Phylogenetic Pattern, Evolutionary Processes and Species Delimitation in the Genus Echinococcus

Global, Regional and National Burden of Human Cystic Echinococcosis from 1990 to 2019: A Systematic Analysis for the Global Burden of Disease Study 2019

BACKGROUND

Cystic echinococcosis (CE) is a neglected tropical parasitic disease that poses huge disease, social and economic burdens worldwide; however, there has been little knowledge on the global morbidity, mortality and disability-adjusted life years (DALYs) of CE until now. This study aimed to collect the most up-to-date data about the global, regional and national disease burden due to CE from 1990 to 2019 and to project trends in the next 10 years.

METHODS

We measured the global, regional and national morbidity, mortality and DALYs of CE from 1990 to 2019 based on the Global Burden of Disease Study 2019 (GBD 2019) data, and we examined the correlation between socioeconomic development levels and the disease burden of CE. In addition, the disease burden due to CE was projected from 2020 to 2030.

RESULTS

The age-standardized incidence rate (ASIR) of CE reduced from 2.65/105 [95% UI: (1.87/105 to 3.7/105)] in 1990 to 2.6/105 [95% UI: (1.72/105 to 3.79/105)] in 2019 (EAPC = -0.18%). The number of deaths, DALYs, age-standardized mortality rate (ASMR) and age-standardized DALY rate due to CE all showed a tendency to decline from 1990 to 2019. A higher disease burden of CE was measured in women than in men in 2019. There was a significant difference in the ASMR of CE by region according to the socio-demographic index (SDI), and lower burdens of CE were estimated in high-SDI regions. The global ASIR of CE is projected to decline from 2020 to 2030; however, the ASMR and age-standardized DALY rate are projected to rise.

CONCLUSIONS

The global burden of CE remains high, and it is recommended that more health resources are allocated to low-SDI regions, women and the elderly aged 55 to 65 years to reduce the disease burden of CE.

Assessing the Potential Apoptotic Effects of Different Hydatid Cyst Fluids on Human Healthy Hepatocytes and Hepatocellular Carcinoma Cells

Cystic Echinococcosis (CE) is a zoonotic infection caused by the larval form of Echinococcus granulosus in humans. Emerging evidence suggests an intriguing inverse association between E. granulosus infection and the occurrence of cancer. This study aimed to investigate the influence of diverse host-derived hydatid cyst fluids (HCF) with distinct genotypes on human liver hepatocytes (HC) and hepatocellular carcinoma cells (HepG2). Specifically, we examined their effects on cell proliferation, apoptosis sensitivity (BAX/BCL-2), apoptosis-related p53 expression, and the expression of cancer-related microRNA (hsa-miR-181b-3p). Cell proliferation assays, real-time PCR, and ELISA studies were conducted to evaluate potential anti-cancer properties. The findings revealed that animal-origin HCF (G1(A)) induced direct cell death by augmenting the susceptibility of HepG2 cells to apoptosis. Treatment with both G1(A) and G1(H) HCF sensitized HepG2 and HC cell lines to apoptosis by modulating the BAX/BCL-2 ratio, accompanied by upregulation of the p53 gene. Additionally, G1(A) HCF and human-derived HCFs (G1(H), G7(H)) reduced the expression of miR-181b-3p in HepG2 cells. Consequently, this study demonstrates the potential anti-cancer effect of HCF in HepG2 cells and provides the first comparative assessment of HCFs from human and animal sources with diverse genotypes, offering novel insights into this field.

First report of Echinococcus ortleppi and E. canadensis (genotype G6) from southern Punjab, Pakistan and a global overview on genetic structure and host adaptation of E. ortleppi

Cystic echinococcosis (CE), caused by Echinococcus granulosus sensu lato, is a neglected tropical disease known mainly for its zoonotic nature. CE is endemic to Pakistan, however, the disease is not given due consideration and millions of people remain at health risk. This study was undertaken to assess the species and genotypes of E. granulosus sensu lato in sheep, buffaloes and cattle, brought to slaughterhouses of two major cities (Multan and Bahawalpur) of south Punjab, Pakistan. A total of 26 hydatid cyst specimens were characterized through complete cox1 mitochondrial gene (1609 bp) sequencing. Species and genotypes of E. granulosus sensu lato discovered in the southern Punjab consisted of E. granulosus sensu stricto (n =21), E. ortleppi (n=4) and E. canadensis G6 genotype (n=1). Of E. granulosus s.s. isolates, the genotype G3 was predominantly involved in causing infections to the livestock of this region. Since all of these species are zoonotic, wide and effective surveillance studies are required to ascertain the risks to human population in Pakistan. Additionally, a global overview on cox1 phylogenetic structure of E. ortleppi was carried out. Despite the widespread occurrence, the species is mostly limited to the southern hemisphere. The highest burden has been reported in the South America (62.15%) and Africa (28.44%) and by far the most common host is cattle, accounting for >90% of cases.

Optimization of single-tube nested PCR for the detection of Echinococcus spp

Echinococcosis is a serious zoonotic life-threatening parasitic disease caused by metacestodes of Echinococcus spp., and appropriate sensitive diagnosis and genotyping techniques are required to detect infections and study the genetic characterization of Echinococcus spp. isolates. In this study, a single-tube nested PCR (STNPCR) method was developed and evaluated for the detection of Echinococcus spp. DNA based on the COI gene. STNPCR was 100 times more sensitive than conventional PCR and showed the same sensitivity to common nested PCR (NPCR); but with a lower risk of cross-contamination. The limit of detection of the developed STNPCR method was estimated to be 10 copies/μL of the recombinant standard plasmids of Echinococcus spp. COI gene. In clinical application, 8 cyst tissue samples and 12 calcification tissue samples were analysed by conventional PCR with outer and inner primers and resulted in 100.00% (8/8) and 8.33% (1/12), 100.00% (8/8) and 16.67% (2/12) positive reactions, respectively, while STNPCR and NPCR were all able to identify the presence of genomic DNA in 100.00% (8/8) and 83.33% (10/12) of the same samples. Due to its high sensitivity combined with the potential for the elimination of cross-contamination, the STNPCR method was suitable for epidemiological investigations and characteristic genetic studies of Echinococcus spp. tissue samples. The STNPCR method can effectively amplify low concentrations of genomic DNA from calcification samples and cyst residues infected with Echinococcus spp. Subsequently, the sequences of positive PCR products were obtained, which were useful for haplotype analysis, genetic diversity, and evolution studies of Echinococcus spp., and understanding of Echinococcus spp. dissemination and transmission among the hosts.

Survey and Molecular Characterization of Echinococcus granulosus sensu stricto from Livestock and Humans in the Altai Region of Xinjiang, China

Cystic echinococcosis (CE), caused by the metacestode Echinococcus granulosus sensu stricto (s.s.), is an important zoonotic parasite, endemic in the Altai region of China. It is a serious human health risk and causes livestock losses. To evaluate the prevalence, genetic variation, and population structure of CE, 2898 sheep and 703 cattle were examined from October 2019 to mid-February 2020 in the Altai region (Altai, Habahe, Fuhai, and Buerjin). Sheep had an infection rate of 4.52% (131/2898) and cattle had an infection rate of 4.84% (34/703). In total, 180 cyst isolates were obtained, including 131 sheep, 34 cattle, and 15 from CE human patients. The cysts were investigated using mitochondrial cytochrome C oxidase subunit 1 (cox1). Polymerase Chain Reaction (PCR) results showed that, among the two genotypes of E. granulosus s.s., there were 22 different haplotypes (Haps). Phylogenetic analysis and parsimony network indicated that seventeen (77.27%) Haps belonged to the sheep strain (G1 genotype) and five Haps (22.73%) belonged to the buffalo strain (G3 genotype). Hap3 was the most common haplotype (65.00%, 112/180), which belongs to the G1 genotype. Hap18−Hap22 were found in human samples, indicating that sheep and cattle reservoirs of human CE. Molecular diversity indices revealed the high levels of haplotype diversity and relatively low levels of nucleotide diversity. Tajima’s D and Fu’s Fs tests displayed that the Altai population had a significant deviation from neutrality. Based on pairwise fixation index (Fst) values, a low level of genetic differentiation was found between the populations of E. granulosus s.s. isolated from different regions. The present survey findings represent an epidemiological survey of CE in the Altai region where there were two genotypes simultaneously and will provide more information on the genetic structure of E. granulosus s.s. within this region.

Molecular Epidemiology of Cystic Echinococcosis in Rural Baluchistan, Pakistan: A Cross-Sectional Study

Cystic echinococcosis (CE), or hydatid cyst disease (HCD), is a zoonosis of significant importance caused by the cestode of Echinococcus granulosus sensu lato (s. l.) that affects mainly nomadic populations and has substantial economic consequences. Due to the 76% rural and nomadic population, Baluchistan is a highly endemic region in Pakistan for CE; however, it has not yet been investigated for CE. For this purpose, this study was carried out to investigate the molecular epidemiology of CE in this region. In total, 23 human hydatid cyst samples were collected from tertiary health care units in Baluchistan and processed for DNA extraction, which was then followed by sequencing of the cox1 mitochondrial gene of all 23 collected samples, genotyping, and phylogenetic and haplotype analysis. Most subjects were livestock owners (39.13%) in rural settings (73.91%). Most patients (73.19%) were pet owners (dogs) and used water from open sources for drinking. The liver was the most affected organ (52.17%), followed by the lungs (17.39%). Sequence analysis based on the cox1 gene revealed that EG genotype 1 (G1) was the most prevalent (56.52%), followed by G3 (34.78%), while some samples (8.7%) were identified as the Echinococcus canadensis (G6/7) genotype. A total of five haplotypes were detected with high haplotype diversity (0.80) and low nucleotide diversity (0.033). Phylogenetic analysis revealed two diverse sub-clades, each of G1 and G3 isolates from Baluchistan, that were evolutionarily related to previously reported G1 and G3 isolates from Pakistan and China. On the other hand, the G6/7 isolates of this study were evolutionarily identical to the already reported G6/7 isolates from Pakistan, Turkey, and Kazakhstan. This study concludes that diverse G1 and G3 EG isolates are present in this part of Pakistan, while the G6/G7 genotype was reported for the first time from Baluchistan.

