of encapsulating formations triggered by single worm tracks in the chronic phase. Blood-brain barrier leakages may subsequently occur due to a fibrinolytic system-dependent mechanism involving plasmin-dependent generation of the proinflammatory peptide bradykinin and activation of bradykinin B2 receptors, after different plasminogen-binding protein agglomeration waves. Interactions between diverse parasitic situations and non-imbalancing fibrinolysis system alterations are for the first time proposed that explain the complexity, heterogeneity and timely variations of neurological disorders. Additionally, inflammation and dilation of blood vessels may be due to contact system-dependent generation bradykinin. This baseline allows for search of indicators to detect neurological risk in fascioliasis patients and experimental work on antifibrinolytic treatments or B2 receptor antagonists for preventing blood-brain barrier leakage.

Fasciola spp. in Armenia: Genetic diversity in a global context

Fasciolosis, a food- and waterborne infection caused by the trematodes Fasciola hepatica and F. gigantica, is recognized by WHO as a neglected zoonotic disease. Whereas F. hepatica is distributed worldwide in cooler climates, F. gigantica occurs mainly in the tropics of Africa and Asia. The southern Caucasus, with Armenia, is one of the most northern regions where both species occur and may produce hybrids. In this study, livestock in central Armenia was surveyed for fasciolosis, the causative species were determined and the genetic diversity of both species was estimated. Total prevalence in sheep (1794), cattle (324) and goats (9) was 21.2%, 15.7% and 44.4%, respectively. After morphological identification and sequencing of a mitochondrial (nad1) and a nuclear marker gene (28S rRNA), 62 collected specimens were allocated to F. hepatica (n = 55) and F. gigantica (n = 7). Intraspecific diversity was evaluated for the complete nad1 gene, resulting in 29 haplotypes of F. hepatica and six haplotypes of F. gigantica. Diversity was higher among F. gigantica than F. hepatica in the Armenian sample set, a difference that was confirmed analyzing available sequences for both species worldwide. Maximum genetic distance between haplotypes in global networks was 49 nucleotide steps for F. gigantica compared to 15 for F. hepatica. In the available sample sets, F. hepatica showed higher diversity in western Asia and the Middle East compared to Europe and eastern Asia, while for F. gigantica loosely structured clusters comprising mainly western/southern Asian and African haplotypes could be identified. A distinct clade comprising haplotypes from Zambia was basal in the phylogenetic tree. Biogeographical implications of these data are discussed.

Molecular detection of natural infection ofLymnaea(Pseudosuccinea)columella(Gastropoda: Lymnaeidae) withFasciola gigantica(Digenea: Fasciolidae) from two provinces of South Africa

The main intermediate host ofFasciola giganticain sub-Saharan Africa isLymnaea(Radix)natalensis.Lymnaea(Pseudosuccinea)columellais capable of transmitting bothF. giganticaandF. hepaticaand has been reported to be present in South Africa. To date, no natural infection withF. giganticahas been reported despite the wide distribution of the snail. The aim of this study was to confirm whetherL.(P.)columellawas transmittingF. giganticaand/orF. hepaticain selected locations of KwaZulu-Natal and Eastern Cape provinces of South Africa.Lymnaea(Pseudosuccinea)columellasnails were collected from two locations in two provinces of South Africa and screened for cercariae shedding. This was followed by humanely sacrificing the screened snails, and whole tissue of each individual snail was homogenized and amplified using primers designed to amplify the ITS-1 region ofFasciolaspp. No cercariae were shed from the screened snails and molecular analysis showed that snails from the two locations were infected withF. gigantica. This study confirms natural infection ofL.(P.)columellawithF. giganticain South Africa, whereF. giganticaandF. hepaticahave already been reported to coexist. AlthoughL.(P.)columellais able to transmit the two species, surprisingly no infection withF. hepaticawas detected from the screened snails. The natural intermediate host ofF. giganticain southern Africa, including South Africa, isLymnaea(Radix)natalensisand comparative studies are needed to determine the competence of the two snail species in the transmission ofF. gigantica.

