Non-Infectious Lower Respiratory Disease

Question 1

what are other names for equine asthma?

Answer 1

broken wind
pulmonary emphysema
COPD
inflammatory airway disease
heaves
recurrent airway obstruction

Question 2

define asthma

Answer 2

chronic airway inflammation
-dyspnea
-wheezing
-coughing
-varying intensity

triggers:
-exercise, allergens, viruses

Question 3

describe mild-moderate clinical presentation of asthma

Answer 3

age: young to middle aged

clinical signs:
-occasional cough (>3 weeks)
-poor performance/exercise intolerant

time course: improves, recurrence low

endoscopy: excess mucus (or tracheal rattle)

cytology: neutrophils, eosinophils, mast cells

lung function: (FYI)
-no airflow limitation
-airway hyperresponsive

Question 4

describe severe asthma/recurrent airway obstruction asthma

Answer 4

age: older (>7 years)

clinical signs:
-frequent cough
-exercise intolerance
-dyspnea AT REST

time course:
-weeks to months
-recurrent and progressive
-control but no cure

endoscopy: excess mucus (or tracheal rattle)

cytology:
-moderate to severe increase in neutrophils
-BAL for diffuse disease!!! TTW will not get to level of alveoli (but sometimes want so you can culture the sample; mucociliary apparatus no work so prone to secondary infection)

lung function: (FYI)
-airflow limitation
-reversible with bronchodilator
-airway hyperresponsive

Question 5

describe seasonality of asthma

Answer 5

summer-pasture associated

-horses grazing on pasture
-hot-humid climate
-adult onset
-neutrophilic
-southeastern US: subtropical grasses, fungi, late summer through fall

Question 6

describe environmental contributors to asthma

Answer 6

1. respirable particles that can get down into lower airways
   - <5um, dust, stalls, hay, arenas
2. organic and inorganic particulates: mold, fungi, pollen, endotoxin, chemicals

Question 7

describe diagnosis of asthma

Answer 7

1. minimum database
   -field versus research setting
2. limited tools in equine medicine
3. history, clinical presentation
4. airway secretions:
   -BAL: for diffuse
   -TTW: to culture
5. endoscopy, imaging
6. clinical diagnosis:
   -repeatable and reversible
   -precipitated by exposure to trigger (seasonal, moldy hay, pasture allergens, heat and pollen count)

Question 8

describe physical exam for asthma

Answer 8

1. complete! upper and lower airway; rule out other conditions
2. nasal discharge, cough, airflow through nostrils
3. auscultation of thorax
4. rebreathing exam:
   -lung sounds
   -tolerance, cough, recovery

Question 9

describe airway secretions/BAL of asthma

Answer 9

1. analyze within 24 hours
2. cell count and percentages:
   -mild neutrophilia (10-25%)
   -increased mast cells (>5%)
   -increased eosinophils (>5%)
   -increased mucus: +/- curshmann’s spirals

Question 10

describe diagnostic testing of asthma

Answer 10

radiographs can be helpful!

-bronchointerstitial pattern

-rule out:
–equine multinodular pulmonary fibrosis (rare)
–diaphragmatic hernia

Question 11

describe treatment and management of asthma (goals and considerations)

Answer 11

goals:
-clinical diagnosis (response to treatment)
-therapeutic

considerations:
-use of horse
-severity of disease
-owner compliance
-prior therapy
-patience! no cure, longterm care!

Question 12

describe treatment of asthma

Answer 12

1. removal of triggering factor: environmental modification
   -barn: stall versus pasture
   -bedding: remove straw, dampen shavings, cardboard or paper
   -cleaning aisles, hay storage
   -complete pelleted feed
   -forage: soak (>10 min), steam, avoid round bales
   (ON EXAM)
2. control of airway and inflammation: environmental modification and/or corticosteroid therapy
   -dexamethasone: systemic
   –pros: easy and affordable
   –cons: cortisol and immune suppression, laminitis

-inhaled glucocorticoids: for mild to severe
–pros: maximal drug concentration in lung, minimize systemic risk, faster elimination
–cons: can cause bronchoconstriction, expensive, limited availability

3. +/- control of bronchospasm:
   -bronchodilatory therapy in conjunction with environmental modification or corticosteroid therapy or both

-beta 2 agonist/clenbuterol
–therapeutic: with glucocorticoids; bronchodilate, inhibit smooth muscle proliferation, improve mucociliary clearance, do NOT replace corticosteroids

-cons: tachyphylaxis, downregulation of receptors for 5 days, albuterol not orally bioavailable (FYI)

Question 13

what would be INEFFECTIVE for asthma?

Answer 13

1. NSAIDs: no reduction in pulmonary inflammation
2. anti-histamines: minimal to no effect
3. immunotherapy