title: Relative prevalence of upper respiratory tract obstructive disorders in two breeds of harness racehorses (185 cases: 1998-2006).
abstract: BACKGROUND
  Two genetically and phenotypically distinct horse breeds are used for harness racing in Scandinavia: the Standardbred (SB) and Coldblooded Trotter. These racehorses have identical environmental, management and racing conditions. Therefore, this study was undertaken to identify and compare the relative prevalence of upper respiratory tract (URT) obstructive disorders in these 2 breeds.
  
  
  OBJECTIVE
  To determine whether these 2 phenotypically different breeds of harness racehorses have different predispositions for URT disorders.
  
  
  METHODS
  Retrospective study of 88 Norwegian Coldblooded Trotters (NCT) and 97 SBs referred to this hospital for URT evaluation between 1998 and 2006. Case records of all horses diagnosed with an URT disorder during resting endoscopy, and all horses undergoing high-speed treadmill videoendoscopy (HSTV) with one or more periods of induced poll flexion were evaluated. The relative prevalence of URT disorders between the 2 breeds was analysed using a Fisher's exact test.
  
  
  RESULTS
  There was a significant (P<0.05) breed predisposition regarding 6 URT disorders. Bilateral dynamic laryngeal collapse associated with poll flexion and flaccid epiglottis was significantly more frequent in the NCT. Alar fold collapse and nasopharyngeal collapse were significantly more frequent in SBs. Epiglottic entrapment and nasal flutter were only diagnosed in the SBs. Dynamic disorders were more common than resting disorders in both breeds.
  
  
  CONCLUSIONS
  URT obstructive disorders (dynamic laryngeal collapse associated with poll flexion, flaccid epiglottis, pharyngeal collapse, alar fold collapse, nasal flutter and epiglottic entrapment) are breed related, indicating an anatomic or functional cause. Periods of induced poll flexion during HSTV was essential to declare harness racehorses free of URT disorders.
  
  
  CONCLUSIONS
  Further anatomic or physiological studies comparing these breeds could potentially provide insight into the pathogenesis of certain URT obstructive disorders. Induced poll flexion should be included in routine HSTV examinations of all harness racehorses.
authors.affiliation: Equine Section, Norwegian School of Veterinary Science, Oslo, Norway. Eric.Strand@nvh.no
authors.forename: E
authors.initials: E
authors.lastname: Strand
authors.forename: C T
authors.initials: CT
authors.lastname: Fjordbakk
authors.forename: K
authors.initials: K
authors.lastname: Sundberg
authors.forename: L
authors.initials: L
authors.lastname: Spangen
authors.forename: H
authors.initials: H
authors.lastname: Lunde
authors.forename: S
authors.initials: S
authors.lastname: Hanche-Olsen
mesh_terms: D000402:Airway Obstruction / Q000453:epidemiology / Q000235:genetics / Q000662:veterinary*; D000818:Animals; D005080:Exercise Test / Q000662:veterinary; D005260:Female; D020022:Genetic Predisposition to Disease; D006734:Horse Diseases / Q000453:epidemiology / Q000235:genetics* / Q000473:pathology; D006736:Horses; D008297:Male; D009664:Norway / Q000453:epidemiology; D010805:Physical Conditioning, Animal; D015995:Prevalence; D015619:Respiratory System Abnormalities / Q000453:epidemiology / Q000235:genetics / Q000473:pathology / Q000662:veterinary*; D012189:Retrospective Studies; D013177:Sports