Chapter 17 IAD

Question 1

What is Inflammatory Airway Disease (IAD) in horses?

Answer 1

A condition characterized by airway inflammation, alterations in pulmonary function, and one or more clinical signs of respiratory disease.

Question 2

What criteria define IAD according to the 2007 ACVIM consensus?

Answer 2

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.

Question 3

What are the exclusion criteria for IAD?

Answer 3

Horses with respiratory difficulty at rest, systemic illness (fever, depression, abnormal blood work), or solely tracheal inflammation are excluded.

Question 4

What is trIAD and brIAD?

Answer 4

TrIAD refers to tracheal inflammatory airway disease, and brIAD refers to bronchoalveolar inflammatory airway disease.

Question 5

What is subclinical IAD?

Answer 5

The presence of inflammation in BALF without concurrent clinical signs.

Question 6

What are common clinical signs of IAD?

Answer 6

Cough, poor performance, prolonged recovery after exercise, and increased airway secretions.

Question 7

Which horses are more commonly affected by tracheal inflammation?

Answer 7

Young racehorses, with prevalence decreasing with age or time spent in training.

Question 8

What is the likely etiopathogenesis of IAD?

Answer 8

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.

Question 9

What environmental factors can induce airway inflammation in horses?

Answer 9

Hay feeding, conventional barn housing, exposure to molds, mites, organic dust particles, peptidoglycans, and noxious gases.

Question 10

What is the association between stabling and airway inflammation?

Answer 10

Stabling induces neutrophilic airway inflammation and is associated with higher endotoxin concentrations and exposure to various irritants.

Question 11

What role do viral and bacterial infections play in IAD?

Answer 11

Active infections are unlikely to play a central role, but respiratory infections at an early age may predispose horses to IAD later in life.

Question 12

What bacterial pathogen is most consistently associated with tracheal inflammation in young racehorses?

Answer 12

Streptococcus zooepidemicus.

Question 13

What is the role of cytokines in IAD?

Answer 13

Different types of inflammation in BALF are associated with different cytokine profiles, indicating the involvement of innate and Th-2 immune responses.

Question 14

What types of cells are typically increased in BALF in horses with IAD?

Answer 14

Neutrophils, eosinophils, or mast cells.

Question 15

What is the significance of neutrophils in BALF for IAD?

Answer 15

High percentages of neutrophils are associated with cough, age, tracheal mucus, and low arterial oxygen tension during exercise.

Question 16

What is the significance of mast cells and eosinophils in BALF for IAD?

Answer 16

Increased eosinophils and mast cells are associated with younger horses, poor performance, and altered baseline lung function.

Question 17

What are common diagnostic methods for IAD?

Answer 17

Clinical history and physical examination, BALF cytology, lung function testing, endoscopy, and radiographic studies.

Question 18

What is the typical cytokine profile in horses with IAD?

Answer 18

Up-regulation of IL-1β, TNFα, IL-4, and IFN-γ in association with different inflammatory cell types in BALF.

Question 19

What is the relationship between IAD and heaves?

Answer 19

IAD shares similarities with heaves, and horses with chronic mild clinical signs of IAD may progress to develop heaves.

Question 20

What is the role of pulmonary function testing in IAD?

Answer 20

To detect mild to moderate airflow limitation, airway hyperresponsiveness, and impaired gas exchange during exercise.

Question 21

What is the significance of abnormal BALF cytology without clinical signs?

Answer 21

Inflammation is frequent in some populations of healthy, well-performing horses, so abnormal cytology alone is not sufficient to diagnose IAD.

Question 22

What environmental management strategies are recommended for IAD?

Answer 22

Reducing exposure to dust, improving ventilation, using low-dust bedding, and feeding soaked or pelleted hay.

Question 23

What pharmacological treatments are commonly used for IAD?

Answer 23

Systemic or inhaled corticosteroids and bronchodilators.

Question 24

What is the role of nebulized sodium cromoglycate in IAD treatment?

Answer 24

It benefits horses with increased mast cells in BALF by stabilizing mast cells and reducing clinical signs and respiratory scores.

Question 25

What is the effect of clenbuterol in IAD treatment?