Fascioliasis

Fascioliasis is a major parasitic disease caused by the digenetic trematodes Fasciola hepatica and Fasciola gigantica. The disease is a well-known veterinary problem of worldwide distribution. Fascioliasis is the vector-borne parasitic disease presenting the widest latitudinal, longitudinal, and altitudinal distribution known at present. In the last two decades, many surveys have shown it to be an important public health problem as well, including estimations of 2.4 million, up to 17 million people, or even higher depending on the hitherto unknown situations mainly in several regions of Asia and Africa. In recent years, the increasing number of human case reports in many countries of the five continents and the results of studies on pathogenicity and immunity, mainly regarding the chronic period of the disease, were the reasons why it was decided to no longer consider fascioliasis merely a secondary zoonotic disease but an important human parasitic disease. In this chapter, we review the most relevant features in relation to fascioliasis, including from the most traditional to the most innovative aspects.

Trematode Genomics and Proteomics

Trematode infections are among the most neglected tropical diseases despite their worldwide distribution and extraordinary ability to parasitise many different host species and host tissues. Furthermore, these parasites are of great socioeconomic, medical, veterinary and agricultural importance. During the last 10 years, there have been increasing efforts to overcome the lack of information on different "omic" resources such as proteomics and genomics. Herein, we focus on the recent advances in genomics and proteomics from trematodes of human importance, including liver, blood, intestinal and lung flukes. We also provide information on the latest technologies applied to study the biology of trematodes as well as on the resources available for the study of the molecular aspects of this group of helminths.

Chitosan-based nanodelivery systems applied to the development of novel triclabendazole formulations

Triclabendazole is a poorly-water soluble (0.24 μg/mL) compound classified into the Class II/IV of the Biopharmaceutical Classification System. It is the drug of choice to treat fascioliasis, a neglected parasitic disease worldwide disseminated. Triclabendazole is registered as veterinary medicine and it is only available for human treatment as 250 mg tablets. Thus, the aim of this work was to develop novel drug delivery systems based on nanotechnology approaches. The chitosan-based nanocapsules and nanoemulsions of triclabendazole were fully characterized regarding their particle size distribution, polydispersity index and zeta potential, in-vitro release and stability in biological media. Cytotoxicity evaluation and cellular uptake studies using CaCo-2 cell line were also investigated. The results indicated an average hydrodynamic size around ~160 nm were found for unloaded nanoemulsions which were slightly increased up to ~190 nm for loaded one. In contrast, the average hydrodynamic size of the nanocapsules increased from ~160 nm up to ~400 nm when loaded with triclabendazole. The stability studies upon 30 days storage at 4, 25 and 37°C showed that average size of nanoemulsions was not modified with varying amounts of loaded TCBZ while an opposite result was seen in case of loaded nanocapsules. In addition, a slight reduction of zeta potential values over time was observed in both triclabendazole nanosystems. Release of TCBZ from nanoformulations over 6 h in simulated gastric fluid was 9 to 16-fold higher than with untreated TCBZ dispersion. In phosphate buffer saline solution there was no drug release for neither nanocapsules nor nanoemulsions. Cell viabilities studies indicated that at certain concentrations, drug encapsulation can lower its cytotoxic effects when compared to untreated drug. Confocal laser scanning microscopy study has shown that nanocapsules strongly interacted with Caco-2 cells in vitro which could increase the passage time of triclabendazole after oral administration. The results of this study constitute the first step towards the development of nanoformulations intended for the oral delivery of anti-parasitic drugs of enhanced bioavailability.

Epidemiology and economic loss of fasciolosis and dicrocoeliosis in Arak, Iran

Aim:

Fasciolosis and dicrocoeliosis are important parasitic diseases worldwide, causing significant financial losses due to decrease in production and viscera condemnation in animals. We performed the current research to assess the epidemiology of these infections and determine their significance from an economic perspective in Arak, Iran.

Materials and Methods:

In total, we evaluated 118,463 sheep, 207,652 goats, and 43,675 cattle through necropsic analysis at the slaughterhouses. The average weight of sheep, goat, and cattle liver was 1000, 900, and 5000 g, respectively. The average price of liver in the market was 8 USD/kg. Moreover, the elimination of fundamental nutrients and vitamins was evaluated in infected livers. The prevalence of fasciolosis and dicrocoeliosis was determined. Analysis of variance test was applied for the statistical analysis, and the significance level was <0.05.

