title: Association of perinatal exposure to airborne Rhodococcus equi with risk of pneumonia caused by R equi in foals.
abstract: OBJECTIVE
  To determine whether the concentrations of airborne virulent Rhodococcus equi in stalls housing foals during the first 2 weeks after birth are associated with subsequent development of R equi pneumonia in those foals.
  
  
  METHODS
  Air samples collected from foaling stalls and holding pens in which foals were housed during the first 2 weeks after birth.
  
  
  METHODS
  At a breeding farm in Texas, air samples (500 L each) were collected (January through May 2011) from stalls and pens in which 121 foals were housed on day 1 and on days 4, 7, and 14 after birth. For each sample, the concentration of airborne virulent R equi was determined with an immunoblot technique. The association between development of pneumonia and airborne R equi concentration was evaluated via random-effects Poisson regression analysis.
  
  
  RESULTS
  Some air samples were not available for analysis. Of the 471 air samples collected from stalls that housed 121 foals, 90 (19%) contained virulent R equi. Twenty-four of 121 (20%) foals developed R equi pneumonia. Concentrations of virulent R equi in air samples from stalls housing foals that developed R equi pneumonia were significantly higher than those in samples from stalls housing foals that did not develop pneumonia. Accounting for disease effects, air sample concentrations of virulent R equi did not differ significantly by day after birth or by month of birth.
  
  
  CONCLUSIONS
  Exposure of foals to airborne virulent R equi during the first 2 weeks after birth was significantly (and likely causally) associated with development of R equi pneumonia.
authors.affiliation: Equine Infectious Disease Laboratory, Department of Large Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77843, USA. ncohen@cvm.tamu.edu
authors.forename: Noah D
authors.initials: ND
authors.lastname: Cohen
authors.forename: M Keith
authors.initials: MK
authors.lastname: Chaffin
authors.forename: Kyle R
authors.initials: KR
authors.lastname: Kuskie
authors.forename: Melissa K
authors.initials: MK
authors.lastname: Syndergaard
authors.forename: Glenn P
authors.initials: GP
authors.lastname: Blodgett
authors.forename: Shinji
authors.initials: S
authors.lastname: Takai
mesh_terms: D000193:Actinomycetales Infections / Q000453:epidemiology* / Q000382:microbiology; D000391:Air Microbiology; D000822:Animal Husbandry; D000818:Animals; D000831:Animals, Newborn; D005260:Female; D006734:Horse Diseases / Q000453:epidemiology* / Q000382:microbiology; D006736:Horses; D006799:Housing, Animal; D015151:Immunoblotting / Q000662:veterinary; D015994:Incidence; D018410:Pneumonia, Bacterial / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D016929:Rhodococcus equi / Q000302:isolation & purification* / Q000472:pathogenicity; D012621:Seasons; D013781:Texas / Q000453:epidemiology; D014774:Virulence