ACVIM Asthma Consensus statement 2017

Overview of ACVIM Consensus Statements

Consensus Statements by the American College of Veterinary Internal Medicine (ACVIM) deliver updated information on important animal diseases in the veterinary field.
The selection of topics and the integrity of the draft process are overseen by the ACVIM Board of Regents.
Evidence-based medicine is prioritized; interpretive comments are provided where evidence is insufficient or conflicting.
Drafts solicit input from ACVIM members before being submitted to the Journal of Veterinary Internal Medicine for publication.
Authors hold sole responsibility for the content of the statements.

Revises and updates previous consensus statements on Inflammatory Airway Disease (IAD) in horses.
Significant evolution in understanding since the last update in 2007 due to numerous scientific publications.

IAD (Inflammatory Airway Disease): A condition affecting horses with subtle symptoms that differ from more severe conditions like recurrent airway obstruction (RAO).
Heaves: Severe airway obstruction characterized by increased coughing and respiratory effort, primarily observed in older horses.

Horses with heaves (RAO): Exhibit marked lower airway inflammation, frequent coughing, increased respiratory effort at rest, and exercise intolerance.
IAD symptoms: Include poor performance and occasional coughing, often without significant changes in breathing at rest.
Mucus Accumulation: Excessive mucus is characteristic of both conditions.

IAD and RAO are akin to asthma in humans, depicting a spectrum of chronic airway inflammation.
Suggestion to categorize affected horses under the term “equine asthma syndrome.”

Clinical Presentation: IAD affects horses of all ages, but most common in younger horses with symptoms of poor performance or chronic coughing.
Diagnostic Tests: Airway endoscopy and bronchoalveolar lavage fluid (BALF) cytology are critical for diagnosing IAD.
- Endoscopy: Excess tracheobronchial mucus scoring is essential for diagnosis.
- BALF: Indicates mild increases in neutrophils, eosinophils, and other cell types.

Signs of systemic infections, increased respiratory effort at rest, and other differentials must be ruled out to confirm IAD diagnosis.

The underlying cause of IAD is not fully understood; non-infectious agents significantly contribute.
Horses in stabling environments are often exposed to high airborne particle concentrations from dust, mold, and endotoxins.
The innate immune response involves the activation of pro-inflammatory cytokines, with different cell types showing variable responses.

IAD symptoms and severity may vary among horses; eosinophilic response is more common in younger horses, while neutrophilic IAD is more prevalent in older horses.

Diagnosis relies on clinical signs, endoscopic findings of mucus, and BALF cytology results:
- Mucus Scoring System: Scores range from 0 (no visible mucus) to 5 (profuse amounts of mucus).
- Higher mucus scores indicate a higher prevalence of IAD, especially in young racehorses.

Evaluation of BALF for neutrophils, eosinophils, and mast cells to confirm IAD.
Reference ranges exist, but values should be interpreted based on the history and clinical findings.

Medical Treatment: Primarily focuses on environmental management and decreasing lung inflammation through glucocorticoids and bronchodilators.
- Corticosteroids: Systemic glucocorticoids like dexamethasone and inhaled forms such as fluticasone are common treatments.
- Bronchodilators: Aim to provide symptomatic relief by reducing airway hyperresponsiveness and mucus accumulation.
- Mucolytics: Used to manage mucus clearance despite limited evidence for efficacy.

Reducing exposure to airborne dust through dietary and stabling changes is crucial for management.
- Switching to low-dust feed and improving barn ventilation can alleviate symptoms.
- Environmental controls, like soaking hay and improving stable designs, can help mitigate triggers.

Explore prevalence and phenotypes of IAD in various equine populations.
Investigate relationships between coughing, mucus, and inflammatory markers in lower airways, and assess systemic biomarkers for diagnosis.
Assess the effects of environmental management and treatment effectiveness through controlled trials.

Acknowledged contributions and potential conflicts of interest by the authors related to commercial consulting and research related to the consensus statement topics.

Detailed reference list of studies and evidence supportive of the statements made regarding IAD.