Rhinitis

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NASAL CAVITY



For an overview of respiratory infections see Respiratory System Inflammation - Pathology


Rhinitis

Mucoid rhinitis (Image sourced from Bristol Biomed Image Archive with permission)
  • Acute or chronic
  • Aetiology
    • Infectious
    • Allergic
    • Toxic
    • Traumatic e.g. foreign bodies
  • Serous cells usually first to respond to a noxious agent, releasing secretions into the mucocilliary blanket
  • Serous rhinitis - typical mild 'runny nose'
    • Loss of cilia and hydropic degeneration of epithelial cells
    • Epithelium becomes susceptible to secondary bacterial infections, including overgrowth of resident nasopharyngeal flora
    • Goblet cells become stimulated, changing the secretions into a thick opaque mucus ->
  • Catarrhal rhinitis
    • Contains mucus, emigrating leukocytes and few sloughed epithelial cells
  • Mucopurulent and then purulent rhinitis
    • When secondary bacterial infection is severe, migrating neutrophils pour into the exudate
    • More severe damage to the nasal mucosa causes vascular permeability and seepage of large molecular weight proteins, including fibrinogen, into the exudate ->
  • Fibrinopurulent and fibrinous rhinitis
  • Fibronecrotic and ulcerative rhinitis are manifestations of very severe damage to the nasal mucosa


Chronic rhinitis

  • Happens when acute rhinitis fails to resolve - common
  • Typically catarrhal or purulent
  • In chronic purulent rhinitis
    • Extensive fibrosis of the lamina propria
    • Atrophy of nasal glands
    • Squamous cell metaplasia
  • -> Impaired local defences
  • Superficial fibrinous membrane can be peeled of without leaving dmaged tissue underneath
  • Deeper fibronecrotic lesions associated with Fusobacterium necrophorum - yellowish fibronecrotic membrane, when removed, leaves ulcerated surface
  • May manifest as nasal polyps, progressive haematoma in horses and nasopharyngeal polyp of cats


Allergic rhinitis

  • Occurs in dogs, cats and horses, may occur seasonally in cattle, especially Channel Island breeds
  • Similar inflammatory changes as above
  • Due to hypersensitivity to inhaled allergens
  • Eosinophils tend to be the dominant infiltrating leukocytes
  • Grossly:
    • Pale, thick, oedematous nasal mucosa
  • Histologically:
    • Hyperplastic, eroded nasal epithelium, eosinophil infiltrate
  • If chronic -> Nasal granuloma
    • Extends caudally, even to larynx and proximal trachea
    • Grossly:
      • Granular hyperplastic epithelium with multiple nodules covered by normal epithelium
    • Hisologically:
      • Centre of granulation tissue surrounded by oedematous lamina propria covered by hyperplastic epithelium
      • Goblet cell hyperplasia
      • Eosinophil infiltration


Sinusitis is a common sequel to rhinitis


Infectious causes of rhinitis

. VIRAL BACTERIAL FUNGAL PARASITIC
Dogs Canine distemper secondary A. fumigatus Linguatula serrata
. Parainfluenza- 2 . C. neoformans Capillaria aerophila
. Canine herpes virus . . .
Cats Feline viral rhinotracheitis secondary Cryptococcus neoformans Linguatula serrata sometimes
. Feline calicivirus . Aspergillus fumigatus Capillaria aerophila
Horses Equine rhinovirus Strangles Aspergillus spp. Parascaris equorum
. Equine influenza Streptococcus equi subsp. zooepidemicus . .
. Equine rhinopneumonitis Glanders . .
. Equine viral arteritis . . .
Cattle Infectious bovine rhinotracheitis secondary . .
. Parainfluenza- 3 subclinical CAR bacillus . .
. Bovine adenovirus . . .
Sheep Parainfluenza- 3 subclinical CAR bacillus . Oestrus ovis larvae
Pigs Inclusion body rhinitis Atrophic rhinitis . .
. Swine influenza . . .


For an overview of respiratory infections see Respiratory System Inflammation - Pathology