Systemic Mycoses

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FUNGI



Adiaspiromycosis

  • Haplomycosis
  • Emmonsia crescens
    • Does not proliferate within the animal body
    • Each spore develops into a thick-walled spherule called an adiaspore
  • Chrysosporium parvum, C. crescens
  • Non-contageous, pulmonary mycosis
  • Worldwide
  • Found in soil
  • Affects burrowing rodents and small animals
  • Respiratory infection
  • Spetate hyphae with large numbers of small, round conidia either singly or in groups on the ends of the short conidiospores can be seen
  • Dimorphic
  • Grows on Sabauraud's Dextrose agar and Blood agar

Aspergillosis

Blastomycosis

  • North America

Coccidioidomycosis

  • 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

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
    • Occurs widely in nature
  • Infection is by inhalation and ingestion
  • Infects lymph nodes of the respiratory and alimentary tract
    • Lymph nodes enlarge and become caseous
    • Can cause stomach and intestinal ulcers
  • Granulomatous lesions which can ulcerate
  • Mostly localised lesions but can be generalised

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