Owner-reported coughing and nasal discharge are associated with clinical findings, arterial oxygen tension, mucus score and bronchoprovocation in horses with recurrent airway obstruction in a field setting.
BACKGROUND
In clinical practice, veterinarians often depend on owner-reported signs to assess the clinical course of horses with recurrent airway obstruction (RAO).


OBJECTIVE
To test whether owner-reported information on frequency of coughing and observation of nasal discharge are associated with clinical, cytological and bronchoprovocation findings in RAO-affected horses in nonstandardised field conditions.


METHODS
Cross-sectional study comparing healthy and RAO-affected horses.


METHODS
Twenty-eight healthy and 34 RAO-affected Swiss Warmblood horses were grouped according to owner-reported 'coughing frequency' and 'nasal discharge'. Differences between these groups were examined using clinical examination, blood gas analyses, endoscopic mucus scores, cytology of tracheobronchial secretion and bronchoalveolar lavage fluid, and airway hyperresponsiveness determined by plethysmography with histamine bronchoprovocation.


RESULTS
Frequently coughing horses differed most markedly from healthy control animals. Histamine bronchoprovocation-derived parameters were significantly different between the healthy control group and all RAO groups. Mucus grades and tracheobronchial secretion and bronchoalveolar lavage fluid neutrophil percentages had particularly high variability, with overlap of findings between groups. Owner satisfaction with the clinical status of the horse was high, even in severely affected horses.


CONCLUSIONS
Owner-reported coughing and nasal discharge are associated with specific clinical and diagnostic findings in RAO-affected horses in field settings. While airway hyperresponsiveness differentiates best between healthy horses and asymptomatic RAO-affected horses, the absence of coughing and nasal discharge does not rule out significant neutrophilic airway inflammation. Owner satisfaction with the clinical status of the horse was uninformative.
Swiss Institute of Equine Medicine, University of Berne and ALP-Haras, Switzerland.
H
H
Rettmer
A M
AM
Hoffman
S
S
Lanz
M
M
Oertly
V
V
Gerber
D000818:Animals; D001986:Bronchial Spasm / Q000139:chemically induced / Q000662:veterinary; D001992:Bronchoalveolar Lavage Fluid; D003371:Cough; D003430:Cross-Sectional Studies; D006632:Histamine / Q000633:toxicity; D006734:Horse Diseases / Q000175:diagnosis / Q000473:pathology*; D006736:Horses; D008173:Lung Diseases, Obstructive / Q000473:pathology / Q000662:veterinary*; D009093:Mucus / Q000737:chemistry*; D010100:Oxygen / Q000097:blood*; D012129:Respiratory Function Tests; D012137:Respiratory System / Q000473:pathology
D006632:Histamine; D010100:Oxygen
airway hyperresponsiveness; clinical signs; histamine; horse; lower airway disease; lung function