Occurrence and Phylogenetic Description of Cystic Echinococcosis Isolate from Egyptian Camel (Camelus Dromedarius)

Cystic echinococcosis is one of the most significant cyclo-zoonotic diseases of major economic and public health significance worldwide. The current study was carried out to determine the epidemiological profile of cystic echinococcosis as well as to investigate its molecular and phylogenic status from one-humped camel (Camelus dromedarius) in the southern region of Egypt. In the present work, 110 camels freshly slaughtered at Daraw abattoirs, Aswan governorate were inspected for the presence of Hydatid cysts (HCs) visually and manually by palpation and incision, over a period of one year (June, 2018 - May, 2019). Furthermore, fourteen fertile hydatid cyst samples were collected from lungs of slaughtered camels. DNA extraction from two fertile samples was successfully achieved followed by phylogenetic analysis on two mitochondrial genes (cox1and nad1). Out of 110 camels slaughtered 11 (10 %) were found harboring hydatid cysts. The infection was found to prevail throughout the year, with the highest peak encountered in winter (45.5 %). The lungs were the most frequently infected organs (72.7 %) with liver cysts occurring at a significantly lower rate (27.3 %). The mean value of total protein, glucose, urea, cholesterol, magnesium, potassium, copper and creatinine was higher in cystic fluid from camels as compared to cattle. Blast and phylogenetic analysis on sequenced genes showed the presence of Echinococcus intermedius, originally the pig genotype (G7) in camels for the first time in Egypt. To the best of our knowledge, the current research provides a description of the current epidemiological and molecular situation of camel hydatidosis in the southern region of Egypt. Furthermore, the current results may have significant implications for hydatid disease control in the studied region.

Genetic diversity of Echinococcus granulosus sensu lato from animals and humans in Bosnia and Herzegovina

BACKGROUND

Cystic echinococcosis (CE) is recognized as one of the most prevalent zoonotic diseases in Bosnia and Herzegovina. However, no systemic investigation of the genetic diversity of Echinococcus granulosus sensu lato circulating among animals and humans in the country has been performed to date.

METHODS

In this preliminary study, we analysed one cyst each from 36 sheep, 27 cattle, 27 pigs, 11 wild boars and 16 human patients for amplification and partial sequencing of the adenosine triphosphate 6 (atp6) and cytochrome c oxidase 1 (cox1) genes. The host species, fertility rate and organ cyst location were recorded for each subject involved in the study.

RESULTS

Overall, the atp6 gene was successfully amplified and sequenced from 110 samples, while 96 of the PCRs for cox1 were positive. Three zoonotic genotypes of E. granulosus sensu stricto (G1 and G3) and Echinococcus canadensis (G7) were identified in our isolates based on analyses of the atp6 gene. These genotypes were represented by 11 different genetic variants (haplotypes), six of which were identified for the first time in the present study.

CONCLUSIONS

This study demonstrates, for the first time, that CE in Bosnia and Herzegovina is predominantly caused by E. granulosus sensu stricto and E. canadensis clusters, which exhibited a lower genetic diversity compared to isolates from other European countries. Further molecular studies employing other mitochondrial and nuclear genes are required to better understand the transmission cycles of E. granulosus sensu stricto among intermediate and definitive hosts in the country.

In Silico Evaluation of the Haplotype Diversity, Phylogenetic Variation and Population Structure of Human E. granulosus sensu stricto (G1 Genotype) Sequences

Echinococcus granulosus sensu lato is the causative agent of cystic echinococcosis (CE), which is a neglected zoonotic disease with an important role in human morbidity. In this study, we aimed to investigate the haplotype diversity, genetic variation, population structure and phylogeny of human E. granulosus sensu stricto (s.s.) (G1 genotype) isolates submitted to GenBank from different parts of the world by sequencing the mitochondrial CO1 and ND1 genes. The sequences of the mt-CO1 (401 bp; n = 133) and mt-ND1 (407 bp; n = 140) genes were used to analyze the haplotype, polymorphism and phylogenetic of 273 E. granulosus s.s. (G1 genotype) isolates. Mutations were observed at 31 different points in the mt-CO1 gene sequences and at 100 different points in the mt-ND1 gene sequences. Furthermore, 34 haplotypes of the mt-CO1 sequences and 37 haplotypes of the mt-ND1 sequences were identified. Tajima’s D, Fu’s Fs, and Fu’s LD values showed high negative values in both mt-CO1 and mt-ND1 gene fragments. The haplotype diversities in the sequences retrieved from GenBank in this study indicate that the genetic variation in human isolates of E. granulosus s.s. in western countries is higher than in eastern countries. This may be due to demographic expansions due to animal trades and natural selections.

Global epidemiology and molecular biology of Taenia multiceps: a comparative meta-analysis and in silico analysis study

In the present study, all published data on the epidemiology and molecular characters of Taenia multiceps were systematically collected from relevant databases (e.g. PubMed, Scopus, National Center for Biotechnology Information), and combined in various statistical and genetic analyses as a contribution to a better understanding of the epidemiology of this ubiquitous taeniid worldwide. While 5.8% of the key hosts (dogs) from various countries had T. multiceps, grey wolves displayed the highest prevalence (21.6%) among the definitive hosts. Small ruminants are the main intermediate hosts and carry the coenuri in various locations, but most commonly in the central nervous system (CNS). Cerebral coenuri were confirmed in 53% of sheep exhibiting neurological symptoms, and infected animals often had only a single coenurus in the brain. Sheep had a higher prevalence (8.8%) of CNS coenuri than goats (5.8%); however, extra-CNS coenuri were detected more frequently in goats than in sheep. In either case, the difference between sheep and goats was statistically insignificant. Analysis of 233 partial cytochrome oxidase subunit I nucleotide sections for T. multiceps revealed high haplotype and low nucleotide diversities. Fifty-one haplotypes were detected circulating in 6 geographic populations. China, Iran and Turkey had 2 major haplotypes, whereas Italy and Egypt shared 3. Haplotypes from Greece circulate worldwide, and displayed similar gene flow values when compared with the other populations. There were no distinct patterns for haplotype distribution in relation to the infected hosts or coenuri locations. The existence of genetic variants in T. multiceps was highlighted, but needs further studies.

Meta-analysis of the prevalence of bovine cystic echinococcosis in China during decade

BACKGROUND

Cystic echinococcosis (CE) is a zoonotic parasitic disease caused by Echinococcus granulosus sensu lato (E. granulosus s.l.) larvae. It is mainly prevalent in western agricultural and pastoral areas in China, seriously affecting the development of public health and animal husbandry.

METHODS

This study conducted a systematic evaluation and meta-analysis of bovine CE in China in the past 10 years (2011-2020). Five databases (PubMed, ScienceDirect, CNKI, Wanfang Data, VIP Chinese Journal Database) were used to collect the relevant references, and finally 77 published articles were obtained.

RESULTS

The total prevalence of bovine CE was estimated to be 9.62% during decade, and decreased year by year after reaching its peak in 2014 (18.75%). The highest E. granulosus s.l. infection rate was found in Qinghai province (14.79%). The infection rate of cattle >4 years old (15.84%) was significantly higher than that of other age groups, and cattle raised by grazing was significantly higher than that of other methods (17.00%). In the groups of geographical and climatic factors, the prevalence of CE was higher in regions with high-altitude (20.76%), cold (20.76%) and rainy areas (11.33%).

CONCLUSION

This study found that old age and grazing were two important factors for the high incidence of bovine CE. The prevalence of CE is higher in low temperature, rainy and high altitude areas, where may be more suitable for the survival of E. granulosus s.l. eggs.

Genetic diversity of Echinococcus granulosus sensu lato in China: Epidemiological studies and systematic review

Cystic echinococcosis (CE) is a neglected tropical zoonosis caused by Echinococcus granulosus sensu lato (s.l.) and remains a major public health concern globally. Here, CE isolates (n = 3310) with clearly defined genotypes and geographical origins in China were retrieved through our epidemiological survey (2016-2020) and systematic review (1992-2020). Existing known genotypes of Echinococcus granulosus sensu lato (E. granulosus s.l.) except for G4 have been found in China, particularly on the Tibetan Plateau, where their genetic diversity is unique to that part of the world. According to the systematic review, genetic compositions of E. granulosus s.l. in China were as follows: E. granulosus (G1, G3), 98.3%; Echinococcus ortleppi (G5), 0.1%; Echinococcus intermedius (G6, G7), 1.4%; and Echinococcus canadensis (G8, G10), 0.2%. Specifically, G1 was responsible for 97.7% of infections and characterized by the broadest host ranges and geographic distributions. Our epidemiological results showed a relatively stable genetic composition of E. granulosus s.l. in sheep and yaks from three CE hyperendemic provinces (Xinjiang, Sichuan, Qinghai). A higher proportion of fertile cysts were found in sheep (287/406, 70.7%) than in yaks (28/184, 15.2%). During the past 29 years, 51 cox1 haplotypes of E. granulosus s.l. were endemic in China. The ancestral haplotype (Hap_2) remained the most common haplotype, 12 relatively common haplotypes were endemic and nine newly reported haplotypes were found during the survey. Overall, our results demonstrate that the compulsory immunization of sheep and the pilot EG95 vaccination campaign in yaks are well matched with the current genotypic situation. In addition to yaks, we advocate for more surveillance of CE isolates from pigs, cattle, goats and camels, since their roles in the transmission and reservation of E. granulosus s.l. have been largely ignored in China.

