Cryptococcosis

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  • Over 19 species
    • C. neoformans only major pathogen
  • Worldwide
  • Occurs in high concentrations in pigeon droppings (high creatinine concentration)
    • The pigeon is not infected
    • C. neoformis colonise the droppings after they have been excreted
    • Also found in fruit, milk and soil
  • Exogenous, inhaled infection which is generally sporadic (non-contageous)
    • Can also be absorbed via skin penetration and ingestion
  • May be a primary pathogen or opportunistic
  • Causes sporadic mastitis in cattle
    • Can spread within the herd
  • Affects the CNS of dogs and cats
  • Causes myxoma-like lesions of the lung and lip in horses
  • Causes cryptococcal meningitis in humans
  • Also affects dolphins, foxes, ferrets, monkeys, birds, cheetahs and guinea-pigs
  • Large yeast with capsule seen using India ink stain
  • Stains with PAS (Periodic acis Schiff)
  • Gram positive
  • Grows on blood agar and Sabouraud's Dextrose agar forming white, granular colonies which become slimy, mucoid and turn creamy/brown within a week
  • Species identified by carbohydrate assimilation tests
  • Antigen and antibody should be tested for as antibody formed by the body is soon overwhelmed and neutralised by abundent polysaccharide antigen from the capsule in active, systemic infections
    • Latex agglutination for antigen, complement fixation, ELISA and IFAT can be used


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