1.1.4: Coughing in small animals Flashcards
Acute coughing ddx in dogs
- Tracheobronchitis (kennel cough)
- Irritation by smoke/dust/chemicals/medicines
- Airway FB
- Pulmonary haemorrhage
- Acute pneumonia e.g. aspiration
- Acute oedema (can be cardiogenic/non-cardiogenic)
- Airway trauma e.g. choke chains, bites
From this list of acute coughing ddx, which ones are often accompanied by dyspnoea, and why is this?
- Tracheobronchitis (kennel cough)
- Irritation by smoke/dust/chemicals/medicines
- Airway FB
- Pulmonary haemorrhage
- Acute pneumonia e.g. aspiration
- Acute oedema (can be cardiogenic/non-cardiogenic)
- Airway trauma e.g. choke chains, bites
- Tracheobronchitis (kennel cough)
- Irritation by smoke/dust/chemicals/medicines
- Airway FB
- Pulmonary haemorrhage
- Acute pneumonia e.g. aspiration
- Acute oedema (can be cardiogenic/non-cardiogenic)
- Airway trauma e.g. choke chains, bites
With these causes, there is alveolar disease, hence the dyspnoea. Sometimes it spills over into/affects airways too, hence the acute onset coughing.
What are some differential diagnoses for chronic coughing in the dog?
- Chronic bronchitis
- L-sided heart failure
- Oslerus/aelurostrongylus/angiostrongylus infestation
- Tracheal collapse
- Airway FB
- Bronchopneumonia
- Pulmonary neoplasia
- Extra-luminal mass lesions
- Eosinophilic disease
- Pulmonary fibrosis
Where are cough receptors located?
- Larynx
- Trachea
- Carina
- Bronchi
Coughing is a reflex designed to protect the lower respiratory tract and the alveoli
What is infectious tracheobronchitis, what can cause it and how do you prevent this?
Infectious tracheobronchitis: infectious disease of canine URT.
Causative agents:
* Canine parainfluenza - live vaccine, injection
* Canine adenovirus-2 - live vaccine, injection
* Bordetella bronchiseptica - live vaccine, intranasal
What is the typical recovery time for infectious tracheobronchitis and when might further treatment be needed?
- Spontaneous recovery tends to occur within 7-10 days
- May need further treatment if pyrexic, systemically unwell, mucopurulent nasal discharge etc.
- Could consider NSAIDs Β± antibiotics if indicated
Signalment and history associated with Canine Chronic Bronchitis
- Daily coughing over >2 months duration
- Harsh cough with attempts at production (usually clear / frothy; yellow would suggest infection)
- Worse on excitement
- Typically seen in small/ toy breeds but can be any age/ breed
- Dogs are usually externally well, often obese. May pant exvessively.
Pathology of Canine Chronic Bronchitis
- Neutrophilic / eosinophilic infiltration of mucosa and thickening of smooth muscle
- Fibrosis and scarring of the lamina propria
- Increased goblet and glandular cell size and number
- Oxidative damage and inflammatory products damage cells -> leads to mucus hypersecretion
- Loss of ciliated epithelial cells and failure of mucociliary clearance and debris
- More mucus which is more sticky
Combination of these events leads to thickening of bronchial trees (donuts and tramlines), overproduction of airway mucus and narrowing of airways (esp terminal bronchi)
Complications of Canine Chronic Bronchitis
- Bronchoectasis (widening of airways)
- Bronchomalacia (weakness of airways)
This combination can lead to dilation and then collapse of airways due to wall weakness.
Aetiology of Canine Chronic Bronchitis
Cause unknown; may be seen secondary to underlying conditions:
* Tracheal collapse
* Chronic barking
* FB
* Previous infections or inhalant toxins
* Environmental factors
* Chronic smoke inhalation / noxious gas
Clinical exam findings of dog with Canine Chronic Bronchitis
- Tracheal pinch positive - animal will cough when you palpate
- Marked sinus arrhythmia
- Often very little to find on exam
Diagnosis of Canine Chronic Bronchitis
- History and clinical exam findings
- Thoracic radiographs: increased bronchial pattern (this is often subtle)
- Bronchoscopy and BAL
What would BAL of a dog with Canine Chronic Bronchitis show?
