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Differential distribution of vapA-positive Rhodococcus equi in affected and unaffected horse-breeding farms
  1. S. Petry, PhD1,
  2. C. Sévin, BSc2,
  3. M. A. Fleury, PhD1,
  4. F. Duquesne, PhD1,
  5. N. Foucher, BSc1,
  6. C. Laugier, MVD, PhD3,
  7. M. Henry-Amar, MD4 and
  8. J. Tapprest, MVD, PhD2
  1. 1ANSES, Dozulé Laboratory for Equine Diseases, Bacteriology and Parasitology Unit, Goustranville 14430, France
  2. 2ANSES, Dozulé Laboratory for Equine Diseases, Epidemiology and Pathology Unit, Goustranville 14430, France
  3. 3ANSES, Dozulé Laboratory for Equine Diseases, Goustranville 14430, France
  4. 4Centre de lutte contre le cancer François Baclesse, Avenue du Général Harris, Caen cedex 5, 14076, France
  1. E-mail for correspondence: sandrine.petry{at}

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Rhodococcus equi causes pulmonary and extrapulmonary infections in animals and humans, with endemic situations and significant young foal mortality in horse-breeding farms worldwide (von Bargen and Haas 2009, Muscatello 2012, Vázquez-Boland and others 2013). R equi virulence is associated with a plasmid encoding virulence-associated proteins (Vap) (Muscatello 2012, Vázquez-Boland and others 2013). Differences in the vap pathogenicity region of the plasmid are associated with animal host-specificity (Letek and others 2008, Valero-Rello and others 2015), with horse isolates being characterised by a vapA plasmid type (Ocampo-Sosa and others 2007, MacArthur and others 2017). Virulent R equi are present in soil of many horse-breeding farms regardless of affected or unaffected status of farms. A correlation between soil concentration of virulent R equi and farm status and/or disease prevalence would be expected but has not been confirmed systematically (Takai and others 1991, Martens and others 2000, Muscatello and others 2006, Cohen and others 2008). Other factors may be significant, including airborne burden (Muscatello and others 2006) and population density of horses (Cohen and others 2008). In this context, the aim of this study was to investigate the distribution of vapA plasmid-positive R equi and its vapA plasmid types from 93 horse-breeding farms in Normandy (the leading horse-breeding region in France).

Samples were collected during a case-control survey performed in 2005 to highlight R equi pneumonia risk factors linked to farm management practices (Tapprest and others 2011). Twenty-nine farms affected by R equi and 64 unaffected farms were investigated. Farms so-called ‘affected’ had reported at least one case of R equi pneumonia in 2004 plus several cases in the four previous years (annual incidence ranging from 2 to 80 per cent with …

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