Comparative Mitochondrial Genomic Analysis Robustly Supported That Cat Tapeworm Hydatigera taeniaeformis (Platyhelminthes: Cestoda) Represents a Species Complex

Hydatigera taeniaeformis is one of the most common intestinal tapeworms that has a worldwide distribution. In this study, we sequenced the complete mitochondrial (mt) genome of H. taeniaeformis from the leopard cat (designated HTLC) and compared it with those of H. taeniaeformis from the cat in China (designated HTCC) and Germany (designated HTCG). The complete mt genome sequence of HTLC is 13,814 bp in size, which is 167 bp longer than that of HTCC and is 74 bp longer than that of HTCG. Across the entire mt genome (except for the two non-coding regions), the sequence difference was 3.3% between HTLC and HTCC, 12.0% between HTLC and HTCG, and 12.1% between HTCC and HTCG. The difference across both nucleotide and amino acid sequences of the 12 protein-coding genes was 4.1 and 2.3% between the HTLC and HTCC, 13.3 and 10.0% between the HTLC and HTCG, and 13.8 and 10.6% between the HTCC and HTCG, respectively. Phylogenetic analysis based on concatenated amino acid sequences of 12 protein-coding genes showed the separation of H. taeniaeformis from different hosts and geographical regions into two distinct clades. Our analysis showed that the cat tapeworm H. taeniaeformis represents a species complex. The novel mt genomic datasets provide useful markers for further studies of the taxonomy and systematics of cat tapeworm H. taeniaeformis.

Species and genotypes belonging to Echinococcus granulosus sensu lato complex causing human cystic echinococcosis in Europe (2000-2021): a systematic review

Background

This study aimed to fill a gap of knowledge by providing a quantitative measure of molecularly identified species and genotypes belonging to Echinococcus granulosussensu lato (s.l.) causing human cystic echinococcosis (CE) in Europe during the period 2000–2021. As these species and genotypes are characterized by genetic, animal host and geographical differences, studying the E. granulosuss.l. complex is epidemiologically relevant.

Methods

A systematic review (SR) was conducted on the basis of both scientific and grey literature considering primary studies between 2000 and 2021 in four databases. From a total of 1643 scientific papers, 51 records were included in the SR. The main inclusion criterion for this study was the molecular confirmation of E. granulosuss.l. at the genotype/species level as a causative agent of human CE cases in selected European countries.

Results

Relevant data were obtained from 29 out of 39 eligible European countries. This SR identified 599 human molecularly confirmed echinococcal cysts: 460 (76.8%) identified as E. granulosussensu stricto (s.s.), 130 (21.7%) as E. canadensis cluster (G6/7 and G10), 7 (1.2%) as E. ortleppi (G5), and 2 as E. vogeli (0.3%). Three geographical hotspots of human CE caused by different species of the E. granulosuss.l. complex were identified: (1) E. granulosuss.s. in Southern and South-eastern Europe (European-Mediterranean and Balkan countries); (2) E. canadensis (G6/7) in Central and Eastern Europe; (3) E. ortleppi in Central and Western Europe. This SR also identified data gaps that prevented a better definition of the geographical distribution of the Echinococcus granulosuss.l. species complex in Europe: western Balkan countries, part of Central Europe, and Baltic countries.

Conclusions

These results mandate longitudinal, multi-centre, intersectoral and transdisciplinary studies which consider both molecular and clinical epidemiology in animals and humans. Such studies would be valuable for a better understanding of the transmission of the E. granulosuss.l. species complex and their potential clinical impact on humans.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05197-8.

Proteomic profiling of hydatid fluid from pulmonary cystic echinococcosis

BACKGROUND

Most cystic echinococcosis cases in Southern Brazil are caused by Echinococcus granulosus and Echinococcus ortleppi. Proteomic studies of helminths have increased our knowledge about the molecular survival strategies that are used by parasites. Here, we surveyed the protein content of the hydatid fluid compartment in E. granulosus and E. ortleppi pulmonary bovine cysts to better describe and compare their molecular arsenal at the host-parasite interface.

METHODS

Hydatid fluid samples from three isolates of each species were analyzed using mass spectrometry-based proteomics (LC-MS/MS). In silico functional analyses of the identified proteins were performed to examine parasite survival strategies.

RESULTS

The identified hydatid fluid protein profiles showed a predominance of parasite proteins compared to host proteins that infiltrate the cysts. We identified 280 parasitic proteins from E. granulosus and 251 from E. ortleppi, including 52 parasitic proteins that were common to all hydatid fluid samples. The in silico functional analysis revealed important molecular functions and processes that are active in pulmonary cystic echinococcosis, such as adhesion, extracellular structures organization, development regulation, signaling transduction, and enzyme activity.

CONCLUSIONS

The protein profiles described here provide evidence of important mechanisms related to basic cellular processes and functions that act at the host-parasite interface in cystic echinococcosis. The molecular tools used by E. granulosus and E. ortleppi for survival within the host are potential targets for new therapeutic approaches to treat cystic echinococcosis and other larval cestodiases.

Echinococcus spp. and genotypes infecting humans in Tibet Autonomous Region of China: a molecular investigation with near-complete/complete mitochondrial sequences

Background

Molecular markers are essential to identify Echinococcus species and genotypes in areas with multiple Echinococcus species to understand their epidemiology and pathology. Tibet Autonomous Region (TAR) is one of the areas worst hit by echinococcosis. However, molecular epidemiology is still missing among echinococcosis patients in TAR. This research explored the Echinococcus species and genotypes infecting humans in TAR and the population diversity and the possible origin of G1 in TAR.

Methods

Cyst samples were collected in one echinococcosis-designated hospital in TAR. Echinococcus species and genotypes were identified through a maximum-likelihood approach with near-complete/complete mtDNA using IQ-TREE. Phylogenetic networks were built with PopART, and the phylogeographical diffusion pattern was identified using a Bayesian discrete phylogeographic method.

Results

Using phylogenetic trees made with near-complete/complete mtDNA obtained from 92 cysts from TAR patients, the Echinococcus species and genotypes infecting humans in TAR were identified as Echinococcus granulosus (s.s.) G1 (81, 88.04%), accounting for the majority, followed by G6 of the E. canadensis cluster (6, 6.52%), E. granulosus (s.s.) G3 (3, 3.26%), and E. multilocularis (2, 2.17%). An expansion trend and a possible recent bottleneck event were confirmed among the G1 samples in TAR. Adding the other near-complete mtDNA of G1 samples globally from the literature, we identified the possible phylogeographic origin of the G1 samples in TAR as Turkey.

Conclusions

Using near-complete/complete mtDNA sequences of Echinococcus spp. obtained from echinococcosis patients, a variety of Echinococcus species and genotypes infecting humans throughout TAR were identified. As far as we know, this is the first comprehensive molecular investigation of Echinococcus species and genotypes infecting humans throughout TAR. We identified, for the first time to our knowledge, the possible origin of the G1 in TAR. We also enriched the long mtDNA database of Echinococcus spp. and added two complete E. multilocularis mtDNA sequences from human patients. These findings will improve our knowledge of echinococcosis, help to refine the targeted echinococcosis control measures, and serve as a valuable baseline for monitoring the Echinococcus species and genotypes mutations and trends of the Echinococcus spp. population in TAR.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05199-6.

Sequence analysis, intra-genotyping variation, and phylogenetic study of nad1 gene in Echinococcus granulosus sensu lato genotypes from intermediate hosts in southwestern Iran

Cystic echinococcosis (CE) is caused by the larval stage of Echinococcus granulosus sensu lato (s. l.). The disease is cosmopolitan, and Iran is a highly endemic area for CE. This parasite exhibits high genetic diversity, which can be related to its life cycle, transmission, and pathogenesis. This study was aimed at determining the phylogenetic relationship and intra-genotyping variation of E. granulosus s.l. in a vast area in the southwest of Iran (SWI). Eighty hydatid cyst isolates of intermediate hosts (i.e., cattle, sheep, goat, buffalo, camel, and human) were collected. The sequence analysis of the nad1 gene exhibited the three genotypes of G1 (n = 70, 87.5%), G3 (n = 8, 10%), and G6/G7 (n = 2, 2.5%). Also, 16, 2, and 1 unique haplotypes were identified for the G1, G3, and G6/G7 genotypes, respectively. According to the phylogenetic tree topology, the nad1 gene similarities were found for some G1 isolates in some vast areas, and the G1 genotype showed a heterogeneous population worldwide. The only SWI G6/G7 haplotype was at a distant position in E. canadensis clade, indicating the notable difference of this haplotype from other isolates from Iran and other countries. The presence of the G6/G7 genotype in the SWI may be due to the transmission of the genotype from other regions or the role of camel/wild boar or other possible hosts in the expansion of this genotype in SWI. The results of the present study can be used in CE control programs, molecular epidemiology, and phylogenetic studies in Iran and other countries for future goals.

A review on invasions by parasites with complex life cycles: the European strain of Echinococcus multilocularis in North America as a model

In a fast-changing and globalized world, parasites are moved across continents at an increasing pace. Co-invasion of parasites and their hosts is leading to the emergence of infectious diseases at a global scale, underlining the need for integration of biological invasions and disease ecology research. In this review, the ecological and evolutionary factors influencing the invasion process of parasites with complex life cycles were analysed, using the invasion of the European strain of Echinococcus multilocularis in North America as a model. The aim was to propose an ecological framework for investigating the invasion of parasites that are trophically transmitted through predator–prey interactions, showing how despite the complexity of the cycles and the interactions among multiple hosts, such parasites can overcome multiple barriers and become invasive. Identifying the key ecological processes affecting the success of parasite invasions is an important step for risk assessment and development of management strategies, particularly for parasites with the potential to infect people (i.e. zoonotic).

