title: Anaplasma marginale superinfection attributable to pathogen strains with distinct genomic backgrounds.
abstract: Strain superinfection occurs when a second pathogen strain infects a host already infected with a primary strain. The selective pressures that drive strain divergence, which underlies superinfection, and allow penetration of a new strain into a host population are critical knowledge gaps relevant to shifts in infectious disease epidemiology. In regions of endemicity with a high prevalence of infection, broad population immunity develops against Anaplasma marginale, a highly antigenically variant rickettsial pathogen, and creates strong selective pressure for emergence of and superinfection with strains that differ in their Msp2 variant repertoires. The strains may emerge either by msp2 locus duplication and allelic divergence on an existing genomic background or by introduction of a strain with a different msp2 allelic repertoire on a distinct genomic background. To answer this question, we developed a multilocus typing assay based on high-throughput sequencing of non-msp2 target loci to distinguish among strains with different genomic backgrounds. The technical error level was statistically defined based on the percentage of perfect sequence matches of clones of each target locus and validated using experimental single strains and strain pairs. Testing of A. marginale-positive samples from tropical regions where A. marginale infection is endemic identified individual infections that contained unique alleles for all five targeted loci. The data revealed a highly significant difference in the number of strains per animal in the tropical regions compared to infections in temperate regions and strongly supported the hypothesis that transmission of genomically distinct A. marginale strains predominates in high-prevalence areas of endemicity.
authors.affiliation: Paul G. Allen School for Global Animal Health, Washington State University, Pullman, Washington, USA.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Vallejo Esquerra
authors.affiliation: Animal Diseases Research Unit, Agricultural Research Service, United States Department of Agriculture, Pullman, Washington, USA.
authors.forename: David R
authors.initials: DR
authors.lastname: Herndon
authors.affiliation: Programa de Salud Animal, INIFAP-CIRGOC, La Posta, Veracruz, México.
authors.forename: Francisco
authors.initials: F
authors.lastname: Alpirez Mendoza
authors.affiliation: Universidad Autónoma de Querétaro, Campus Juriquilla, México.
authors.forename: Juan
authors.initials: J
authors.lastname: Mosqueda
authors.affiliation: Paul G. Allen School for Global Animal Health, Washington State University, Pullman, Washington, USA gpalmer@vetmed.wsu.edu.
authors.forename: Guy H
authors.initials: GH
authors.lastname: Palmer
mesh_terms: D042322:Anaplasma marginale / Q000145:classification* / Q000235:genetics* / Q000276:immunology / Q000302:isolation & purification; D000712:Anaplasmosis / Q000382:microbiology*; D000818:Animals; D000942:Antigens, Bacterial / Q000235:genetics* / Q000276:immunology; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000276:immunology; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D014644:Genetic Variation; D005838:Genotype; D058885:Multilocus Sequence Typing; D015163:Superinfection / Q000382:microbiology / Q000662:veterinary*
chemical_list: D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D004269:DNA, Bacterial; C103348:msp2 protein, Anaplasma marginale