Respiratory Fungal Infections - Pathology

()Map CARDIORESPIRATORY SYSTEM (Map) RESPIRATORY SYSTEM INFLAMMATION

Aspergillosis

Cryptococcus neoformans

• Cryptococcus neoformans
• Causes a granulomatous rhinitis, gelatinous exudate, granulomatous pneumonia
• Nodules or destructive masses which often result in facial swelling
• In severe cases, extension from nasal cavity to involve skin and oral mucosa can occur
• Can invade through adjacent structures, eg: through the cribiform plate into the brain! These cases therefore can present as a primary neurological disease.
• Microscopic:
  • Large number of fungi and only few macrophages, lymphocytes and giant cells

Blastomycosis

• Caused by Blastomyces dermatitidis
• Occurs mainly in the Americas, Middle East and Africa, occasionally in Europe
• Mainly in young dogs, occasionally other species
• Can involve almost any tissue after spread from lungs
• Gross lesions:
  • Granulomatous pneumonia
• Microscopic lesions:
  • Yeast fungi with thich walls in nodules with macrophages, neutrophils and giant cells

Histoplasmosis

• Caused by Histoplasma capsulatum
• Gross lesions in lungs:
  • Firm encapsulated granulomas (granulomatous pneumonia)
• Microscopic lesions:
  • Macrophages with inracytoplasmic yeasts
• Also in other tissues

Pneumocystis carinii

• Important cause of pneumonia in humans associated with immunodeficiency states
• It has been occasionally reported in young or immunosuppressed animals (e.g. Arabian foals with congenital immunodeficiency)
• Grossly:
  • Diffuse interstitial pneumonia
  • Patches of firmness or consolidation
• Histologically:
  • Alveoli are filled with pale staining acidophilic material (= trophozoite and cyst forms of the organism)
• It is thought that as P. carinii is often present as a latent infection, alveolar macrophages normally control the organism - a process which fails in immunodeficient states