Equis ISSN 2398-2977

Cryptococcosis

Synonym(s): Systemic mycosis

Contributor(s): Melissa Kennedy

Introduction

  • Cause: infection with the opportunistic saprophytic fungusCryptococcus neoformans  Cryptococcus spp  in an immunocompromised host.
  • Signs: depend on site of infection; respiratory disease, meningitis, weight loss, nasal discharge, cough, abdominal pain; abortion, neonatal pneumonia; skin granulomas.
  • Diagnosis: direct microscopy, culture; endoscopy, radiography; biopsy and histopathology; post mortem.
  • Treatment: fluconazole, itraconazole, amphotericin B; surgical removal.
  • Prognosis: poor.

Pathogenesis

Etiology

  • Cryptococcus neoformans  Cryptococcus spp  most commonly associated; several varieties have caused disease in mammals:
    • C. neoformansvargattii, saprophytic, associated with the river red gumEucalyptus camaldulensis, an Australian native tree exported worldwide (E. rudisalso implicated).
    • C. neoformansvarneoformans, often found in bird feces.
  • C. albidusandC. laurentiialso implicated in some diseases.
  • Dissemination ofC. neoformansvargattiiis associated with flowering of the tree (late spring).
  • Cryptococcosis is a prevalent systemic mycosis in humans, caused usually byC. neoformansvarneoformans.
  • Asymptomatic infection in apparently healthy host, with uneventful resolutions, is probably relatively common.
  • Clinical disease is associated with immunocompromise, eg in humans with human immunodeficiency virus (HIV).

Predisposing factors

General
  • Organism found in soil with high nitrogen, eg bird droppings.
  • Geographic location - regions whereC. neoformansis endemic.
  • Presence of the eucalyptus tree,E. camaldulensisorE. rudis.
  • Season - first signs of disease may be associated with late spring or coincident with flowering of the eucalyptus.

Specific

Pathophysiology

  • Exposure to soil containing spores ofC. neoformans  →   inhalation or ingestion   →   failure of normal immune mechanisms to suppress colonization   →   hematogenous or direct spread to other body systems.
  • Sporadic disease in horses.
  • Inhalation   →  
    • Fungal particles deposited in nasal mucosa   →   colonization   →   invasion into paranasal sinuses   →   infection extends via cribriform plate to meninges   →   diffuse meningitis.
    • Spores small enough to penetrate alveoli reach the dorsocaudal lung   →   presence of devitalized tissue, eg EIPH   Lung: EIPH (exercise-induced pulmonary hemorrhage)  , or neutrophil dysfunction   →   tissue invasion   →   hematogenous spread to local lymph nodes and formation of disseminated nodules.
  • Ingestion of fungal elements   →   infection of the gastrointestinal tract   →   mesenteric lesions   →  
    • Non-specific gastrointestinal disease   →   anorexia, weight loss, abdominal pain.
    • Hematogenous spread to the lungs   →   disseminated pulmonary disease.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Petrites-Murfy M B et al (1996) Equine cryptococcal endometritis and placentitis with neonatal cryptococcal pneumonia. J Vet Diagn Invest (3), 383-386 PubMed.
  • Chandna V K et al (1993) Localized subcutaneous cryptococcal granuloma in a horse.Equine Vet J 25 (2), 166-168 VetMedResource.
  • Blanchard P C et al (1992) Cryptococcal pneumonia and abortion in an equine fetus. JAVMA 201 (10), 1591-1592 PubMed.
  • Riley C B et al (1992) Cryptococcosis in seven horses. Aust Vet J 69, 135-139 PubMed.

Other sources of information

  • Sweeney C R (1997) Fungal diseases of the Lower Respiratory Tract. In: Current Therapy in Equine Medicine 4. Ed: N E Robinson. W B Saunders, USA. ISBN 0-7216-2633-5.
  • Mayhew I G & Mackay R J (1982) The Nervous System. In: Equine Medicine and Surgery. Ed: R A Mansmann, E S McAllister & P W Pratt. American Veterinary Publications, USA. Cat No. 81-70196.


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