Difference between revisions of "Dermatophytosis"

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<br>
  
 +
[[Image: Microsporum canis lesions.jpg|100px|thumb|right|<small><center>''Microsporum canis'' alopecia and scaling lesions (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>]]
 +
 +
==General==
  
 +
*Pigmented, saprophytic organisms called '''Phaeohyphomycetes'''
 +
**Previously called 'Fungi Imperfecti'
  
*Dermatophytes in [[Mycotic skin infections - Pathology#Dermatophytoses|dermatophytosis]]
+
*The two main species of veterinary interest are ''Microsporum'' and ''Trichophton''
  
[[Image: Microsporum canis lesions.jpg|100px|thumb|right|<small><center>''Microsporum canis'' alopecia and scaling lesions (Courtesy of Bristol BioMed Image Archive)</center></small>]]
+
*Worldwide
[[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>]]
+
*They are usually secondary invaders
 +
 
 +
*Able to penetrate all layers of skin, but are generally restricted to the keratin layer and its appendages
 +
**Therefore, most often seen in subcuticular or cutaneous sites
 +
**Lack of tolerance to body temperature and antifungal activity in serum and body fluids prevent the fungi invading subcutaneously
 +
 
 +
*Transmitted by direct or indirect contact
 +
 
 +
*Immunuocompromised hosts may develop systemic infections
  
Dermatiaceous fungi are pigmented, saprophytic organisms - Phaeohyphomycetes
+
*''Microsporum'' - zoophilic
*They usually infect animals secondary to traumatic implantation of the organisms, and are therefore most often seen in subcuticular or cutaneous sites.
+
**Parasites of animals
*In immunuocompromised hosts they may develop systemic infections.
 
  
Phaeohyphomycosis:
+
*''Trichophyton'' - geophilic
*It occurs sporadically in cats, horses, cattle, fish, reptiles, amphibians, and birds, and rarely in dogs. 
+
**Inhabits soil
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.
 
  
 +
*''Epidermophyton'' - anthropophilic
 +
**Parasites of people
  
*Caused by [[Fungi|dermatophytes]]
 
**''Microsporum'' - zoophilic
 
**''Trichophyton'' - geophilic
 
**''Epidermophyton'' - anthropophilic
 
 
*Common in many species, especially cats
 
*Common in many species, especially cats
 +
 
*Hot, humid environment predisposes and viable fungi peripherally
 
*Hot, humid environment predisposes and viable fungi peripherally
 +
 
*More common in young animals
 
*More common in young animals
 +
 
*Produce proteolytic enzymes to penetrate surface lipid
 
*Produce proteolytic enzymes to penetrate surface lipid
 +
 
*Fungal hyphae invade keratin -> break into arthrospores
 
*Fungal hyphae invade keratin -> break into arthrospores
 +
 +
*Phaeohyphomycosis:
 +
**Occurs sporadically in cats, horses, cattle, fish, reptiles, amphibians, birds, and rarely in dogs 
 +
**Examples 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
 +
 +
==Pathogenesis==
 +
 
*Epidermal hyperplasia ([[Skin Glossary - Pathology|hyperkeratosis, parakeratosis, acanthosis]]) and inflammation
 
*Epidermal hyperplasia ([[Skin Glossary - Pathology|hyperkeratosis, parakeratosis, acanthosis]]) and inflammation
 +
 
*Superficial perivascular dermatitis -> exocytosis (migration through epidermal layers) -> intracorneal microabscesses
 
*Superficial perivascular dermatitis -> exocytosis (migration through epidermal layers) -> intracorneal microabscesses
 +
 
*Exocytosis -> folliculitis -> furunculosis
 
*Exocytosis -> folliculitis -> furunculosis
 +
 
*Highly variable lesions
 
*Highly variable lesions
 +
 
*Normal -> eruptive nodular -> pseudomycetoma -> onychomycosis
 
*Normal -> eruptive nodular -> pseudomycetoma -> onychomycosis
 +
 +
*Secondary invasion by ''Staphylococcus aureus'' and ''Staphylococcus intermedius'' are common and cause pustules in the hair follicles
 +
 
*Grossly:
 
*Grossly:
 
**Circular or irregular lesion, may coalesce
 
**Circular or irregular lesion, may coalesce
Line 47: Line 76:
 
**Follicular papules and pustules
 
**Follicular papules and pustules
 
**Peripheral red ring ('''ringworm''') due to dead fungi in areas of inflammation at centre of lesions and viable fungi peripherally
 
**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
+
*More common in housed animals, rather than animals turned out to pasture
**Epidermal hyperplasia
+
 
