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Pneumonia
Introduction
- 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 - including fluid support, possible airway humidification.
- 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 (with or without secondary pyothorax), death.
Presenting signs
- Coughing.
- Dyspnea, tachypnea, hyperpnea.
- Fungal pneumonia may present with non-specific signs, eg weight loss Respiratory fungal disease.
- Nasal discharge
.
Acute presentation
- Acute, severe interstitial or bronchopneumonia may present with acute dyspnea, cyanosis or collapse.
Geographic incidence
- Fungal infections are more common in America and Africa, but rare overall.
Cost considerations
- Prolonged antimicrobials and supportive care, eg IV fluids may be expensive, but uncomplicated courses are relatively inexpensive to treat.
Pathogenesis
Etiology
Infectious agents
- Viral infections:
- Feline calicivirus Feline calicivirus (FCV).
- Feline rhinotracheitis virus Feline herpes virus: feline rhinotracheitis virus often results in secondary bacterial pneumonia.
- Pox virus Cat pox virus.
- Fungal infections:
- Histoplasma Histoplasma capsulatum.
- Blastomyces Blastomyces dermatitidis.
- Coccidioides Coccidioides immitis.
- Toxoplasma.
- Primary bacterial infections:
- Nocardia Nocardia spp.
- Actinomyces Actinomyces pyogenes.
- Mycobacterium bovis Mycobacterium bovis.
- Secondary bacterial infections, common isolates include:
- Pasteurella multocida Pasteurella multocida.
- Klebsiella pneumoniae Klebsiella pneumoniae.
- Bordetella bronchiseptica Bordetella bronchiseptica.
- Streptococcus canis Streptococcus spp.
- Escherichia coli Escherichia coli.
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
General
- Immunosuppression, eg Feline leukemia virus (FeLV) Feline leukemia virus disease, Feline immunodeficiency virus (FIV) Feline immunodeficiency virus disease, immunosuppressive drugs.
- Previous viral respiratory infections, eg Feline viral rhinotracheitis Feline herpes virus: feline rhinotracheitis virus, calicivirus Feline calicivirus disease may predispose to bacterial pneumonia.
- Trauma → pulmonary contusions.
- Megaesophagus Megaesophagus.
- Laryngeal paralysis alone or following palliative treatment with arytenoid lateralization Larynx disease.
- Primary ciliary dyskinesia (very rare but reported in cats).
Pathophysiology
- 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, megaesophagus → 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.
- Smoke inhalation 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 seizing. Acidic gastric contents → severe pulmonary damage if aspirated → pulmonary edema.
Timecourse
- Days to weeks for bacterial pneumonia. Acute aspiration may result in signs within hours.
- Fungal pneumonia may have insidious onset.
- Acute for viral, toxoplasma, trauma or aspiration.
Diagnosis
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Treatment
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Prevention
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Outcomes
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Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
- Dear J D Hulsebosch, S E & Johnson LR (2024) Recognition and diagnosis of underlying disease processes in bacterial pneumonia. Animals (Basel) 14 (11), 1601 PubMed.
- Kang D, Womble M, Cullen J M et al (2023) Severe bronchiectasis resulting from chronic bacterial bronchitis and bronchopneumonia in a jungle cat. J Vet Diag Invest 36 (1), 131-136 PubMed.
- Slaviero M, Ehlers L P, Argenta F F et al (2021) Causes and lesions of fatal pneumonia in domestic cats. J Comp Pathol 189, 59-71 PubMed.
- 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.