Equis ISSN 2398-2977

Cryptococcus spp

Contributor(s): Susan Dawson, Richard Walker




  • Genus:Cryptococcusis a fungus, predominately found in yeast form. (Strains have been experimentally converted to a mycelial, sexually reproducing phase and given the nameFilobasidiella neoformans.)


  • Gk:kruptos- hidden;kokkos- grain, berry, seed.

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Clinical Effects



  • Lives in soil and dust.
  • Dried pigeon droppings - can survive in droppings for over a year.


  • Can affect any mammal. Pigeons often carry the agent but are rarely affected clinically - temperature too high for growth of agent.


  • Respiratory, occasionally percutaneous. Non-contagious.

Pathological effects

  • Human infection often associated with pre-existing immunosuppression.
  • Capsular polysaccharides induce complement depletion, antibody masking and immunosuppression.
  • Antibodies and cell-mediated immunity (phagocytes) required for defense.
  • Virulence is largely associated with the antifagocytic and immunosuppressive capsule.
  • Route of infection: usually respiratory, resulting in lesions in nasal cavity or sinuses with possible extension to the brain (involvement of the optic nerve causing blindness), and meninges.
  • Subcutaneous granulomas may occur, most commonly in the neck and feet.
  • Equine cryptococcosis may involve the respiratory tract, central nervous system or reproductive tract, but is relatively rare.
  • Mastitis   Mammary gland: mastitis  , with severe swelling and very rare spread to lungs, may occur in cattle. Infection may be introduced during intramammary medication.
  • Granulomas of subcutaneous tissue and the nose with possible central nervous system (CNS) involvement in dogs and cats; nasal passage granulomas in horses, mastitis in cattle, respiratory disease and meningitis in humans.
  • Dogs - cryptococcosis   →   most commonly CNS, ocular signs.
  • Cats - cryptococcosis   →   most commonly respiratory, CNS, ocular signs.
  • Cattle - most commonly mastitis.

Other Host Effects

  • Carried subclinically in gastrointestinal tract of birds, especially pigeons.


Control via chemotherapies

  • Amphotericin B   Amphotericin B  plus flucytosine (orally) , fluconazole   Fluconazole  .
  • Treatment rarely attempted in horses.

Control via environment

  • Avoid areas contaminated with pigeon droppings.


  • Not available.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Chandna V K, Morris E, Gliatto J M & Paradis M R (1993) Localized subcutaneous cryptococcal granuloma in a horse. Equine Vet J 25 (2), 166-168 VetMedResource.
  • Riley C B, Bolton J R, Mills J N & Thomas J B (1992) Cryptococcosis in seven horses. Austr Vet J 69 (6), 135-139 PubMed.