**Intracorneal microabscesses
+
*Highest incidence of disease during the winter
**Septate hyphae or spores may be found in stratum corneum and keratin of hair follicles
+
**May resolve spontaneously in the spring and summer
 +
 
 +
==Microscopically==
 +
 
 +
*Perifolliculitis, folliculitis or furunculosis
 +
 
 +
*Epidermal hyperplasia
 +
 
 +
*Intracorneal microabscesses
 +
 
 +
*Septate hyphae or spores may be found in stratum corneum and keratin of hair follicles
 +
 
 +
==Diagnosis==
 +
 
 +
*Wood's Lamp
 +
**UV light
 +
**Florourescence if fungi present
 +
 
 +
*Samples can be examined in 10-20% KOH for the presence of hyphae or arthrospores
 +
**Lactophenol Cotton Blue enhances visualisation
 +
 
 +
*Sabouraud's Dextrose agar containing cyclohexamide and chloramphenicol at room temperature for a month for culture
 +
 
 +
*Dermatophyte Test Medium
 +
**Saubouraud's Dextrose agar with phenol red indicator
 +
**Medium changed from yellow to red
 +
 
 +
==Treatment==
 +
 
 +
*Isolation of infected animal
 +
 
 +
*Precautions should be taken to prevent human infection
 +
 
 +
*Griseofulvin best method
 +
**Expensive
 +
**Oral dosage
 +
**Prolonged treatment required
 +
 
 +
*Whitfield's ointment
 +
**Salicylic and benzoic acid
 +
 
 +
*Other tretment:
 +
**Aqueous lime sulphur topically for dogs
 +
**Iodine
 +
**Antibiotics, e.g. natamycin
 +
**Imidiazole derivatives
 +
 
 +
==Further Links==
 +
 
 +
*Pathology of [[Mycotic skin infections - Pathology#Dermatophytoses|dermatophytosis]]

Revision as of 19:06, 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)

General

  • Pigmented, saprophytic organisms called Phaeohyphomycetes
    • Previously called 'Fungi Imperfecti'
  • The two main species of veterinary interest are Microsporum and Trichophton
  • Worldwide
  • They are usually secondary invaders
  • Able to penetrate all layers of skin, but are generally restricted to the keratin layer and its appendages
    • Therefore, most often seen in subcuticular or cutaneous sites
    • Lack of tolerance to body temperature and antifungal activity in serum and body fluids prevent the fungi invading subcutaneously
  • Transmitted by direct or indirect contact
  • Immunuocompromised hosts may develop systemic infections
  • Microsporum - zoophilic
    • Parasites of animals
  • Trichophyton - geophilic
    • Inhabits soil
  • Epidermophyton - anthropophilic
    • Parasites of people
  • 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
  • Phaeohyphomycosis:
    • Occurs sporadically in cats, horses, cattle, fish, reptiles, amphibians, birds, and rarely in dogs
    • Examples 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

Pathogenesis

  • Superficial perivascular dermatitis -> exocytosis (migration through epidermal layers) -> intracorneal microabscesses
  • Exocytosis -> folliculitis -> furunculosis
  • Highly variable lesions
  • Normal -> eruptive nodular -> pseudomycetoma -> onychomycosis
  • Secondary invasion by Staphylococcus aureus and Staphylococcus intermedius are common and cause pustules in the hair follicles
  • 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
  • More common in housed animals, rather than animals turned out to pasture
  • Highest incidence of disease during the winter
    • May resolve spontaneously in the spring and summer

Microscopically

  • Perifolliculitis, folliculitis or furunculosis
  • Epidermal hyperplasia
  • Intracorneal microabscesses
  • Septate hyphae or spores may be found in stratum corneum and keratin of hair follicles

Diagnosis

  • Wood's Lamp
    • UV light
    • Florourescence if fungi present
  • Samples can be examined in 10-20% KOH for the presence of hyphae or arthrospores
    • Lactophenol Cotton Blue enhances visualisation
  • Sabouraud's Dextrose agar containing cyclohexamide and chloramphenicol at room temperature for a month for culture
  • Dermatophyte Test Medium
    • Saubouraud's Dextrose agar with phenol red indicator
    • Medium changed from yellow to red

Treatment

  • Isolation of infected animal
  • Precautions should be taken to prevent human infection
  • Griseofulvin best method
    • Expensive
    • Oral dosage
    • Prolonged treatment required
  • Whitfield's ointment
    • Salicylic and benzoic acid
  • Other tretment:
    • Aqueous lime sulphur topically for dogs
    • Iodine
    • Antibiotics, e.g. natamycin
    • Imidiazole derivatives

Further Links