Red foxes harbor two genetically distinct, spatially separated Echinococcus multilocularis clusters in Brandenburg, Germany

Background

Alveolar echinococcosis (AE) is a clinically serious zoonosis caused by the fox tapeworm Echinococcus multilocularis. We studied the diversity and the distribution of genotypes of E. multilocularis isolated from foxes in Brandenburg, Germany, and in comparison to a hunting ground in North Rhine-Westphalia.

Methods

Echinococcus multilocularis specimens from 101 foxes, 91 derived from Brandenburg and 10 derived from North Rhine-Westphalia, were examined. To detect potential mixed infections with different genotypes of E. multilocularis, five worms per fox were analyzed. For genotyping, three mitochondrial markers, namely cytochrome c oxidase subunit 1 (Cox1), NADH dehydrogenase subunit 1 (Nad1), and ATP synthase subunit 6 (ATP6), and the nuclear microsatellite marker EmsB were used. To identify nucleotide polymorphisms, the mitochondrial markers were sequenced and the data were compared, including with published sequences from other regions. EmsB fragment length profiles were determined and confirmed by Kohonen network analysis and grouping of Sammon’s nonlinear mapping with k-means clustering. The spatial distribution of genotypes was analyzed by SaTScan for the EmsB profiles found in Brandenburg.

Results

With both the mitochondrial makers and the EmsB microsatellite fragment length profile analyses, mixed infections with different E. multilocularis genotypes were detected in foxes from Brandenburg and North Rhine-Westphalia. Genotyping using the mitochondrial markers showed that the examined parasite specimens belong to the European haplotype of E. multilocularis, but a detailed spatial analysis was not possible due to the limited heterogeneity of these markers in the parasite population. Four (D, E, G, and H) out of the five EmsB profiles described in Europe so far were detected in the samples from Brandenburg and North Rhine-Westphalia. The EmsB profile G was the most common. A spatial cluster of the E. multilocularis genotype with the EmsB profile G was found in northeastern Brandenburg, and a cluster of profile D was found in southern parts of this state.

Conclusions

Genotyping of E. multilocularis showed that individual foxes may harbor different genotypes of the parasite. EmsB profiles allowed the identification of spatial clusters, which may help in understanding the distribution and spread of the infection in wildlife, and in relatively small endemic areas.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-05038-0.

The First Record of Echinococcus ortleppi (G5) Tapeworms in Grey Wolf (Canis lupus)

The aim of this study is to confirm the presence and molecular identification of Echinococcus tapeworms in wolves from south-eastern Poland. An investigation was carried out on the intestines of 13 wolves from south-eastern Poland. The small intestines were divided into three equal segments. Each segment was separately examined using the sedimentation and counting technique (SCT). The detected Echinococcus tapeworms were isolated and identified by PCRs and sequencing (nad1 and cox1 genes). Additionally, DNA isolated from the feces of wolves positive for Echinococcus tapeworms was examined with two diagnostic PCRs. The intestines of one wolf were positive for E. granulosus s.l. when assessed by SCT; the intestine was from a six-year-old male wolf killed in a communication accident. We detected 61 adult tapeworms: 42 in the anterior, 14 in the middle, and 5 in the posterior parts of the small intestine. The PCRs conducted for cox1 and nad1 produced specific products. A sequence comparison with the GenBank database showed similarity to the deposited E. ortleppi (G5) sequences. An analysis of the available phylogenetic sequences showed very little variation within the species of E. ortleppi (G5), and identity ranged from 99.10% to 100.00% in the case of cox1 and from 99.04% to 100.00% in the case of nad1. One of the two diagnostic PCRs used and performed on the feces of Echinococcus-positive animals showed product specific for E. granulosus. This study showed the presence of adult E. ortleppi tapeworms in wolves for the first time.

Advances in research on echinococcoses epidemiology in China

Echinococcoses are serious zoonotic diseases in China's vast, western and north-western pastoral areas that has one of the highest prevalence in the world. The two most common forms, cystic echinococcosis (CE) and alveolar echinococcosis (AE), are co-epidemic in some areas causing a grave threat to people's health and economic development. Echinococcus spp. are transmitted through domestic, sylvatic and mixed cycles involving many kinds of host. Successful transmission requires a favourable environment for the growth of the parasites and survival of their eggs, while the unique customs and religious beliefs in the endemic areas pose a challenge to the prevention and control of these parasites. Based on previous epidemiological studies, this paper reviews the particular factors affecting the transmission of Echinococcus parasites in China, with a focus on biological (parasite genotype and the species, age, sex and density of hosts), environmental (landscape and climate) and social (age, gender, ethnicity, education, occupation, life style, cultural customs, living conditions and hygiene practices of humans in the endemic areas). These three factors interact with each other and jointly determine the parasites' transmission intensity, the study of which supports the formulation of the strategies and measures that are significant for control of these infections.

Deep amplicon sequencing highlights low intra-host genetic variability of Echinococcus multilocularis and high prevalence of the European-type haplotypes in coyotes and red foxes in Alberta, Canada

Echinococcus multilocularis (Em) is a zoonotic parasite considered a global emergent pathogen. Recent findings indicate that the parasite is expanding its range in North America and that European-type haplotypes are circulating in western Canada. However, genetic analyses are usually conducted only on a few parasites out of thousands of individuals within each definitive host, likely underestimating the prevalence of less common haplotypes. Moreover, mixed infections with several mtDNA haplotypes in the same host have been reported, but their relative abundance within the host was never estimated. We aimed to 1) estimate the frequency of co-infections of different Em haplotypes in coyotes (Canis latrans) and red foxes (Vulpes vulpes) from western Canada and their relative abundance within the definitive hosts, 2) detect less prevalent haplotypes by sampling a larger proportion of the parasite subpopulation per host, and 3) investigate differences in the distribution of Em haplotypes in these main definitive hosts; foxes and coyotes. We extracted DNA from ~10% of the worm subpopulation per host (20 foxes and 47 coyotes) and used deep amplicon sequencing (NGS technology) on four loci, targeting the most polymorphic regions from the mitochondrial genes cox1 (814 bp), nad1 (344 bp), and cob (387 bp). We detected the presence of mixed infections with multiple Em haplotypes and with different Echinococcus species including Em and E. granulosus s.l. genotypes G8/G10, low intraspecific diversity of Em, and a higher abundance of the European-type haplotypes in both hosts. Our results suggest a population expansion of the European over the North American strain in Alberta and a limited distribution of some European-type haplotypes. Our findings indicate that deep amplicon sequencing represents a valuable tool to characterize Em in multiple hosts, to assess the current distribution and possible origins of the European strain in North America. The potential use of next-generation sequencing technologies is particularly important to understand the patterns of geographic expansion of this parasite.

Genetic Evolution and Implications of the Mitochondrial Genomes of Two Newly Identified Taenia spp. in Rodents From Qinghai-Tibet Plateau

The larva of Taeniidae species can infect a wide range of mammals, causing major public health and food safety hazards worldwide. The Qinghai-Tibet Plateau (QTP), a biodiversity hotspot, is home to many species of rodents, which act as the critical intermediate hosts of many Taeniidae species. In this study, we identified two new larvae of Taenia spp., named T. caixuepengi and T. tianguangfui, collected from the plateau pika (Ochotona curzoniae) and the Qinghai vole (Neodon fuscus), respectively, in QTP, and their mitochondrial genomes were sequenced and annotated. Phylogenetic trees based on the mitochondrial genome showed that T. caixuepengi has the closest genetic relationship with T. pisiformis, while T. tianguangfui was contained in a monophyletic group with T. crassiceps, T. twitchelli, and T. martis. Biogeographic scenarios analysis based on split time speculated that the speciation of T. caixuepengi (∼5.49 Mya) is due to host switching caused by the evolution of its intermediate host. Although the reason for T. tianguangfui (∼13.11 Mya) speciation is not clear, the analysis suggests that it should be infective to a variety of other rodents following the evolutionary divergence time of its intermediate host and the range of intermediate hosts of its genetically close species. This study confirms the species diversity of Taeniidae in the QTP, and speculates that the uplift of the QTP has not only a profound impact on the biodiversity of plants and animals, but also that of parasites.

First report of cystic echinococcosis in rhinos: A fertile infection of Echinococcus equinus in a Southern white rhinoceros (Ceratotherium simum simum) of Kruger National Park, South Africa

Despite being a parasitic disease known since ancient times, some epidemiological aspects of cystic echinococcosis (CE) remain unclear. Many studies describe its prevalence and genotyping in populations of domestic animals and livestock, but data regarding wildlife are often scarce and incomplete. The available literature suggests that CE has never been reported in African rhinos. Considering the fragile conservation status of these species due to continued poaching, this study tries to clarify some neglected epidemiological aspects. In February 2020, an adult female of the Southern white rhinoceros, Ceratotherium simum simum (Burchell, 1817), was killed by poachers. The subsequent necropsy performed by the state veterinary team revealed the presence of seven cysts within the pulmonary tissue (four cysts in the right medio-caudal lobe and three cysts in the left medio-caudal lobe) with a diameter of between 1.5 and 2.3 cm. Given the state of decomposition of the carcass, only two of these were suitable for microscopic examination. Specimens were examined under 10x and 40x microscopic magnification for the confirmation of fertility of the cysts, based on the presence of numerous protoscoleces in different stages of maturation. A histopathological examination was also performed to describe the relationship between parasite and host tissue reaction. Cyst samples were subjected to PCR. The primers successfully amplified the expected fragments of the cox-1 and the nad-1 gene from the isolated genomic DNA, revealing high sequence identity with published sequences of Echinococcus equinus Williams & Sweatman, 1963 isolate G4 and E. equinus isolate SLG5-G4.

