Rhinitis

()Map CARDIORESPIRATORY SYSTEM (Map) 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