1.1.4: Feline asthma and chronic bronchitis Flashcards
Signalment for feline asthma
Young adult to middle aged cats; but can affect cats of any age
* Older cats -> more suspicious of other diseases e.g. neoplasia, cardiac disease, hyperthyroidism
* Younger cats -> more suspicious of infectious diseases
History and clinical signs associated with feline asthma
- Lower airway disease in cats is variable in presentation
- Usually low grade, chronic disease
- Sometimes “acute on chronic” emergency presentation
Clinical signs
* Coughing (dry, harsh cough)
* Audible wheezing
* Exercise intolerance (less playful, reluctance to jump or play, being lazy etc.)
* If emergency presentation: acute development of clinical signs such as resp distress, mouth breathing, tachypnoea
Questions to ask when you suspect feline asthma
- Any trigger factors (these are rare) e.g. environment, new cat litter, passive smoking, seasonal?
- Is the cough productive?
- Is anything brought up? (Often confused with hairballs)
- Any significant weight loss, anorexia -> helps w/ other differentials e.g. heart failure, neoplasia
Discuss your approach to clinical exam of cat with breathing problems / history of a cough
These cats have minimal respiratory reserve and are easy to destabilise. If you stress them you can kill them.
* Initial exam: hands-off
* Remember transport to vets / being in consult room may be stressful
* Prioritise oxygenation - this is low risk and high benefit. Ensure cat does not overheat in an oxygen cage.
* Watch breathing
* Auscultate and listen for expiratory wheeze
* Auscultate and listen to heart rate, rhythm, check for murmurs etc. Remember that cats with heart disease may not have signs on auscultation!
You suspect a dyspnoiec cat to have heart disease such as HCM. On clinical exam, you find the cat is open-mouth breathing and stressed. On auscultation, there is no heart murmur. How does this alter your primary differential in this case?
- Not all cats with heart disease have murmurs!
- You cannot necessarily rule out HCM based on this finding alone - consider an echo / TFAST.
- It would be sensible to reduce stress and provide oxygen to this cat before further diagnostics
Signs of upper airway disease
Laryngeal disease
* laboured inspiration (stridor, increased effort, slow inspiratory phase)
* ± change in purr or vocalisation (in dogs, bark becomes more high pitched)
- Dysphagia ± salivation
- Coughing/ gagging might be triggered by eating or drinking
- Head shaking or behavioural signs may suggest nasal disease
Signs of lower airway disease
Often more subtle than upper airway disease.
* Laboured expiration: prolonged expiratory phase, additional expiratory push, audible expiratory wheeze
* Increased airway resistance due to bronchospasm, mucus, and bronchial wall thickening
* Occasionally may see paroxysmal cough (owners may think it’s a furball)
When does bronchial wall thickening occur and how long does it last?
- Bronchial wall thickeneing occurs with repeated / prolonged lower airway disease
- Over time, this becomes permanent
Characteristics of feline asthma
- Reversible
- Occurs secondary to inhaled allergen and airway hyperreactivity
- There is bronchoconstriction
- There is eosinophilic airway inflammation
Clinical signs of feline asthma
- Episodic resp distress
- Dyspnoea
- Coughing
Clinical signs of chronic bronchitis
- Coughing is a key feature
Characteristics of chronic bronchitis
- Occurs in response to infectiion or inhaled irritants
- There is airway damage and excess mucus
- There is neutrophilic airway inflammation
True/false: feline asthma and chronic bronchitis are two distinctly different conditions.
False: it is basically a continuum between the two. They can be difficult to diagnose and overlap in presentation. They are also managed in similar ways.
What is air trapping and how could a cat with lower airway disease develop a pneumothorax?
Air trapping: trapping of air behind mucus and constricted airways, causing destruction of the alveoli.
* In rare cases, alveolar damage is so bad that leakage of air occurs (pneumothorax)
True/false: spontaneous rib fractures may be seen in cats with chronic lower airway disease.
True
Why do cats with lower airway disease present with dyspnoea?
- Acute bronchoconstriction in response to a trigger factor
- Inflammation of the bronchial mucosal lining with histamine and leukotriene release
- Hyperreactivity of the bronchial smooth muscle in a Type ! hypersensitivity reaction. There is mucociliary imbalance.
Airway obstruction occurs due to bronchoconstriction, inflammation, and mucus plugs in the narrowed bronchioles.
True/false: lack of eosinophilia on haematology means feline asthma can be ruled out.
False
We may see an inflammatory haemogram inclduing eosinophilia in a cat with feline asthma. However, absence of eosinophilia does not mean we can rule out feline asthma.
Differentials for coughing in cats
- URT disease
- Inflammatory lower airway disease
- Infectious cause: bacterial, viral, parasitic
- Foreign body
- Neoplasia
- (Heart disease rarely causes coughing in cats; would expect them to present with dyspnoea).
Where is oedema formation typically in cats with heart failure and how does this impact their presenting signs?
- Oedema is in pleura or abdomen
- Even in there is alveolar oedema, cats tend not to cough
- Tend to present with dyspnoea
Differentials for hyperpnoea / tachypnoea in cats
- Stress / pain / fear
- Cardiac disease (causing pleural effusion / pulmonary oedema)
- Resp disease (airways, lung parenchymal disease)
- Pleural space disease
- Mediastinal disease
- Ruptured diaphragm
- (Pericardial peritoneal diaphragmatic hernia - usually congenital and animals are fine)
- Anaemia / hypovolaemia
- CNS disease
- Heatstroke
When might you do a faecal analysis in a cat presenting with lower airway disease?