- Increased mucus
- Non-degenerate neutrophils, eosinophils, macrophages
- Cushmannβs spirals (airway mucus casts)
- Presence of bacteria / particulate matter are less common and would suggest an underlying cause somewhere
Management of Canine Chronic Bronchitis
- General: weight control, use harness rather than collar/ lead, avoid irritants/ smoking environment
- Mucus is easier to shift if hydrated: avoid v dry environments, use steamy bathrooms and coupage to encourage coughing mucus up
- Warn owener that these animals will always cough (the damage is irreversible)
What lung pattern and radiographic changes are shown in the circle?
Bronchial pattern - images from a dog with Canine Chronic Bronchitis
* We can see tramlines
* Airways are dilated (they should taper)
What radiographic changes can be seen in this circle?
- There is bronchoectasis (dilated and weak airways)
- The hilus of the lungs is a good place to look for this
- This image is from a dog with Canine Chronic Bronchitis
How would Canine Chronic Bronchitis appear on bronchoscopy?
- Airways may look pale, scarred, fibrotic
- There is mucus stuck to the airway walls
True/false: in a dog with Canine Chronic Bronchitis you would not expect to see donuts or tramlines on thoracic radiographs
False
You WOULD expect to see these findings but they may be subtle
What disease is shown on the right? Describe the changes visible.
Canine Chronic Bronchitis
* Chronic, permanent change in the airway walls with increased numbers of goblet cells (mucus metaplasia)
* There is more mucus than usual
* Ciliary loss affecting the airways, which is now overlain by stratified squamous epithelium (squamous metaplasia)
Medical managament of Canine Chronic Bronchitis
- Glucocorticoids (oral and inhaled)
- Bronchodilator therapy often prescribed but damaged resp tract may not be able to respond ;theophyline, beta agonists (terbutaline, salbutamol, salmeterol)
- The purpose of inhaled medications is to reduce side effects of the disease not cure it
- Coupage
- AVOID using cough suppressants unless absolutely necessary (mucus will just build up)
- ONLY use antimicrobials if there is evidence of need
Describe how you would determine if antimicrobial therapy was needed in a dog with Canine Chronic Bronchitis
- Infection is rare in these dogs; should only use antimicrobials if evidence of infection
- Evidence of infection: intracellular, growth from BAL, neutrophilic inflammation on cytology
- Remember that URT and larger airways will have commensal bacteria and numbers will increase if the mucociliary escalator is damaged
- Can request a quantitative culture (rare in vet med but common in humans)
What are the problems with diagnosing infection based on culture from BAL?
- There is risk of contamination from URT - might conclude there is an infection present when there is not
- Equally, in vet med, BAL is often perfomed after antibiotic therapy has failed, but antibiotics remain in the lung for sufficient quantities for 7+ days - might conclude there is no infection when in fact there is
What are the broad treatment options for lower airway disease?
- Inhaled medications: corticosteroids, bronchodilators, nebulisers
- Oral therapy: anti-inflammatories (e.g. corticosteroids, NSAIDs, anti-leukotrienes), bronchodilators (terbutaline, theophylline), antibiotics & anthelmintics as indicated, mucolytics (N-acetyl cysteine)
What are the benefits of inhaled over oral medications?
β
Useful in management of chronic airway disease
β
Minimal absorption into systemic circulation -> less side effects esp with steroids
β
Faster onset of action compared to oral meds
What is salbutamol and when might you use it?
