New mitogenome and nuclear evidence on the phylogeny and taxonomy of the highly zoonotic tapeworm Echinococcus granulosus sensu stricto

Abstract

Cystic echinococcosis, a zoonotic disease caused by Echinococcus granulosus sensu lato (s. l.), is a significant global public health concern. Echinococcus granulosus s. l. is currently divided into numerous genotypes (G1-G8 and G10) of which G1-G3 are the most frequently implicated genotypes in human infections. Although it has been suggested that G1-G3 could be regarded as a distinct species E. granulosus sensu stricto (s. s.), the evidence to support this is inconclusive. Most importantly, data from nuclear DNA that provide means to investigate the exchange of genetic material between G1-G3 is lacking as none of the published nuclear DNA studies have explicitly included G2 or G3. Moreover, the commonly used relatively short mtDNA sequences, including the complete cox1 gene, have not allowed unequivocal differentiation of genotypes G1-G3. Therefore, significantly longer mtDNA sequences are required to distinguish these genotypes with confidence. The main aim of this study was to evaluate the phylogenetic relations and taxonomy of genotypes G1-G3 using sequences of nearly complete mitogenomes (11,443bp) and three nuclear loci (2984bp). A total of 23 G1-G3 samples were analysed, originating from 5 intermediate host species in 10 countries. The mtDNA data demonstrate that genotypes G1 and G3 are distinct mitochondrial genotypes (separated by 37 mutations), whereas G2 is not a separate genotype or even a monophyletic cluster, but belongs to G3. Nuclear data revealed no genetic separation of G1 and G3, suggesting that these genotypes form a single species due to ongoing gene flow. We conclude that: (a) in the taxonomic sense, genotypes G1 and G3 can be treated as a single species E. granulosus s. s.; (b) genotypes G1 and G3 should be regarded as distinct genotypes only in the context of mitochondrial data; (c) we recommend excluding G2 from the genotype list.

The echinococcoses: the present situation and genotypes differentiation (review)

“…Третійаналіз повного геному [39]. Останній підхідце порівняння мітохондріальної (гаплоїдної) та ядерної (диплоїдної) ДНК дискордантності для гібридизації видів, що застосовується для визначення генотипів Е. canadensis G6/7, G8 і G10 [26] та E. granulosus s. s. G1, G2 і G3 [40]. На рисунку 2 представлено розподіл 6 видів Echinococcus, виявлених у Північній півкулі, а також трьох додаткових видів, зареєстрованих в Африці та Південній Америці.…”

Species detection within the Echinococcus granulosus sensu lato complex by novel probe-based Real-Time PCRs

“…complex, while others are retained as genotypes within some of these species. Thus, E. granulosus sensu stricto (s.s.) is composed of genotypes G1 and G3, while G2 is no longer considered a distinct genotype [10]. In addition, the G1-G3 cluster includes other closely related haplotypes, which -depending on the de nition -may or may not belong to these genotypes.…”

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

“…The complex is considered to include genotypes G1-G8, G10 encompassing at least four species currently recognized (E. granulosus sensu stricto, E. equinus, E. ortleppi, E. canadensis), and E. felidis . Recently, genotype G2 of E. granulosus s.s. was recommended to be deleted from the genotype list based on the complex mitogenome and nuclear evidence (Kinkar et al, 2017). According to the latest records, the known range of E. multilocularis has markedly extended across Europe and it is assumed to be currently distributed over the most of its territory.…”