Diseases of the nasal cavity and sinuses

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Clinical signs and locations of sinonasal pathology

Nasal discharge

  • Bilateral discharge:
    • Lesion is caudal to nasal septum eg: pharyngeal lesion; LRT lesion in horses
    • Lesion has resulted in nasal septum destruction
      • Neoplasia
      • Fungal infection
  • Unilateral discharge:
    • Lesion is cranial to nasal septum eg: nasal or sinus lesion; pharyngeal or guttaral pouch lesion in horses.

Type of discharge

    • Serous
    • Catarrhal
    • Purrulent
    • Haemorrhage

Clinical signs

    • Sneezing - nasal
    • Facial swelling - nasal, pharyngeal
    • Pain - any location
    • Coughing - pharynx, larynx, trachea
    • Dyspnoea/altered air flow
    • Respiratory noise

Functional anatomy


  • Mucosal epithelium
    • Nares and epiglottis- stratified squamous
    • Nasal cavity, paranasal sinuses, larynx, trachea - pseudostratified, columnar, cilliated
  • Submucosa
    • Submucosal glands
    • Lymphoid tissue
  • Blood vessels, lymphatics and nerves
    • Very rich blood supply to nasal mucosa

Nasal chambers and turbinates

  • Scrolls of turbinate bone
  • Arrangements vary with species

Nasal septum

  • Full length of nasal chamber in horses
    • 2 openings into pharynx
  • Partial length in other species
    • Single opening into pharynx


  • Size, arrangement and number vary with species
  • Poorly developed in carnivores
    • Poor communication of frontal sinus in cats with nasal cavity
      • Predisposed to frontal sinus bacterial infections
    • Maxillary sinus opening very large - 'maxillary recess'
      • Maxillary sinus infections very uncommon in carnivores
    • Highly developed in horses
    • Slit-like, high openings in horses
    • Predisposed to bacterial infections
    • Cheek teeth embedded within the maxillary sinuses
    • Maxillary sinusitis secondary to tooth root abscesses

Guttural pouch

  • Horses
    • Diverticulum of the eustachian tube with a thin slit-like opening at the rostroventral aspect into the pharynx.
    • Mucous secretions drain out of the pouch when the horse lowers its head
    • Lined by respiratory epithelium
    • Bordered by glossopharyngeal, vagus, accessory and hypoglossal nerves; sympathetic trunk; internal and external carotid arteries
  • Pathology
    • Mycotic infections eg: Aspergillus fumigatus
      • Bacterial infections eg: Streptococcus equi var. equi ('Strangles') or S.equi var zooepidemicus
    • Tympany - associated with dysfunction of the pharyngotubal opening resulting from thickening (oedema, inflammation) or obstruction by a mucosal fold (eg: foals)

Defense mechanisms

Particle deposition

  • Coiled nature of turbinates promotes turbulent airflow and impaction of large particles >10 μm in diameter onto the nasal mucosa

Mucociliary escalator

  • Cilia on the respiratory epithelium beat in a co-ordinated manner
    • Cilia beat in a caudal direction in nasal cavity
    • Cilia beat in a cranial direction in trachea and lower airways
    • Mucus is swallowed when it reaches the nasopharynx
    • Constant movement reduces chances that pathogens can adhere to the respiratory epithelium


  • Produced by the goblet cells of the respiratory epithelium and the submucosal glands with contribution from lacrimal glands draining into the nose
  • Traps particles for transportation away and subsequent swallowing
  • Physical barrier against mucosal damage
  • Prevents dessication of the mucosal epithelium
  • Contains antimicrobial substances
  • Immunoglobulin - IgA
    • IgA produced by mucosal plasma cells
    • IgA can attach to specific pathogen antigens (viruses, bacteria) trapping them in the mucus for clearance
  • Lysosyme
    • Direct action on bacterial cell walls
    • Lactoferrin
      • Inhibits bacterial growth as sequesters iron, an essential co-factor for many bacteria

Commensal bacteria

  • The normal bacterial flora of the nasal cavity, pharynx, larynx and proximal portion of the trachea compete with potentially pathogenic bacteria and help to prevent their colonisation (competitive exclusion).
  • The airway environment distal to the mid-portion of the trachea is effectively sterile.