Results:

In total, Fasciola hepatica and Dicrocoelium dendriticum were detected in 0.56% (confidence interval CI, 0.54-0.59) and 0.77% (CI, 0.75-0.81) of the animals, respectively (p=0.1). The annual economic loss attributed to fasciolosis and dicrocoeliosis was 26698.4 and 30479.2 USD, respectively. The total economic loss was 10,880, 9079.2, and 10,520 dollars in sheep, cattle, and goats, respectively. On the other hand, financial loss resulting from fasciolosis was 7160, 6098.4, and 13,440 dollars in sheep, goats, and cattle, respectively. In addition, economic loss due to dicroceliasis was 10,880, 9079.2, and 10,520 dollars, respectively.

Conclusion:

Overall, fasciolosis and dicrocoeliosis in Iran always remain common in sheep, goats, and cattle that afford major economic loss of all the country also exist in Arak province. The present study could provide basic information for further examination of liver fluke infections in Iran.

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

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

Histopathological findings of Fasciola hepatica infection in non-native European hare (Lepus europaeus) in Southern Chile

Fasciola hepatica is a parasite introduced in America from Europe, being considered of concern for public health and animal production, especially in countries with endemic areas as occur in Chile. In this country, the research has been focused mainly in domestic ruminants, with native and introduced wildlife being largely ignored. Thus, the aim of this study was to report the infection by Fasciola hepatica in an introduced mammal, the European hare, which is distributed along a vast area of the country. One in 42 hares hunted showed histological lesions compatible with F. hepatica, and harbored a parasitic load of 6 liver flukes. This is the first report of this lagomorph acting as host of this helminth in the country and the third in South America. Yet, we found no previous reports regard the pathology of this fluke in the species. Thus, we emphasize the importance of more studies regarding introduced mammals which could be acting as reservoirs for this important fluke.

Fasciola hepatica infection in children actively detected in a survey in rural areas of Mardan district, Khyber Pakhtunkhawa province, northern Pakistan

Human fascioliasis is a freshwater snail borne, zoonotic disease caused by Fasciola liver flukes which are widely spread throughout Pakistan and has recently proved to be endemic in humans of the Punjab province. To verify whether fasciolids are also affecting humans outside this province, studies were conducted in four communities comprising rural and urban areas of Mardan district, Khyber Pakhtunkha province, northern Pakistan. Activities comprised two surveys, a coprological one to look for Fasciola infection and another to get information on potential human infection sources and risk factors by means of a questionnaire. Out of 540 subjects of all ages surveyed, only 4 children (0.74%) were found positive for Fasciola eggs: two 9- and 13-year old boys and two 7- and 16-year old girls. Burden per child ranged 73-146 eggs per gram of faeces (epg), with an average of 106 ± 15.4 epg. Based on the egg size, the infection was diagnosed to be caused by F. hepatica. Serum analyses showed eosinophilia and elevated enzyme values in liver function tests. The Mardan area fits well to all transmission and epidemiological requirements of F. hepatica, namely the presence of infected livestock reservoirs throughout, the appropriate climatic factors (mainly monthly temperature variation along the year), and the existence of adequate freshwater collections. The existence of the specific lymnaeid snail vector species for F. hepatica transmission was reported in the neighbouring Swat valley time ago. Results show that human fascioliasis may be widespread in Pakistan and that both F. hepatica and F. gigantica may be involved.

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

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

Fasciola hepatica-Pseudosuccinea columella interaction: effect of increasing parasite doses, successive exposures and geographical origin on the infection outcome of susceptible and naturally-resistant snails from Cuba

BACKGROUND

Pseudosuccinea columella is one of the most widespread vectors of Fasciola hepatica, a globally distributed trematode that affects humans, livestock and wildlife. The exclusive occurrence in Cuba of susceptible and naturally-resistant populations to F. hepatica within this snail species, offers a fascinating model for evolutionary biology, health sciences and vector control strategies. In particular, resistance in P. columella is characterized by the encapsulation of the parasite by host's immune cells and has been experimentally tested using different Cuban F. hepatica isolates with no records of successful infection. Here, we aimed to explore for the first time, the effect of different parasite doses, successive exposures and different parasite origins on the infection outcomes of the two phenotypes of P. columella occurring in Cuba.

