Long-range dispersal moved Francisella tularensis into Western Europe from the East

Chinmay Dwibedi, Dawn Birdsell, Adrian Lärkeryd, Kerstin Myrtennäs, Caroline Öhrman, Elin Nilsson, Edvin Karlsson, Christian Hochhalter, Andrew Rivera, Sara Maltinsky, Brittany Bayer, Paul Keim, Holger C. Scholz, Herbert Tomaso, Matthias Wittwer, Christian Beuret, Nadia Schuerch, Paola Pilo, Marta Hernández Pérez, David Rodriguez-LazaroRaquel Escudero, Pedro Anda, Mats Forsman, David M. Wagner, Pär Larsson, Anders Johansson

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


For many infections transmitting to humans from reservoirs in nature, disease dispersal patterns over space and time are largely unknown. Here, a reversed genomics approach helped us understand disease dispersal and yielded insight into evolution and biological properties of Francisella tularensis, the bacterium causing tularemia. We whole-genome sequenced 67 strains and characterized by single-nucleotide polymorphism assays 138 strains, collected from individuals infected 1947-2012 across Western Europe. We used the data for phylogenetic, population genetic and geographical network analyses. All strains (n=205) belonged to a monophyletic population of recent ancestry not found outside Western Europe. Most strains (n=195) throughout the study area were assigned to a star-like phylogenetic pattern indicating that colonization of Western Europe occurred via clonal expansion. In the East of the study area, strains were more diverse, consistent with a founder population spreading from east to west. The relationship of genetic and geographic distance within the F. tularensis population was complex and indicated multiple long-distance dispersal events. Mutation rate estimates based on year of isolation indicated null rates; in outbreak hotspots only, there was a rate of 0.4 mutations/genome/year. Patterns of nucleotide substitution showed marked AT mutational bias suggestive of genetic drift. These results demonstrate that tularemia has moved from east to west in Europe and that F. tularensis has a biology characterized by long-range geographical dispersal events and mostly slow, but variable, replication rates. The results indicate that mutation-driven evolution, a resting survival phase, genetic drift and long-distance geographical dispersal events have interacted to generate genetic diversity within this species.

Original languageEnglish (US)
Pages (from-to)e000100
JournalMicrobial Genomics
Issue number12
StatePublished - Dec 1 2016


  • Francisella tularensis
  • disease transmission
  • epidemiology
  • genetic variation
  • human
  • population genetics

ASJC Scopus subject areas

  • Epidemiology
  • Microbiology
  • Molecular Biology
  • Genetics


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