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Line 9: + + + + + + + − + − [[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>]]+ + + + + + + + + − Dermatiaceous fungi are pigmented, saprophytic organisms - Phaeohyphomycetes+ − + − *In immunuocompromised hosts they may develop systemic infections. − Phaeohyphomycosis:+ − + − 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. − + + − *Caused by [[Fungi|dermatophytes]] − **''Microsporum'' - zoophilic − **''Trichophyton'' - geophilic − **''Epidermophyton'' - anthropophilic + + + + + + + + + + + + + + + + + + + Line 47:
Line 76: − + − **Perifolliculitis, folliculitis or furunculosis+ − **Epidermal hyperplasia+ − **Intracorneal microabscesses+ − **Septate hyphae or spores may be found in stratum corneum and keratin of hair follicles+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
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[[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''
*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
*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
*''Trichophyton'' - geophilic
*It occurs sporadically in cats, horses, cattle, fish, reptiles, amphibians, and birds, and rarely in dogs.
**Inhabits soil
*Culture is necessary for definitive diagnosis.
*''Epidermophyton'' - anthropophilic
**Parasites of people
*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
**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:
*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==
*Pathology of [[Mycotic skin infections - Pathology#Dermatophytoses|dermatophytosis]]