Molecular Epidemiology of Ascariasis: A Global Perspective on the Transmission Dynamics of Ascaris in People and Pigs

Abstract

Background. The roundworm Ascaris lumbricoides infects 0.8 billion people worldwide, and Ascaris suum infects innumerable pigs across the globe. The extent of natural cross-transmission of Ascaris between pig and human hosts in different geographical settings is unknown, warranting investigation.Methods. Adult Ascaris organisms were obtained from humans and pigs in Europe, Africa, Asia, and Latin America. Barcodes were assigned to 536 parasites on the basis of sequence analysis of the mitochondrial cytochrome c oxidase I gene. Genotyping of 410 worms was also conducted using a panel of microsatellite markers. Phylogenetic, population genetic, and Bayesian assignment methods were used for analysis.Results. There was marked genetic segregation between worms originating from human hosts and those originating from pig hosts. However, human Ascaris infections in Europe were of pig origin, and there was evidence of cross-transmission between humans and pigs in Africa. Significant genetic differentiation exists between parasite populations from different countries, villages, and hosts.Conclusions. In conducting an analysis of variation within Ascaris populations from pig and human hosts across the globe, we demonstrate that cross-transmission takes place in developing and developed countries, contingent upon epidemiological potential and local phylogeography. Our results provide novel insights into the transmission dynamics and speciation of Ascaris worms from humans and pigs that are of importance for control programs.

DNA Typing of Ancient Parasite Eggs from Environmental Samples Identifies Human and Animal Worm Infections in Viking-Age Settlement

“…Whether Ascaris in humans and pigs are distinct species is still being discussed, as they are morphologically indistinguishable and genetically very closely related (Leles et al, 2012). However, recent analysis of the cytochrome C oxidase 1 (cox1) gene and associated microsatellite data has segregated most of the tested worms (Betson et al, 2014). It is believed that Ascaris speciation is relatively recent and possibly occurred as a result of pig domestication in the Neolithic era.…”

Heavy metal intoxication compromises the host cytokine response inAscaris Suummodel infection

“…The immunotoxicity of heavy metals and their modulation of parasite-host interactions were tested on model of Ascaris suum helminth infection. Ascariosis is a widespread parasitosis in which the roundworm Ascaris lumbricoides infects about 1 billion people worldwide, and also affects innumerable pigs across the globe (Betson et al, 2014). Interference of this nematode species with heavy metals is very likely.…”

“…Contingent upon epidemiological potential and local phylogeography the natural cross-transmission of Ascaris spp. between pig and human hosts takes place in developing and developed countries (Šnábel et al, 2012;Betson et al, 2014). The use of a murine experimental model for Ascaris infection provides detailed information about the biology at early stage of infection and larval migration what is diffi cult to follow in naturally occurring infections.…”

Genetic Variability and Geographic Diversity of the Common Bed Bug (Hemiptera: Cimicidae) Populations from the Midwest Using Microsatellite Markers

“…The short tandem repeats of microsatellites are widespread in DNA and assumed to be evenly distributed over genomes (Stallings 1992, Dietrich et al 1996, Primmer et al 1996. Microsatellite markers have emerged as a reliable source to investigate the genetic structuring of populations to estimate the links and patterns of gene flow among populations (Vargo 2000, Balloux and Lugon-Moulin 2002, Betson et al 2014). …”