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
Teivi Laurimäe, Liina Kinkar, Epp Moks, Thomas Romig, Rihab A. Omer, Adriano Casulli, Gérald Umhang, Guna Bagrade, Malik Irshadullah, Mitra Sharbatkhori, Hossein Mirhendi, Francisco Ponce-Gordo, Silvia V. Soriano, Antonio Varcasia, Mohammad Rostami-Nejad, Vanessa Andresiuk, Urmas Saarma
Journal: Parasitology / Volume 145 / Issue 14 / December 2018
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.
Genetic diversity and phylogeography of the elusive, but epidemiologically important Echinococcus granulosus sensu stricto genotype G3
Liina Kinkar, Teivi Laurimäe, Ibrahim Balkaya, Adriano Casulli, Houria Zait, Malik Irshadullah, Mitra Sharbatkhori, Hossein Mirhendi, Mohammad Rostami-Nejad, Francisco Ponce-Gordo, Steffen Rehbein, Eshrat Beigom Kia, Sami Simsek, Viliam Šnábel, Gérald Umhang, Antonio Varcasia, Urmas Saarma
Journal: Parasitology / Volume 145 / Issue 12 / October 2018
Published online by Cambridge University Press: 17 April 2018, pp. 1613-1622
Cystic echinococcosis (CE) is a severe parasitic disease caused by the species complex Echinococcus granulosus sensu lato. Human infections are most commonly associated with E. granulosus sensu stricto (s.s.), comprising genotypes G1 and G3. The objective of the current study was to provide first insight into the genetic diversity and phylogeography of genotype G3. Despite the epidemiological importance of the genotype, it has remained poorly explored due to the ambiguity in the definition of the genotype. However, it was recently demonstrated that long sequences of mitochondrial DNA (mtDNA) provide a reliable method to discriminate G1 and G3 from each other. Therefore, we sequenced near-complete mtDNA of 39 G3 samples, covering most of the known distribution range and host spectra of the genotype. The phylogenetic network revealed high genetic variation within E. granulosus s.s. G3 and while G3 is significantly less prevalent worldwide than G1, the genetic diversity of both of the genotypes is equally high. We also present the results of the Bayesian phylogeographic analysis, which yielded several well-supported diffusion routes of genotype G3 originating from Turkey and Iran, suggesting the Middle East as the origin of the genotype.