Chapter 17 IAD Flashcards
What is Inflammatory Airway Disease (IAD) in horses?
A condition characterized by airway inflammation, alterations in pulmonary function, and one or more clinical signs of respiratory disease.
What criteria define IAD according to the 2007 ACVIM consensus?
Poor performance, exercise intolerance, or coughing, with or without excess tracheal mucus; and non-septic inflammation detected by cytological examination of BALF or pulmonary dysfunction.
What are the exclusion criteria for IAD?
Horses with respiratory difficulty at rest, systemic illness (fever, depression, abnormal blood work), or solely tracheal inflammation are excluded.
What is trIAD and brIAD?
TrIAD refers to tracheal inflammatory airway disease, and brIAD refers to bronchoalveolar inflammatory airway disease.
What is subclinical IAD?
The presence of inflammation in BALF without concurrent clinical signs.
What are common clinical signs of IAD?
Cough, poor performance, prolonged recovery after exercise, and increased airway secretions.
Which horses are more commonly affected by tracheal inflammation?
Young racehorses, with prevalence decreasing with age or time spent in training.
What is the likely etiopathogenesis of IAD?
It is a clinical syndrome with multifactorial etiopathogenesis, including environmental disease, early stage or milder phenotype of heaves, and infectious processes with secondary lower airway inflammation.
What environmental factors can induce airway inflammation in horses?
Hay feeding, conventional barn housing, exposure to molds, mites, organic dust particles, peptidoglycans, and noxious gases.
What is the association between stabling and airway inflammation?
Stabling induces neutrophilic airway inflammation and is associated with higher endotoxin concentrations and exposure to various irritants.
What role do viral and bacterial infections play in IAD?
Active infections are unlikely to play a central role, but respiratory infections at an early age may predispose horses to IAD later in life.
What bacterial pathogen is most consistently associated with tracheal inflammation in young racehorses?
Streptococcus zooepidemicus.
What is the role of cytokines in IAD?
Different types of inflammation in BALF are associated with different cytokine profiles, indicating the involvement of innate and Th-2 immune responses.
What types of cells are typically increased in BALF in horses with IAD?
Neutrophils, eosinophils, or mast cells.
What is the significance of neutrophils in BALF for IAD?
High percentages of neutrophils are associated with cough, age, tracheal mucus, and low arterial oxygen tension during exercise.
What is the significance of mast cells and eosinophils in BALF for IAD?
Increased eosinophils and mast cells are associated with younger horses, poor performance, and altered baseline lung function.
What are common diagnostic methods for IAD?
Clinical history and physical examination, BALF cytology, lung function testing, endoscopy, and radiographic studies.
What is the typical cytokine profile in horses with IAD?
Up-regulation of IL-1β, TNFα, IL-4, and IFN-γ in association with different inflammatory cell types in BALF.
What is the relationship between IAD and heaves?
IAD shares similarities with heaves, and horses with chronic mild clinical signs of IAD may progress to develop heaves.
What is the role of pulmonary function testing in IAD?
To detect mild to moderate airflow limitation, airway hyperresponsiveness, and impaired gas exchange during exercise.
What is the significance of abnormal BALF cytology without clinical signs?
Inflammation is frequent in some populations of healthy, well-performing horses, so abnormal cytology alone is not sufficient to diagnose IAD.
What environmental management strategies are recommended for IAD?
Reducing exposure to dust, improving ventilation, using low-dust bedding, and feeding soaked or pelleted hay.
What pharmacological treatments are commonly used for IAD?
Systemic or inhaled corticosteroids and bronchodilators.
What is the role of nebulized sodium cromoglycate in IAD treatment?
It benefits horses with increased mast cells in BALF by stabilizing mast cells and reducing clinical signs and respiratory scores.
What is the effect of clenbuterol in IAD treatment?
It transiently increases mucociliary clearance and reduces airway sensitivity to inhaled histamine, but may cause tachyphylaxis.
What is the role of interferon alpha in IAD treatment?
It decreases total protein concentrations and procoagulant activity in BALF, and has a mild positive effect in young racehorses with tracheal inflammation.
What is the prognosis for horses with IAD?
IAD is considered transient in young athletic horses, and improvement can be achieved with environmental management and medical treatment.
What are the clinical outcomes for older horses with IAD?
Clinical signs can be controlled in most cases, but there is no curative treatment, and horses may eventually develop heaves.
What diagnostic tools are used to exclude other respiratory diseases in horses with IAD?
Complete blood count, thoracic radiographs, and bacterial culture of tracheal aspirate.
What are common clinical signs of IAD based on history and physical examination?
Cough, nasal discharge, poor performance, in the absence of systemic signs of infection.
What are the reference ranges for BALF cell counts in horses with IAD?
Eosinophils and mast cells are abnormal above 1% and 2%, respectively, and neutrophils are considered abnormal between 5% and 10%.
What is the significance of bacterial colonization in the trachea in IAD?
Increased bacterial colonization can contribute to lower airway inflammation and cough, and may require antimicrobial treatment.
What is the importance of environmental control in managing IAD?
It significantly reduces clinical signs and airway inflammation by minimizing exposure to irritants and allergens.
What are the benefits of inhaled corticosteroids compared to systemic corticosteroids in IAD?
They provide targeted anti-inflammatory effects with fewer systemic side effects.
What is the role of pulmonary function testing in diagnosing IAD?
To detect subtle alterations in pulmonary function that are more difficult to measure than those observed in heaves.
What are the diagnostic criteria for IAD according to the ACVIM consensus?
Non-septic inflammation in BALF or pulmonary dysfunction, poor performance, exercise intolerance, or coughing with or without excess tracheal mucus.
What are the potential side effects of long-term corticosteroid use in horses with IAD?
Adrenocortical suppression, laminitis, hepatopathy, muscle wasting, altered bone metabolism, and increased susceptibility to infection.
What is the role of bronchodilators in IAD treatment?
They relieve bronchospasm but do not address the underlying inflammation.
What are the common symptoms of IAD during an acute episode?
Increased expiratory effort, respiratory frequency, mild nasal discharge, flared nostrils, and markedly increased abdominal expiratory effort.
What is the ‘heaves line’ in horses with IAD?
Hypertrophy of the external abdominal oblique muscle due to strong and continuous respiratory effort.
What is the genetic predisposition associated with IAD?
Genes associated with smooth muscle remodeling, leukotriene metabolism, and IL-4 receptor polymorphisms.
What is the significance of tracheal mucus in diagnosing IAD?
Tracheal mucus is associated with poor performance and airway inflammation, but tracheal inflammation alone is not sufficient to diagnose IAD.
What are the clinical signs of severe IAD?
Extended head and neck positioning, flared nostrils, increased abdominal expiratory effort, and possibly fever and anorexia.
What environmental factors contribute to the chronicity of IAD?
Persistent exposure to dust, molds, and other irritants in the barn environment.
What are the potential benefits of nebulized sodium cromoglycate in IAD treatment?
Stabilizes mast cells and reduces clinical signs and respiratory scores in horses with increased mast cells in BALF.
What is the prevalence of IAD in horses?
The exact prevalence is not clear, but it is considered higher than that of heaves.
What are the common diagnostic methods for assessing pulmonary function in horses with IAD?
Forced expiration method, induced hyperventilation, and impulse oscillometry.
