Coccidioidomycosis

Coccidioidomycosis spherule histopathology - Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath

• Coccidioides immitis

• Ocurs in the soil
  • Respiratory infections
  • Most commonly seen following dust storms

• Occurs in arid regions
  • E.g. South West USA and Mexico

• Non-contageous, systemic mycosis

• Affects dogs, cattle, sheep and humans

• Mainly affects the lungs
  • Dissemination can occur to other organs

• Causes nodule or granuloma formation
  • Localised
  • Gross lesions resemble Tb in cattle as are usually seen in the bronchial and mediastinal lymph nodes and occasionally lungs
  • Dissemination can occur, especially in primates and dogs, to the lungs, liver, spleen, brain and bones

• Thick-walled spherules in tissue
  • Large sporangia burst leaving 'ghost' spherules

• Saprophytic phase consists of coarse, septate, branching hyphae which fragment into thick-walled, barrel-shaped arthrospores which alternate with empty cells
  • Stained by Lactose Phenol Cotton Blue

• Grows on Sabouraud's Dextrose agar and Blood agar
  • Flat, moist colonies which develop a coarse, cotton-like aerial mycelium which varies from white to brown in colour

• Complement fixation test, latex agglutination and immunodiffusion tests can all be used
  • A positive skin test indicates exposure

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Coccidioidomycosis Flashcards