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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