Occurrence of Echinococcusgranulosussensulato and Other Taeniids in Bhutan

The present research shows the results of a national study documenting the occurrence and genetic diversity of Echinococcus and Taenia species across Bhutan. Environmental dog faecal samples (n = 953) were collected from 2016 to 2018 in all 20 Bhutanese districts, mainly in urbanised areas. Cystic echinococcosis cysts were isolated from 13 humans and one mithun (Bos frontalis). Isolation of taeniid eggs from faeces was performed by sieving/flotation technique, followed by DNA isolation, PCR and sequence analyses for species identification (gene target: small subunit of ribosomal RNA). Genetic diversity of E. granulosuss.s. was based on the sequence (1609 bp) of the cox1 gene. A total of 67 out of 953 (7%) dog faecal samples were positive for at least one taeniid species. From the 670 free-roaming dog faecal samples, 40 (5.9%) were positive for taeniid DNA, 22 (3.2%) of them were identified as E. granulosuss.s. and four (0.5%) as E. ortleppi (G5). From the 283 faecal samples originating from yak-grazing areas, 27 (9.5%) were taeniid positive, including eight (2.8%) infected with E. granulosuss.s. and four (1.4%) with E. ortleppi. E. granulosuss.s. was identified in all isolates from human and the cyst from mithun. A haplotype network (cox1 gene) from E. granulosuss.s, including isolates from 12 dogs, two human and one mithun, revealed eight different haplotypes. The most common cox1 haplotype was the globally distributed Eg01, followed by Eg40 and Eg37 (previously described in China). Five new cox1 haplotypes (EgBhu1–5) originated from human, dogs, and a mithun were identified. The study indicated the contamination of urban areas and pastures with Echinococcus eggs in seven districts in Bhutan. The molecular characterisation of E. granulosuss.l. revealed different E. granulosuss.s. haplotypes as well as E. ortleppi. The transmission of T. multiceps was documented only in the western part of the country. Considering the zoonotic feature of E. granulosus s.s. and E. ortleppi and the economic impact of coenurosis caused by T. multiceps (also known as gid) in Bhutan, the findings of this study represent a significant contribution towards an epidemiological baseline for the establishment of a national control programme.

First description of the emergence of Echinococcus ortleppi (G5 genotype) in sheep and goats in Iran

Cystic echinococcosis is one of the most important cyclozoonotic helminthic diseases caused by various genotypes of Echinococcus granulosus SENSU lato complex in the Middle East. Echinococcus ortleppi G5 genotype has been previously reported to infect camels in Iran. However, no molecular data are available on the circulation of the cattle genotype from other animal intermediate hosts. Overall, 30 hydatid cyst samples were collected from 2015 to 2016 from sheep (n; 15) and goat (n; 15) isolates in Mazandaran province, northern Iran. The DNA of larval stages was extracted, amplified and sequenced by targeting of mitochondrial 12S rRNA marker. Based on sequencing and phylogenetic analyses, 28 isolates were identified as E. granulosus G1. However, two fertile hydatid cyst samples isolated from sheep and goat liver were confirmed as E. ortleppi with 99.8%-100% identity to species isolated from a buffalo in India. The first emergence of fertile cattle cysts from sheep and goats may have implications in the zoonotic importance of E. ortleppi in human infection and de-worming regime of infected dogs due to the shorter maturation time of G5 genotype compared with G1 genotype. Since the distribution of E. ortleppi in Iran is not fully known, further studies are urgently needed to appraise the evolutionary and epidemiology scenarios. These studies can ascertain the transmission dynamics of E. ortleppi inferred by full-length concatenated mitogenomes on the domestic and wildlife hosts, as well as humans in wider areas of Iran and the neighboring countries.

Survey of coyotes, red foxes and wolves from Wyoming, USA, for Echinococcus granulosus s. l

The paraphyletic group Echinococcus granulosus sensu lato is comprised of parasitic tapeworms of wild and domestic canids such as wolves (Canis lupus) and coyotes (Canis latrans), which serve as definitive hosts, and ungulates, which are the intermediate hosts. Members of this tapeworm group are characterized by both cosmopolitan distribution and zoonotic disease potential. This survey (conducted from 2012 through 2017) was designed to provide insight into the prevalence and distribution of this parasite in wild canids in Wyoming. Echinococcus sp. infections were documented in 14 of 22 gray wolves (63.6%), 1 of 182 coyotes (0.55%) and 0 of 5 red foxes (Vulpes fulva). Echinococcus granulosus s. l. was confirmed in 4 of these 14 specimens obtained from wolves with two parasite specimens corresponding morphologically with E. canadensis (G8/G10). These results suggest that wolves serve as the major definitive host of E. granulosus s. l. in Wyoming, while coyotes do not play an equivalent role. Limited sample size precludes evaluation of the importance of the red fox as a favorable definitive host. Whereas this study documents the occurrence of E. granulosus s. l. in Wyoming, the zoonotic disease risk does not appear to be high. Education remains the key to disease prevention, coupled with good hygienic practices by humans and anthelmintic treatment of domestic dogs exhibiting elevated risk of exposure.

Asian Admixture in European Echinococcus multilocularis Populations: New Data From Poland Comparing EmsB Microsatellite Analyses and Mitochondrial Sequencing

The cestode Echinococcus multilocularis is the causative agent of a severe zoonotic disease: alveolar echinococcosis (AE). The parasite is distributed over a vast area in northern Eurasia and North America, but the impact of AE on human health is highly uneven between different regions. One hypothetical reason for this difference in virulence may be the genetic structure of E. multilocularis which—based on mitochondrial sequences and EmsB microsatellite profiles—forms four distinct clades. These clades correspond approximately to their continents of origin: Asia, Europe, and North America, with a fourth clade apparently restricted to Mongolia and neighboring regions, even though this clade has not yet been described by EmsB genotyping. However, there are various records of genetic variants from the “wrong” region, e.g., “European” haplotypes in Western Canada, which may be the result of introduction or natural migration of host animals. One such example, prompting this study, is the recent record of an “Asian” mitochondrial haplotype in worms from foxes in Poland. At the time, this could not be confirmed by EmsB microsatellite analysis, a method that has proven to possess greater discriminatory power with the E. multilocularis nuclear genome than sequencing of mitochondrial markers. Therefore, worms collected from foxes in Poland were examined both by EmsB analysis and sequencing of the full mitochondrial cox1 gene in order to allocate the samples to the European or Asian cluster. Based on EmsB analyses of 349 worms from 97 Polish red foxes, 92% of the worms clearly showed “European-type” EmsB profiles, but 27 worms (8%) from seven foxes showed profiles that clustered with samples of Asian origin. According to cox1 sequences, a total of 18 worms from 8 foxes belonged to the Asian cluster of haplotypes. The two methods did not fully agree: only 13 worms from three foxes belonged to Asian clusters by both EmsB and cox1, whereas 18 worms from nine foxes belonged to different clusters, according to each marker. Cross-fertilization between worms of Asian origin and those from the European Polish population may explain these conflicting results. The presence of clearly Asian elements in the Polish E. multilocularis population could be the result of introduction of E. multilocularis with host animals (e.g., domestic dogs), or the migration of foxes. In the absence of genetic data from eastern European countries, especially those bordering Poland, it cannot be concluded whether this Asian admixture is typical for a larger area toward central/eastern Europe, or the Polish parasite population is the western extreme of a gradient where both European and Asian elements mingle. Further studies are needed on this subject, preferably using both mitochondrial sequencing and EmsB microsatellite analysis.

The Molecular Epidemiology of Echinococcus Infections

Molecular epidemiology (ME) is the application of molecular tools to determine the causation of disease. With infectious diseases, such as echinococcosis, this applies to identifying and characterising the aetiological agents and elucidating host range. Such an approach has been very successful with the causative agents of echinococcosis, species of Echinococcus, initially by providing a workable and practical taxonomy and subsequently determining transmission patterns in endemic areas. This review summarises the taxonomy and nomenclature of species of Echinococcus and provides an update on ME investigations of the ecology of Echinococcus transmission, particularly in areas where more than one species of Echinococcus is maintained in cycles of transmission that may interact.

International consensus on terminology to be used in the field of echinococcoses

Echinococcoses require the involvement of specialists from nearly all disciplines; standardization of the terminology used in the field is thus crucial. To harmonize echinococcosis terminology on sound scientific and linguistic grounds, the World Association of Echinococcosis launched a Formal Consensus process. Under the coordination of a Steering and Writing Group (SWG), a Consultation and Rating Group (CRG) had the main missions of (1) providing input on the list of terms drafted by the SWG, taking into account the available literature and the participants’ experience; and (2) providing independent rating on all debated terms submitted to vote. The mission of the Reading and Review Group (RRG) was to give an opinion about the recommendation paper in terms of readability, acceptability and applicability. The main achievements of this process were: (1) an update of the current nomenclature of Echinococcus spp.; (2) an agreement on three names of diseases due to Echinococcus spp.: Cystic Echinococcosis (CE), Alveolar Echinococcosis (AE) and Neotropical Echinococcosis (NE), and the exclusion of all other names; (3) an agreement on the restricted use of the adjective “hydatid” to refer to the cyst and fluid due to E. granulosus sensu lato; and (4) an agreement on a standardized description of the surgical operations for CE, according to the “Approach, cyst Opening, Resection, and Completeness” (AORC) framework. In addition, 95 “approved” and 60 “rejected” terms were listed. The recommendations provided in this paper will be applicable to scientific publications in English and communication with professionals. They will be used for translation into other languages spoken in endemic countries.

