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Moraxella catarrhalis





  • Kingdom: Bacteria.
  • Phylum: Proteobacteria.
  • Class: Gammaproteobacteria.
  • Order: Pseudomonadales.
  • Family: Moraxellaceae.
  • Genus:Moraxella.
  • Species:catarrahalis.


  • Moraxellais named after Victor Morax, a Swiss ophthalmologist who first described this genus of bacteria.
  • Catarrhalis is derived from the Greek word catarrh, meaning to flow down:
    • GK: cata- - down;-rrh - flow.
    • This describes the discharge from eyes and nose.

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Clinical Effects



  • Normal nasal flora in healthy rabbits but can cause disease if nasal mucosa compromised.


  • Most mammalian infections are airborne and disease usually occurs due to underlying factors such as immunosuppression, high ammonia levels or secondary due to upper respiratory infection or dental disease.
  • Commensal bacteria can move from the nasopharynx via the eustachian tube and colonize the middle ear.

Pathological effects

  • Can cause disease if nasal mucosa compromised.
  • M. catarrhaliswas previously thought to be an exclusively extracellular pathogen. However, in recent publications in human medicine, it was found thatM. catarrhalisinvades multiple cell types, including bronchial epithelial cells, small airway epithelial cells, and type 2 alveolar cells.

Other Host Effects

  • Commensals of upper respiratory tract.


Control via animal

  • Optimum husbandry essential, including adequate ventilation and hygiene levels.
  • Control can prove difficult asM. catarrhalisis a normal commensal of healthy individual animals.
  • Reducing stress and overcrowding will be beneficial.
  • Address underlying causes.

Control via chemotherapies

  • Nebulization with mucolytics (N-acetylcysteine) and saline to loosen nasal exudate in rhinitis.
  • Nebulization with antibiotics.
  • Non-steroidal anti-inflammatory medication   Therapeutics: non-steroidal anti-inflammatory drugs  .
  • Nasolacrimal duct flushing   Nasolacrimal cannulation  .
  • Topical antibiotics (chloramphenicol, gentamicin or ciprofloxacin) into eyes or nares.
  • Topical ciprofloxacin and chloramphenicol are not licensed for use in rabbits. The responsibility for prescribing unlicensed products lies with the prescribing veterinary surgeon.
  • Systemic antibiotics may be indicated depending on bacteriological culture and sensitivity results.

Many drugs discussed are not licensed for use in rabbits, unless stated, and the legal implications regarding the cascade should be considered when prescribing these medications for pet rabbits.

Control via environment

  • This can be difficult as most infections are from the host itself or are airborne.
  • Usually a commensal in the nasal cavity in rabbits but can cause disease if nasal mucosa is compromised such as in cases where there is high ammonia build up. Essential to minimize stress and overcrowding.
  • Provide a solid barrier at animal height and good hygiene.
  • Fogging the environment with F10 diluted 1:250 may reduce airborne organisms. F10 contains biguanide and quaternary ammonium compounds and is viricidal, bactericidal, fungicidal and sporicidal. Used at a dilution of 1:250 F10 appears clinically safe.


  • There are noMoraxellavaccines available.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Murphy T F & Parameswaran G I (2009) Moraxella catarrhalis, a human respiratory tract pathogen. Clin Infect Dis 49 (1), 124-131 PubMed.
  • Rougier S, Galland D, Boucher S et al (2006) Epidemiology and susceptibility of pathogenic bacteria responsible for upper respiratory tract infections in pet rabbits. Vet Microbiol 115 (1-3), 192-198 PubMed.

Other sources of information

  • Hedley J (2014) Respiratory Disease. In:BSAVA Manual of Rabbit Medicine and Surgery. 3rd edn. Eds: Meredith A & Reusch B. BSAVA, Gloucester.
  • Oglesbee B (2011) Conjunctivitis. In:Blackwells Five-Minute Veterinary Consult: Small Mammal. Wiley Blackwell, Iowa.
  • Keeble E (2006) Nervous and Musculoskeletal Disorders. In:BSAVA Manual of Rabbit Medicine and Surgery. 2nd edn. Eds: Meredith A & Flecknell P. BSAVA, Gloucester.
  • Meredith A (2006) Respiratory Disorders. In:BSAVA Manual of Rabbit Medicine and Surgery. 2nd edn. Eds: Meredith A & Flecknell P. BSAVA, Gloucester. 

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