Atrophic Rhinitis

• B. bronchiseptica causes Atrophic rhinitis of pigs in association with Pasteurella multocida
• Colonises nasopharynx
• Infection must occur during first few weeks of life
• Produces dermonecrotic toxin which damages osteoblasts, preventing bone formation
• Leads to turbinate atrophy without distortion of the snout in uncomplicated infections
• Atrophic rhinitis results when Pasteurella multocida colonises and produces osteolytic toxin, leading to bone resorption
• Malformation of snout in growing pigs as well as poor growth
• increases with high stocking density and poor ventilation
• Vaccine available

Severe atrophic rhinitis (Image sourced from Bristol Biomed Image Archive with permission)

• Atrophy of nasal turbinates and distortion and shortening of the snout
• Caused by co-infection of the nasal mucosa with
  • Bordetella bronchiseptica
    • Appears to facilitate colonisation of nasal epithelium by the toxigenic Pasteurella
  • Toxin-producing strain of Pasteurella multocida capsular type D (or sometimes A)
    • Experimental evidence shows that the toxin acts directly on bone cells of the nasal turbinates to cause bone loss, each pathogen can cause atrophy itself but greater damage when together
• Exacerbated by adverse dietary and managemental factors
• In rapidly growing young pigs (4-12 weeks old)
• Clinical signs
  • Progressive facial deformity with rhinitis, catarrhal nasal discharge
  • Sneezing, coughing, can progress to dyspnoea and anorexia

• Gross pathology
  • Overlying skin on shortened snout is thrown into folds
  • Deviation of the snout to most affected side
  • Various loss of turbinate bone, ventral usually more affected
  • Deviation of nasal septum away from affected chamber
  • Inflammatory, haemorrhagic and ulcerative lesions in the nasal mucosa
• Micro pathology
  • Reduction in the amount of bone in the turbinates
  • No osteoid laid down between osteoblasts and existing bone
  • Increased fibrous tissue
  • Non-specific mucosal inflammation

• 2 forms of the disease
  • 'Progressive' atrophic rhinitis
    • Due to infection of the nasal turbinates by P.multocida strains carrying the toxA gene that encodes for an osteolytic toxin. P.multocida adheres poorly to mucous membranes, and therefore requires a predisposing nasal insult to assist colonisation eg: co-infection with B.bronchiseptica or Porcine cytomegalovirus (inclusion body rhinitis)
    • Turbinate bone atrophy is permanent and progressive
  • 'Non-progressive' atrophic rhinitis
    • Due to infection of the nasal turbinates by Bordetella bronchiseptica strains alone, that carry a gene that encodes for a dermonecrotic toxin.
    • Turbinate bone can regenerate by the time of slaughter

• Bordetella bronchiseptica also causes bronchopneumonia