Salbutamol = beta 2 agonist, can be delivered by inhalation
* Fast onset of action
* Lasts >3 hrs
* Metabolised and cleared renally
* Side effects: tachycardia, arrhythmias, tremors
Used in cats with asthma
What is the difference between salbutamol and salmeterol?
Salmeterol is longer acting
What drugs might you use to treat a dog with CCB?
- Corticosteroids e.g. fluticasone propionate, beclomethasone
- Cromolyn sodium / sodium cromoglicate -> to inhibit mast cell degranulation
Characteristics of fluticasone propionate for treatment of CCB
- Slowly absorbed from lungs (long dwell time)
- Rapid first pass metabolism in the liver -> less systemic side effects
- Long half life
- Least bioavailable
- Side effects: oral infections due to immune response suppression e.g. candidiasis, coughing, wheezing
- (The above may hold true for all inhaled glucocorticoids)
Why are inhaled glucocorticoids useful?
- Inhaled version valuable in reduced systemic exposure and side effects
- Effective in acute situations
- Very useful in asthmatic cats
Benefits of glucocorticoids on the airways
β
Bronchodilatory
β
Anti-inflammatory -> inhibit both prostaglandin and leukotriene synthesis
β
Potentiate beta-2 adrenergic activity
β
Reduce leukocyte accumulation
β
Reverse increased vascular permeability
β
Inhibit fibroblast growth
β
Modulate the immune system
Remember they do have side effects so limited the dose is important!
Benefits of bronchodilators on the airway
β
Reduce spasm of lower airways
β
Decrease intrathoracic pressres
β
Decrease tendency of large airways to collapse
β
Improve diaphragmatic function
β
Improve mucociliary clearance
β
Inhibit mast cell granulation -> reduced released of mediators of bronchoconstriction
Possibly also: improve pulmonary circulation, improved cardiac function, reduced respiratory effort but not always.
Disadvantages of inhaled medications
β Expensive
β Time-consuming
β Owner compliance
β Patient compliance
What should you bear in mind if considering antibiotic use for chronic bronchitis?
- Most chronic bronchitis cases do not have bacterial infection as a causal agent. If there is a secondary infection, this requires immediate therapy due to compromised resistance mechanism.
- Antibiotics are indicated if: C&S positive, or intracellular bacteria found on BAL
- Tale care re fluoroquinolones and theophylline -> they inhibit metabolism of theophylline meaning conc increased and risk of toxicity
Prognosis of Canine Chronic Bronchitis
- Long-term control is possible; cure is not. The dog will always cough.
- Major goal is to prevent sequelae e.g. secondary pneumonia, bronchiectasis / bronchomalacia, emphysema
What are the other names for feline bronchial disease? What causes it and who is predisposed?
Feline bronchial disease = feline asthma, feline allergic airway disease, etc.
* There is a continuum between acute asthma and chronic bronchitis and cough
* Type 1 hypersensitivity reaction to inhaled allergens e.g. smoke, feathers, aerosol inhalation, dust, cat litters, sometimes seasonality
* Suspected genetic predisposition as some breeds (e.g. Siamese) more commonly affected
True/false: bacterial bronchopneumonia (primary infection) is common in dogs and cats.
False.
Primary infections are rare in healthy dogs and cats.
If present, look for an underlying cause!
If you found a dog with a primary bacterial bronchopneumonia?
- Bordetella bronchiseptica
- Streptococcus equi subsp zooepidemicus
- Mycobacteria
Many infections are mixed
Characteristics and clinical signs of Strep equi subsp zooepidemicus infection?