METHODS

To increase the chances for F. hepatica to establish, we challenged Cuban P. columella with increasing single parasite doses of 5, 15 or 30 miracidia and serial exposures (three-times) of 5 miracidia using a sympatric F. hepatica isolate from Cuba, previously characterized by microsatellite markers. Additionally, we exposed the snails to F. hepatica from different geographical origins (i.e. Dominican Republic and France). Parasite prevalence, redial burden and survival of snails were recorded at 25 days post-exposure.

RESULTS

No parasite development was noted in snails from the resistant populations independent of the experimental approach. Contrastingly, an overall increase in prevalence and redial burden was observed in susceptible snails when infected with high miracidia doses and after serial exposures. Significant differences in redial burden between single 15 miracidia and serial 3 × 5 miracidia infected snails suggest that immune priming potentially occurs in susceptible P. columella. Compatibility differences of allopatric (Caribbean vs European) F. hepatica with susceptible snails were related to the geographical scale of the combinations.

CONCLUSIONS

Here, the effectiveness of P. columella resistance to F. hepatica does not decline with increasing parasite doses, successive infection or different geographical origins of parasite isolates, while presenting new evidence for specificity for infection in susceptible P. columella snails. Understanding the peculiarities of the P. columella-F. hepatica interaction and the extent of the resistant phenotype is crucial for an effective parasite control and for developing alternatives to tackle fasciolosis transmission.

Genetic diversity of an avian nasal schistosome causing cercarial dermatitis in the Black Sea-Mediterranean migratory route

This study is part of an effort to document the diversity of avian schistosomes in ducks and snails in Northern Iran, a major flyway (Black Sea/Mediterranean) for migratory birds and where cercarial dermatitis (CD) is prevalent in rice growing areas. CD is an allergic skin reaction from schistosome trematodes that emerge from aquatic snails. Most CD cases are reported from recreational swimmers or aquaculture farmers. Much of the work on the epidemiology of CD has focused in recreational waters in the Americas and Europe, with fewer studies in aquaculture, particularly in Iran. The artificial environment at aquaculture sites support dense populations of snails that are hosts to schistosomes, as well as domestic ducks. Thus, are domestic ducks reservoir hosts of species of Trichobilharzia, one of the main etiological agents of CD in Northern Iran? This study focused on a survey of domestic ducks for the presence of the nasal schistosome, T. regenti, that has been reported widely in Europe. Trichobilharzia regenti were found in domestic ducks in the Guilan Province of Iran based on morphological and molecular analyses. The presence of this species in Northern Iran indicates that the domestic duck can serve as a reservoir host for this species and that one of the local snail species is likely the intermediate host. The continued study and surveillance of this species is important because it is a neuropathic schistosome that can use a diversity of bird definitive hosts and Radix snails that are widespread across Eurasia.

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.

Human case of Fasciola gigantica-like infection, review of human fascioliasis reports in Nepal, and epidemiological analysis within the South Central Asia

The diagnosis of a 22 year-old male patient from Kerabari, Morang District, Nepal led to the review of human fascioliasis cases and analysis of the epidemiological situation in that country not included in the WHO fascioliasis map. Symptom onset one month before egg detection and normal levels of ALT and AST did not agree with the 3-4-month migratory period of fascioliasis. A shorter acute phase may happen when the main biliary duct is reached by the migratory juveniles directly from the intestinal lumen. The causal agent was ascribed to F. gigantica-like worms after considering adult fluke morphology, altitude of the patient's infection area, fasciolid characteristics in the neighbouring Bangladesh, and lymnaeid snail vector species known in Nepal and in the patient's infection area. Previous reports of human infection by Fasciola in Nepal are reviewed. The patient in question proved to be the twelfth case and the first in whom a F. gigantica-like infection is reported. In Nepal, the wide geographical distribution of livestock fascioliasis, with high prevalences in buffaloes, cattle and goats, and the reports of Fasciola-infected schoolchildren close to the capital Kathmandu, give rise to concern on the situation in remote rural areas in a country where most of the population lives in rural areas. Moreover, the climate change impact in Nepal remembers Pakistan, where human fascioliasis emergence has been related to climate change and man-made irrigation. All in all, the present analysis suggests that human infection by Fasciola may be underestimated in Nepal.

