Lower respiratory tract conditions affecting the individual horse Flashcards
Name 3 common causes of lower respiratory tract disease in adult horses
Recurrent airway obstruction/’heaves’
Inflammatory airway disease
Viral and bacterial infections
Name 3 fairly common causes of lower respiratory tract disease in adult horses
Exercise Induced Pulmonary Haemorrhage (EIPH)
Pleuropneumonia
Aspiration pneumonia
Name the uncommon causes of lower respiratory tract disease in adult horses
- Pulmonary abscess
- Lungworm
- Tracheal stenosis/collapse
- Interstitial pneumonia
- Pulmonary nodular fibrosis
- Neoplasia
- African Horse Sickness or other exotic diseases
Equine asthma is made up of which 2 conditions?
Recurrent airway obstruction/heaves
Inflammatory airway disease
Of the two conditions that cause equine asthma which one induces mild asthma and which induces severe asthma?
Inflammatory airway disease = mild/moderate
Recurrent airway obstruction = severe
List some causes of allergic asthma
- Moulds
- Bacteria / endotoxin
- Mites
- Plant debris
- Inorganic dust
- Noxious gases
Describe the pathophysiology of equine asthma
Primary insult -> inflammatory mediator release ->
- Airway smooth muscle tone
- Increased blood flow and vascular permeability
- Cell accumulation and activation
- Antibacterial activity
- Mucus production
- Neural reflex mechanisms
When dust, spore, gases, etc get into the airway, describe the 2 mechanisms which lead to bronchoconstriction
- Inflammation increases the activity of muscarinic receptors which cause peribronchiolar smooth muscle contraction
- Inflammation decreases activity of B2 adrenergic receptors which reduced bronchodilation
List the consequences of narrowing airways
- Mucosal hyperplasia/inflammatory infiltrate
- Goblet cell, increase mucus production
- Decreased mucociliary escalator
- Increased inflammatory cells
- Chronic -> fibrosis
Describe the typical clinical presentation of mild/moderate equine asthma - age, signs, history, etc
- Usually young to middle ages
- Occasional coughing
- Poor performance
- No increased respiratory effort at rest
- Often improve spontaneously
- History of exposure to a stable environment
Describe the typical clinical presentation of severe equine asthma - age, signs, history, etc
- Older than 7yo
- Regular/frequent coughing, exercise intolerant
- Increased respiratory effort at rest
- Lasts weeks/months before diagnosis
- Cant be cured but signs can be controlled
Describe the pathogenesis of chronic asthma
- Smooth muscle hypertrophy
- Peribronchiolar fibrosis
- Epithelial cell hyperplasia
- Mucus plugging
–> airway remodelling
–> Progressive impairment of lung function
Describe how increased respiratory effort in severe equine asthma presents on clinical exam
- Flared nostrils when breathing
- Expiratory +/- inspiratory wheeze
- Forced expiration -> biphasic expiratory effort = “Heaves”
- “Heave line”
- Severe cases - respiratory disease and weight loss
How is equine asthma diagnosed?
- Compatible clinical signs
- Endoscopy (resting or dynamic)
- Airway cytology
Describe the findings seen on endoscopy in cases of equine asthma
Excess mucus in tracheobronchial tree
Describe the findings seen on airway cytology in cases of equine asthma
Mild increases in neutrophils, eosinophils
Neutrophils above …% on tracheal cytology = inflammation
40
What would be seen on tracheal cytology to indicate a bacterial infection?
Lots of intracellular bacteria + degenerate neutrophils
How many cells need to be counted on a BAL to determine that qualitative cytology?
200
Neutrophils above …% on BAL cytology = abnormal
25
Severe asthma = greater increase
Mild/mod asthma = milder increase
When should you suspect other DDx for cases of ‘equine asthma’ based on your finding?
- Clinical signs at rest in < 7 years old
- ‘Sick’ (Dull / anorexic / pyrexic / weight loss)
- Diagnostic tests don’t show lower airway inflammation
- Lack of response to therapy
Describe the pyramid of asthma management
Short term - Bronchodilators
Mid term - Corticosteroids
Long term - Environmental control
What are the aims of environmental control for asthma management?
Reduction of respirable particles including dust, moulds, fungi, endotoxins, gases
- Airflow, time outside ideal
Compare the best and worst feeds for asthma management
Pasture = Best
Complete pelleted feed
Haylage
Soaked hay
Hay = worst