- When suspicious of Aelurostrongylus abstrussus
What might you need to take into account if performing bronchoscopy / BAL on a cat with asthma?
- Take care - the airway is already hypersensitivie
- You could cause severe bronchospasm
When might you perform a trans-tracheal wash in a cat?
Never.
The risk of iatrogenic damage is too great.
Could instead perform an endotracheal wash.
True/false: it is important to obtain a definitive diagnosis before treating the cat with dyspnoea.
False
You may choose to pursue a treatment trial (e.g. for feline asthma) if the cat is unstable and further investigations are risky, or if finances are limited.
A cat presents with dyspnoea. After clinical exam you suspect airway disease. What do you do next?
- Take care with handling - do not stress!
- Pre-oxygenate the cat
- Consider imaging e.g. TFAST to rule out cardiac disease, check for pleural effusion etc. Also consider thoracic rads (only GA your patient if they are stable!)
- After initial imaging, you could then rule out other causes of coughing and dyspnoea e.g. via bronchoscopy, BAL / blind tracheal wahs
A cat presents in dyspnoea and it is in crisis. You suspect airway disease. What are your next steps? Consider especially which drugs you will use.
- Avoid stressing the cat
- Oxygenate
- Manage inflammation -> IV dexamethasone
- Manage bronchospasm -> terbutaline (can give SC), consider also inhaled salbutamol
You take thoracic radiographs in a cat with airway disease. What might you see?
- Bronchial pattern ± interstitial pattern
- May also see patchy alveolar pattern
- Hyperinflation which is caused by air trapping. This leads to flattened diaphragm and large gap between diaphragm and heart.
- May be normal (20% cats) - airway disease might not be severe enough to give you a clear bronchial
What might you see on bronchoscopy of the cat with airway disease?
- Hyperaemia
- Oedema
- Excess mucus
- Decreased airway diameter
Risks of bronchoscopy in the cat with airway disease
⚠️ Could aggravate irritable airways
⚠️ Could move mucus plugs
⚠️ Could cause bronchospasm (consider pre-treating with terbutaline and preoxygenate)
You find eosinophilic inflammation on BAL. What are your differentials?
- Feline inflammatory airway disease (asthma or bronchitis
- Viral pneumonia
- Parasitic cause
- Hypereosinophilic syndrome (HES)
True/false: heart failure is an absolute contraindication for BAL.
True
Do not perform BAL in a cat with heart failure.
Long term management of cat with asthma
- Reduce allergens - unlikely to be successful but some clients will try
- Prednisolone PO for 2-3 weeks to allow cat time to accept inhaled treatment
- Inhaled fluticasone (if improved)
- If no response to prednisolone: repeat test for Mycoplasma, rule out lungworm. Consider ciclosporin.
What disease can you cause by giving steroids to cat and which side effect should you look out for?
- Steroids can lead to diabetes
- If side effects include PUPD, steroid treatment must stop
How does terbutaline work and what should you do before giving it?
- Selective beta-2 receptor agonist
- -> smooth muscle relaxant that causes bronchodilation
- Rule out heart failure before giving it!
How does salbutamol work and how do you give it?
- Salbutamol = selective beta-2 receptor agonist. Give via inhaled route.
- Can give every 30 mins for 2-4hrs
- Stop if it stresses the patient
What is feline lungworm and how do cats become infected?
Feline lungworm = Aelurostrongylus abstrusus
* Cats become infected by eating paratenic host (rodents, bird)
* Prepatent period = 1-2 months
Clinical presentation of feline lungworm
- Usually young cats affected
- Most cats are asymptomatic
- Some show mild coughing, may develop dyspnoea
What might you see on radiographs of a cat with lungworm?
- Similar appearance to inflammatory airway disease (bronchial ± interstitial pattern) + alvelar component if severe
Diagnosis of feline lungworm
- Identify L1 larvae (remember false -ves are possible)
- Consider faecal flotation / Baermann’s technique
- Airway wash analysis
- Trial treatment: fenbendazole
Treatment of feline lungworm
Fenbendazole PO (Panacur)
How does Mycoplasma felis cause disease in cats?
- Mycoplasma felis causes URT signs, but also lower airway disease
- It may be a contributing factor in feline inflammatory airway disease
- However, some cats carry Mycoplasma without any issues
Clinical signs of Mycoplasma infection
- Fever
- Cough
- Tachypnoea
- Lethargy
Diagnosis and treatment of Mycoplasma
- Diagnosis: PCR on tracheal wash
- Treatment: doxycycline 10mg/kg daily PO (warn owner re risk of oesophageal strictures so should always give with food or water)
Clinical signs of mycobacterial pneumonia
- Pneumonia is a late stage systemic spread of infection with M. bovis or M. microti
- Early cutaneous signs: infection after bite from an infected vole or rodent. Non-healing sores or nodules ± large LNs
- Early GI signs: infection after ingestion e.g. contaminated milk. Vomiting, diarrhoea, weight loss, poor appetite. Lesion = inflammatory granulomas.
Mycobacterial pneumonia - diagnosis
- Histopath, PCR
- Seek advice - we need to consider zoonotic aspects
- If it is M. bovis -> this is reportable!
Treatment of mycobacterial pneumonia
- Difficult
- May take months of antibiotics (consider success rate, antimicrobial stewardship, and zoonotic risk - treatment may not be advised)
- Usually need a combination e.g. macrolide + quinolone + rifampicin and possibly others