Complete mitochondrial genome analysis confirms the presence of Echinococcus granulosus sensu lato genotype G6 in Nigeria

Cystic echinococcosis (CE) is common in Africa especially in northern and eastern countries where it is highly prevalent and mainly caused by Echinococcus granulosus sensu stricto and Echinococcus granulosus sensu lato (G6/7). In a recent epidemiological survey in Nigeria, the G6/7 genotype was reportedly responsible for the majority of CE infection. In this study, considering the taxonomic challenges of the G6/7 genotype and the limitation of the cox1/nad1 genes in resolving the differences, we sequenced the complete mitochondrial (mt) genome of seven larval isolates of E. granulosus s.l. G6/7 haplotypes recently reported in Nigeria to correctly assign them to either (G6/7) genotype and to understand the mt genome variation with isolates from other geographical regions. On analysis, a total of 13,731 bp in a covalently closed circular molecule were realized. The total mt length was ≥10 bp than previously reported G6 and G7 mt genome sequences. Also, the median-joining network and phylogeny based on the 12 protein-coding sequences correctly identified them as G6 genotype. Since longer mt genome sequences have shown some advantage over individual genes in resolving taxonomic challenges, we confirm that the genotype responsible for the majority of CE infection in livestock in Nigeria is the G6 genotype and the availability of the complete mt genome from different Nigerian intermediate hosts will prove useful in future genetic population studies across the country and the West African sub-region.

Prevalence and distribution of Echinococcus spp. in wild and domestic animals across Africa: A systematic review and meta-analysis

Cystic echinococcosis (CE), a worldwide zoonosis, is highly prevalent in Africa particularly in northern and eastern Africa where data are more abundant than other regions. However, harmonization of available data through systematic review and meta-analysis may foster improved transboundary cooperation for the control of CE in Africa. Using the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines, research articles (from 2000 to 2019) were retrieved from ScienceDirect, PubMed, African Journals OnLine and Google Scholar databases. A total of 98 studies of 806,624 animals from 13 countries comprising 264,016 goats, 247,326 sheep, 251,106 cattle, 28,314 camels, 4,764 buffaloes, 2,920 equids, 1,966 pigs, 408 wild boars and 50 Norway rats were available for systematic review and meta-analysis of pooled prevalence including 5,048 dogs, 345 lions, 220 hyenas, 94 wolves and 47 jackals/foxes analysed for Echinococcus infection. In total, 46,869 animals were infected and pooled prevalence of CE in intermediate hosts was highest in camels (17.1%; 95% CI: 12.1-22.8) and lowest in pigs (0.3%; 95% CI: 0.1-0.6). Results also showed uneven species/genotype distribution across the continent such that Echinococcus granulosus sensu stricto (G1, G3) constituted 74.45% of the total isolates from East Africa, E. canadensis (G6/7) accounted for 60.3% and 97.4% in North and West Africa, respectively, while 81.3% of E. ortleppi (G5) were recorded for southern Africa. The comparatively higher prevalence estimates for eastern and northern Africa than other regions indicate where efforts on CE management should now be given greater attention in Africa. Additionally, this study also advocates for better cooperation between countries within the same sub-region and the establishment of joint CE control programmes.

Review of Cystic Echinococcosis in Nigeria: A Story of Neglect

Purpose

Cystic echinococcosis (CE) caused by Echinococcus granulosus sensu lato is a widespread zoonotic disease of global concern. In Nigeria, the exact picture/status of CE is unclear, as most of the states are largely uninvestigated. Yet, as with every parasitic zoonosis, the first step towards planning a comprehensive management and control programme involves assessment of available national/regional prevalence data, host range, and risk factors at play in the transmission dynamics.

Methods

Published articles on echinococcosis were searched on PubMed and Africa Journal Online (AJOL) databases. Inclusion criteria were based on studies reporting prevalence of echinococcosis in animals and humans (including case reports) from 1970 to 2018.

Results

In this study, we evaluated and summarized cystic echinococcosis reports in Nigeria and found that post 1970–80s, studies on cystic echinococcosis have remained sparse regardless of the high prevalence recorded in the early years of CE investigation. In addition, information on the genetic population structure and the role of wildlife in CE transmission is still lacking.

Conclusions

This study appraises the prevalence and distribution of CE in Nigeria and identified areas where surveillance and control efforts should be focused and intensified.

Genetic variation of Echinococcus spp. in yaks and sheep in the Tibet Autonomous Region of China based on mitochondrial DNA

Background

Cystic echinococcosis (CE) in humans and livestock is caused by Echinococcus granulosus (sensu lato). In China where CE is endemic, a number of studies have shown that Echinococcus granulosus (sensu stricto) is majorly responsible for CE. However, E. canadensis (G6) which is the second leading cause of CE is now being detected in most parts of the country. In this study, the species diversity and genetic variation of Echinococcus granulosus (s.l.) in four counties in Tibet Autonomous Region of China were investigated.

Methods

Infection with Echinococcus granulosus (s.s.) in yaks and sheep was identified using NADH dehydrogenase subunit 1 and 5 (nad1 and nad5) mitochondrial genes while the genotype G6 of E. canadensis initially diagnosed with NADH dehydrogenase subunit 1 (nad1) was further confirmed by analysis of the complete mitochondrial genome and a phylogenetic network constructed based on the nad2 and nad5 genes.

Results

Out of 85 hydatid cyst samples collected from slaughtered sheep (n = 54) and yaks (n = 31), 83 were identified as E. granulosus (s.s.) G1 (n = 77), G3 (n = 6) and 2 were identified as E. canadensis G6. Analysis of the nad1/nad5 genes revealed 16/17 mutations with 9/14 parsimony informative sites resulting in 15/14 haplotypes, respectively. Haplotype diversity (Hd) and nucleotide diversity (π) of E. granulosus (s.s.) population were 0.650 and 0.00127 for nad1 and 0.782 and 0.00306 for nad5, respectively, with an overall negative Tajima’s D and Fu’s Fs. A low F_ST indicated no genetic difference between isolates from sheep and yaks.

Conclusion

Pockets of infection with E. canadensis (G6, G7, G8 and G10) have been previously reported in sheep, goats, yaks and/or humans in different parts of China. While the G6 genotype has been previously reported in sheep in the Tibet Autonomous Region, the detection in a yak in the present study represents the first to the best of our knowledge. Therefore, we recommend future surveys and control efforts to comprehensively investigate other potential intermediate hosts for the prevalence and genetic diversity of the E. canadensis group (G6, G7, G8 and G10) across the country and their inclusion into the existing CE control programme.

First report of Echinococcus granulosus sensu stricto (G1) in Nigeria, West Africa

Echinococcus granulosus sensu stricto is regarded to have the highest zoonotic potential of all Echinococcus taxa. Globally, human infection due to this species constitutes over 88.44% of the total cystic echinococcosis (CE) burden. Here, we report a CE infection in a Nigerian camel caused by E. granulosus G1 genotype. To the best of our knowledge, this report is the first encounter of the G1 genotype in the West Africa sub-region where the G6 genotype is reportedly prevalent, suggesting that the epidemiology of this highly zoonotic group could have a wider host range and distribution in the sub-region, and emphasizes the need for further investigation into the genetic diversity of Echinococcus spp. in Nigeria and across the sub-region.

Genetic diversity of Echinococcus vogeli in the western Brazilian Amazon

Human polycystic echinococcosis is a parasitic infection caused by the larval stage of Echinococcus vogeli, which occurs in rural areas of Central and South America. Until now, little information on the genetic variability of E. vogeli is available. Here, 32 samples from human-excised E. vogeli cysts had a 396-bp sequence of the mitochondrial cytochrome oxidase I (COI) gene sequenced and compared to another 17 COI sequences representing nine Echinococcus species. A Bayesian COI tree revealed that all E. vogeli sequences formed a monophyletic and well-supported clade with an E. vogeli reference sequence. The occurrence of geographically restricted E. vogeli COI haplotypes suggests retention of ancestral polymorphisms with little migration in Acre, Brazil.

Green Micro- and Nanoemulsions for Managing Parasites, Vectors and Pests

The management of parasites, insect pests and vectors requests development of novel, effective and eco-friendly tools. The development of resistance towards many drugs and pesticides pushed scientists to look for novel bioactive compounds endowed with multiple modes of action, and with no risk to human health and environment. Several natural products are used as alternative/complementary approaches to manage parasites, insect pests and vectors due to their high efficacy and often limited non-target toxicity. Their encapsulation into nanosystems helps overcome some hurdles related to their physicochemical properties, for instance limited stability and handling, enhancing the overall efficacy. Among different nanosystems, micro- and nanoemulsions are easy-to-use systems in terms of preparation and industrial scale-up. Different reports support their efficacy against parasites of medical importance, including Leishmania, Plasmodium and Trypanosoma as well as agricultural and stored product insect pests and vectors of human diseases, such as Aedes and Culex mosquitoes. Overall, micro- and nanoemulsions are valid options for developing promising eco-friendly tools in pest and vector management, pending proper field validation. Future research on the improvement of technical aspects as well as chronic toxicity experiments on non-target species is needed.

Isolated Human and Livestock Echinococcus granulosus Genotypes Using Real-Time PCR of cox1 Gene in Northeast Iran

PURPOSE

Cystic echinococcosis (CE), caused by the metacestode of Echinococcus granulosus, is highly endemic over large parts of Iran. The purpose of this study was to investigate the prevalence rate of hydatidosis and mitochondrial cox1 real-time PCR with high-resolution melting curve (HRM) analysis of E. granulosus isolated from human and livestock.

METHODS

In this cross-sectional study, 61 formalin-fixed paraffin-embedded tissue isolates were collected from human CE cases and 83 hydatid cysts from the liver and lung lesions of the livestock in Khorasan Razavi province, Northeast Iran. DNA was extracted from each isolate and amplified by real-time PCR and analyzed using the HRM method.

