Genotyping Echinococcus multilocularis in Human Alveolar Echinococcosis Patients: An EmsB Microsatellite Analysis

Challenging the phylogenetic relationships among Echinococcus multilocularis isolates from main endemic areas

Alveolar echinococcosis (AE) is a rare but severe disease that affects more than 18,000 people worldwide per year. The complete sequencing of the mitochondrial genome of Echinococcus multilocularis has made it possible to study the genetic diversity of the parasite and its spatial and temporal evolution. We amplified the whole mitochondrial genome by PCR, using one uniplex and two multiplex reactions to cover the 13,738 bp of the mitogenome, and then sequenced the amplicons with Illumina technology. In total, 113 samples from Europe, Asia, the Arctic and North America were analyzed. Three major haplogroups were found: HG1, which clustered samples from Alaska (including Saint-Lawrence Island), Yakutia (Russia) and Svalbard; HG2, with samples from Asia, North America and Europe; and HG3, subdivided into three micro-haplogroups. HG3a included samples from North America and Europe, whereas HG3b and HG3c only include samples from Europe. In France, HG3a included samples from patients more recently diagnosed in a region outside the historical endemic area. A fourth putative haplogroup, HG4, was represented by only one isolate from Olkhon Island (Russia). The increased discriminatory power of the complete sequencing of the E. multilocularis mitogenome has made it possible to highlight four distinct geographical clusters, one being divided into three micro-haplogroups in France.

Genetic diversity of Echinococcus multilocularis specimens isolated from Belgian patients with alveolar echinococcosis using EmsB microsatellites analysis

The genetic diversity of Echinococcus multilocularis (E. multilocularis) specimens isolated from patients with alveolar echinococcosis (AE), is a major field of investigation to correlate with sources of infection, clinical manifestations and prognosis of the disease. Molecular markers able to distinguish samples are commonly used worldwide, including the EmsB microsatellite. Here, we report the use of the EmsB microsatellite polymorphism data mining for the retrospective typing of Belgian specimens of E. multilocularis infecting humans. A total of 18 samples from 16 AE patients treated between 2006 and 2021 were analyzed through the EmsB polymorphism. Classification of specimens was performed through a dendrogram construction in order to compare the similarity among Belgian samples, some human referenced specimens on the EWET database (EmsB Website for the Echinococcus Typing) and previously published EmsB profiles from red foxes circulating in/near Belgium. According to a comparison with human European specimens previously genotyped in profiles, the 18 Belgian ones were classified into three EmsB profiles. Four specimens could not be assigned to an already known profile but some are near to EWET referenced samples. This study also highlights that some specimens share the same EmsB profile with profiles characterized in red foxes from north Belgium, the Netherlands, Luxembourg and French department near to the Belgian border. Furthermore, Belgian specimens present a genetic diversity and include one profile that don't share similarities with the ones referenced in the EWET database. However, at this geographical scale, there is no clear correlation between EmsB profiles and geographical location. Further studies including additional clinical samples and isolates from foxes and rodents of south Belgium are necessary to better understand the spatial and temporal circumstances of human infections but also a potential correlation between EmsB profiles and parasite virulence.

Detection of Asian genetic components in autochthonous human Echinococcus multilocularis infections from endemic Warmia-Masuria (north-eastern Poland)

Alveolar echinococcosis is a life-threatening zoonotic disease caused by the larval stage of the cestode Echinococcus multilocularis. People are aberrant intermediate hosts accidentally infected with the parasite eggs via faecal-oral route, usually by the consumption of unwashed fruit and vegetable or direct contact with definitive hosts. The recently reported presence of Asian admixture in E. multilocularis tapeworms from Polish red foxes prompted the question of metacestode descent in the human population. In this study, a Maximum Likelihood tree based on partial sequences of E. multilocularis mitochondrial genes cox1, cob, and nad2 coupled with a hierarchical clustering analysis of microsatellite EmsB profiles and supplemented by Sammon's nonlinear mapping with k-means clustering revealed Asian genetic components, to date associated only with the sylvatic cycle, in two autochthonous samples from alveolar echinococcosis patients living in endemic Warmia-Masuria, north-eastern Poland. The red fox is the most likely source of contamination in the environment shared by people and wildlife that led to these infections. Our results confirm that Asian genetic variants participate in the synanthropic cycle in north-eastern Poland and indicate that they may be present in the human population in other areas where Asian genetic variants were detected in red foxes.

