Systemic Mycoses

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FUNGI



Adiaspiromycosis


Aspergillosis


Blastomycosis


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

Entomophthoromycisus

  • Basidiobolmycosis
  • Caused by Basidiobolus and Conidiobulus fungi
  • Causes ulcerative granulomas in subcutaneous tissue
  • Affects the oral and nasal mucous membranes
  • Basidiobolus causes large lesions which may involve skin on the head, neck and chest
  • Produce flat, waxy colonies which become white and fizzy over time
  • Microscopically:
    • Septate hyphae

Histoplasmosis

  • Histoplasma capsulatum
  • Non-contageous, systemic mycosis
  • Commonly pulmonary infections occur
    • Other organs can be involved
    • Involves the reticuloendothelial system
    • Intestinal form can also occur
  • Acute and chronic disease can occur
  • Endemic to the USA
    • Isolated cases have been reported in Europe
  • Respiratory infection
    • Infection via ingestion can also occur
  • Affects dogs, cats, cattle, horses and humans
  • Found in soil contaminated by bird droppings, decaying vegetation and in caves inhabited by bats
  • Fine, branching, septate hyphae with smooth-walled pyriform to spherical microconidia and large, thick-walled tuberculate macroconidia on simple conidiophores
  • Dimorphic fungi
  • Hard to demonstrate in smears as the organisms is very small
    • Stain with Giemsa or Wright and examine under oil immersion lens
  • Present intracellularly in macrophages as oval yeast cells with few buds
    • Clear halo is seen around the darker staining central material
  • Grows on Sabouraud's Dextrose agar
    • Creamy white colonies, turning tan coloured and then brown
  • Also grows on Blood agar
    • Small, white yeast-like colonies
  • Test using immunodiffusion, complement fixation and counterimmunoelectrophoresis
    • Skin test of little value as it only indicates exposure
  • The prognosis is poor in acute and disseminated cases


Zygomycosis

  • Also known as mucormycosis, hyphomycosis and phycomycosis
  • Caused by strains of Mucor, Absidia, Rhizopus and Mortierella
    • Mucor circinelloides(rare), Rhizomucor pusillus and R. meihi
    • Absidia corymbifera often causes zygomycosis in cattle and pigs
    • Rhizopus arrhizus, R. microsporus and R. rhizopodormis
    • Mortierella wolfi implicated in bovine abortion (mycotic placentitis), M. hygrophila in fowl and M.polycephala in cattle
  • Occurs widely in nature
  • Infection is by inhalation and ingestion


  • Granulomatous lesions which can ulcerate
  • Mostly localised lesions but can be generalised
  • Pigs
    • Mediastinal and submandibular lymph nodes lesions
    • Embolic tumours in the liver and lungs
    • Can also be present in gastric ulcers
  • Horses, dogs, cats, sheep, mink, guinea-pigs and mice can also be infected
  • Microscopically:
    • Fragments of non-septate hyphae which are branched and coarse
    • Rhizomucor produce a thick, grey mycelium and have short, black, spherical sporangia
    • Mucor produce thick, colourless mycelium with no rhizoids. Globose spoangia with small spores are present and sporagiospores are simple or branched.
    • Absidia resemble Rhizopus grossly
    • Mortierella produce white, velvet colonies on Sabouraud's Dextrose and Blood agar
  • Grows on Sabauraud's Dextrose agar
    • Common contaminants
  • Treatment is with Amphotericin B
    • Surgery is also an option in treatment

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