Human liver flukes

Liver fluke infections occur in people worldwide. In some low-income regions, a combination of ecological, agricultural, and culinary factors leads to a very high prevalence of infection but, in higher-income regions, infections are uncommon. Infection is associated with substantial morbidity and several liver fluke species are recognised as biological carcinogens. Here, we review the epidemiology, clinical significance, and diagnostic and treatment strategies of human infection with these pathogens.

Ovicidal in vitro activity of 2-aryl-3-(2-morpholinoethyl)thiazolidin-4-ones and 2-aryl-3-(3-morpholinopropyl)thiazolidin-4-ones against Fasciola hepatica (Linnaeus, 1758)

Although there is a variety of biological activity reports regarding compounds derived from thiazolidin-4-ones, no data related to ovicidal activity against trematodes, particularly Fasciola hepatica are available. Since there are reports about anthelmintic resistance in F. hepatica, new drugs are required. Thus, this study evaluated ovicidal action in vitro against F. hepatica eggs in two systematic series of thiazolidin-4-ones: 2-aryl-3-(2-morpholinoethyl)thiazolidin-4-ones (1a-h) and 2-aryl-3-(3-morpholinopropyl)thiazolidin-4-ones (2a-h) at different concentrations (20, 2, 0.2, 0.02 and 0.002 μg/ml). The egg hatch assay (EHA) was used to evaluate the ovicidal action property of such compounds. In addition, potential negative effects of the compounds on metabolic activity of bovine kidney (MDBK) cells were evaluated by determining mitochondrial dehydrogenase activity. The eggs used in the EHA were obtained from parasites removed from the liver of cattle, which were discarded by slaugh after sanitary inspection. The results of EHA showed that compounds 2a-h exhibited ovicidal activity, especially compounds 2b which showed 90% ovicidal activity and viability of 93% MDBK cells at the concentration of 2 μg/ml; and 2e with 96-99% ovicidal activity at 0.2 μg/ml, 0.02 μg/ml and 0.002 μg/ml. The results show the potential of compound 2b to continue the studies in the production of new compounds with anthelmintic action.

Human fascioliasis infection sources, their diversity, incidence factors, analytical methods and prevention measures

Human fascioliasis infection sources are analysed for the first time in front of the new worldwide scenario of this disease. These infection sources include foods, water and combinations of both. Ingestion of freshwater wild plants is the main source, with watercress and secondarily other vegetables involved. The problem of vegetables sold in uncontrolled urban markets is discussed. Distinction between infection sources by freshwater cultivated plants, terrestrial wild plants, and terrestrial cultivated plants is made. The risks by traditional local dishes made from sylvatic plants and raw liver ingestion are considered. Drinking of contaminated water, beverages and juices, ingestion of dishes and soups and washing of vegetables, fruits, tubercles and kitchen utensils with contaminated water are increasingly involved. Three methods to assess infection sources are noted: detection of metacercariae attached to plants or floating in freshwater, anamnesis in individual patients, and questionnaire surveys in endemic areas. The infectivity of metacercariae is reviewed both under field conditions and experimentally under the effects of physicochemical agents. Individual and general preventive measures appear to be more complicated than those considered in the past. The high diversity of infection sources and their heterogeneity in different countries underlie the large epidemiological heterogeneity of human fascioliasis throughout.

