Difference between revisions of "Atrophic Rhinitis"

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[[Category:Pig]]
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[[Category:Respiratory Diseases - Pig]]
 
[[Category:Respiratory_Bacterial_Infections]]
 
[[Category:Respiratory_Bacterial_Infections]]

Revision as of 18:50, 17 January 2011

  • 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