8.2.2: Equine asthma Flashcards
1
Q
How do we categorise equine asthma?
A
- Mild-moderate equine asthma (IAD)
- Severe equine asthma (RAO)
Equine asthma was formerly known as broken wind, heaves, chronic obstructive pulmonary disease (COPD), recurrent airway obstruction (RAO), inflammatiry airway disease)
2
Q
True/false: in mild-moderate equine asthma, there are subtle clinical signs at rest.
A
False
Only in severe equine asthma are there signs at rest.
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1
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4
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2
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5
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3
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6
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4
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7
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5
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8
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6
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9
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7
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10
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8
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11
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9
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12
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10
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13
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11
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14
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12
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15
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13
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16
Q
On cytology for severe asthma, neutrophils make up what % of the TNCC?
A
25%
17
Q
On cytology for mild-moderate asthma, neutrophils make up what percentage of the TNCC?
A
10-25%
We also see increased mast cells in mild-moderate asthma
18
Q
True/false: all horses which have mild asthma will eventually develop into those with severe asthma.
A
False
Not all horses will mild form show progression to severe form
19
Q
Aetiology of equine asthma
A
- Strong association with environment and feeding
- Mechanisms are poorly understood
- It is a non-allergic inflammatory response e.g. to endotoxins, moulds, noxious gases; but there can also be an allergic reaction component that involves Type I and Type III hypersensitivity
- There seems to be a familial risk for moderate and severe equine asthma so some suggest genetic testing should be performed
20
Q
How can environment and feeding impact equine asthma?
A
- Airborne respiratory dust (ARD) causes and exacerbates the disease
- Some particles in the breathing zone and stable zone, if small enough (<5µm) will make it into the lower airways but not back out - these particles e.g. moulds and fungi trigger disease
- There is a lower concentration of these in steamed hay
- Hay dust exacerbates asthma - even a horse in remission can be affected
- Higher concentrations from nets (4x higher respirable dust)
- The breathing zone is 30cm around the horse’s nose
21
Q
Which organisms may play a role in the hypersensitivity allergic reactions that may come with asthma?
A
- Faenia rectivirgula
- Aspergillus fumigatus
- Thermoactivenomyces vulgaris
22
Q
Pathophysiology of equine asthma
A
- Airway hyper-responsiveness
- Bronchospasm
- Inflammation
- Mucus accumulation
- Tissue remodelling
23
Q
Discuss how bronchospasm occurs in equine asthma
A
- Occurs secondary to inflammation
- Bronchodilators are effective
24
Q
Discuss the signs of inflammation we can see on cytology of the horse with equine asthma
A
- Airway neutrophilia
- Activation of macrophages occurs
25
Describe how mucus accumulation plays a role in equine asthma
* Consistent finding in equine asthma
* Perhaps associated with the neutrophilia but not sure
* Long persistence (even during remission)
* Exacerbations increase viscoelasticity (and just generally will increase the production of mucus by goblet cells)
26
Describe how tissue remodelling plays a role in equine asthma
* Increased smooth muscle mass -> increased contraction force
* Peribronchial fibrosis
* Epithelial hyperplasia
* Bronchiectasis: inflow of air into some segments of lower airways, and outflow impaired by these issues. This means there is too much air in the alveoli -> they burst and form larger balloon-like structures
27
Which small particles (<5µm) can cause disease?
* Moulds and fungi
* Pollen
* Endotoxins
* Chemicals: ammonia, smoke, exhaust fumes
28
Diagnosis of equine asthma
* History
* Physical exam
* Auscultation - use a rebreathing bag
* Endoscopy
29
How can a rebreathing bag be used to help diagnose equine asthma?
* Place bag around the horse's muzzle. This will increase CO2, and thereby increase depth ad effort of respiration
* This makes it easier to hear respiratory sounds on auscultation
* Check for tolerance, cough, recovery
* This is especially important for horses with mEA -> they will not tolerate the bag for very long
* May hear wheezes, crackles, tracheal rattles
⚠️Do not use a rebreathing bag if the horse is in respiratory distress⚠️
30
How can endoscopy be helpful in investigation of equine asthma?
* Rule out upper airway disease
* Can see tracheal mucus
* Perform 1hr post exercise
* Make sure to visualise the carina
31
Who has equine asthma?
Horse 1
32
1
33
2
34
3
35
4
36
SPAOPA
Summer pasture-associated obstructive pulmonary disease
37
What broad classes of drugs can be used to treat horses with asthma?
Horses with mEA only may benefit from:
* Immune modulation (interferon-alpha)
* Omega-3 supplementation
Horses with mEA and sEA may benefit from:
* Glucocorticoids
* Bronchodilators
38
Why are glucocorticoids used to treat equine asthma?
* High efficacy and extensive use
* Impact on lung function, airway inflammation, bronchial remodelling
* Side effects include: adrenal suppression, adrenal gland atrophy, immune suppression, laminitis
* Inhaled therapy may be preferable to systemic for long-term treatment
39
How could you use glucocorticoids to treat the horse with acute sEA?
* IV dexamethasone (0.04-0.1mg/kg SID)
* Followed by PO dexamethasone 0.05 mg/kg OR prednisolone 1mg/kg SID - give until respiratory effort and nasal discharge resolve
* Then follow with inhaled glucocorticoids: ideally fluticasone 2000µg BID, otherwise Beclomethasone diproprionate 3750µg BID
40
Characteristics of ciclesonide for treatment of sEA
Ciclesonide
* Glucocorticoid
* Pro-drug
* Does not affect cortisol
* Dose: 8 activations BID for 5 days, then 12 activations SID
41
Glucocorticoid treatment protocol for mEA
* Start PO dexamethasone 0.05mg/kg OR prednisolone 1mg/kg SID - for 4 weeks
* Follow this with inhaled glucocorticoids:
* Initially fluticasone 2000µg BID, tapered over 4 weeks to 1000µg every 48hrs
* Can then use Beclomethasone diproprionate 500-1500µg BID
42
What bronchodilators are available for treatment of equine asthma and how should you use them?
Use bronchodilators alongside glucocorticoids
* There are beta-adrenergic and parasympatholytic options
Beta-adrenergic
* e.g. Clenbuterol, albuterol, salbutamol
* Give inhaled for mEA, systemic for sEA
* Systemic: Clenbuterol PO starting at 0.8µg/kg BID then increasing to 3.2µg/kg BID; clenbuterol IV not recommended due to side effects
* Inhaled: salmeterol (0.5-1µg/kg q6hrs) or albuterol (0.8-2µg/kg q1-6hrs)
Parasympatholytic
* = ipratropium bromide (0.4-0.8µg/kg q4hrs)
43
How could you use interferon-alpha in the treatment of equine asthma?
* 50-150 U / horse/ day
* May see positive response to treatment and decreased relapse rate
* However practical experience is mixed
44
How could cromoglicate be used in treatment of equine asthma?
* Used in mast-cell mediated mEA
45
How could omega-3 fatty acids be used in treatment of equine asthma?
* 1.5-3g DHA for both mEA and sEA
46
Side effects of glucocorticoids
* Adrenal suppression
* Adrenal gland atrophy
* Immune suppression
* Laminitis
47
Systemic beta-adrenergic bronchodilators
* Cardiovascular remodelling
* Tachyphylaxis
48
What must you take into account and warn the owner about if their horse is on long term treatment for equine asthma? Where is a good place to look for the required information?
* Each drug and delivery method has a detection time
* The treatment should be discontinued before that time
* Times may vary according to pathology and other factors
* These times change so should be rechecked regularly (see BHA website or individual competition information)
