Phylogeography of Ascaris lumbricoides and A. suum from China

Abstract

In order to obtain further understanding of genetic structure and evolutionary relationship of Ascaris from humans and pigs, phylogeography study on 12 populations from six endemic regions in China was conducted using mitochondrial DNA markers (cytochrome c oxidase subunit 1 (COX1) and NAD1) and the software programs of DnaSP 5.0, Arlequin 3.0, MEGA 4.0, and NETWORK 4.5.1.6. Results showed that (a) genetic diversity of Ascaris varied with hosts and locations, but no distinct geographical distribution pattern was found, (b) a higher level of genetic diversity and differentiation was found in pig-derived populations in contrast to human-derived ones, and in populations of human-derived Ascaris from the southern regions in comparison to that from the middle and northern locations, but similar geographical difference was not observed within pig-derived populations, (c) historical population expanding was detected from a large part of human-derived Ascaris populations but not in pig-derived Ascaris, (d) a high level of gene flow was detected between human- and pig-derived Ascaris and also among human-derived populations, and (e) network analysis from haplotype of COX1 indicated an ancestral haplotype from human-derived Ascaris. In conclusion, the present study revealed new information on Ascaris on the aspects of genetic diversity, population differentiation and historical demographic patterns, gene flow, phylogenesis reconstruction, and haplotype network, discussed the results with historical demographic migration of humans and domestication of wild boar in China, and raised a different assumption about the evolutionary relationship of the two roundworms. This study should have certain enlightenment for the epidemiology and the evolutionary and taxonomy relationship of Ascaris from humans and pigs.

Comparative analyses of the complete mitochondrial genomes of Ascaris lumbricoides and Ascaris suum from humans and pigs

“…A series of recent studies employing a large number of Ascaris individuals from humans and pigs from different endemic regions in China using ITS-1 and cox1 and nad1 datasets have demonstrated the existence of 5 different genotypes in human-and pigderived worms, with high level gene flow between Ascaris of humans and that of pigs, as well as among the human-derived Ascaris populations (Peng et al, 2003(Peng et al, , 2005(Peng et al, , 2007Zhou et al, 2011), which also provided some support to our proposal that A. lumbricoides and A. suum represent a single species.…”

“…Most metazoans have a compact, circular mitochondrial genome which is approximately 14 to 20 kb in length (Boore, 1999). mtDNA sequences have been extensively used as genetic markers not only for studying population or ecological genetics, but also for phylogenetic, phylogeographical and evolutionary analyses, due to its conservation in protein-coding sequences, rapid evolutionary rate, and lack of genetic recombination (eg., Lei et al, 2010;Lin et al, 2011;Xie et al, 2011;Zhou et al, 2011). Comparison of complete mitochondrial sequences can reveal information about gene order and its variation, as well as gene and genome evolution (Meganathan et al, 2011;Uda et al, 2011).…”

Assessing the zoonotic potential ofAscaris suumandTrichuris suis: looking to the future from an analysis of the past

“…Sequence analysis of the cox1 gene (mitochondrial) indicates that Ascaris does not assort into two different monophyletic groups based on host origin, but instead splits into three or more groups, all but one of which include worms from both hosts (Nejsum et al, 2010;Betson et al, 2011;Zhou et al, 2011). This likewise suggests a complex evolutionary history and might be the reason why a single diagnostic marker is presently hard or impossible to find, which is further supported by the recent published complete mitochondrial DNA (mtDNA) genomes of A. suum and A. lumbricoides (Liu et al, 2012a).…”

The Intestinal Expulsion of the Roundworm Ascaris suum Is Associated with Eosinophils, Intra-Epithelial T Cells and Decreased Intestinal Transit Time

“…Because of the identical life cycle, the high genetic similarity between these parasites [3], and because A. suum is a zoonosis [4], [5], A. suum infections in pigs make an ideal model for A. lumbricoides infections in humans. Cross infections and gene flow between the 2 species also occurs [6], [7], which led to the debate whether or not they belong to the same species [8], [9].…”