Diseases of the nasal cavity and sinuses

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

Mucosa

• 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

Sinuses

• 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

Mucus

• 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.

Reflexes

• • • Sneezing
    • Coughing

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
  • 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
      • Herpesviruses
        • 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.bronchoseptica; 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 bronchoseptica 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.bronchoseptica infection of the nasal mucosa
          • Clinical signs (nasal discharge, sneezing) result from an acute to chronic rhinitis.
      • Streptococcus equi
        • Streptococcus equi subsp. equi
        • 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
  • Insecta
  • Oestrus ovis larvae in the nasal cavity of sheep and goats
  • 'Nasal bots'