Mitochondrial genetic diversity and phylogenetic relationships of Echinococcus multilocularis in Europe

The cestode Echinococcus multilocularis is the causative agent of alveolar echinococcosis, a fatal zoonotic parasitic disease of the northern hemisphere. Red foxes are the main reservoir hosts and, likely, the main drivers of the geographic spread of the disease in Europe. Knowledge of genetic relationships among E. multilocularis isolates at a European scale is key to understanding the dispersal characteristics of E. multilocularis. Hence, the present study aimed to describe the genetic diversity of E. multilocularis isolates obtained from different host species in 19 European countries. Based on the analysis of complete nucleotide sequences of the cob, atp6, nad2, nad1 and cox1 mitochondrial genes (4,968 bp), 43 haplotypes were inferred. Four haplotypes represented 62.56 % of the examined isolates (142/227), and one of these four haplotypes was found in each country investigated, except Svalbard, Norway. While the haplotypes from Svalbard were markedly different from all the others, mainland Europe appeared to be dominated by two main clusters, represented by most western, central and eastern European countries, and the Baltic countries and northeastern Poland, respectively. Moreover, one Asian-like haplotype was identified in Latvia and northeastern Poland. To better elucidate the presence of Asian genetic variants of E. multilocularis in Europe, and to obtain a more comprehensive Europe-wide coverage, further studies, including samples from endemic regions not investigated in the present study, especially some eastern European countries, are needed. Further, the present work proposes historical causes that may have contributed to shaping the current genetic variability of E. multilocularis in Europe.

Human alveolar echinococcosis in Slovakia: Epidemiology and genetic diversity of Echinococcus multilocularis, 2000-2023

Human alveolar echinococcosis (AE) is a serious parasitic disease caused by larval stages of Echinococcus multilocularis. Between January 2000 and October 2023, 137 AE cases were confirmed in Slovakia. The average annual incidence increased from 0.031 per 100,000 inhabitants between 2000 and 2011, to an average of 0.187 since 2012, i.e. about six times. Among patients, 45.3% were men and 54.7% were women; the mean age at the time of diagnosis was 52.8 years. Most cases were diagnosed in the age groups 51-60 years and 61-70 years (33 cases each), and eight patients fell into the age category ≤ 20 years. To better recognize the gene diversity in clinical samples, metacestodes from 21 patients collected between 2013 and 2021 were subjected to DNA sequencing of four mitochondrial genes. Using concatenated sequences of cob (603 bp), nad2 (882 bp) and cox1 (789 bp) gene fragments, 14 isolates (66.7%) were assigned to the European E5 profile of E. multilocularis, two isolates (9.5%) to the E5a subtype, four isolates (19%) to the E4 profile, and one isolate (4.8%) to haplogroup E1/E2. The E5-type profiles and E4 profiles were distributed throughout the country, whereas the E1/E2 profile was found in the patient from western Slovakia. According to the data obtained and GenBank sequences, the E5-type dispersal is so far limited to central-eastern Europe and the variant seems to be indigenous to that region. The admixture with the haplotypes E4 and E1/E2 could have taken place from a historical endemic focus during the fox expansion in the last decades. By employing the nad1 fragment, a typical European haplotype was observed in all 21 resolved Slovak samples. The acceleration in the AE incidence in the last decade suggests the emergence of the disease and the need for further research on human and animal isolates.

Neglected Diseases—Parasitic Infections among Slovakian Children from Different Populations and Genotypes of Giardia duodenalis

Children are most prone to parasitic infections. The objectives of the study were to examine the occurrence of parasitic infections in children from different populations and to perform molecular characterization of human Giardia duodenalis isolates. We examined 631 stool samples from Roma and non-Roma children for the presence of parasitic developmental stages. Samples were collected from three eastern Slovakia districts. The ages of the children ranged from 1 months to 17 years. Subsequently, the molecular characterization of human G. duodenalis isolates by PCR detected triosephosphate isomerase (tpi) and beta-giardin (bg) genes was performed. The overall prevalence of parasitic infection was 19.8%. Ascaris lumbricoides eggs were the most frequent, with an occurrence of about 13.8%. G. duodenalis cysts were present in 6.3% of samples. G. duodenalis isolates obtained from 13 children were subjected to DNA sequencing with tpi and bg genes. Five isolates were categorized as bearing subassemblage BIII, the three isolates as subassemblage BIV, one person was infected with a mixture of subassemblages BIII and BIV, four children had subassemblage AII, and one isolate revealed a structure corresponding with subassemblage AI. Our work is proof that poverty and poor hygiene contribute the most to public health problems associated with neglected parasitic diseases.