- New causative organisms recognised with increasing frequency
- Often associated with outbreaks
- Has been linked to acute fatal haemorrhagic pneumonia
- Highly contagious
- Sudden onset
- Clinical signs: pyrexia, dyspnoea, haemorrhagic nasal discharge, haemoptysis
Factors predisposing to bacterial bronchopneumonia
- Debilitation
- Prolonged recumbency
- Systemic immunosuppression (e.g. HAC, chemo, preds)
- Immunodeficiency states
- Defective respiratory defences
- Damaged respiratory epithelium
- Aspiration
- Airway obstruction
- Bronchiectasis
- Systemic sepsis
Clinical signs of bronchopneumonia
- Variable; occasionally only minor clinical signs
- Cough
- Respiratory distress
- Exercise intolerance
- More severe infections may produce hyperthermia
- Anorexia and lethargy
- Increased / decreased lung sounds (depending on how consolidated the lung is; might be so thick you canβt hear, or may hear crackles)
- Respiratory distress and cyanosis may develop in severe cases
Diagnosis of bronchopneumonia
- CBC, biochemistry, UA, faecal sample
- Thoracic radiographs: would see alveolar pattern with variable distribution. Early disease may show only interstitial pattern.
- Airway sampling helpful: TTW / BAL; culture and cytology on fluid (integration of inflammation and bacterial culture)
In aspiration pnuemonia, which lung pattern would you expect and with what distribution?
- Alveolar pattern with cranio-ventral distribution
Treatment of bronchopneumonia
- Broad spectrum antibiotics
- Humidified oxygen
- IVFT -> must keep hydrated and high RR / panting means much water loss; want to keep mucus wet and easy to cough up
- Anti-inflammatories
- Bronchodilators
- Mucolytics
- Physio
- Nebulisation
- Surgery if localised disease very difficult to move
History associated with bronchial foreign bodies
- High frequency in working dogs / dogs in rural environments
- Often signs after exercising in agricultural fields
- May see good initial response to antibiotics (as some localised pnuemonia) but will not resolve without foreign body removal
Clinical signs of bronchial foreign bodies
- Sudden onset coughing and gagging
- Halitosis may be present and progressive due to rotting material in lungs
- May see weight loss if significant infection associated with FB
- More substantial resp signs may suggest progression to pleural disease (i.e. FB working way out of lung into pleural space -> causing secondary pyothorax)
Diagnosis of bronchial foreign body
- Thoracic radiographs (check if lobar or diffuse disease, and for signs of pleural involvement)
- Bronchoscopy: visualisation and removal of object, BAL and culture for antibiotic therapy (may need to refer for bronchoscopy)
In which lung lobe do most inhaled FBs end up?
- Right diaphragmatic lobe bronchus (this is the most straight direction if you look down the airway)
Which are more common: primary or secondary lung neoplasias?
Secondary (i.e. metastases) far more common than primary tumours.
Common metastases that end up in lungs:
* Oral melanoma
* Thyroid carcinoma
* Osteosarcoma
* Haemangiosarcoma
* Mammary carcinoma
What is the most common primary lung tumour and what clinical signs does it cause?
Bronchogenic carcinomas
* Signalment: older dogs (median age 11yrs)
* Often found in right caudal lobe
* Causes non-productive cough or exercise intolerance
* May see hypertrophic osteopathy as a rare paraneoplastic disease (=proliferation of periosteum in limbs)
Secondary pulmonary neoplasia (metastatic disease)
Interstitial disease
Presents with breathlessness
Primary pulmonary neoplasia
* Presents with cough
* Often found in R caudal lobe
* >50% of these masses are solitary
Primary pulmonary neoplasia
Presents with cough
Primary pulmonary neoplasia
Presents with cough
Secondary pulmonary neoplasia (metastasis)
Interstitial disease
Presents with breathlessness
Diagnosis of primary pulmonary neoplasia
- Ultrasound-guided transthoracic FNA (donβt do this if the animal canβt clot, the lesion is full of air, or infection is suspected)
- Fluoroscopy / CT can also guide
- BAL rarely helpful
Contraindications for transthoracic FNA
- Pulmonary bullae or cysts
- Coagulopathies
- Pulmonary hypertension
- Pre-existing pneumothorax
- Suspected infectious process
Potential complications of transthoracic FNA
- Pneumothorax
- Empyema
- Bleeding
- Implantation
- Seeding of neoplasia through body wall
Treatment and prognosis of primary lung neoplasia
- Depends on size, location (resectability) and spread
- Adjunctive chemo often little use
- Best case scenario = adenocarcinoma, has better survival than SqCC
How does secondary pulmonary neoplasia (a.k.a. metastatic disease) present?