  • Sneezing

Pathology of the upper airways

Developmental abnormalities

  • Palatoschisis
  • Nasal deviation
  • All brachycephalic dog and cat breeds!
    • Esp. English Bulldogs - stenotic nares, wide/long soft palate, hypoplastic trachea

CIrculatory diseases

  • Epistaxis
    • Haemorrhage from the nose
    • Causes
      • Inflammation eg: ulcerative rhinitis
      • Neoplasia eg: infiltrating tumour, haemangioma
      • Trauma
      • Clotting defects
    • Horse:
      • Haemorrhagic nasal polyp
        • 'Ethmoid haematoma', 'Progressive haematoma' - arise from the ethmoid region and can extend to fill the nasal cavity. They can be difficult to control as they can recur after surgery.
        • Histology - multiple areas of acute to chronic haemorrhage within a fibrous tissue stroma.
      • Exercise-induced pulmonary haemorrhage

Inflammatory disease

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  • Inflammation in the URT can be classified on:
    • Location
      • Nasal cavity - rhinitis
      • Paranasal sinuses - sinusitis
      • Guttural pouch and eustachian tube - eustachitis
      • Pharynx - pharyngitis
    • Type
      • Grossly many inflammatory processes (eg: response to viral or bacterial infection) in the URT will begin as a serous discharge, and then progress to a catarrhal exudate, and then to purulent/pseudomembranous/haemorrhagic as neutrophils are recruited
      • Serous - transparent fluid exudate (acute inflammation)
      • Catarrhal - mucous exudation (acute to subacute inflammation)
      • Pseudomembrnaous - fibrin exudation
      • Purulent - pus
      • Ulcerative
      • Haemorrhagic
      • Granulomatous (chronic inflammation)
      • Polypoid (chronic inflammation)
    • Timecourse
      • Acute, subacute, chronic
    • Causes
      • Infectious agent - viral, bacterial, fungal, parasitic
      • Trauma or foreign body (eg: grass seed)
      • Irritant or allergens
      • Neoplasia

Viral infections

  • Bovine herpesvirus -1
    • Causes Infectious bovine rhinotracheitis (IBR)
    • Highly infectious URT disease of cattle
    • High morbidity, low mortality
    • Aerosol transmission - requires close contact between animals
    • BHV-1 infects the respiratory mucosal epithelial cells (intranuclear inclusion eosinophilic inclusion bodies)from nasal mucosa down to bronchioles
      • leading to neutrophilic inflammation of varying severity.... serous -> catarrhal -> purulent nasal discharge, sneezing, coughing.
      • with secondary bacterial infection (eg: Pasturella spp., Mycoplasma spp., Fusobacterium necrophorum) can lead to fibrinous to necrotizing inflammation; mucosal sloughing, ulceration... pyrexia, dyspnoea ... inhalation pneumonia... death.
    • Clinical signs include coughing, discharge, lacrimation, and increased respiratory rate.
    • Clinical disease most severe in young calves - can develop mucosal ulcerative lesions in the oesophagus and forestomachs and viraemia with multiorgan infection.
    • Cause of abortion >5 months of gestation

