Difference between revisions of "Dermatophytosis"
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| + | {{unfinished}} | ||
| − | + | {{toplink | |
| + | |backcolour = | ||
| + | |linkpage =Fungi | ||
| + | |linktext =FUNGI | ||
| + | |pagetype=Bugs | ||
| + | }} | ||
| + | <br> | ||
| + | |||
| + | [[Image: Microsporum canis lesions.jpg|150px|thumb|right|''Microsporum canis'' alopecia and scaling lesions - Courtesy of Bristol BioMed Image Archive]] | ||
| + | [[Image: Ringworm dog.jpg|150px|thumb|right|Ringworm in a dog -Courtesy of Bristol BioMed Image Archive]] | ||
| + | [[Image: Trichophyton mentagrophytes dog.jpg|150px|thumb|right|Trichophyton mentagrophytes in a dog - Courtesy of Bristol BioMed Image Archive]] | ||
| + | [[Image:Ringworm on human arm.jpg|thumb|right|150px|Ringworm on a human arm - Wikimedia Commons]] | ||
| + | |||
| + | ==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 - Anatomy & Physiology|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 to infection | |
| − | |||
| − | + | *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== |
| − | + | *Epidermal hyperplasia ([[Skin Glossary - Pathology|hyperkeratosis, parakeratosis, acanthosis]]) and [[Inflammation - WikiBlood|inflammation]] | |
| − | + | *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 spp.|''Staphylococcus aureus'']] and [[Staphylococcus spp.|''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 - WikiBlood|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 | ||
| − | + | ==Histology== | |
| − | + | *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|chloramphenicol]] at room temperature for a month for culture | |
| − | |||
| − | | | ||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | + | *Dermatophyte Test Medium | |
| + | **Saubouraud's Dextrose agar with phenol red indicator | ||
| + | **Medium changes from yellow to red if fungi present | ||
| − | + | ==Treatment== | |
| − | + | *Isolation of infected animal | |
| − | + | *Precautions should be taken to prevent human infection | |
| − | + | *[[Antifungal Drugs#Griseofluvin|Griseofulvin]] best method of treatment | |
| + | **Expensive | ||
| + | **Oral dosage | ||
| + | **Prolonged treatment required | ||
| − | + | *Whitfield's ointment | |
| + | **Salicylic and benzoic acid | ||
| − | + | *Other treatments: | |
| + | **Aqueous lime sulphur topically for dogs | ||
| + | **Iodine | ||
| + | **[[Antibiotics|Antibiotics]] | ||
| + | **[[Antifungal Drugs#Polyene Antifungals|Natamycin]] antifungal | ||
| + | **[[Antifungal Drugs#The Azoles|Imidiazole]] derivatives | ||
| − | + | ==Further Links== | |
| − | |||
| − | + | *Pathology of [[Mycotic skin infections - Pathology#Dermatophytoses|dermatophytosis]] | |
| − | |||
| − | [[ | + | *[[Antifungal Drugs]] |
| − | |||
Revision as of 20:06, 28 April 2009
 |
This article is still under construction. |
|
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 to infection
- 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
- 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
- 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
Histology
- 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 changes from yellow to red if fungi present
Treatment
- Isolation of infected animal
- Precautions should be taken to prevent human infection
- Griseofulvin best method of treatment
- Expensive
- Oral dosage
- Prolonged treatment required
- Whitfield's ointment
- Salicylic and benzoic acid
- Other treatments:
- Aqueous lime sulphur topically for dogs
- Iodine
- Antibiotics
- Natamycin antifungal
- Imidiazole derivatives
Further Links
- Pathology of dermatophytosis