title: High prevalence and two dominant host-specific genotypes of Coxiella burnetii in U.S. milk.
abstract: BACKGROUND
  Coxiella burnetii causes Q fever in humans and Coxiellosis in animals; symptoms range from general malaise to fever, pneumonia, endocarditis and death. Livestock are a significant source of human infection as they shed C. burnetii cells in birth tissues, milk, urine and feces. Although prevalence of C. burnetii is high, few Q fever cases are reported in the U.S. and we have a limited understanding of their connectedness due to difficulties in genotyping. Here, we develop canonical SNP genotyping assays to evaluate spatial and temporal relationships among C. burnetii environmental samples and compare them across studies. Given the genotypic diversity of historical collections, we hypothesized that the current enzootic of Coxiellosis is caused by multiple circulating genotypes. We collected A) 23 milk samples from a single bovine herd, B) 134 commercial bovine and caprine milk samples from across the U.S., and C) 400 bovine and caprine samples from six milk processing plants over three years.
  
  
  RESULTS
  We detected C. burnetii DNA in 96% of samples with no variance over time. We genotyped 88.5% of positive samples; bovine milk contained only a single genotype (ST20) and caprine milk was dominated by a second type (mostly ST8).
  
  
  CONCLUSIONS
  The high prevalence and lack of genotypic diversity is consistent with a model of rapid spread and persistence. The segregation of genotypes between host species is indicative of species-specific adaptations or dissemination barriers and may offer insights into the relative lack of human cases and characterizing genotypes.
authors.affiliation: Center for Microbial Genetics and Genomics, Northern Arizona University, Flagstaff, AZ 86011-4073, USA. talima.pearson@nau.edu.
authors.forename: Talima
authors.initials: T
authors.lastname: Pearson
authors.forename: Heidie M
authors.initials: HM
authors.lastname: Hornstra
authors.forename: Remy
authors.initials: R
authors.lastname: Hilsabeck
authors.forename: Lauren T
authors.initials: LT
authors.lastname: Gates
authors.forename: Sonora M
authors.initials: SM
authors.lastname: Olivas
authors.forename: Dawn M
authors.initials: DM
authors.lastname: Birdsell
authors.forename: Carina M
authors.initials: CM
authors.lastname: Hall
authors.forename: Sabrina
authors.initials: S
authors.lastname: German
authors.forename: James M
authors.initials: JM
authors.lastname: Cook
authors.forename: Meagan L
authors.initials: ML
authors.lastname: Seymour
authors.forename: Rachael A
authors.initials: RA
authors.lastname: Priestley
authors.forename: Ashley V
authors.initials: AV
authors.lastname: Kondas
authors.forename: Christine L
authors.initials: CL
authors.lastname: Clark Friedman
authors.forename: Erin P
authors.initials: EP
authors.lastname: Price
authors.forename: James M
authors.initials: JM
authors.lastname: Schupp
authors.forename: Cindy M
authors.initials: CM
authors.lastname: Liu
authors.forename: Lance B
authors.initials: LB
authors.lastname: Price
authors.forename: Robert F
authors.initials: RF
authors.lastname: Massung
authors.forename: Gilbert J
authors.initials: GJ
authors.lastname: Kersh
authors.forename: Paul
authors.initials: P
authors.lastname: Keim
mesh_terms: D000818:Animals; D002417:Cattle; D016997:Coxiella burnetii / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D014644:Genetic Variation; D005838:Genotype; D006041:Goats; D008892:Milk / Q000382:microbiology*; D017720:Molecular Epidemiology; D058889:Molecular Typing / Q000379:methods*; D015995:Prevalence; D011778:Q Fever / Q000382:microbiology / Q000662:veterinary*; D014481:United States / Q000453:epidemiology