Disentangling hybridization and host colonization in parasitic roundworms of humans and pigs

Charles D. Criscione, Joel D. Anderson, Dan Sudimack, Weidong Peng, Bharat Jha, Sarah Williams-Blangero, Timothy J.C. Anderson

Research output: Contribution to journalArticlepeer-review

96 Scopus citations


Knowledge of cross-transmission and hybridization between parasites of humans and reservoir hosts is critical for understanding the evolution of the parasite and for implementing control programmes. There is now a consensus that populations of pig and human Ascaris (roundworms) show significant genetic subdivision. However, it is unclear whether this has resulted from a single or multiple host shift(s). Furthermore, previous molecular data have not been sufficient to determine whether sympatric populations of human and pig Ascaris can exchange genes. To disentangle patterns of host colonization and hybridization, we used 23 microsatellite loci to conduct Bayesian clustering analyses of individual worms collected from pigs and humans. We observed strong differentiation between populations which was primarily driven by geography, with secondary differentiation resulting from host affiliation within locations. This pattern is consistent with multiple host colonization events. However, there is low support for the short internal branches of the dendrograms. In part, the relationships among clusters may result from current hybridization among sympatric human and pig roundworms. Indeed, congruence in three Bayesian methods indicated that 4 and 7% of roundworms sampled from Guatemala and China, respectively, were hybrids. These results indicate that there is contemporary cross-transmission between populations of human and pig Ascaris.

Original languageEnglish (US)
Pages (from-to)2669-2677
Number of pages9
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1626
StatePublished - Nov 7 2007
Externally publishedYes


  • Ascaris spp.
  • Hybridization
  • Microsatellites
  • Molecular epidemiology
  • Nematode
  • Parasite

ASJC Scopus subject areas

  • Immunology and Microbiology(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Environmental Science(all)
  • Agricultural and Biological Sciences(all)


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