  • Cytomegaloviruses
    • Porcine cytomegalovirus
      • Causes Inclusion body rhinitis
        • Disease of suckling piglets 1-5 wks of age
        • Clinical signs: those associated with acute/subacute rhinitis (ie: serous nasal discharge, progressing to catarrhal or purulent discharge with time and secondary bacterial infections; sneezing; pyrexia)
        • Morbitity high, mortality low
        • Histology: large basophilic intranuclear inclusion bodies in the nasal and sinus respiratory epithelium with lymphocytic infiltration of the mucosa.
        • Can develop viraemic stage, with inclusions in other organs eg: renal tubular epithelium. Piglets can die during this phase.
  • Equine herpesvirus - 1, 4
  • Feline herpesvirus -1
    • One of the causes of Feline viral rhinotracheitis
      • Viruses and bacteria are involved in the complex. The most frequent aetiologic agent is FHV-1, and less frequently feline calicivirus and/or Chlamydophia psittaci (NB: previously called Chlamydia psittaci var felis)
      • All three agents infect URT respiratory epithelium, although FHV-1 has the highest affinity for this epithelium
      • Feline calicivirus more frequently infects the oral mucosa -> ulcerative stomatitis
      • C.psittaci more frequently infects the conjunctival epithelium -> chronic conjunctivitis
      • Infection of the respiratory epithelium by FHV-1 results in a typical neutrophilic rhinitis with intraepitheial intranuclear eosinophilic inclusion bodies, with expected clinical signs
      • Resolution of clinical signs usually occurs by 7-14 days.
      • FHV-1 remains latent in the trigeminal ganglion, and can reactivate at times of stress. Can infect the cornea -> ulcerative keratitis.
      • Occasional mortality in kitten or immunocompromised animals usually associated with secondary bacterial infection.

Bacterial infections

  • Pasturella multocida
    • Atrophic rhinitis in pigs
    • Pigs aged 4-12 weeks old show clinical signs
    • Catarrhal nasal discharge (due to an acute rhinitis), sneezing, coughing, can progress to dyspnoea and anorexia.
    • Shortening and distortion of snout, secondary to nasal turbinate bone loss (histological evidence of osteolysis)
    • 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 Bordatella bronchiseptica strains alone, that carry a gene that encodes for a dermonecrotic toxin.
        • Turbinate bone can regenerate by the time of slaughter
    • 'Snuffles' in rabbits
        • Most often P.multocida and/or B.bronchiseptica infection of the nasal mucosa
        • Clinical signs (nasal discharge, sneezing) result from an acute to chronic rhinitis.

Category:RVC, Category:R(D)SVS, Category:CUVS, Category:PG,

  • Streptococcus equi
    • Streptococcus equi subsp. equi

Purulent nasal discharge horse.jpg

      • Cause of 'Strangles' in horses
      • Infection with Streptococcus equi occurs after contact with contaminated feed, water bowls or an infected carrier horse
      • Organism remains viable in environment for months
      • Possibility of other sources of infection - in pharynx of in-contact dogs?
      • Colonisation of nasopharynx causing:
      • Chronic purulent rhinitis, sinusitis, eustachitis
      • Can progress to development of nodular masses in the guttural pouch consisting of inspissated pus and viable bacteria (guttural pouch empyema) - 'carrier' state
      • Regional suppurative lymphadenitis - can rupture onto skin of neck
      • Bacteraemia with abscess formation in other organs (eg: liver, kidneys) - Bastard Strangles!
    • Streptococcus equi subsp. zooepidemicus
      • Can infect the respiratory tract (nasal cavity, paranasal sinuses, trachea and bronchi/bronchioles)
      • URT infection can be indistinguishable clinically from Strangles, but does not cause suppurative lymphadenitis (cf: S.equi subsp. equi)

Fungal infections

  • Filamentous fungal organisms
    • Aspergillus fumigatus
      • Guttural pouch infections in horses - fungal plaques form on the adventitia of the carotid arteries can lead to catastrophic haemorrhage following erosion of carotid arteries!
      • Nasal infection in dogs and cats - plaques develop on the nasal or paranasal sinus epithelium. Result in severe neutrophilic rhinitis/sinusitis. Can occur secondary to areas of mucosal compromise eg: adjacent to a space-occupying lesion.
    • Mucor spp.
  • Yeast-like fungal organisms
    • Cryptococcus neoformans
      • Most commonly in cats and dogs
      • Chronic granulomatous rhinitis
      • Can invade through adjacent structures, eg: through the cribiform plate into the brain! These cases therefore can present as a primary neurological disease.

Parasitic infections

  • Oestrus ovis larvae in the nasal cavity of sheep and goats = Nasal bots

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