Complete mitochondrial exploration of Echinococcus multilocularis from French alveolar echinococcosis patients

Alveolar echinococcosis (AE) is a parasitosis that is expanding worldwide, including in Europe. The development of genotypic markers is essential to follow its spatiotemporal evolution. Sequencing of the commonly used mitochondrial genes cob, cox1, and nad2 shows low discriminatory power, and analysis of the microsatellite marker EmsB does not allow nucleotide sequence analysis. We aimed to develop a new method for the genotyping of Echinococcus multilocularis based on whole mitochondrial genome (mitogenome) sequencing, to determine the genetic diversity among 30 human visceral samples from French patients, and compare this method with those currently in use. Sequencing of the whole mitochondrial genome was carried out after amplification by PCR, using one uniplex and two multiplex reactions to cover the 13,738 bp of the mitogenome, combined with Illumina technology. Thirty complete mitogenome sequences were obtained from AE lesions. One showed strong identity with Asian genotypes (99.98% identity) in a patient who had travelled to China. The other 29 mitogenomes could be differentiated into 13 haplotypes, showing higher haplotype and nucleotide diversity than when using the cob, cox1, and nad2 gene sequences alone. The mitochondrial genotyping data and EmsB profiles did not overlap, probably because one method uses the mitochondrial genome and the other the nuclear genome. The pairwise fixation index (F_st) value between individuals living inside and those living outside the endemic area was high (F_st = 0.222, P = 0.002). This is consistent with the hypothesis of an expansion from historical endemic areas to peripheral regions.

Past and Present of Diagnosis of Echinococcosis: A Review (1999-2021)

The larval forms of taeniid cestodes belonging to the genus Echinococcus are the source of the zoonotic infection known as echinococcosis. Alveolar and cystic echinococcosis are caused by Echinococcus multilocularis and Echinococcus granulosus (s. s) respectively. It is endemic in several regions of the world. In this systematic review, we describe diagnosis, and the species (human, canids, livestock, and small rodents) affected by cystic (CE) and alveolar echinococcosis (AE). From 1999 to 2021, we searched the online directory through PubMed, SCOPUS, Web of Science, and google scholar. Among the 37,700 records found in the online databases, 187 publications met our eligibility requirements. The majority of investigations employed a range of diagnostic methods, such as ELISA, imaging, copro-PCR, necropsy or arecoline hydrobromide purgation, morphological cestode confirmation, and fecal sieving/flotation to detect and confirm Echinococcus infection. ELISA was the most commonly used method followed by PCR, and imaging. The research team retrieved data describing the incidence or assessment of the diagnostic test for E. multilocularis in humans (N = 99), canids (N = 63), small ruminants (N = 13), large ruminants (N= 3), camel (N= 2), pigs (N=2) and small mammals (N= 5). This study was conducted to explore the diagnostic tools applied to detect echinococcosis in humans as well as animals in prevalent countries, and to report the characteristic of new diagnostic tests for disease surveillance. This systematic review revealed that ELISA (alone or in combination) was the most common method used for disease diagnosis and diagnostic efficacy and prevalence rate increased when recombinant antigens were used. It is highly recommended to use combination protcols such as serological with molecular and imaging technique to diagnose disease. Our study identified scarcity of data of reporting echinococcosis in humans/ animals in low-income or developing countries particularly central Asian countries. Study reports in small rodents indicate their role in disease dissemination but real situation in these host is not refected due to limited number of studies. Even though echinococcosis affects both public health and the domestic animal sector, therefore, it is important to devise new and strengthe implementation of the existing monitoring, judging, and control measures in this estimate.

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.

Assessment of the Genetic Diversity of Echinococcus multilocularis from Copro-Isolated Eggs

The genetic diversity of the parasite Echinococcus multilocularis, the infectious agent of alveolar echinococcosis, is generally assessed on adult worms after fox necropsy. We aimed to investigate E. multilocularis polymorphism through the microsatellite EmsB marker using a noninvasive approach. We tested batches of isolated eggs (1, 5, and 10) from 19 carnivore fecal samples collected in a rural town located in a highly endemic area in France to determine the best strategy to adopt using a minimal quantity of parasite DNA while avoiding genetic profile overlapping in the analysis. Several molecular controls were performed to formally identify the Taeniidae eggs. In total, 112 egg batches were isolated and 102 EmsB electrophoregrams were obtained in duplicate. Quality sorting was performed through the Pearson correlation coefficient (r) between each EmsB duplicate. Forty-nine batches with r > 0.9 remained in the analysis, mainly 5- or 10-egg batches. Three EmsB profiles were emphasized by hierarchical clustering and matched those from human lesions and adult worms previously genotyped and collected in the same area. We show that the genetic diversity of the parasite can be assessed from isolated E. multilocularis eggs in a spatiotemporal context using a noninvasive approach.