Answer 25

It transiently increases mucociliary clearance and reduces airway sensitivity to inhaled histamine, but may cause tachyphylaxis.

Question 26

What is the role of interferon alpha in IAD treatment?

Answer 26

It decreases total protein concentrations and procoagulant activity in BALF, and has a mild positive effect in young racehorses with tracheal inflammation.

Question 27

What is the prognosis for horses with IAD?

Answer 27

IAD is considered transient in young athletic horses, and improvement can be achieved with environmental management and medical treatment.

Question 28

What are the clinical outcomes for older horses with IAD?

Answer 28

Clinical signs can be controlled in most cases, but there is no curative treatment, and horses may eventually develop heaves.

Question 29

What diagnostic tools are used to exclude other respiratory diseases in horses with IAD?

Answer 29

Complete blood count, thoracic radiographs, and bacterial culture of tracheal aspirate.

Question 30

What are common clinical signs of IAD based on history and physical examination?

Answer 30

Cough, nasal discharge, poor performance, in the absence of systemic signs of infection.

Question 31

What are the reference ranges for BALF cell counts in horses with IAD?

Answer 31

Eosinophils and mast cells are abnormal above 1% and 2%, respectively, and neutrophils are considered abnormal between 5% and 10%.

Question 32

What is the significance of bacterial colonization in the trachea in IAD?

Answer 32

Increased bacterial colonization can contribute to lower airway inflammation and cough, and may require antimicrobial treatment.

Question 33

What is the importance of environmental control in managing IAD?

Answer 33

It significantly reduces clinical signs and airway inflammation by minimizing exposure to irritants and allergens.

Question 34

What are the benefits of inhaled corticosteroids compared to systemic corticosteroids in IAD?

Answer 34

They provide targeted anti-inflammatory effects with fewer systemic side effects.

Question 35

What is the role of pulmonary function testing in diagnosing IAD?

Answer 35

To detect subtle alterations in pulmonary function that are more difficult to measure than those observed in heaves.

Question 36

What are the diagnostic criteria for IAD according to the ACVIM consensus?

Answer 36

Non-septic inflammation in BALF or pulmonary dysfunction, poor performance, exercise intolerance, or coughing with or without excess tracheal mucus.

Question 37

What are the potential side effects of long-term corticosteroid use in horses with IAD?

Answer 37

Adrenocortical suppression, laminitis, hepatopathy, muscle wasting, altered bone metabolism, and increased susceptibility to infection.

Question 38

What is the role of bronchodilators in IAD treatment?

Answer 38

They relieve bronchospasm but do not address the underlying inflammation.

Question 39

What are the common symptoms of IAD during an acute episode?

Answer 39

Increased expiratory effort, respiratory frequency, mild nasal discharge, flared nostrils, and markedly increased abdominal expiratory effort.

Question 40

What is the 'heaves line' in horses with IAD?

Answer 40

Hypertrophy of the external abdominal oblique muscle due to strong and continuous respiratory effort.

Question 41

What is the genetic predisposition associated with IAD?

Answer 41

Genes associated with smooth muscle remodeling, leukotriene metabolism, and IL-4 receptor polymorphisms.

Question 42

What is the significance of tracheal mucus in diagnosing IAD?

Answer 42

Tracheal mucus is associated with poor performance and airway inflammation, but tracheal inflammation alone is not sufficient to diagnose IAD.

Question 43

What are the clinical signs of severe IAD?

Answer 43

Extended head and neck positioning, flared nostrils, increased abdominal expiratory effort, and possibly fever and anorexia.

Question 44

What environmental factors contribute to the chronicity of IAD?

Answer 44

Persistent exposure to dust, molds, and other irritants in the barn environment.

Question 45

What are the potential benefits of nebulized sodium cromoglycate in IAD treatment?

Answer 45

Stabilizes mast cells and reduces clinical signs and respiratory scores in horses with increased mast cells in BALF.

Question 46

What is the prevalence of IAD in horses?

Answer 46

The exact prevalence is not clear, but it is considered higher than that of heaves.

Question 47

What are the common diagnostic methods for assessing pulmonary function in horses with IAD?

Answer 47

Forced expiration method, induced hyperventilation, and impulse oscillometry.