Cryptococcosis

• 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

• Targets the respiratory system
  • Including the paranasal sinuses
  • Also can be systemic, cutaneous, visceral, skeletal or ocular

• Causes sporadic mastitis in cattle
  • Can spread within the herd

• Affects the CNS of dogs and cats
  • paranasal sinuses and pharynx can be infected with dissemination to the CNS and other tissues
    • E.g. Lungs, kidneys and joints
  • Also causes subcutaneous granulomas
  • The tip of the nose is a common site of infection in cats
    • See here

• 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