Solving the Delivery Problems of Triclabendazole Using Cyclodextrins

Triclabendazole is the first-line drug of choice to treat and control fasciolasis, a neglected parasitic human disease. It is a class II/IV compound according to the Biopharmaceutics Classification System. Thus, the aim of this study was to improve aqueous solubility and dissolution rate of triclabendazole complexed with 2-hydroxylpropyl-β-cyclodextrin (HP-β-CD) and methyl-β-cyclodextrin (Me-β-CD) at 1:1 and 1:2 M ratio. The impact of storage on the solubility, dissolution profile, and solid-state properties of such complexes was also investigated. Drug-carrier interactions were characterized by infrared spectroscopy, differential scanning calorimetry, X-ray diffractometry, and scanning electron microscopy. The solubility of triclabendazole improved up to 256- and 341-fold using HP-β-CD and Me-β-CD, respectively. In particular, the drug complexed with Me-β-CD showed a positive deviation from linearity, suggesting that its solubility increases with an increasing concentration of Me-β-CD concentration in a nonlinear manner. The drug dissolution was found to be improved through complex formation with HP-β-CD and Me-β-CD. In particular, the 1:2 M ratio complexes exhibited higher dissolution than the corresponding 1:1 M ratio complexes. The physicochemical characterization of the systems showed strong evidence of amorphous phases and/or of the formation of an inclusion complex. Stored at 25 °C, 60% RH for 24 months, drug complexed with β-cyclodextrins (CDs) at 1:2 M ratio remained amorphous. Based on these findings, it is postulated that the formation of triclabendazole-CD inclusion complexes produced significant enhancement in both the dissolution and solid-state properties of the drug, which may lead to the development of triclabendazole novel formulations with improved biopharmaceutical characteristics.

Revealing genetic hybridization and DNA recombination of Fasciola hepatica and Fasciola gigantica in nuclear introns of the hybrid Fasciola flukes

Fasciola hepatica and F. gigantica are ruminant liver flukes that are found worldwide. They can occur sympatrically and hybridize, consequently producing an intermediate form (Fasciola sp.), especially in Africa and Asia. The bridge intron (TkBridgeInt) and intron 4 of domain 2 (TkD2Int4) of the taurocyamine kinase gene were cloned and sequenced from 14 F. hepatica, 18 F. gigantica, and 12 Fasciola sp. These intron regions could be used to differentiate F. hepatica from F. gigantica and revealed genetic hybridization and DNA recombination between F. hepatica and F. gigantica in Fasciola sp. from Japan and Bangladesh. Two specimens of F. hepatica from Ecuador revealed cryptic diversity. A combination of three haplotypes observed in a Fasciola sp. specimen from Japan suggested triploidy. Thus, the intron region of the taurocyamine kinase gene is a potential marker for detecting the hybrid status of the Fasciola flukes.

A duplex PCR for the simultaneous detection of Fasciola hepatica and Clonorchis sinensis

Both Fasciola hepatica and Clonorchis sinensis are endemic in China, South Korea, Japan and other Southeast Asian countries. Reliable and sensitive diagnostic methods are needed for detecting their infections in humans and animals. Differential simplex and duplex polymerase chain reaction (PCR) methods were developed. The PCRs targeted the second internal transcribed spacer (its2) (408 bp) of F. hepatica, and NADH dehydrogenase subunit 2 gene (nad2) (527 bp) of C. sinensis. Both simplex PCRs detected as little as 2 pg genomic DNA in one microliter in a 25 μL PCR reaction system. The duplex PCR had similar detection limit as well, and detected as low as one egg in 200 mg feces. These methods were analytical specific with no amplification being observed from the gemonic DNA of Fasciolopsis buski, Haemonchus contortus, Ascaris ovis or Eimeri ahsata. Of 158 sheep fecal samples collected from various farms, four and one samples were PCR-positive for F. hepatica and C. sinensis, respectively. The duplex PCR method described here is time-saving and convenient, and may prove to be an invaluable tool for molecular detection and epidemiological investigation of F. hepatica and C. sinensis in endemic area.

Anti-Fas2 IgM antibodies in Fasciola hepatica infected patients with positive IgG serology

Background

Fascioliasis is an infectious disease caused by parasites Fasciola hepatica and F. gigantica. Humans are infected by the consumption of vegetables and water contaminated with the infective form of the parasite.

Materials and Methods

In this study, an IgM-ELISA with the cysteine proteinase Fas2 antigen was evaluated with sera from 76 patients infected with F. hepatica, 24 patients with other parasite infections and 84 healthy volunteers.