The occurence of endoparasites in Slovakian household dogs and cats

Pets play a pivotal role as definitive or reservoir hosts for many zoonotic parasites. Dogs and cats without any clinical signs may be a carrier for the infection. In a one-year study, collected fecal samples of 257 dogs and 50 cats were examined coproscopically for endoparasite infections. Out of 307 investigated fecal samples, 107 (34.9%) were positive for the presence of the propagative stages of endoparasites In 257 dogs fecal samples, following 12 different species of endoparasites were detected: Giardia duodenalis, Cystoisospora spp., Sarcocystis spp., Hammondia/Neospora-like eggs, Angiostrongylus vasorum larvae, Capillaria aerophila, Crenosoma vulpis, Toxocara spp., Toxascaris leonina, Trichuris vulpis, Strongyloides stercoralis, and eggs from the family Ancylostomatidae. Only 4 different parasitic species were found in 50 domestic cat fecal samples - G. duodenalis cysts Cystoisospora spp., T. cati, and larvae of Aelurostrongylus abstrusus. It was confirmed that significant differences were found concerning age for G. duodenalis, T. canis, S. stercoralis, and family Ancylostomatidae. Close and frequent contact between pets and people increases the risks for the transmission of zoonotic diseases.

On the geographic genetic variants of the cestode Echinococcus multilocularis with reference to the original descriptions from Bowles et al. (1992) and Bowles and McManus (1993), and their use

Alveolar echinococcosis, caused by the larval stages of the tapeworm Echinococcus multilocularis (Leuckart, 1863), is of increasing concern in the northern hemisphere. Most cases of alveolar echinococcosis (excluding Alaska) appear to be linked with European and Asian genotypes that highlight the need for a more precise delimiting of their actual distribution and tracing historical episodes of their translocations and introductions into new areas. We have herein summarized previous available research studies, which mentioned firstly described geographic M1/M2 variants of E. multilocularis using molecular tools (established by sequencing of mitochondrial genes cox1, 366 bp and nad1, 471 bp), in an attempt to consolidate their correct affiliations with the geographic origin in sense of the original description from the early 1990´s. Since 2009, inverted designations (M1 named as M2 and vice versa) are being prevailing in research literature (we found ten erroneous vs. three correct classifications) that might bias genetic interpretation of comparative data in specific cases. When comparing M1/M2 profiles to those obtained from mitochondrial evidences over the last decades, the phylogenetic analysis revealed that the M1 strain (originally described from China, Alaska, North America) grouped with the Asian clade of E. multilocularis more recently established, whereas the M2 strain (described from the German vole) had a specific structure, in cox1 clustering with the North American clade. It is presumed that events of intercontinental expansion and isolation covering glacial and interglacial periods during the late Pleistocene have likely accounted for the transmission of this discrete genotype from Beringia into endemic area of western and central Europe via circumpolar movements of foxes.

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.

Distinguishing Echinococcus granulosus sensu stricto genotypes G1 and G3 with confidence: A practical guide

Cystic echinococcosis (CE), a zoonotic disease caused by tapeworms of the species complex Echinococcus granulosus sensu lato, represents a substantial global health and economic burden. Within this complex, E. granulosus sensu stricto (genotypes G1 and G3) is the most frequent causative agent of human CE. Currently, there is no fully reliable method for assigning samples to genotypes G1 and G3, as the commonly used mitochondrial cox1 and nad1 genes are not sufficiently consistent for the identification and differentiation of these genotypes. Thus, a new genetic assay is required for the accurate assignment of G1 and G3. Here we use a large dataset of near-complete mtDNA sequences (n = 303) to reveal the extent of genetic variation of G1 and G3 on a broad geographical scale and to identify reliable informative positions for G1 and G3. Based on extensive sampling and sequencing data, we developed a new method, that is simple and cost-effective, to designate samples to genotypes G1 and G3. We found that the nad5 is the best gene in mtDNA to differentiate between G1 and G3, and developed new primers for the analysis. Our results also highlight problems related to the commonly used cox1 and nad1. To guarantee consistent identification of G1 and G3, we suggest using the sequencing of the nad5 gene region (680 bp). This region contains six informative positions within a relatively short fragment of the mtDNA, allowing the differentiation of G1 and G3 with confidence. Our method offers clear advantages over the previous ones, providing a significantly more consistent means to distinguish G1 and G3 than the commonly used cox1 and nad1.

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.

