Chapter 16 RAO

Question 1

What is Recurrent Airway Obstruction (RAO) also known as?

Answer 1

Heaves and formerly as chronic obstructive pulmonary disease (COPD).

Question 2

What environmental factors are associated with RAO?

Answer 2

Exposure to barn dusts and airborne antigens present at pasture.

Question 3

What are the clinical signs of RAO and SPAOPD?

Answer 3

Respiratory distress at rest, bronchospasm, airway tissue remodeling, neutrophilic inflammation, and mucus secretions.

Question 4

What is the mainstay treatment strategy for RAO?

Answer 4

Antigen avoidance strategies.

Question 5

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

Answer 5

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

Question 6

What is the ‘heaves line’?

Answer 6

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

Question 7

What is the common age of onset for RAO?

Answer 7

Seven years of age or older.

Question 8

Which breeds have a predisposition to RAO?

Answer 8

Thoroughbred horses and possibly other breeds, with females at greater risk than males.

Question 9

What triggers the exacerbations of SPAOPD?

Answer 9

Exposure to high environmental counts of fungal spores and grass pollen grains during summer.

Question 10

What are the primary immune cells involved in RAO?

Answer 10

Neutrophils.

Question 11

What cytokines are increased in the bronchial epithelium of horses with RAO?

Answer 11

Interleukin-8 (IL-8).

Question 12

What is the role of IL-17 in RAO?

Answer 12

Promotes neutrophil chemotaxis and activation.

Question 13

What immune response is primarily associated with RAO?

Answer 13

A Th2 and Th17 driven immune response.

Question 14

What is the significance of BALF in diagnosing RAO?

Answer 14

The presence of neutrophilic inflammation (usually >20%) in BALF cytology is a characteristic finding.

Question 15

What environmental management strategies help control RAO?

Answer 15

Reducing exposure to dust, molds, and mites by changing food and bedding materials and increasing ventilation.

Question 16

What are the common anti-inflammatory drugs used in RAO treatment?

Answer 16

Corticosteroids such as dexamethasone, prednisolone, and fluticasone.

Question 17

What is the effect of bronchodilators in RAO treatment?

Answer 17

They relieve bronchospasm but do not have anti-inflammatory properties.

Question 18

What are the genetic factors associated with RAO?

Answer 18

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

Question 19

What is the role of corticosteroids in RAO treatment?

Answer 19

They control clinical signs and partially reverse tissue remodeling.

Question 20

What are the possible side effects of long-term corticosteroid use in horses?

Answer 20

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

Question 21

What are the potential triggers for RAO exacerbations?

Answer 21

Organic dust, fungal spores, moldy hay, grass pollen grains, and possibly viral infections.

Question 22

What is the role of IL-4 in RAO?

Answer 22

It activates neutrophils, promoting chemotaxis and inducing expression of inflammatory proteins.

Question 23

What are the effects of inhaled corticosteroids compared to systemic corticosteroids in RAO?

Answer 23

Inhaled corticosteroids have fewer systemic effects and are more targeted to the airways.

Question 24

What diagnostic tools are used to assess RAO?

Answer 24

Thoracic auscultation, BALF cytology, lung function testing, endoscopy, and radiographic studies.

Question 25

What is SPAOPD?

Answer 25

Summer Pasture-Associated Obstructive Pulmonary Disease, similar to RAO but associated with pasturing during summer.

Question 26

What is the prevalence of heaves in horses?

Answer 26

Heaves affects 10-20% of the adult equine population in temperate climates.

Question 27

What is the typical BALF cytology finding in RAO during exacerbation?

Answer 27

Predominantly neutrophils, often exceeding 20% of the cell population.

Question 28

What is the role of mast cells in RAO?

Answer 28

Mast cells are increased within the airway wall and contribute to inflammation by releasing histamine and other mediators.

Question 29

What are common clinical signs of severe RAO?

Answer 29

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

Question 30

What is the treatment approach during an acute RAO episode?

Answer 30

Immediate administration of bronchodilators and corticosteroids.

Question 31

What is the role of genetic predisposition in RAO?

Answer 31

Certain families and lineages are more susceptible, with identified genetic loci associated with the disease.

Question 32

What are the signs of RAO during remission?

Answer 32

Coughing episodes during exercise or eating, exercise intolerance, and possibly unremarkable thoracic auscultation.

Question 33

What is the effect of endotoxins on horses with RAO?

Answer 33

Endotoxins act as non-specific inflammatory stimuli, exacerbating the condition when combined with other antigens.

Question 34

What are the immunologic mechanisms involved in RAO?

Answer 34

Both acquired (Th2 and Th17 responses) and innate (epithelial cells and macrophages) immune mechanisms.

Question 35

What environmental changes help manage SPAOPD?

Answer 35

Removing horses from pasture during exacerbation periods and placing them in a low-dust environment.

Question 36

What is the effect of long-term environmental control on RAO?

Answer 36

Significant reduction in clinical signs and airway inflammation, though complete reversal may take several weeks.

Question 37

What is the clinical significance of IL-17 in RAO?

Answer 37

It is associated with neutrophil recruitment and activation, contributing to airway inflammation.

Question 38

What role do smooth muscle cells play in RAO?

Answer 38

They produce IL-8, contributing to neutrophil accumulation in the airway lumen.

Question 39

What are the main goals of RAO treatment?

Answer 39

To reduce inflammation, relieve bronchospasm, and minimize exposure to environmental antigens.

Question 40

What are the limitations of bronchodilators in RAO treatment?

Answer 40

They do not address the underlying inflammation and are primarily used for symptomatic relief.

Question 41

What is the significance of IL-8 in RAO?

Answer 41

It is a potent neutrophil chemotactic factor, contributing to the inflammation observed in RAO.

Question 42

What are common clinical signs of mild RAO?

Answer 42

Occasional cough, mild nasal discharge, and increased respiratory effort during exercise.

Question 43

What factors contribute to the chronicity of RAO?

Answer 43

Persistent exposure to environmental antigens, genetic predisposition, and sustained inflammatory responses.

Question 44

What are the potential benefits of inhaled corticosteroids in RAO?

Answer 44

Targeted anti-inflammatory effects with fewer systemic side effects compared to systemic corticosteroids.

Question 45

What diagnostic methods help differentiate RAO from other respiratory conditions?

Answer 45

Clinical history, BALF cytology, lung function tests, endoscopy, and radiographic studies.

Question 46

What are common treatments for severe RAO exacerbations?

Answer 46

Systemic corticosteroids, bronchodilators, and immediate removal from the offending environment.

Question 47

What is the importance of client education in managing RAO?

Answer 47

Educating clients on environmental control and proper management techniques to reduce antigen exposure and prevent exacerbations.