title: Effects of genetic and environmental factors on chronic lower airway disease in horses.
abstract: BACKGROUND
  Environment and genetics influence the manifestation of recurrent airway obstruction (RAO), but the associations of specific factors with mild, moderate, and severe clinical signs are unknown.
  
  
  OBJECTIVE
  We hypothesized that sire, feed, bedding, time outdoors, sex, and age are associated with clinical manifestations of mild, moderate, and severe lower airway disease.
  
  
  METHODS
  Direct offspring of 2 RAO-affected Warmblood stallions (F1S1, n = 172; F1S2, n = 135); maternal half-siblings of F1S1 (mHSS1, n = 66); and an age-matched, randomly chosen control group (CG, n = 33).
  
  
  METHODS
  A standardized questionnaire was used to assess potential risk factors and to establish a horse owner assessed respiratory signs index (HOARSI 1-4, from healthy to severe) according to clinical signs of lower airway disease.
  
  
  RESULTS
  More F1S1 and F1S2 horses showed moderate to severe clinical signs (HOARSI 3 and HOARSI 4 combined, 29.6 and 27.3%, respectively) compared with CG and mHSS1 horses (9.1 and 6.2%, respectively; contingency table overall test, P < .001). Sire, hay feeding, and age (in decreasing order of strength) were associated with more severe clinical signs (higher HOARSI), more frequent coughing, and nasal discharge.
  
  
  CONCLUSIONS
  There is a genetic predisposition and lesser but also marked effects of hay feeding and age on the manifestation of moderate to severe clinical signs, most markedly on coughing frequency. In contrast, mild clinical signs were not associated with sire or hay feeding in our populations.
authors.affiliation: Equine Clinic, Vetsuisse-Faculty, University of Berne, Switzerland.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Ramseyer
authors.forename: Claude
authors.initials: C
authors.lastname: Gaillard
authors.forename: Dominik
authors.initials: D
authors.lastname: Burger
authors.forename: Reto
authors.initials: R
authors.lastname: Straub
authors.forename: Ursula
authors.initials: U
authors.lastname: Jost
authors.forename: Cornel
authors.initials: C
authors.lastname: Boog
authors.forename: Eliane
authors.initials: E
authors.lastname: Marti
authors.forename: Vincent
authors.initials: V
authors.lastname: Gerber
mesh_terms: D000818:Animals; D002908:Chronic Disease; D020022:Genetic Predisposition to Disease; D006734:Horse Diseases / Q000209:etiology* / Q000235:genetics*; D006736:Horses; D008297:Male; D012140:Respiratory Tract Diseases / Q000209:etiology / Q000235:genetics / Q000662:veterinary*; D012307:Risk Factors