Canis ISSN: 2398-2942

Lung: bacterial pneumonia

Synonym(s): Bronchopneumonia

Contributor(s): Lesley G King


  • Cause: bacterial infection, may be primary but often secondary to underlying pulmonary disease.
  • Signs: cough, lethargy, exercise intolerance, dyspnea, +/- fever.
  • Diagnosis: signs, radiography, cytology.
  • Treatment: antibiotics, physical therapy, supportive care.
  • Prognosis: good to guarded.



Predisposing factors


  • Unvaccinated (increased risk of infections, ie primary bacterial respiratory pathogens, viral or parasitic disease).
  • Management, eg boarding kennel, shelter animal.
  • Any vomiting or regurgitation (risk for aspiration).
  • Anesthesia or heavy sedation (atelectasis Lung: atelectasis , risk for aspiration Lung: aspiration pneumonia ).
  • Debility or malnutrition.
  • Age (young and old are at increased risk of severe disease).
  • Conformational abnormalities, eg brachycephalic conformation.
  • Hunting dogs (increased risk of inhaled foreign bodies because nose on ground while panting with mouth wide open).
  • Certain breed predisposition to inherited deficiencies in pulmonary defences, eg Bichon Frise Bichon Frise or Newfoundland Newfoundland for primary ciliary dyskinesia Primary ciliary dyskinesia.


  • Bacteria normally present colonizing pharynx and airways can invade and proliferate if there is:
    • Inflammation:
      • Chronic, eg chronic bronchitis.
      • Acute, eg viral infection, aspiration of GI contents.
    • Epithelial denudation, eg aspiration of GI contents.
    • Ciliary escalator dysfunction:
      • Ciliary dyskinesia.
      • Bronchiectasis acquired or congenital.
      • Bordetella bronchiseptica infection.
    • Atelectasis, ie bacterial trapping in collapsed alveoli.
    • Decreased ability to cough, eg pain, physical weakness.
    • Inherent immunosuppression, eg very young or old age, drug therapy.
    • Foreign body nidus.
  • Hematogenous pneumonia may occur if septic emboli are present due to:
  • In dogs, secondary bacterial pneumonia is usually caused by gram negative aerobic pathogens such as E. coli Escherichia coli , Pseudomonas spp Pseudomonas , or Klebsiella Klebsiella pneumoniae. In a minority of cases, gram positive cocci such as Staphylococci Staphylococcus spp may occur.


  • Variable. Acute onset over days or chronic over months even years.
  • May be superimposed on chronic disease.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Dear J D (2014) Bacterial pneumonia in dogs and cats. Vet Clin North Am Small Anim Pract 44 (1), 143-159 PubMed.
  • Proulx A, Hume D Z, Drobaz K J, Reineke E L (2014) In vitro bacterial isolate susceptibility to empirically selected antimicrobials in 111 dogs with bacterial pneumonia. J Vet Emer Crit Care 24 (2), 194-200 PubMed.
  • Byun J W, Yoon S S, Woo G H et al (2009) An outbreak of fatal hemorrhagic pneumonia caused by Streptoccus equi subsp zooepidemicus in shelter dogs. J Vet Sci 10 (3), 269-271 PubMed.
  • Schultz R M, Zwingenberger A (2008) Radiographic, computed tomography and ultrasonographic findings with migrating intrathoracic grass awns in dogs and cats. Vet Radiol Ultra 49 (3), 249-255 PubMed.
  • Jameson P H, King C A, Lappin M R & Jones R L (1995) Comparison of clinical signs, diagnostic findings, organisms isolated and clinical outcome in dogs with bacterial pneumonia - 93 cases (1986 -1991). JAVMA 206 (2), 206-209 PubMed.