- Interstitial disease -> presents with breathlessness
Which lungworms affect dogs?
- Oslerus osleri
- Filaroides spp.
- Crenosoma vulpis
- Angiostrongylus vasorum
- Capilaria aerophilia
Which lungworms affect cats?
- Aelurostrongylus abstrusus
- Capilaria aerophilia
Characteristics and epidemiology of Oslerus osleri
- Prevalent in UK; rarer now due to routine worming of dogs
- More common in greyhounds and kennelled dogs
- PPP: 10-18 weeks
- Worms live in trachea, immune response causes worm to encapsulate in trachea and bronchus
- Nodules in which worms live appear 2 months from infection
Clinical signs of Oslerus osleri
- May include chronic cough: dry rasping, particular after exercise
- This is most notable in young (6-12 month old) dogs
Diagnosis of Oslerus osleri
- Bronchoscopy -> visualisation of nodules, sampling of tracheal mucus to identify eggs and larvae
- BAL: can see L1s and eosinophils
- Faecal sample: L1 count unreliable due to variable shedding; requires experienced parasitologist
Oslerus osleri nodule in trachea
Oslerus osleri nodules
Treatment of Oslerus osleri
- Can be hard as nodules may remain and calcify
- Cough may persist
- Fenbendazole (e.g. panacur) at 50 mg/kg daily for 10 days. Often need to repeat 4 weeks later.
Presentation, diagnosis and treatment of Filaroides hirthi
- Life cycle same as Oslerus osleri but F. hirthi not considered pathogenic
- Originally found in breeding colonies of beagles
- Infection generally asymptomatic; usually diagnosed at PM
- Worms live in alveoli
- Radiographs show diffuse broncho-interstitial patterns, rarely alveolar pattern
- Treatment rarely indicated; if needed, fenbendazole for 10 days, then repeate 4 weeks later (same as O. osleri)
Epidemiology and life cycle of Crenosoma vulpis
- Found in UK, occasionally seen in practice
- Usually affects foxes and wolves, occasionally dogs π¦πΊπΆ
- Indirect life cycke: slugs and snails = intermediate hosts; paratenic hosts eat slugs and snails and are infective
- PPP 3 weeks
- Highest incidence in autumn due to summer infection (seasonality of snail host)
- Larvae visible to naked eye unlike other lungworm
Clinical presentation, diagnosis and treatment of Crenosoma vulpis
- Adults live in bronchi and bronchioles where they cause bronchitis; do not form nodules
- Leads to chronic bronchopulmonary disease and productive cough
- Diagnosis: bronchoscopy, BAL, thoracic rads
- Treatment: fenbendazole 10 days then 4 weeks later; often rapid response cf O. osleri
Diagnostic plan for investigation of coughing in the dog and what each would detect
Radiography
* If bronchial pattern, consider Chronic Bronchitis, EBP
* If cardiac enlargement, consider left-sided heart failure
* May suggest foreign body
Radiography / CT very useful for airway disease investigation.
Endoscopy / bronchoscopy
* Good for foreign bodies
Other options: TTW, tracheal wash, BAL, haematology.
BAL and faecal exam
* Useful for parasites.
What are some anti-tussives and when should you use them?
Anti-tussives e.g. butorphanol, codeine
* Only use when absolutely necessary - they suppress cough, and in most cases coughing is protective
* Useful in anatomical airway disease e.g. tracheal collapse
* Useful in non-productive pathological cough e.g. neoplasia, heart failure that is receiving treatment but cough not resolving