Equis ISSN 2398-2977

Cryptococcus spp

Contributor(s): Susan Dawson, Richard Walker

Introduction

Classification

Taxonomy

  • 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.)

Etymology

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

Active Forms

This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login

Clinical Effects

Epidemiology

Habitat

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

Lifecycle

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

Transmission

  • 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

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.

Vaccination

  • Not available.

Diagnosis

This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login

Further Reading

Publications

Refereed papers

  • Chandna V K, Morris E, Gliatto J M and Paradis M R (1993)Localized subcutaneous cryptococcal granuloma in a horse.Equine Vet J25(2), 166-168.
  • Riley C B, Bolton J R, Mills J N and Thomas J B (1992)Cryptococcosis in seven horses.Austr Vet J69(6), 135-139.

ADDED