title: 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.
authors.affiliation: Department of Production and Population Health, Royal Veterinary College, Hatfield, Hertfordshire, United Kingdom Department of Parasitology, Pembroke Place, Liverpool School of Tropical Medicine, United Kingdom.
authors.forename: Martha
authors.initials: M
authors.lastname: Betson
authors.affiliation: Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark.
authors.forename: Peter
authors.initials: P
authors.lastname: Nejsum
authors.affiliation: Department of Clinical Microbiology, Royal Cornwall Hospital, Truro.
authors.forename: Richard P
authors.initials: RP
authors.lastname: Bendall
authors.affiliation: Department of Parasitology, Pembroke Place, Liverpool School of Tropical Medicine, United Kingdom.
authors.forename: Rinki M
authors.initials: RM
authors.lastname: Deb
authors.affiliation: Department of Parasitology, Pembroke Place, Liverpool School of Tropical Medicine, United Kingdom.
authors.forename: J Russell
authors.initials: JR
authors.lastname: Stothard
mesh_terms: D000818:Animals; D001196:Ascariasis / Q000453:epidemiology* / Q000662:veterinary; D001200:Ascaris / Q000235:genetics; D051545:Cyclooxygenase 1 / Q000235:genetics; D018509:DNA, Helminth / Q000235:genetics; D006239:Haplotypes / Q000235:genetics; D006801:Humans; D018895:Microsatellite Repeats / Q000235:genetics; D017720:Molecular Epidemiology; D013552:Swine; D013553:Swine Diseases / Q000453:epidemiology* / Q000469:parasitology; D015047:Zoonoses / Q000453:epidemiology / Q000235:genetics / Q000469:parasitology
chemical_list: D018509:DNA, Helminth; D051545:Cyclooxygenase 1
keywords: Ascaris; barcode; giant roundworm; microsatellite; neglected tropical disease; population genetics; soil-transmitted helminth; zoonosis