title: Recombination Is a Major Driving Force of Genetic Diversity in the AnaplasmataceaeEhrlichia ruminantium.
abstract: The disease, Heartwater, caused by theAnaplasmataceae E. ruminantium, represents a major problem for tropical livestock and wild ruminants. Up to now, no effective vaccine has been available due to a limited cross protection of vaccinal strains on field strains and a high genetic diversity ofEhrlichia ruminantiumwithin geographical locations. To address this issue, we inferred the genetic diversity and population structure of 194E. ruminantiumisolates circulating worldwide using Multilocus Sequence Typing based onlipA, lipB, secY, sodB, andsucA genes. Phylogenetic trees and networks were generated using BEAST and SplitsTree, respectively, and recombination between the different genetic groups was tested using the PHI test for recombination. Our study reveals the repeated occurrence of recombination betweenE. ruminantiumstrains, suggesting that it may occur frequently in the genome and has likely played an important role in the maintenance of genetic diversity and the evolution ofE. ruminantium. Despite the unclear phylogeny and phylogeography,E. ruminantiumisolates are clustered into two main groups: Group 1 (West Africa) and a Group 2 (worldwide) which is represented by West, East, and Southern Africa, Indian Ocean, and Caribbean strains. Some sequence types are common between West Africa and Caribbean and between Southern Africa and Indian Ocean strains. These common sequence types highlight two main introduction events due to the movement of cattle: from West Africa to Caribbean and from Southern Africa to the Indian Ocean islands. Due to the long branch lengths between Group 1 and Group 2, and the propensity for recombination between these groups, it seems that the West African clusters of Subgroup 2 arrived there more recently than the original divergence of the two groups, possibly with the original waves of domesticated ruminants that spread across the African continent several thousand years ago.
authors.affiliation: CIRAD, UMR CMAEEPetit-Bourg, Guadeloupe, France; INRA, UMR1309 CMAEEMontpellier, France; Centro de Biotecnologia-UEM, Eduardo Mondlane UniversityMaputo, Mozambique; Université des AntillesPointe-à-Pitre, Guadeloupe, France.
authors.forename: Nídia
authors.initials: N
authors.lastname: Cangi
authors.affiliation: CIRAD, UMR CMAEEPetit-Bourg, Guadeloupe, France; INRA, UMR1309 CMAEEMontpellier, France.
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: Gordon
authors.affiliation: CIRAD, UMR CMAEEPetit-Bourg, Guadeloupe, France; INRA, UMR1309 CMAEEMontpellier, France.
authors.forename: Laure
authors.initials: L
authors.lastname: Bournez
authors.affiliation: CIRAD, UMR CMAEEPetit-Bourg, Guadeloupe, France; INRA, UMR1309 CMAEEMontpellier, France.
authors.forename: Valérie
authors.initials: V
authors.lastname: Pinarello
authors.affiliation: CIRAD, UMR CMAEEPetit-Bourg, Guadeloupe, France; INRA, UMR1309 CMAEEMontpellier, France.
authors.forename: Rosalie
authors.initials: R
authors.lastname: Aprelon
authors.affiliation: INRA, UMR1309 CMAEE Montpellier, France.
authors.forename: Karine
authors.initials: K
authors.lastname: Huber
authors.affiliation: INRA, UMR1309 CMAEE Montpellier, France.
authors.forename: Thierry
authors.initials: T
authors.lastname: Lefrançois
authors.affiliation: Centro de Biotecnologia-UEM, Eduardo Mondlane UniversityMaputo, Mozambique; Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of PretoriaOnderstepoort, South Africa.
authors.forename: Luís
authors.initials: L
authors.lastname: Neves
authors.affiliation: CIRAD, UMR CMAEEPetit-Bourg, Guadeloupe, France; INRA, UMR1309 CMAEEMontpellier, France.
authors.forename: Damien F
authors.initials: DF
authors.lastname: Meyer
authors.affiliation: CIRAD, UMR CMAEEPetit-Bourg, Guadeloupe, France; INRA, UMR1309 CMAEEMontpellier, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Vachiéry
mesh_terms: D000349:Africa / Q000453:epidemiology; D000710:Anaplasmataceae / Q000235:genetics*; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology / Q000382:microbiology; D004269:DNA, Bacterial; D016995:Ehrlichia ruminantium / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity; D019143:Evolution, Molecular; D014644:Genetic Variation / Q000235:genetics*; D005838:Genotype; D006357:Heartwater Disease / Q000097:blood / Q000453:epidemiology / Q000382:microbiology; D007195:Indian Ocean Islands / Q000453:epidemiology; D009073:Mozambique / Q000453:epidemiology; D058885:Multilocus Sequence Typing / Q000379:methods; D010802:Phylogeny; D016133:Polymerase Chain Reaction / Q000379:methods; D011995:Recombination, Genetic; D013482:Superoxide Dismutase / Q000235:genetics; D013987:Ticks / Q000382:microbiology
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; C079999:LipA protein, Bacteria; C088618:lipase activator protein, Bacteria; C087504:SodB protein, Bacteria; D013482:Superoxide Dismutase
keywords: Ehrlichia ruminantium; MLST; genetic diversity; genetic population structure; recombination