title: Multiple host transfers, but only one successful lineage in a continent-spanning emergent pathogen.
abstract: Emergence of a new disease in a novel host is thought to be a rare outcome following frequent pathogen transfers between host species. However, few opportunities exist to examine whether disease emergence stems from a single successful pathogen transfer, and whether this successful lineage represents only one of several pathogen transfers between hosts. We examined the successful host transfer and subsequent evolution of the bacterial pathogen Mycoplasma gallisepticum, an emergent pathogen of house finches (Haemorhous (formerly Carpodacus) mexicanus). Our principal goals were to assess whether host transfer has been a repeated event between the original poultry hosts and house finches, whether only a single host transfer was ultimately responsible for the emergence of M. gallisepticum in these finches, and whether the spread of the pathogen from east to west across North America has resulted in spatial structuring in the pathogen. Using a phylogeny of M. gallisepticum based on 107 isolates from domestic poultry, house finches and other songbirds, we infer that the bacterium has repeatedly jumped between these two groups of hosts but with only a single lineage of M. gallisepticum persisting and evolving in house finches; bacterial evolution has produced monophyletic eastern and western North American subclades.
authors.affiliation: Lab of Ornithology, Cornell University, Ithaca, NY 14850, USA. wmh6@cornell.edu
authors.forename: Wesley M
authors.initials: WM
authors.lastname: Hochachka
authors.forename: André A
authors.initials: AA
authors.lastname: Dhondt
authors.forename: Andrew
authors.initials: A
authors.lastname: Dobson
authors.forename: Dana M
authors.initials: DM
authors.lastname: Hawley
authors.forename: David H
authors.initials: DH
authors.lastname: Ley
authors.forename: Irby J
authors.initials: IJ
authors.lastname: Lovette
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D005075:Biological Evolution; D001715:Bird Diseases / Q000382:microbiology / Q000635:transmission*; D021821:Communicable Diseases, Emerging / Q000662:veterinary*; D004269:DNA, Bacterial / Q000737:chemistry / Q000302:isolation & purification; D046369:Finches / Q000382:microbiology*; D006239:Haplotypes; D054884:Host-Pathogen Interactions; D009175:Mycoplasma Infections / Q000635:transmission / Q000662:veterinary; D045686:Mycoplasma gallisepticum / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D010802:Phylogeny; D011200:Poultry / Q000382:microbiology; D011201:Poultry Diseases / Q000382:microbiology / Q000635:transmission
chemical_list: D004269:DNA, Bacterial
keywords: Carpodacus; Haemorhous mexicanus; Mycoplasma gallisepticum; host transfer; house finch; phylogeny