RESULTS

The HRM analysis using the cox1 gene of 40 E. granulosus human isolates showed that 35 (87.5%), 4 (10%), and 1 (2.5%) of the isolates were categorized as G1, G3, and G6 genotypes, respectively. Out of the total 1342 livestock inspected, 39 (4%) goats and 44(12%) cattle were found harboring hydatid cysts all belonging to E. granulosus sensu stricto.

CONCLUSION

The results confirmed that the high prevalence of E. granulosus sensu stricto in intermediate hosts is remarkable in northeast of Iran coupled with the high prevalence of infection in livestock, which reinforced the need for hydatidosis control programs in this region.

Determination of Echinococcus Granulosus Genotypes in Livestock Slaughtered in Shush County, Southwest Iran Using PCR-RFLP

Echinococosis is a zoonotic disease caused by the larval stages of Echinococcus spp. that occurs in most parts of the world. Herein, we aimed to evaluate the genotypes of isolated hydatid cysts from slaughtered animals in Shush county, southwestern Iran. Totally, 96 hydatid cysts were collected, including 11 buffaloes, 13 cattle, 12 goat and 60 sheep. The PCR was done by a primer pair (BDI and 4s) to amplify ITS1 fragment. Four restriction endonucleases including AluI, HpaII, RsaI, and TaqI were used for RFLP products and enzymatic reactions were electrophoresed. Finally, twenty PCR products were sent for sequencing and phylogenetic tree was drawn with MEGA6. Molecular identification of 96 hydatid cysts demonstrated a distinctive 1000 bp fragment in all samples from four animal hosts. RFLP analysis showed similar digestion patterns in all samples. AluI digestion yielded 800 bp and 200 bp fragments, HpaII digestion made 700 bp and 300 bp fragments and RsaI digestion entailed 655 and 345segments. Moreover, TaqI rendered no digestion pattern on rDNA-ITS1 region. Additionally, E. granulosus sensu stricto (G1-3 complex) was the prevailing genotype in all livestock samples, according to PCR-RFLP and sequencing analyses.

Revisiting the Phylogenetic History of Helminths Through Genomics, the Case of the New Echinococcus oligarthrus Genome

The first parasitic helminth genome sequence was published in 2007; since then, only ∼200 genomes have become available, most of them being draft assemblies. Nevertheless, despite the medical and economical global impact of helminthic infections, parasite genomes in public databases are underrepresented. Recently, through an integrative approach involving morphological, genetic, and ecological aspects, we have demonstrated that the complete life cycle of Echinococcus oligarthrus (Cestoda: Taeniidae) is present in South America. The neotropical E. oligarthrus parasite is capable of developing in any felid species and producing human infections. Neotropical echinococcosis is poorly understood yet and requires a complex medical examination to provide the appropriate intervention. Only a few cases of echinococcosis have been unequivocally identified and reported as a consequence of E. oligarthrus infections. Regarding phylogenetics, the analyses of mitogenomes and nuclear datasets have resulted in discordant topologies, and there is no unequivocal taxonomic classification of Echinococcus species so far. In this work, we sequenced and assembled the genome of E. oligarthrus that was isolated from agoutis (Dasyprocta azarae) naturally infected and performed the first comparative genomic study of a neotropical Echinococcus species. The E. oligarthrus genome assembly consisted of 86.22 Mb which showed ∼90% identity and 76.3% coverage with Echinococcus multilocularis and contained the 85.0% of the total expected genes. Genetic variants analysis of whole genome revealed a higher rate of intraspecific genetic variability (23,301 SNPs; 0.22 SNPs/kb) rather than for the genomes of E. multilocularis and Echinococcus canadensis G7 but lower with respect to Echinococcus granulosus G1. Comparative genomics against E. multilocularis, E. granulosus G1, and E. canadensis G7 revealed 38,762, 125,147, and 170,049 homozygous polymorphic sites, respectively, indicating a higher genetic distance between E. oligarthrus and E. granulosus sensu lato species. The SNP distribution in chromosomes revealed a higher SNP density in the longest chromosomes. Phylogenetic analysis using whole-genome SNPs demonstrated that E. oligarthrus is one of the basal species of the genus Echinococcus and is phylogenetically closer to E. multilocularis. This work sheds light on the Echinococcus phylogeny and settles the basis to study sylvatic Echinococcus species and their developmental evolutionary features.

Cystic echinococcosis in Nigeria: first insight into the genotypes of Echinococcus granulosus in animals

Background

Cystic echinococcosis (CE) is a zoonosis caused by cestodes of Echinococcus granulosus (sensu lato) complex. In Nigeria, reports on the prevalence of CE, although limited, have been found to vary with location and host with higher prevalence and fertility rate observed in camels than other livestock. Until now, information regarding the molecular characteristics, genetic population structure, and genotypes of Echinococcus is lacking. Therefore, this study was aimed at addressing these gaps in knowledge.

Methods

We describe the genetic status of 31 Echinococcus isolates collected from slaughtered livestock (camels, cattle and goats) based on the full-length mitochondrial cytochrome c oxidase subunit 1 (cox1) and NADH dehydrogenase subunit 1 (nad1) genes.

Results

The resulting nucleotide sequences via the NCBI BLAST algorithm and Bayesian phylogeny of cox1 and cox1–nad1 genes using MrBayes v.3.1.2 showed that all isolates were clearly E. canadensis (G6/G7) and were 99–100% identical to previously reported G6/G7 haplotypes across Europe, Asia, North and East Africa.

Conclusions

Although, the G1 genotype is believed to be responsible for the majority of global CE burden, reports from a number of West African countries including Nigeria suggest that E. canadensis G6/G7 genotype could be the major causative agent of CE in the subregion. This study provides for the first time insight into the genetic population structure of Echinococcus species as well as implications for CE control in Nigeria.

Electronic supplementary material

The online version of this article (10.1186/s13071-019-3644-z) contains supplementary material, which is available to authorized users.

Echinococcus multilocularis Infection, Southern Ontario, Canada

Alveolar echinococcosis, the disease caused by infection with the intermediate stage of the Echinococcus multilocularis tapeworm, is typically fatal in humans and dogs when left untreated. Since 2012, alveolar echinococcosis has been diagnosed in 5 dogs, 3 lemurs, and 1 chipmunk in southern Ontario, Canada, a region previously considered free of these tapeworms. Because of human and animal health concerns, we estimated prevalence of infection in wild canids across southern Ontario. During 2015–2017, we collected fecal samples from 460 wild canids (416 coyotes, 44 foxes) during postmortem examination and analyzed them by using a semiautomated magnetic capture probe DNA extraction and real-time PCR method for E. multilocularis DNA. Surprisingly, 23% (95% CI 20%–27%) of samples tested positive. By using a spatial scan test, we identified an infection cluster (relative risk 2.26; p = 0.002) in the western-central region of the province. The cluster encompasses areas of dense human population, suggesting zoonotic transmission.

Analysis of nad2 and nad5 enables reliable identification of genotypes G6 and G7 within the species complex Echinococcus granulosus sensu lato

The larval stages of tapeworms in the species complex Echinococcus granulosus sensu lato cause a zoonotic disease known as cystic echinococcosis (CE). Within this species complex, genotypes G6 and G7 are among the most common genotypes associated with human CE cases worldwide. However, our understanding of ecology, biology and epidemiology of G6 and G7 is still limited. An essential first step towards this goal is correct genotype identification, but distinguishing genotypes G6 and G7 has been challenging. A recent analysis based on complete mitogenome data revealed that the conventional sequencing of the cox1 (366 bp) gene fragment mistakenly classified a subset of G7 samples as G6. On the other hand, sequencing complete mitogenomes is not practical if only genotype or haplogroup identification is needed. Therefore, a simpler and less costly method is required to distinguish genotypes G6 and G7. We compared 93 complete mitogenomes of G6 and G7 from a wide geographical range and demonstrate that a combination of nad2 (714 bp) and nad5 (680 bp) gene fragments would be the best option to distinguish G6 and G7. Moreover, this method allows assignment of G7 samples into haplogroups G7a and G7b. However, due to very high genetic variability of G6 and G7, we suggest to construct a phylogenetic network based on the nad2 and nad5 sequences in order to be absolutely sure in genotype assignment. For this we provide a reference dataset of 93 concatenated nad2 and nad5 sequences (1394 bp in total) containing representatives of G6 and G7 (and haplogroups G7a and G7b), which can be used for the reconstruction of phylogenetic networks.

First detection of zoonotic tapeworm Echinococcus granulosus sensu lato genotype G7 in continental Italy

The larval stage of the species complex Echinococcus granulosus sensu lato (s.l.) is the cause of a widespread zoonotic disease known as cystic echinococcosis (CE). The disease is highly prevalent in southern Italy and represents a serious public health issue. The main aim of this study was to characterize E. granulosus s.l. genotypes from wild boar on a continental area of Italy (Campania region), using recently developed mtDNA markers of nad2 and nad5 for reliable identification of different genotypes. Here, nad5 (680 bp) allowed for a clear identification of G1 and G3, whereas a combination of nad2 (714 bp) and nad5 (1394 bp in total) did the same for genotype G7 and its haplogroups G7a and G7b. The results of this study revealed for the first time the presence of genotype G7 in continental Italy. While haplogroup G7b was previously shown to be restricted to the islands of Corsica and Sardinia, here we demonstrate that haplogroup G7b is also present on the mainland of Italy. This work has implications in designing future strategies to reduce CE in Italy.