Results

IgM-ELISA resulted in 43% positives in F. hepatica patients with positive serology to Fas2-ELISA, but no positives resulted from testing healthy volunteers and individuals infected with other parasites. The IgM-ELISA diagnostic parameters showed a sensitivity of 43.4% (95% CI 0.321-0.553), specificity of 100% (95% CI 0.957-1), and no cross-reactivity with other parasitic infection. Interference by rheumatoid factor in the IgM immunoassay was controlled by treating sera with rheumatoid factor absorbent before testing.

Conclusions

Fas2 antigen is detected by circulating IgM in patients infected with F. hepatica and IgM-ELISA using Fas2 appears as a specific immunoassay to detect the acute phase of the acute phase of F. hepatica infection in humans.

Identification and characterization of the Fasciola hepatica sodium- and chloride-dependent taurine transporter

The parasitic liver fluke Fasciola hepatica infests mainly ruminants, but it can also cause fasciolosis in people, who ingest the metacercariae encysted on plants. The drug of choice to treat fasciolosis is triclabendazole (TBZ), which has been on the market for several decades. This is also true for the other available drugs. Accordingly, drug-resistant flukes have been emerging at an increasing rate making it desirable to identify alternative drug targets. Here, we focused on the fact that adult F. hepatica persists in the hostile environment of the bile ducts of infected organisms. A common way to render bile acids less toxic is to conjugate them to taurine (2-aminoethanesulfonic acid). We cloned a transporter from the solute carrier-6 (SLC6) family, which was most closely related to the GABA-transporter-2 of other organisms. When heterologously expressed, this F. hepatica transporter supported the high-affinity cellular uptake of taurine (KM = 12.0 ± 0.5 μM) but not of GABA. Substrate uptake was dependent on Na+- and Cl- (calculated stoichiometry 2:1). Consistent with the low chloride concentration in mammalian bile, the F. hepatica transporter had a higher apparent affinity for Cl- (EC50 = 14±3 mM) than the human taurine transporter (EC50 = 55±7 mM). We incubated flukes with unconjugated bile acids in the presence and absence of taurine: taurine promoted survival of flukes; the taurine transporter inhibitor guanidinoethansulfonic acid abolished this protective effect of taurine. Based on these observations, we conclude that the taurine transporter is critical for the survival of liver flukes in the bile. Thus, the taurine transporter represents a candidate drug target.

Design and synthesis of a new peptide derived from Fasciola gigantica cathepsin L1 with potential application in serodiagnosis of fascioliasis

Fascioliasis is a global parasitic disease that affects domestic animals and causes considerable economic losses in the process of domestic animal breeding in endemic regions. The cause of the disease involves a liver trematode of the genus Fasciola, which secretes materials into a host's body (mainly proteins) in order to protect it from the host's immune system. These materials can be involved in the migration, growth, and nutrition of the parasite. Among the expressive proteins of Fasciola, proteases have been introduced as the appropriate targets for diagnosis, treatment, and vaccination against parasites. Cathepsin L (CL) is a member of cysteine proteases; it is widely expressed in the Fasciola species. The aim of this study was to evaluate two synthetic peptides from F. gigantica CL1 for improving serological diagnosis of the Fasciola infection. Therefore, the potential diagnostic value of the surface epitopes of CL1 was assessed using ELISA. In the current study, bioinformatics tools were applied to select two appropriate epitopes of Fasciola Cathepsin L1 as synthetic antigens. Their diagnostic values were evaluated by two methods of indirect ELISA and dot blot analysis. The findings revealed that the first peptide at a dilution ratio of 1:400 and the second peptide at a dilution ratio of 1:100 had the best results and the best concentration of antigens was introduced at 4 μg/ml. Moreover, 191 sera samples were analyzed by both peptides by using the ELISA method, including fascioliasis sera, other parasitic sera and negative sera. The sensitivity of the peptides 1-ELISA and peptide 2-ELISA for the diagnosis of the various cases was 100%. The specificity of the first peptide was 87.3% and its efficacy was determined to be 93.65%. The specificity and the efficacy of the second peptide were 79% and 89.5%, respectively. The positive predictive values of the first and second peptides were obtained to be 86.27% and 79.27% respectively, and the negative predictive values of both peptides was calculated as 100%. In conclusion, the results of this study indicated that the peptide 1 from CL1 may be used as an appropriate antigen for the diagnosis of fascioliasis if the findings are backed up by using other serodiagnostic methods for checking serological cross-reactivity linked to other parasites.

