title: Airway inflammation and mucus in two age groups of asymptomatic well-performing sport horses.
abstract: BACKGROUND
  Horses housed in conventional stable environments are exposed to high dust loads. Long-term exposure to inhaled dust may lead to subclinical airway disease.
  
  
  OBJECTIVE
  Airway inflammation and mucus accumulation are 1) common in asymptomatic well-performing sport horses, 2) increased in older compared to younger individuals and 3) correlated.
  
  
  METHODS
  Mucus quantity and quality (endoscopic scoring) and BALF differential cytology were assessed in 13 younger horses (mean age 5 years) and 13 older horses (mean age 15 years), which had no historical or clinical evidence of lower airway disease, were performing well and were housed permanently in a conventional stable environment.
  
  
  RESULTS
  1) Airway inflammation and/or mucus accumulation were very common. All sport horses showed evidence of subclinical inflammatory airway disease (IAD). 2) Older horses, having been exposed for 10 more years to a conventional stable environment, did not show increased subclinical airway inflammation or mucus accumulation. The only differences between the age groups were increased BALF total and lymphocyte cell counts in the younger horses. 3) Mucus quantity and quality scores were not significantly correlated with each other or with BALF neutrophil percentages and absolute numbers.
  
  
  CONCLUSIONS
  Although clinically healthy and performing well, all of the examined horses housed in a conventional stable environment showed evidence of IAD. The degree of IAD was not increased in older horses that had not developed clinical signs.
  
  
  CONCLUSIONS
  The effect of subclinical degrees of IAD on performance in dressage and show jumping should be investigated further to better understand the clinical significance of IAD in sport horses.
authors.affiliation: Pulmonary Laboratory, Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, USA.
authors.forename: V
authors.initials: V
authors.lastname: Gerber
authors.forename: N E
authors.initials: NE
authors.lastname: Robinson
authors.forename: S
authors.initials: S
authors.lastname: Luethi
authors.forename: E
authors.initials: E
authors.lastname: Marti
authors.forename: B
authors.initials: B
authors.lastname: Wampfler
authors.forename: R
authors.initials: R
authors.lastname: Straub
mesh_terms: D000367:Age Factors; D000818:Animals; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology*; D005260:Female; D005434:Flow Cytometry / Q000662:veterinary; D006734:Horse Diseases / Q000503:physiopathology*; D006736:Horses; D006799:Housing, Animal; D007249:Inflammation / Q000662:veterinary; D007958:Leukocyte Count / Q000662:veterinary; D008297:Male; D009093:Mucus / Q000378:metabolism*; D010805:Physical Conditioning, Animal; D012129:Respiratory Function Tests / Q000662:veterinary; D012140:Respiratory Tract Diseases / Q000503:physiopathology / Q000662:veterinary*; D013177:Sports