Low genetic variation in Echinococcus multilocularis from the Western Sichuan Plateau of China revealed by microsatellite and mitochondrial DNA markers

The prevalence of E. multilocularis is a major public health problem in China. To better understand the molecular epidemiology and evolutionary patterns of E. multilocularis, an adequate dataset regarding the genetic variance of this parasite is necessary. However, for now, available genetic data of E. multilocularis is still insufficient. In the study, the EmsB microsatellite and the partial mitochondrial cox1 gene were combined to investigate the genetic diversity of 64 E. multilocularis samples from human, dogs and voles. These samples were collected in the Western Sichuan Plateau, where the highest village-based human prevalence of alveolar echinococcosis was recorded worldwide. The aim of the study is to gather more informative genetic data of E. multilocularis in the areas, especially those obtained using the EmsB marker. The microsatellite analysis revealed 7 different EmsB profiles, 1 of which was found in 90.63% of the total samples collected from all 3 hosts. This major profile was identical to the one detected in the same area 16 years ago. The rest of the 6 profiles, each represented by only 1 isolate, did not correspond to any of the profiles previously reported. All the profiles detected in the study belonged to the Asian cluster. Meanwhile, according to sequence analysis of the 758 bp cox1 region, 4 haplotypes all assigned to the Asian clade were detected among the isolates. A star-like haplotype network was exhibited with a centrally positioned haplotype found in 93.75% of the samples. The overall haplotype and nucleotide diversities were both low. These findings provided evidence for a founder event or bottleneck and subsequent population expansion in E. multilocularis. The EmsB profiles were not fully consistent with the cox1 haplotypes. The same correspondence relationship was mainly observed in samples with the major profile P5 and the main haplotype EmHa1. A total of 54 isolates assigned to profile P5 were classified to the EmHa1 haplotype. In conclusion, both the microsatellite and mtDNA markers showed low variability within the Tibetan population of E. multilocularis. An EmsB profile and a cox1 haplotype were found to be predominant in the study area, which appears to remain steady for over a decade. The results reinforce the higher potential of the microsatellite DNA marker with high discriminative power to identify the very low genetic polymorphism of E. multilocularis than that of the partial cox1 sequencing. The data obtained in the study would be helpful to enlarge the data pool to further probe the possible origins and dispersal of E. multilocularis in China.

Hepatic Alveolar Echinococcosis

Hepatic alveolar echinococcosis (HAE) is a rare but severe zoonosis caused by the pseudotumoral intrahepatic development of the larval stage of the tapeworm Echinococcus multilocularis. HAE is present only in the Northern Hemisphere, predominantly in China. Currently, there is a significant resurgence of cases in historically endemic areas associated with emergence of HAE in countries not previously concerned. Today, in European countries, HAE is often discovered by chance; however, clinicians should be made aware of opportunistic infections that progressively emerged recently as a result of therapeutic or pathological immunosuppression. Ultrasonography is the key first-line diagnostic procedure, with specific serology providing confirmation in 95% of the cases. Albendazole, only parasitostatic, is the mainstay for treatment. Surgical resection, if feasible, is the gold standard for treatment, and more patients are currently eligible for this option because of an earlier diagnosis. The prognosis has considerably improved but remains poor in countries where access to care is less favorable.

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.

Extrahepatic alveolar echinococcus on multi-slice computed tomography and magnetic resonance imaging