Global phylogeography and genetic diversity of the zoonotic tapeworm Echinococcus granulosus sensu stricto genotype G1

Echinococcus granulosus sensu stricto (s.s.) is the major cause of human cystic echinococcosis worldwide and is listed among the most severe parasitic diseases of humans. To date, numerous studies have investigated the genetic diversity and population structure of E. granulosus s.s. in various geographic regions. However, there has been no global study. Recently, using mitochondrial DNA, it was shown that E. granulosus s.s. G1 and G3 are distinct genotypes, but a larger dataset is required to confirm the distinction of these genotypes. The objectives of this study were to: (i) investigate the distinction of genotypes G1 and G3 using a large global dataset; and (ii) analyse the genetic diversity and phylogeography of genotype G1 on a global scale using near-complete mitogenome sequences. For this study, 222 globally distributed E. granulosus s.s. samples were used, of which 212 belonged to genotype G1 and 10 to G3. Using a total sequence length of 11,682 bp, we inferred phylogenetic networks for three datasets: E. granulosus s.s. (n = 222), G1 (n = 212) and human G1 samples (n = 41). In addition, the Bayesian phylogenetic and phylogeographic analyses were performed. The latter yielded several strongly supported diffusion routes of genotype G1 originating from Turkey, Tunisia and Argentina. We conclude that: (i) using a considerably larger dataset than employed previously, E. granulosus s.s. G1 and G3 are indeed distinct mitochondrial genotypes; (ii) the genetic diversity of E. granulosus s.s. G1 is high globally, with lower values in South America; and (iii) the complex phylogeographic patterns emerging from the phylogenetic and geographic analyses suggest that the current distribution of genotype G1 has been shaped by intensive animal trade.

A frequent roundworm Baylisascaris transfuga in overpopulated brown bears (Ursus arctos) in Slovakia: a problem worthy of attention

The genus Baylisascaris (order Ascaridida) includes numerous relatively host-specific nematodes, which are common in intestines of wild mammals. Some of them may have impact on veterinary and public health, as their larvae have the potential to cause visceral, ocular, and/or neural larva migrans in a wide range of mammals, birds, and humans. Baylisascaris transfuga is a parasite occurring in a range of bear species throughout the world. We present the current data on B. transfuga occurrence in brown bears from a relatively restricted territory of the Poľana Protected Landscape Area in Central Slovakia, obtained by traditional methods (faecal examination, morphology). Species affiliation was confirmed by employing molecular markers generating nuclear 28S and mitochondrial cox1 sequences in adult worms. Based on 17 examined samples (15 excrements and two intestines of young bear females), the occurrence of B. transfuga in the surveyed area was assessed as 52.9%. Both bear females were infected with adult and juvenile worms. Due to the high density of bears in the locality, the high infection rate with ascarids, and the huge number of eggs produced by the parasites, it is apparent that the respective environment, including the inhabited areas, might be markedly contaminated by Baylisascaris eggs. The ability of B. transfuga to serve as a zoonotic agent has not been unambiguously proved; however, this attribute should be considered and subjected to further research.

Cystic echinococcosis in Poland: genetic variability and the first record of Echinococcus granulosus sensu stricto (G1 genotype) in the country

Cystic echinococcosis is one of the most important zoonotic diseases affecting humans and livestock worldwide, and is endemic in Poland. A set of six isolates on larval stages of Echinococcus granulosus sensu lato tapeworms collected from three humans, two pigs and one sheep from Polish foci of CE was examined by DNA sequencing of two mitochondrial genes (cox1, rrnS). The results demonstrated the presence of E. canadensis and E. granulosus sensu stricto in the investigated hydatid cysts. The former species was found in all five isolates from pigs and humans derived from central Poland. In a sheep hydatid cyst originating from Lesser Poland Voivodeship in southern Poland, E. granulosus s. s. (G1 genotype) was identified. This is the first report of an unambiguously autochthonous infection with E. granulosus s. s. in Poland. The global distribution and host affiliations of the commonly occurring G1 microvariant with nucleotide change 56C/T in cox1, detected here in Polish sheep, are discussed. The finding that sheep harboured E. granulosus s. s. may have important consequences for developing effective hydatid control programmes in Poland due to its longer maturation rate in dogs compared with E. canadensis G7. This may lead to greater expenditures for purchasing anthelmintics to provide an appropriate dosing regime in sheep-raising areas of the country.

Genetic survey of alveolar and cystic echinococcoses in Romania: first molecular evidence of Echinococcus multilocularis in humans in the country

Cystic echinococcosis (CE) and alveolar echinococcosis (AE) are considered as one of the most important zoonotic diseases in Romania, where they are subject to mandatory reporting. To obtain more knowledge about the genetic diversity of Echinococcus causative agents of these diseases, 11 isolates from humans and ungulate intermediate hosts from the two regions of Romania were genotyped using mitochondrial markers. In clinical samples of five patients from north-eastern Romania (Iasi, Botosani, Vaslui counties), Echinococcus multilocularis was identified as causal agent by cox1 sequence analysis. To the best of our knowledge this finding presents the first molecular evidence of E. multilocularis in humans from Romania. Only two cases of AE in patients were previously documented in the country by serological methods. In our four patients the most widespread European variant E5 of E. multilocularis was recorded, whereas in isolate from Vaslui county three nucleotide substitutions were detected as compared to the most related E5 haplotype. One of these mutations (411T/G) matched N1 and N2 haplotypes described previously from North America. In six CE samples retrieved from western Romania (Caras-Severin and Timis counties), two human isolates were diagnosed as Echinococcus canadensis G7, one as E. granulosus s.s. G1 and one as E. granulosus s.s. G3 using atp6 and rrnS sequencing. In ungulates, the cattle isolate was allocated to E. granulosus s.s. G1 and pig isolate to E. canadensis G7. The two G7 findings in humans reinforced the recent view that G7 was underestimated as compared to the E. granulosus s.s. regarding human CE threat that can be further employed for identifying sources of infections and establishing suitable preventive measures.