Climate Change and the Neglected Tropical Diseases

Climate change is expected to impact across every domain of society, including health. The majority of the world's population is susceptible to pathological, infectious disease whose life cycles are sensitive to environmental factors across different physical phases including air, water and soil. Nearly all so-called neglected tropical diseases (NTDs) fall into this category, meaning that future geographic patterns of transmission of dozens of infections are likely to be affected by climate change over the short (seasonal), medium (annual) and long (decadal) term. This review offers an introduction into the terms and processes deployed in modelling climate change and reviews the state of the art in terms of research into how climate change may affect future transmission of NTDs. The 34 infections included in this chapter are drawn from the WHO NTD list and the WHO blueprint list of priority diseases. For the majority of infections, some evidence is available of which environmental factors contribute to the population biology of parasites, vectors and zoonotic hosts. There is a general paucity of published research on the potential effects of decadal climate change, with some exceptions, mainly in vector-borne diseases.

Comparison of recombinant cathepsins L1, L2, and L5 as ELISA targets for serodiagnosis of bovine and ovine fascioliasis

Infections caused by Fasciola hepatica are of great importance in the veterinary field, as they cause important economic losses to livestock producers. Serodiagnostic methods, typically ELISA (with either native or recombinant antigens), are often used for early diagnosis. The use of native antigens, as in the MM3-SERO ELISA (commercialized as BIO K 211, BIO-X Diagnostics), continues to be beneficial in terms of sensitivity and specificity; however, there is interest in developing ELISA tests based on recombinant antigens to avoid the need to culture parasites. Of the antigens secreted by adult flukes, recombinant procathepsin L1 (rFhpCL1) is the most commonly tested in ELISA to date. However, although adult flukes produce three different clades of CLs (FhCL1, FhCL2, and FhCL5), to our knowledge, the diagnostic value of recombinant FhCL2 and FhCL5 has not yet been investigated. In the present study, we developed and tested three indirect ELISAs using rFhpCL1, rFhpCL2, and rFhpCL5 and evaluated their recognition by sera from sheep and cattle naturally infected with F. hepatica. Although the overall antibody response to these three rFhpCLs was similar, some animals displayed preferential recognition for particular rFhpCLs. Moreover, for cattle sera, the highest sensitivity was obtained using rFhpCL2 (97%), being equal for both rFhpCL1 and rFhpCL5 (87.9%), after adjusting cut-offs for maximum specificity. By contrast, for sheep sera, the sensitivity was 100% for the three rFhpCLs. Finally, the presence of truncated and/or partially unfolded molecules in antigen preparations is postulated as a possible source of cross-reactivity.

Cross-Sectional Serological Survey of Human Fascioliasis in Canutama Municipality in Western Amazon, Brazil

Background

Fascioliasis is an important parasitic disease. In the northern region of Brazil, a human parasite infection has been reported through a coprological survey. Eggs of Fasciola hepatica were found in fecal samples of 11 individuals. Knowledge of the infection in animals or the presence of snails is necessary to address the possibility of the parasite cycle occurrence in that region. The aim of this study was to describe the transmission of human fascioliasis in Canutama, Amazonas, in Western Amazonia, Brazil.

Methods

Serological (ELISA and Western Blot, WB) and parasitological analyses were carried out in humans. In addition, the presence of the intermediate snail host within the community was examined.

Results

A total of 434 human samples were included in the study, of which 36 (8.3%) were reactive by ELISA and 8 (1.8%) were reactive by WB. Fasciola hepatica eggs were found in one human sample. The occurrence of the intermediated host was recorded and 31/43 specimens were identified as Lymnaea columella. Conclusion. Canutama constitutes a focus of transmission of human fascioliasis. This study describes the first serological survey for human fascioliasis, as well as its simultaneous occurrence in human hosts and possible intermediates performed in northern Brazil.