Alveolar echinococcus (AE) is a severe health problem in endemic areas. In recent years, the incidence of this disease in China has been increasing. The study was designed to illustrate the multi-slice computed tomography (MSCT) and magnetic resonance imaging (MRI) features of extrahepatic AE. A cohort of 33 patients who suffered from extrahepatic AE was enrolled consecutively from January 2012 to December 2017. The MSCT and MRI features of extrahepatic AE were recorded and analyzed by experienced radiologists. All cases secondary to hepatic AE, except two primary extrahepatic AE, were found in this study. Locations of extrahepatic AE included 19 (57.6%) lung, 10 (30.3%) adrenal gland, 9 (27.3%) brain, 5 (15.2%) peritoneal cavity, 5 (15.2%) spleen, 4 (12.1%) diaphragm, 3 (9.1%) kidney, 3 (9.1%) retroperitoneal, and 2 (6.1%) vertebra; Involvement of 1 (3.0%) heart, 1 (3.0%) mediastinum, 1 (3.0%) muscle, and 1 (3.0%) pancreas was rare. AE of the lung usually appeared as irregular and scattered nodules with small vacuoles or cavities inside and peripheral distribution. Multiple cerebral nodules with calcification and surrounding edema were the most common features seen in brain AE. Adrenal gland AE presented as plaques containing different sizes of hypodense areas and different amounts of calcification. Injection of contrast medium showed no enhancement of lesions except in the brain. MSCT and MRI are reliable imaging methods for the diagnosis of extrahepatic AE. When one AE patient is clinically confirmed, MSCT scan from the chest to the abdomen should be performed to exclude other organs AE.

Unravelling the genetic diversity and relatedness of Echinococcus multilocularis isolates in Eurasia using the EmsB microsatellite nuclear marker

The cestode Echinococcus multilocularis is the causative agent of alveolar echinococcosis, a severe helminthic zoonotic disease distributed in the Northern Hemisphere. The lifecycle of the parasite is mainly sylvatic, involving canid and rodent hosts. The absence of genetic data from most eastern European countries is a major knowledge gap, affecting the study of associations with parasite populations in Western Europe. In this study, EmsB microsatellite genotyping of E. multilocularis was performed to describe the genetic diversity and relatedness of 785 E. multilocularis isolates from four western and nine eastern European countries, as well as from Armenia and the Asian parts of Russia and Turkey. The presence of the same E. multilocularis populations in the Benelux resulting from expansion from the historical Alpine focus can be deduced from the main profiles shared between these countries. All 33 EmsB profiles obtained from 528 samples from the nine eastern European countries belonged to the European clade, except one Asian profile form Ryazan Oblast, Russia. The expansion of E. multilocularis seems to have progressed from the historical Alpine focus through Hungary, Slovakia, the Czech Republic and southern Poland towards Latvia and Estonia. Most of the samples from Asia belong to the Asian clade, with one EmsB profile shared between Armenia and Turkey, and two between Turkey and Russia. However, two European profiles were described from two foxes in Turkey, including one harboring worms from both European and Asian clades. Three EmsB profiles from three Russian samples were associated with the Arctic clade. Two E. multilocularis profiles from rodents from Lake Baikal belonged to the Mongolian clade, described for the first time here using EmsB. Further worldwide studies on the genetic diversity of E. multilocularis using both mitochondrial sequencing and EmsB genotyping are needed to understand the distribution and expansion of the various clades.

Echinococcus multilocularis genetic diversity in Swiss domestic pigs assessed by EmsB microsatellite analyzes

Assessing the genetic diversity of the parasite Echinococcus multilocularis provides key information about the temporal and spatial strain flow in a given area. Previous studies indicated that a historical endemic area conventionally presents a relatively high genetic diversity, whereas peripheral or newly endemic areas exhibit a more restricted variability of the parasite. The Swiss plateau region is part of the European historically endemic area, and the genetic diversity has already been investigated by assessing either human metacestode isolates or adult worms from foxes. To date, there have been no studies covering the whole geographical area affected by the parasite. The aim of the present study was to make use of the domestic pig to investigate the genetic diversity of E. multilocularis in relation to spatial distribution. A total of 55 E. multilocularis-induced hepatic lesions from slaughtered pigs from Switzerland were studied using EmsB microsatellite analyzes, and findings were compared to already published data (originating from human, primate, foxes, and rodent samples). A total of 12 EmsB profiles were described among the domestic pigs, some of them presenting a clear spatial organization in the Swiss plateau, with three of the main profiles geographically separated. One of the 12 EmsB profiles has been newly identified for Switzerland in this study, while the other 11 profiles had been previously described in other Swiss E. multilocularis isolates from other hosts. Overall, a total of 18 EmsB profiles have so far been described within the Swiss endemic area. Six profiles appeared only among human, primate, rodent, and fox samples. Based on a richness and diversity accumulation analysis, the sampling efficiency for the whole studied area has now been improved considerably by compilation of 178 E. multilocularis specimens obtained from four different intermediate and one definitive host species in Switzerland.

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.