Background: The taxonomic distinctiveness of Ascaris lumbricoides and A. suum, two of the world's most significant nematodes, still represents a much-debated scientific issue. Previous studies have described two different scenarios in transmission patterns, explained by two hypotheses: (1) separated host-specific transmission cycles in highly endemic regions, (2) a single pool of infection shared by humans and pigs in non-endemic regions. Recently, A. suum has been suggested as an important cause of human ascariasis in endemic areas such as China, where cross-infections and hybridization have also been reported. The main aims of the present study were to investigate the molecular epidemiology of human and pig Ascaris from non-endemic regions and, with reference to existing data, to infer the phylogenetic and phylogeographic relationships among the samples. Methodology: 151 Ascaris worms from pigs and humans were characterized using PCR-RFLP on nuclear ITS rDNA. Representative geographical sub-samples were also analysed by sequencing a portion of the mitochondrial cox1 gene, to infer the extent of variability at population level. Sequence data were compared to GenBank sequences from endemic and non-endemic regions. Principal Findings: No fixed differences between human and pig Ascaris were evident, with the exception of the Slovak population, which displays significant genetic differentiation. The RFLP analysis confirmed pig as a source of human infection in non-endemic regions and as a corridor for the promulgation of hybrid genotypes. Epidemiology and host-affiliation seem not to be relevant in shaping molecular variance. Phylogenetic and phylogeographical analyses described a complex scenario, involving multiple hosts, sporadic contact between forms and an ancestral taxon referable to A. suum. Conclusions/Significance: These results suggest the existence of homogenizing gene flow between the two taxa, which appear to be variants of a single polytypic species. This conclusion has implications on the systematics, transmission and control programs relating to ascariasis.

Phylogeographical Studies of Ascaris spp. Based on Ribosomal and Mitochondrial DNA Sequences / Cavallero, Serena; Viliam, Snabel; Francesca, Pacella; Vitantonio, Perrone; D'Amelio, Stefano. - In: PLOS NEGLECTED TROPICAL DISEASES. - ISSN 1935-2735. - ELETTRONICO. - 7:4(2013), p. e2170. [10.1371/journal.pntd.0002170]

Phylogeographical Studies of Ascaris spp. Based on Ribosomal and Mitochondrial DNA Sequences

CAVALLERO, Serena;D'AMELIO, Stefano
2013

Abstract

Background: The taxonomic distinctiveness of Ascaris lumbricoides and A. suum, two of the world's most significant nematodes, still represents a much-debated scientific issue. Previous studies have described two different scenarios in transmission patterns, explained by two hypotheses: (1) separated host-specific transmission cycles in highly endemic regions, (2) a single pool of infection shared by humans and pigs in non-endemic regions. Recently, A. suum has been suggested as an important cause of human ascariasis in endemic areas such as China, where cross-infections and hybridization have also been reported. The main aims of the present study were to investigate the molecular epidemiology of human and pig Ascaris from non-endemic regions and, with reference to existing data, to infer the phylogenetic and phylogeographic relationships among the samples. Methodology: 151 Ascaris worms from pigs and humans were characterized using PCR-RFLP on nuclear ITS rDNA. Representative geographical sub-samples were also analysed by sequencing a portion of the mitochondrial cox1 gene, to infer the extent of variability at population level. Sequence data were compared to GenBank sequences from endemic and non-endemic regions. Principal Findings: No fixed differences between human and pig Ascaris were evident, with the exception of the Slovak population, which displays significant genetic differentiation. The RFLP analysis confirmed pig as a source of human infection in non-endemic regions and as a corridor for the promulgation of hybrid genotypes. Epidemiology and host-affiliation seem not to be relevant in shaping molecular variance. Phylogenetic and phylogeographical analyses described a complex scenario, involving multiple hosts, sporadic contact between forms and an ancestral taxon referable to A. suum. Conclusions/Significance: These results suggest the existence of homogenizing gene flow between the two taxa, which appear to be variants of a single polytypic species. This conclusion has implications on the systematics, transmission and control programs relating to ascariasis.
2013
01 Pubblicazione su rivista::01a Articolo in rivista
Phylogeographical Studies of Ascaris spp. Based on Ribosomal and Mitochondrial DNA Sequences / Cavallero, Serena; Viliam, Snabel; Francesca, Pacella; Vitantonio, Perrone; D'Amelio, Stefano. - In: PLOS NEGLECTED TROPICAL DISEASES. - ISSN 1935-2735. - ELETTRONICO. - 7:4(2013), p. e2170. [10.1371/journal.pntd.0002170]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/514870
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