Introduction

• Cause: acute inflammatory syndrome of the skin. Can be a sequel to suboptimal husbandry or difficulty grooming due to another inciting cause, eg dental disease, obesity. Also reported secondary to respiratory infection.
• Signs: pain, alopecia, matted fur, purulent exudate, edema, anorexia, ileus, pyrexia, sepsis.
• Diagnosis: history, clinical signs, bacteriology, cytology, microscopy, histopathology.
• Treatment: clipping and cleaning of the area, topical and systemic antibiotics, cold compresses, management of predisposing cause (if known), severe cases may require surgical management.
• Prognosis: guarded to good.

Pathogenesis

Etiology

• Staphylococcus aureus Staphylococcus aureus is frequently associated with outbreaks of mammary cellulitis Staphylococcosis:
  • Rapid transmission can occur between rabbits where hygiene is suboptimal.
  • Bacterial genotype does not correlate with the development of cellulitis.
  • Outbreaks are more common with seasonal temperature fluctuations – spring and fall outbreaks are common.
  • Up to 20% of animals in a group may be affected.
• Pasteurella multocida Pasteurella multocida has been implicated in all types of cellulitis Pasteurellosis:
  • P. multocida is carried sub-clinically by many rabbits as a component of respiratory flora.
  • Stressors can lead to immune suppression which enables overgrowth and systemic spread.
  • Frequently associated with respiratory disease, dental and facial abscessation.
• Bordetella bronchiseptica Bordetella bronchiseptica:
  • Associated with respiratory disease in rabbits Bordetella bronchiseptica infection.
  • Rarely implicated in head and neck cellulitis following respiratory infections.

Predisposing factors

• General factors include:
  • Immunosuppression.
  • Bacterial disease with risk of localized and systemic spread:
    • Intertrigo due to obesity Obesity and large dewlaps in females Dewlap: conditions and treatment:
      • Often affects the ventral neck and perineal areas.
      • Affected rabbits are unable to groom normally and prevent fur matting.
    • Pododermatitis Ulcerative pododermatitis (Bumble foot) due to obesity Obesity, hygiene and musculoskeletal disorders.
    • Dental disease Teeth: dental disease - overview and abscessation Abscess.
• Specific factors include:
  • Head and neck cellulitis:
    • Associated with rabbits kept indoors.
    • May develop after recent respiratory disease.
  • Orbital cellulitis:
    • Brachycephalic facial structure.
    • Recurrent dental disease or abscessation.
  • Mammary cellulitis:
    • Trauma to the affected teat facilitates entry of pathogenic bacteria:
      • Use of rough bedding material causing irritation to cutaneous tissues.
      • Sharp objects in nest box, eg nails.
      • Bites from conspecifics.
      • Injuries during suckling.
    • Poor environmental hygiene.
    • Systemic infection: hematogenous spread of bacteria from other locations is possible, eg metritis, ulcerative pododermatitis, dental disease.
    • Mammary impaction: milk retention due to neonatal death or early weaning can facilitate bacterial colonization.

Pathophysiology

• Head and neck cellulitis:
  • Hematogenous or local spread from pre-existing respiratory infection or ascending infection through an external wound → superficial pyoderma, rhinitis → failure to resolve infection leads to penetration into deeper subcutaneous tissues → cellulitis → necrosis, sloughing and rupture of cellulitis areas.
• Orbital cellulitis:
  • Hematogenous or local spread from pre-existing dental infection or ascending infection through an external wound → tooth root abscessation, rhinitis → failure to resolve infection leads to osteomyelitis of the skull and penetration into deeper orbital tissues → retrobulbar abscess with cellulitis → exophthalmos.
• Mammary cellulitis:
  • Hematogenous spread from pre-existing infection or ascending infection through the teat canal or external wound → suppurative mastitis → failure to resolve infection leads to penetration into deeper subcutaneous tissues → cellulitis and deep abscessation with fistula formation → necrosis, sloughing and rupture of mammary tissue.

Timecourse

• Cellulitis is an acute syndrome and develops rapidly over 1-2 days.
• Underlying or inciting pathological processes may be chronic.

Epidemiology

• Mammary cellulitis:
  • Outbreaks tend to occur sporadically in breeding groups.
  • Risk of infection transmission highest with S. aureus outbreaks: very high risk if cross-fostering is performed and young are transferred from an infected female to a naïve foster rabbit.

Diagnosis

Treatment

Prevention

Outcomes