Felis ISSN 2398-2950


Contributor(s): Philip K Nicholls, Elizabeth Rozanski


  • Rare in adult cats unless immunosuppressed.
  • Lung inflammation:
    • Affecting alveoli and associated airways = bronchopneumonia.
    • Affecting interstitium = interstitial pneumonia.
    • Limited to single lung lobe = lobar pneumonia.
  • Cause: bacterial, viral, fungal, toxoplasma (common with clinical toxoplasmosis in cats).
  • Signs: cough, dyspnea, tachypnea (hyperpnea), exercise intolerance, systemic signs.
  • Diagnosis: clinical signs, radiography, bronchoscopy, bronchoalveolar lavage.
  • Treatment: antimicrobials, nursing care, airway humidification, mucolytics.
  • Prognosis: good if responds rapidly to antimicrobial treatment but poor if fail to control disease process   →   chronic bronchopneumonia, chronic interstitial disease, alveolar fibrosis, cor pulmonale, pulmonary abscessation, death.



Infectious agents

Causes of secondary bacterial infection

  • Foreign bodies.
  • Aspiration, eg food/fluid.
  • Inhaled allergens.
  • Inhaled irritants, eg acrolein, soot, smoke.
  • Parasites, eg migrating ascarid larvae, Aelurostrongylus abstrusus Aelurostrongylus abstrusus.
  • Toxins, eg paraquat Paraquat poisoning, urea Uremia.
  • Autoimmune conditions.

Predisposing factors



  • Type of pneumonia classified by predominant cell type, eg eosinophilic pneumonia, cause, eg aspiration pneumonia, and the lung reaction type, eg lipoid pneumonia.
  • Primary viral, protozoal or bacterial infections (+/- immunosuppression, eg FeLV)   →   inflammation of airways and interstitium.
  • Trauma   →   pulmonary contusions and reduced lung expansion/coughing due to pain   →   secondary infections (unlikely).
  • Pharyngeal dysphagia/regurgitation, eg laryngeal paralysis, megaoesophagus, cleft palate   →   food/fluids inhaled   →   damage depending on volume and acidity (especially gastric content) of material inhaled and effectiveness of normal lung protective mechanisms.
  • Ingested/inhaled material:
    • Relatively inert liquid   →   removed by macrophages   →   enters the lymphatic drainage system   →   condition resolves.
    • Foreign body, eg grass   →   localized bronchopneumonia if they lodge in smaller airways and not removed within a few days.
    • Allergen, may   →   eosinophilic pneumonia.
    • Toxin, eg paraquat   →   interstitial lung damage and fibrosis.
    • Smoke inhalation  →   surfactant activity reduced   →   atelectasis Lung: atelectasis (may see peribronchial densities due to edema formation).
  • Particular risk of aspiration if animal anesthetized, weak or seizuring.
    Acidic gastric contents   →   severe pulmonary damage if aspirated   →   pulmonary edema.


  • Days to weeks for bacterial pneumonia.
  • Fungal pneumonia may have insidious onset.
  • Acute for viral, toxoplasma, trauma or aspiration.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Foster S F, Martin P, Davis W et al (1999) Chronic pneumonia caused by Mycobacterium thermoresistibile in a cat. JSAP 40 (9), 433-438 PubMed.
  • Dye J A, McKiernan B C, Rozanski E A et al (1996) Bronchopulmonary disease in the cat: historical, physical, radiographic, clinicopathologic, and pulmonary functional evaluation of 24 affected and 15 healthy cats. JVIM 10 (6), 385-400 PubMed.
  • Welsh R D (1996) Bordetella bronchiseptica infections in cats. JAAHA 32 (2), 153-158 PubMed.