Molecular identification of Ascaris lumbricoides and Ascaris suum recovered from humans and pigs in Thailand, Lao PDR, and Myanmar

Abstract

Ascaris lumbricoides is the largest roundworm known from the human intestine while Ascaris suum is an internal parasite of pigs. Ascariasis, caused by Ascaris lumbricoides, has a worldwide distribution. Here, we have provided the first molecular identification of Ascaris eggs and adults recovered from humans and pigs in Thailand, Lao PDR, and Myanmar. We amplified and sequenced nuclear ribosomal DNA (ITS1 and ITS2 regions) and mitochondrial DNA (cox1 gene). Sequence chromatograms of PCR-amplified ITS1 region revealed a probable hybrid genotype from two human ascariasis cases from Chiang Mai Province, northern Thailand. All complete ITS2 sequences were identical and did not differ between the species. Phylogenetic trees and haplotype analysis of cox1 sequences showed three clusters with 99 haplotypes. Forty-seven samples from the present study represented 14 haplotypes, including 7 new haplotypes. To our knowledge, this is the first molecular confirmation of Ascaris species in Thailand, Lao PDR, and Myanmar. Zoonotic cross-transmission of Ascaris roundworm between pigs and humans probably occurs in these countries.

Genetic diversity of Ascaris spp. infecting humans and pigs in distinct Brazilian regions, as revealed by mitochondrial DNA

“…suum samples from Brazil. The number of different cox 1 haplotypes obtained in this study– 17 haplotypes to cox 1 and 32 haplotypes to nad 1 –is similar to that found in previous studies in Asia and Africa [32,35]. Although some localities present low prevalence, these results suggest that there is raised cox 1 genetic diversity in Ascaris across Brazil.…”

“…The ML tree and MJ network analysis based in both cox 1 and nad 1 revealed three main clusters (A-C). Several studies demonstrate this topology for Ascaris mitochondrial targets, in which two main groups are formed with i) clusters A and C; and ii) cluster B [34,35]. Our main finding is that, despite this division, there is no separation between specimens obtained from humans and from pigs, presumably A .…”

“…Interestingly, it has been found in all Brazilian localities studied to date (this study and previous studies by [21] and [20]). This haplotype is widespread in four continents–Asia, Africa, the Americas, and Europe–mainly in human samples [33,35,38]. Furthermore, Ascaris sp.…”

Real-time detection and identification of nematode eggs genus and species through optical imaging

“…This methodology could assist the clinical method for diagnosis of ascariasis, in particular at the diagnostic stage (eggs) rather than infectious stage (juveniles). Compared with prior reports on detection of species 41,52 , the present study clearly distinguishes the species of nematodes with 90% certainty. To the best of our knowledge, there is no similar report on identification of species of nematodes through their lifetime measurements.…”

Molecular evidence of hybridization between pig and human Ascaris indicates an interbred species complex infecting humans

“…Population genetic studies of A. lumbricoides have drawn varying conclusions about whether zoonotic transmission is frequent ( Anderson and Jaenike, 1997 ; Dutto and Petrosillo, 2013 ; Nejsum et al, 2012 ; Nejsum et al, 2005a ). Some studies have shown that cross-species transmission occurs between pigs and humans living in close proximity ( Anderson, 1995 ; Betson et al, 2014 ; Miller et al, 2015 ; Monteiro et al, 2019 ; Nejsum et al, 2005b ; Peng and Criscione, 2012 ; Sadaow et al, 2018 ; Takata, 1951 ; Zhu et al, 1999 ). This is especially common in non-endemic regions, probably because zoonotic transmission is less likely to be identified in areas where human-to-human transmission is common.…”