Long-read sequencing reveals a 4.4 kb tandem repeat region in the mitogenome of Echinococcus granulosus (sensu stricto) genotype G1

Background

Echinococcus tapeworms cause a severe helminthic zoonosis called echinococcosis. The genus comprises various species and genotypes, of which E. granulosus (sensu stricto) represents a significant global public health and socioeconomic burden. Mitochondrial (mt) genomes have provided useful genetic markers to explore the nature and extent of genetic diversity within Echinococcus and have underpinned phylogenetic and population structure analyses of this genus. Our recent work indicated a sequence gap (> 1 kb) in the mt genomes of E. granulosus genotype G1, which could not be determined by PCR-based Sanger sequencing. The aim of the present study was to define the complete mt genome, irrespective of structural complexities, using a long-read sequencing method.

Methods

We extracted high molecular weight genomic DNA from protoscoleces from a single cyst of E. granulosus genotype G1 from a sheep from Australia using a conventional method and sequenced it using PacBio Sequel (long-read) technology, complemented by BGISEQ-500 short-read sequencing. Sequence data obtained were assembled using a recently-developed workflow.

Results

We assembled a complete mt genome sequence of 17,675 bp, which is > 4 kb larger than the complete mt genomes known for E. granulosus genotype G1. This assembly includes a previously-elusive tandem repeat region, which is 4417 bp long and consists of ten near-identical 441–445 bp repeat units, each harbouring a 184 bp non-coding region and adjacent regions. We also identified a short non-coding region of 183 bp, which includes an inverted repeat.

Conclusions

We report what we consider to be the first complete mt genome of E. granulosus genotype G1 and characterise all repeat regions in this genome. The numbers, sizes, sequences and functions of tandem repeat regions remain to be studied in different isolates of genotype G1 and in other genotypes and species. The discovery of such ‘new’ repeat elements in the mt genome of genotype G1 by PacBio sequencing raises a question about the completeness of some published genomes of taeniid cestodes assembled from conventional or short-read sequence datasets. This study shows that long-read sequencing readily overcomes the challenges of assembling repeat elements to achieve improved genomes.

Praziquantel treatment of dogs for four consecutive years decreased the transmission of Echinococcus intermedius G7 to pigs in villages in Lithuania

Echinococcus granulosus sensu lato comprises a number of recognized species which cause cystic echinococcosis (CE) in humans and intermediate hosts. These species have particular geographic distributions, with E. granulosus sensu stricto (genotypes G1/2/3 and micro variants) being most widely spread. In Lithuania, E. intermedius (G7) is known to be the only species circulating between pigs and dogs but is also infecting cattle and humans. In fact, recent reports showed a rise of the incidence to 1.13 human cases/100,000 inhabitants/year. Most of the pigs reared on the backyard farms in Lithuania are slaughtered on site during the cold season (October–April) and are used for own consumption. Therefore, in this study, we examined the impact on taeniid transmission of treating dogs with baits containing an oral formulation of praziquantel every two months during the pig slaughtering season in endemic villages in Lithuania. This study started in November 2006 and ended in January 2011; the first dog treatment was administered in February 2007. The results show that the prevalence of E. intermedius, E. multilocularis and Taenia spp. decreased significantly in treated dogs from the second year of the study when compared to untreated dogs. The treatment of dogs also had an impact on reducing the incidence of CE in fattener pigs from 17.6% (2006-2007) to 3.8% (2008; P < 0.05) and in sows from 26.9% (2006-2007) to 3.6% (2008), and eventually to zero in 2010 (P < 0.05) in fatteners and sows as compared to animals from “control” areas (30.7% and 63.7%, respectively). The results document a significant decrease in the transmission of E. intermedius (G7) after treatment of dogs with praziquantel in a relatively short time on farm level in Lithuania. Taeniid prevalence in dogs remained low in 2017 in the areas where anthelmintic intervention was performed until 2010 and, surprisingly, it was also strongly reduced in control areas. Reduction of taeniid transmission is likely associated with a decrease in the number of dogs in the villages as well as an overall decline in backyard pig farming after 2014 due to the outbreaks of African swine fever in Lithuania.

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The prevalence of E. intermedius, E. multilocularis and Taenia spp. decreased significantly in dogs treated strategically during the home slaughter season for pigs.

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Dog treatment also reduced the incidence and intensity of CE in fattener pigs and sows.

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Treatment should target all dogs, not just free-roaming dogs.

Public health risks associated with food-borne parasites

Parasites are important food‐borne pathogens. Their complex lifecycles, varied transmission routes, and prolonged periods between infection and symptoms mean that the public health burden and relative importance of different transmission routes are often difficult to assess. Furthermore, there are challenges in detection and diagnostics, and variations in reporting. A Europe‐focused ranking exercise, using multicriteria decision analysis, identified potentially food‐borne parasites of importance, and that are currently not routinely controlled in food. These are Cryptosporidium spp., Toxoplasma gondii and Echinococcus spp. Infection with these parasites in humans and animals, or their occurrence in food, is not notifiable in all Member States. This Opinion reviews current methods for detection, identification and tracing of these parasites in relevant foods, reviews literature on food‐borne pathways, examines information on their occurrence and persistence in foods, and investigates possible control measures along the food chain. The differences between these three parasites are substantial, but for all there is a paucity of well‐established, standardised, validated methods that can be applied across the range of relevant foods. Furthermore, the prolonged period between infection and clinical symptoms (from several days for Cryptosporidium to years for Echinococcus spp.) means that source attribution studies are very difficult. Nevertheless, our knowledge of the domestic animal lifecycle (involving dogs and livestock) for Echinoccocus granulosus means that this parasite is controllable. For Echinococcus multilocularis, for which the lifecycle involves wildlife (foxes and rodents), control would be expensive and complicated, but could be achieved in targeted areas with sufficient commitment and resources. Quantitative risk assessments have been described for Toxoplasma in meat. However, for T. gondii and Cryptosporidium as faecal contaminants, development of validated detection methods, including survival/infectivity assays and consensus molecular typing protocols, are required for the development of quantitative risk assessments and efficient control measures.

Epidemiological survey on cystic echinococcosis in wild boar from Central Italy

Despite the wide distribution of wild boar populations in Italy and the increase of its diffusion in urbanized areas, only one case report has described the occurrence of Echinococcus granulosus s.l. in a wild boar from Marche (Central Italy). The present study investigated the presence of E. granulosus sensu lato with an epidemiological survey on wild boars from central Italy that had been killed during hunting season. Seven hundred sixty-five (765) adult wild boars were examined during the 2016-2017 hunting season. Of these animals, 1.0% (8/765) were positive to E. granulosus s.l. with a fertility of 0.3% (2/765), and 2.9% animals (22/765) were positive for the metacestode stage of Taenia hydatigena (Cysticercus tenuicollis), while 0.5% (4/765) showed mixed infection (E. granulosus s.l. + T. hydatigena). Sixteen hydatids were found, of which 12.5% were fertile, 37.5% were sterile, 31.3% were caseous, and 18.8% were calcified. Eight hydatids (two fertile and six sterile cysts) were molecularly characterized by analysis of the mitochondrial gene, cytochrome c oxidase subunit 1 (cox1), and the NADH dehydrogenase subunit 1 (ND1). Hydatids found in wild boars were characterized as E. granulosus sensu stricto (G1 genotype). The present survey represents the first epidemiological study on cystic echinococcosis in wild boar in Italy which highlights the need for more extensive epidemiological investigations to determine the causal factors, economic impact, and public health importance of the disease in this livestock-wildlife setting.

The benefits of analysing complete mitochondrial genomes: Deep insights into the phylogeny and population structure of Echinococcus granulosus sensu lato genotypes G6 and G7

Cystic echinococcosis (CE) is a zoonotic disease caused by the larval stage of the species complex Echinococcus granulosus sensu lato. Within this complex, genotypes G6 and G7 have been frequently associated with human CE worldwide. Previous studies exploring the genetic variability and phylogeography of genotypes G6 and G7 have been based on relatively short mtDNA sequences, and the resolution of these studies has often been low. Moreover, using short sequences, the distinction between G6 and G7 has in some cases remained challenging. The aim here was to sequence complete mitochondrial genomes (mitogenomes) to obtain deeper insight into the genetic diversity, phylogeny and population structure of genotypes G6 and G7. We sequenced complete mitogenomes of 94 samples collected from 15 different countries worldwide. The results demonstrated that (i) genotypes G6 and G7 can be clearly distinguished when mitogenome sequences are used; (ii) G7 is represented by two major haplogroups, G7a and G7b, the latter being specific to islands of Corsica and Sardinia; (iii) intensive animal trade, but also geographical isolation, have likely had the largest impact on shaping the genetic structure and distribution of genotypes G6 and G7. In addition, we found phylogenetically highly divergent haplotype from Mongolia (Gmon), which had a higher affinity to G6.

Molecular phylogeny based on six nuclear genes suggests that Echinococcus granulosus sensu lato genotypes G6/G7 and G8/G10 can be regarded as two distinct species

Tapeworms of the species complex of Echinococcus granulosus sensu lato (s. l.) are the cause of a severe zoonotic disease - cystic echinococcosis, which is listed among the most severe parasitic diseases in humans and is prioritized by the World Health Organization. A stable taxonomy of E. granulosus s. l. is essential to the medical and veterinary communities for accurate and effective communication of the role of different species in this complex on human and animal health. E. granulosus s. l. displays high genetic diversity and has been divided into different species and genotypes. Despite several decades of research, the taxonomy of E. granulosus s. l. has remained controversial, especially the species status of genotypes G6-G10. Here the Bayesian phylogeny based on six nuclear loci (7387 bp in total) demonstrated, with very high support, the clustering of G6/G7 and G8/G10 into two separate clades. According to the evolutionary species concept, G6/G7 and G8/G10 can be regarded as two distinct species. Species differentiation can be attributed to the association with distinct host species, largely separate geographical distribution and low level of cross-fertilization. These factors have limited the gene flow between genotypic groups G6/G7 and G8/G10, resulting in the formation of distinct species. We discuss ecological and epidemiological differences that support the validity of these species.