Subcutaneous Mycoses

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FUNGI



Chromoblastomycosis

Chromomycosis

  • Also called Phaeohyphomycosis
  • Opportunistic
  • Infects horses, dogs and humans
    • Found in wounds and abrasions
  • Caused by dematiaceous fungi
    • Dactylaria gallopava, Exophiala pisciphila, E. salmonis, Scolecobasidium humicola, S. tshawytschae, Drechslera, Exophilia jeanselmeri, E. verrucosa, Fonsecaea pelrosoi
  • Nodular and ulcerating lesions of the skin on the feet, legs and occasionally eyes (in turkeys)
    • Regional granulomatous lymphadenitis
  • Single cells or clusters, spherical and thick-walled
  • Brown pigmented fungal elements
  • Multiply by cross-wall formation or splitting (not budding)
  • Grows on Sabauraud's Dextrose agar ar room temperature
    • Slow growth
    • Takes one month

Epizootic Lymphangitis

Eumycotic Mycetoma

  • Pseudoallescheria boydii, Curvularia geniculata, Cochliobolus spicifer, Helminthosporium spp.
  • Lives in soil
  • Enters the body via wounds
  • Granulomatous abscesses
  • Microcolonies can be seen grossly in exudate or lesions
    • Grains or granules
    • Brown or black embedded in granulation tissue
    • Small, irregularly shaped
  • Infrequent infections of dogs, cats, cattle and horses
  • Usually affect the extremities
    • Can infect the nasal mucosa
      • E.g. Bovine nasal granuloma
    • Can also infect the peritoneum and skin
  • Microscopically:
    • Grains of maduromycosis with wide mycelia (compared to actinomycotic granules)
    • Chlamydospores present
  • Grows on Sabauraud's Dextrose agar
    • Slow
    • Takes 2-3 weeks

Hyphomycosis

Pythiosis

  • Causes Mycotic Swamp Fever
  • Also called phycomycosis
  • Occurs in the USA, Australia, New Guinea, India, Brazil, Colombia, Japan, Costa Rica and Indonesia
  • Pythium insidiosum
  • Granulomatous infection
    • Necrosis and fistulous tracts
    • Yellow lesions
  • Branching, separated fungi
  • Progressive (rather than systemic) disease
  • Surgery is needed

Rhinosporidiosis

Sporotrichosis

  • Sporothrix schenckii
  • Occurs in soil, wood and vegetation
  • Worldwide
  • Exogenous infections through wounds
  • Causes subcutaneous nodules or granulomas
    • Nodules ulcerate discharging pus
  • The bones and viscera can be involved which terminates in mortality
    • This is rare
    • Reported in dogs and horses
  • Affects dogs, horses, cats, monkeys, mules, camels, donkeys, cattle, fowl and rodents
    • Most commonly seen in horses as an ascending lymphocutaneous infection of the legs
  • Single cell, cigar shaped
    • Usually found within neutrophils
    • Yeast cell clusters with peripheral eosinophilic rays can be seen in tissue sections
  • Stained using PAS, fluorescent antibody and Calcofluor White
  • Latex agglutination and immunodiffusion serology can be performed
  • Grows on Blood agar and Sabouraud's Dextrose agar in one to three weeks
    • At 37°C:
      • Colonies are smooth, cream to tan coloured and soft
      • No mycelium can be seen
    • At 25°C to 27°C:
      • Colonies turn from white and soft to tan to brown to black
      • Leathery, wrinkled and coarse
      • Mycelium can be seen as branching septate hyphae
      • Conidiospores can also be seen

Further Links