Association of soil concentrations of Rhodococcus equi and incidence of pneumonia attributable to Rhodococcus equi in foals on farms in central Kentucky

Am J Vet Res. 2008 Mar;69(3):385-95. doi: 10.2460/ajvr.69.3.385.


Objective: To determine whether soil concentrations of total or virulent Rhodococcus equi differed among breeding farms with and without foals with pneumonia caused by R equi.

Sample population: 37 farms in central Kentucky. Procedures-During January, March, and July 2006, the total concentration of R equi and concentration of virulent R equi were determined by use of quantitative bacteriologic culture and a colony immunoblot technique, respectively, in soil specimens obtained from farms. Differences in concentrations and proportion of virulent isolates within and among time points were compared among farms.

Results: Soil concentrations of total or virulent R equi did not vary among farms at any time point. Virulent R equi were identified in soil samples from all farms. Greater density of mares and foals was significantly associated with farms having foals with pneumonia attributable to R equi. Among farms with affected foals, there was a significant association of increased incidence of pneumonia attributable to R equi with an increase in the proportion of virulent bacteria between samples collected in March and July.

Conclusions and clinical relevance: Results indicated that virulent R equi were commonly recovered from soil of horse breeding farms in central Kentucky, regardless of the status of foals with pneumonia attributable to R equi on each farm. The incidence of foals with pneumonia attributable to R equi can be expected to be higher at farms with a greater density of mares and foals.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actinomycetales Infections / epidemiology
  • Actinomycetales Infections / microbiology
  • Actinomycetales Infections / veterinary*
  • Animals
  • Horse Diseases / epidemiology
  • Horse Diseases / microbiology*
  • Horses
  • Immunoblotting / veterinary
  • Incidence
  • Kentucky / epidemiology
  • Pneumonia, Bacterial / epidemiology
  • Pneumonia, Bacterial / microbiology
  • Pneumonia, Bacterial / veterinary*
  • Rhodococcus equi / growth & development*
  • Seasons
  • Soil Microbiology*
  • Surveys and Questionnaires
  • Virulence Factors / analysis


  • Virulence Factors