Relationship of horse owner assessed respiratory signs index to characteristics of recurrent airway obstruction in two Warmblood families.
BACKGROUND
The horse owner assessed respiratory signs index (HOARSI-1-4, healthy, mildly, moderately and severely affected, respectively) is based on owner-reported clinical history and has been used for the investigation of recurrent airway obstruction (RAO) genetics utilising large sample sizes. Reliable phenotype identification is of paramount importance in genetic studies. Owner reports of respiratory signs have shown good repeatability, but the agreement of HOARSI with an in-depth examination of the lower respiratory tract has not been investigated.


OBJECTIVE
To determine the correlation of HOARSI grades 3/4 with the characteristics of RAO and of HOARSI-2 with the characteristics of inflammatory airway disease. Further, to test whether there are phenotypic differences in the manifestation of lung disease between families.


METHODS
Seventy-one direct offspring of 2 RAO-affected Warmblood stallions (33 from the first family, 38 from the second) were graded as HOARSI-1-4 and underwent a clinical examination of the respiratory system, arterial blood gas analysis, endoscopic mucus scoring, cytology of tracheobronchial secretion (TBS) and bronchoalveolar lavage fluid (BALF), and clinical assessment of airway reactivity to methacholine chloride.


RESULTS
HOARSI-3/4 animals in clinical exacerbation showed signs consistent with RAO: coughing, nasal discharge, abnormal lung sounds and breathing pattern as well as increased numbers of neutrophils in TBS and BALF, excessive mucus accumulation and airway hyper-responsiveness to methacholine. HOARSI-3/4 horses in remission only had increased amounts of tracheal mucus and TBS neutrophil percentages. Clinical phenotypes were not significantly different between the 2 families.


CONCLUSIONS
HOARSI reliably identifies RAO-affected horses in our population.
Equine Clinic, Department of Veterinary Clinical Sciences, Vetsuisse-Faculty, University of Berne, Switzerland.
E
E
Laumen
M G
MG
Doherr
V
V
Gerber
D000402:Airway Obstruction / Q000175:diagnosis / Q000235:genetics / Q000662:veterinary*; D000818:Animals; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry / Q000166:cytology; D005260:Female; D020022:Genetic Predisposition to Disease; D006734:Horse Diseases / Q000175:diagnosis* / Q000235:genetics; D006736:Horses; D008297:Male; D016210:Methacholine Chloride; D015588:Observer Variation
D016210:Methacholine Chloride