Difference between revisions of "Dermatophytosis"

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[[Dermatiaceous fungi]]
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*Dermatophytes in [[Mycotic skin infections - Pathology#Dermatophytoses|dermatophytosis]]
 
*Dermatophytes in [[Mycotic skin infections - Pathology#Dermatophytoses|dermatophytosis]]
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[[Image: Ringworm dog.jpg|100px|thumb|right|<small><center>Ringworm in a dog (Courtesy of Bristol BioMed Image Archive)</center></small>]]
 
[[Image: Ringworm dog.jpg|100px|thumb|right|<small><center>Ringworm in a dog (Courtesy of Bristol BioMed Image Archive)</center></small>]]
 
[[Image: Trichophyton mentagrophytes dog.jpg|100px|thumb|right|<small><center>Trichophyton mentagrophytes in a dog (Courtesy of Bristol BioMed Image Archive)</center></small>]]
 
[[Image: Trichophyton mentagrophytes dog.jpg|100px|thumb|right|<small><center>Trichophyton mentagrophytes in a dog (Courtesy of Bristol BioMed Image Archive)</center></small>]]
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Dermatiaceous fungi are pigmented, saprophytic organisms - Phaeohyphomycetes
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*They usually infect animals secondary to traumatic implantation of the organisms, and are therefore most often seen in subcuticular or cutaneous sites.
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*In immunuocompromised hosts they may develop systemic infections.
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Phaeohyphomycosis:
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*It occurs sporadically in cats, horses, cattle, fish, reptiles, amphibians, and birds, and rarely in dogs. 
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Fungi implicated in animal phaeohyphomycosis include:  Exophiala sp., Phialophora sp., Pseudomicrodochium sp., Bipolaris sp., Moniella sp., Cladosporium sp., Wangiella sp., Curvularia spp., Exserohilum sp., Alternaria sp., Staphylotrichum sp., and Xylohypha sp. 
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*Culture is necessary for definitive diagnosis.
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*Caused by [[Fungi|dermatophytes]]
 
*Caused by [[Fungi|dermatophytes]]

Revision as of 18:44, 28 April 2009



Infectious agents and parasitesWikiBugs Banner.png
FUNGI




Microsporum canis alopecia and scaling lesions (Courtesy of Bristol BioMed Image Archive)
Ringworm in a dog (Courtesy of Bristol BioMed Image Archive)
Trichophyton mentagrophytes in a dog (Courtesy of Bristol BioMed Image Archive)

Dermatiaceous fungi are pigmented, saprophytic organisms - Phaeohyphomycetes

  • They usually infect animals secondary to traumatic implantation of the organisms, and are therefore most often seen in subcuticular or cutaneous sites.
  • In immunuocompromised hosts they may develop systemic infections.

Phaeohyphomycosis:

  • It occurs sporadically in cats, horses, cattle, fish, reptiles, amphibians, and birds, and rarely in dogs.

Fungi implicated in animal phaeohyphomycosis include: Exophiala sp., Phialophora sp., Pseudomicrodochium sp., Bipolaris sp., Moniella sp., Cladosporium sp., Wangiella sp., Curvularia spp., Exserohilum sp., Alternaria sp., Staphylotrichum sp., and Xylohypha sp.

  • Culture is necessary for definitive diagnosis.


  • Caused by dermatophytes
    • Microsporum - zoophilic
    • Trichophyton - geophilic
    • Epidermophyton - anthropophilic
  • Common in many species, especially cats
  • Hot, humid environment predisposes and viable fungi peripherally
  • More common in young animals
  • Produce proteolytic enzymes to penetrate surface lipid
  • Fungal hyphae invade keratin -> break into arthrospores
  • Epidermal hyperplasia (hyperkeratosis, parakeratosis, acanthosis) and inflammation
  • Superficial perivascular dermatitis -> exocytosis (migration through epidermal layers) -> intracorneal microabscesses
  • Exocytosis -> folliculitis -> furunculosis
  • Highly variable lesions
  • Normal -> eruptive nodular -> pseudomycetoma -> onychomycosis
  • Grossly:
    • Circular or irregular lesion, may coalesce
    • Scaly to crusty patches
    • Alopecia due to broken hair shafts and hairs lost from inflammed follicles
    • Follicular papules and pustules
    • Peripheral red ring (ringworm) due to dead fungi in areas of inflammation at centre of lesions and viable fungi peripherally
  • Microscopically:
    • Perifolliculitis, folliculitis or furunculosis
    • Epidermal hyperplasia
    • Intracorneal microabscesses
    • Septate hyphae or spores may be found in stratum corneum and keratin of hair follicles