DNA-Sequence Variation Among Schistosoma mekongi Populations and Related Taxa; Phylogeography and the Current Distribution of Asian Schistosomiasis

Abstract

BackgroundSchistosomiasis in humans along the lower Mekong River has proven a persistent public health problem in the region. The causative agent is the parasite Schistosoma mekongi (Trematoda: Digenea). A new transmission focus is reported, as well as the first study of genetic variation among S. mekongi populations. The aim is to confirm the identity of the species involved at each known focus of Mekong schistosomiasis transmission, to examine historical relationships among the populations and related taxa, and to provide data for use (a priori) in further studies of the origins, radiation, and future dispersal capabilities of S. mekongi.Methodology/Principal FindingsDNA sequence data are presented for four populations of S. mekongi from Cambodia and southern Laos, three of which were distinguishable at the COI (cox1) and 12S (rrnS) mitochondrial loci sampled. A phylogeny was estimated for these populations and the other members of the Schistosoma sinensium group. The study provides new DNA sequence data for three new populations and one new locus/population combination. A Bayesian approach is used to estimate divergence dates for events within the S. sinensium group and among the S. mekongi populations.Conclusions/SignificanceThe date estimates are consistent with phylogeographical hypotheses describing a Pliocene radiation of the S. sinensium group and a mid-Pleistocene invasion of Southeast Asia by S. mekongi. The date estimates also provide Bayesian priors for future work on the evolution of S. mekongi. The public health implications of S. mekongi transmission outside the lower Mekong River are also discussed.

Genetic structure of Trypanosoma cruziin Colombia revealed by a High-throughput Nuclear Multilocus Sequence Typing (nMLST) approach

“…This incongruence at nuclear level may suggest recombination and/or chromosomal rearrangements among the dataset. This event of phylogeny incongruence has been reported in other organisms such as Leishmania, Schistosoma and Giardia duodenalis where genetic exchange has been suggested [32-34]. Despite of this pattern, many authors imply that T. cruzi displays clonal propagation with rare recombination events [35].…”

Genetic diversity and population structure ofSynthesium pontoporiae(Digenea, Brachycladiidae) linked to its definitive host stocks, the endangered Franciscana dolphin,Pontoporia blainvillei(Pontoporiidae) off the coast of Brazil and Argentina

“…Molecular studies on digenean trematodes with an indirect life cycle are more often motivated by the need to understand the epidemiology of parasites of medical and economical importance, such as Schistosoma (Shrivastava et al, 2005;Attwood et al, 2008). Additionally, other studies have focused on the genetic structure of digeneans from marine habitats (Vilas et al, 2003;Prugnolle et al, 2005a;Criscione et al, 2006Criscione et al, , 2011Hansen & Poulin, 2006;Criscione & Blouin, 2007).…”

“…Semyenova et al, 2003;Théron et al, 2004;Morgan et al, 2005;Shrivastava et al, 2005;Mattiucci & Nascetti, 2007;Zhu et al, 2007;Attwood et al, 2008;Mattiucci et al, 2008;Klimpel et al, 2010). From the Brachycladiidae family (Trematoda: Digenea), the marine mammal parasites, only the 18S rDNA gene and mtDNA NADH dehydrogenase subunit 3 (ND3) gene sequences are available and have been used in phylogenetic studies (Fernández et al, 1998a, b).…”

Out of Animals and Back Again: Schistosomiasis as a Zoonosis in Africa

“…Known naturally infected definitive host groups are shown by the icons. The points 'A', 'B' and 'C' indicate the three suggested points where species adapted to infect humans; molecular clock estimates place the date of each divergence at roughly 3.8 MYA (millions of years ago) for point A and less than 1 million years ago for points B and C (Morgan et al, 2005, Webster et al, 2006, Attwood et al, 2008). The lines marked 'H' demonstrate clades with known hybridization between species (see section 4.1).…”