title: Whipworms in humans and pigs: origins and demography.
abstract: BACKGROUND
  Trichuris suis and T. trichiura are two different whipworm species that infect pigs and humans, respectively. T. suis is found in pigs worldwide while T. trichiura is responsible for nearly 460 million infections in people, mainly in areas of poor sanitation in tropical and subtropical areas. The evolutionary relationship and the historical factors responsible for this worldwide distribution are poorly understood. In this study, we aimed to reconstruct the demographic history of Trichuris in humans and pigs, the evolutionary origin of Trichuris in these hosts and factors responsible for parasite dispersal globally.
  
  
  METHODS
  Parts of the mitochondrial nad1 and rrnL genes were sequenced followed by population genetic and phylogenetic analyses. Populations of Trichuris examined were recovered from humans (n = 31), pigs (n = 58) and non-human primates (n = 49) in different countries on different continents, namely Denmark, USA, Uganda, Ecuador, China and St. Kitts (Caribbean). Additional sequences available from GenBank were incorporated into the analyses.
  
  
  RESULTS
  We found no differentiation between human-derived Trichuris in Uganda and the majority of the Trichuris samples from non-human primates suggesting a common African origin of the parasite, which then was transmitted to Asia and further to South America. On the other hand, there was no differentiation between pig-derived Trichuris from Europe and the New World suggesting dispersal relates to human activities by transporting pigs and their parasites through colonisation and trade. Evidence for recent pig transport from China to Ecuador and from Europe to Uganda was also observed from their parasites. In contrast, there was high genetic differentiation between the pig Trichuris in Denmark and China in concordance with the host genetics.
  
  
  CONCLUSIONS
  We found evidence for an African origin of T. trichiura which were then transmitted with human ancestors to Asia and further to South America. A host shift to pigs may have occurred in Asia from where T. suis seems to have been transmitted globally by a combination of natural host dispersal and anthropogenic factors.
authors.affiliation: Department of Veterinary Disease Biology, Faculty of Health Sciences, Copenhagen University, Dyrlaegevej 100, DK-1870, Frederiksberg C, Copenhagen, Denmark. mfahmy@sci.cu.edu.eg.|Zoology Department, Faculty of Science, Cairo University, Giza, Egypt. mfahmy@sci.cu.edu.eg.
authors.forename: Mohamed B F
authors.initials: MB
authors.lastname: Hawash
authors.affiliation: Department of Production and Population Health, Royal Veterinary College, Hatfield, Hertfordshire, UK. m.betson@surrey.ac.uk.|School of Veterinary Medicine, University of Surrey, Guildford, Surrey, UK. m.betson@surrey.ac.uk.
authors.forename: Martha
authors.initials: M
authors.lastname: Betson
authors.affiliation: Department of Veterinary Disease Biology, Faculty of Health Sciences, Copenhagen University, Dyrlaegevej 100, DK-1870, Frederiksberg C, Copenhagen, Denmark. azmi_mmbb@yahoo.com.
authors.forename: Azmi
authors.initials: A
authors.lastname: Al-Jubury
authors.affiliation: Ross University School of Veterinary Medicine, West Indies, Basseterre, St Kitts and Nevis. JKetzis@RossU.edu.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Ketzis
authors.affiliation: Ross University School of Veterinary Medicine, West Indies, Basseterre, St Kitts and Nevis. awillingham@rossvet.edu.kn.
authors.forename: Arve
authors.initials: A
authors.lastname: LeeWillingham
authors.affiliation: Centre for Zoo and Wild Animal Health, Copenhagen Zoo, Frederiksberg, Copenhagen, Denmark. mfb@zoo.dk.
authors.forename: Mads F
authors.initials: MF
authors.lastname: Bertelsen
authors.affiliation: Institute of Infection and Immunity, St George's University of London, London, UK. Phil.Cooper@lstmed.ac.uk.
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Cooper
authors.affiliation: Department of Life Sciences, Natural History Museum, London, UK. t.littlewood@nhm.ac.uk.
authors.forename: D Tim J
authors.initials: DT
authors.lastname: Littlewood
authors.affiliation: Lanzhou Veterinary Research Institute, State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Veterinary Parasitology of Gansu Province, Chinese Academy of Agricultural Sciences, Lanzhou, Gansu Province, 730046, P R China. xingquanzhu1@hotmail.com.
authors.forename: Xing-Quan
authors.initials: XQ
authors.lastname: Zhu
authors.affiliation: Department of Veterinary Disease Biology, Faculty of Health Sciences, Copenhagen University, Dyrlaegevej 100, DK-1870, Frederiksberg C, Copenhagen, Denmark. pn@sund.ku.dk.
authors.forename: Peter
authors.initials: P
authors.lastname: Nejsum
mesh_terms: D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D002681:China; D018509:DNA, Helminth / Q000737:chemistry / Q000235:genetics; D004272:DNA, Mitochondrial / Q000737:chemistry / Q000235:genetics; D003710:Demography; D003718:Denmark; D004484:Ecuador; D005828:Genetics, Population; D006801:Humans; D008969:Molecular Sequence Data; D010802:Phylogeny; D011323:Primates; D017422:Sequence Analysis, DNA; D013552:Swine; D013553:Swine Diseases / Q000469:parasitology*; D014257:Trichuriasis / Q000469:parasitology*; D014258:Trichuris / Q000235:genetics* / Q000302:isolation & purification; D014454:Uganda; D014481:United States
chemical_list: D018509:DNA, Helminth; D004272:DNA, Mitochondrial