A molecular survey of Echinococcus granulosus sensu lato in central-eastern Europe

Central-eastern Europe is an endemic region for cystic echinococcosis where multiple species of intermediate hosts are commonly infected with Echinococcus granulosus sensu lato tapeworms of major medical and veterinary importance. Investigations of the genetic variation of 25 Echinococcus isolates from five countries (Slovakia, Romania, Ukraine, Hungary, Poland) were undertaken using three mitochondrial DNA markers. The 18 isolates from pigs derived from Slovakia and Ukraine and the four human isolates from Slovakia, Poland and Ukraine were identified as E. canadensis G 7, whereas the three human isolates from Romania and Hungary were classified as E. granulosus sensu stricto G1. This study reports the first confirmed human case of E. granulosus s.s. in Hungary. The haplotype G7A with two polymorphic sites relative to the most common regional variant of E. canadensis G7 was recorded in both pigs from Ukraine and in a single pig isolate from Slovakia. The results of this study support the circumstantial evidence that E. canadensis G7 with low infectivity for humans is highly prevalent in the northern parts of the region (Poland, Slovakia, forest-steppe zone of Ukraine), while infections with E. granulosus s.s. which are highly infectious for humans are more commonly encountered in Romania and Hungary.

Molecular identification of Heterakis spumosa obtained from brown rats (Rattus norvegicus) in Japan and its infectivity in experimental mice

Heterakis spumosa is a nematode of invasive rodents, mainly affiliated with Rattus spp. of Asian origin. Despite the ecological importance and cosmopolitan distribution, little information is available on the genetic characteristics and infectivity to experimental animals of this roundworm. Heterakis isolates obtained from naturally infected brown rats caught in 2007 in the city of Sagamihara, east central Honshu, Japan, and maintained by laboratory passages were subjected to mitochondrial sequence analysis and experimental infection in mice. Sequencing of the cox1 gene revealed that nucleotides of H. spumosa and previously examined Heterakis isolonche isolates from gallinaceous birds in Japan differed by 11.2-12.2% that conforms to the range expected for interspecific differences. The two H. spumosa isolates differed by a single 138T/C non-synonymous substitution in the 393-bp mt sequence. In a dendrogram, the H. spumosa samples formed a subcluster with members of the nematode superfamily Heterakoidea, H. isolonche and Ascaridia galli. In an experimental infection study, ICR, AKR, B10.BR and C57BL/6 mice strains were inoculated with 200 H. spumosa eggs/head and necropsied at 14 and 90 days post-inoculation (DPI) when the number of worms was recorded. Eggs were initially detected in faeces from 32-35 DPI in ICR, AKR and B10.BR mice and the highest mean number of eggs per gram of faeces (EPG) was 4,800 at 38 DPI, 2,200 at 58 DPI and 800 at 44 and 72 DPI in ICR, AKR and B10.BR mice, respectively. No eggs were observed in faeces of the C57BL/6 mouse strain during the experiment. A similar number of juvenile worms were isolated from all mouse strains at 14 DPI, whereas no adult worms were detected in C57BL/6 mice at 90 DPI.

A comparative study of the fish parasites Proteocephalus exiguus and P. percae (Cestoda: Proteocephalidae): morphology, isoenzymes, and karyotype

The two closely related cestodes Proteocephalus exiguus (= P. neglectus) and P. percae, parasites of coregonid and salmonid fishes and of perch, respectively, were compared using morphological, biochemical, and cytogenetic methods. Three morphological forms of similar appearance were observed in both P. exiguus and P. percae. Although the two species were strikingly similar in general morphological appearance, some of the features analyzed morphometrically (width of scolex, diameter of apical organ, length and width of hermaphroditic proglottis, length of cirrus sac) exhibited consistent differences. Fixed genetic differences distinguish the species at five loci in EST, GOT, and PGM enzymes. Nei's interspecific genetic distance was 0.305. Both species have 18 chromosomes with comparable absolute lengths. However, the morphology of most chromosome pairs differed. On the basis of these results, discriminative characteristics for P. exiguus and P. percae are given.