Difference between revisions of "Dermatophytosis"

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 +
{{unfinished}}
  
−
Also known as: '''''Ringworm'''''
+
==General==
 +
[[Image: Trichophyton mentagrophytes dog.jpg|200px|thumb|right|''Trichophyton mentagrophytes'' in a dog - Courtesy of Bristol BioMed Image Archive]]
  
−
== Introduction  ==
+
*Pigmented, saprophytic organisms called '''Phaeohyphomycetes'''
−
[[Image:Microsporum canis lesions.jpg|thumb|right|200px|<small><center><i>Microsporum canis</i> alopecia and scaling lesions (Courtesy of Bristol BioMed Image Archive)</center></small>]] [[Image:Ringworm dog.jpg|thumb|right|200px|<small><center>Ringworm in a dog (Courtesy of Bristol BioMed Image Archive)</center></small>]] [[Image:Trichophyton mentagrophytes dog.jpg|thumb|right|200px|<small><center>''Trichophyton mentagrophytes'' in a dog (Courtesy of Bristol BioMed Image Archive)</center></small>]]
+
**Previously called 'Fungi Imperfecti'
−
Dermatophytes are pigmented, saprophytic organisms called Phaeohyphomycetes and were previously called 'Fungi Imperfecti'. The two main species of veterinary interest are ''Microsporum'' and ''Trichophton ''and these are found worldwide.
 
  
−
They are usually secondary invaders and are able to penetrate all layers of [[Skin - Anatomy & Physiology|skin]], but are generally restricted to the keratin layer and its appendages. Therefore the condition is most often seen in subcuticular or cutaneous sites. A lack of tolerance to body temperature and antifungal activity in serum and body fluids prevent the fungi invading subcutaneously. Secondary invasion by ''[[Staphylococcus aureus]]'' and ''Staphylococcus intermedius'' are common and cause pustules in the hair follicles. Epidermal hyperplasia then follows with inflammation.
+
*The two main species of veterinary interest are ''Microsporum'' and ''Trichophton''
  
−
Dermatophytes are transmitted by direct or indirect contact e.g. on brushes, fomites etc. Signs vary in severity, but immunocompromised hosts may develop systemic infections.
+
*Worldwide
  
−
There are certain types of dermatophytes: ''Microsporum'' is zoophilic and so parasitises animals, ''Trichophyton'' is geophilic and inhabits soil but will also parasitise animals. ''Epidermophyton'' is anthropophilic and so is a parasite of people.
+
*They are usually secondary invaders
  
−
''Microsporum canis'' is the most common dermatophyte to infect small animals and will be the cause of 90% of feline infections and 60% of canine infections. ''Trichophyton mentagrophytes'' affects around 30% of dogs, especially Terrier breeds. ''Trichophyton verrucosum'' causes most cases in cattle and sheep and ''Trichophyton equinum'' is the commonest cause in horses.
+
*Able to penetrate all layers of [[Skin - Anatomy & Physiology|skin]], but are generally restricted to the keratin layer and its appendages
−
About 25% of wild hedgehogs are carriers of ''Trichophyton erinacei'' which can also infect dogs and humans.
+
**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
  
−
== Signalment ==
+
*Transmitted by direct or indirect contact
  
−
The condition is common in many species, with certain strains affecting certain species more commonly. Hot, humid environments predispose to infection and young animals tend to be more commonly affected. The condition is more common in housed animals, rather than animals turned out to pasture and the highest incidence of the disease occurs during the winter months. It may resolve spontaneously in the spring and summer.
+
*Immunuocompromised hosts may develop systemic infections
  
−
== Clinical Signs  ==
+
*''Microsporum'' - zoophilic
 +
**Parasites of animals
  
−
There will be circular or irregular lesions (dependent on infectant organism) and these may coalesce. Scaly and crusty patches and alopecia will be seen in these areas due to broken hair shafts and hairs lost from inflammed regions of he skin. Follicular papules and pustules will also be present. There will be a peripheral red ring (ringworm) due to dead fungi in areas of inflammation at centre of lesions and viable fungi peripherally. There is usually a varying degree of pruritus. 
+
*''Trichophyton'' - geophilic
 +
**Inhabits soil
  
−
== Diagnosis  ==
+
*''Epidermophyton'' - anthropophilic
 +
**Parasites of people
  
−
Clinical signs are characteristic of the disease. '''Wood's Lamp''' can be used to shine UV light onto the lesion and it will fluoresce in 50% of cases (if ''Microsporum'' fungi are present). Therefore it is a good diagnostic tool in small animals but is not incredibly reliable. If there is no fluoresence, it does not mean there are no dermatophytes or no ''Microsporum''.
+
*Common in many species, especially cats
  
−
Samples can be taken and examined in '''10-20% KOH''' for the presence of hyphae or arthrospores. '''Lactophenol Cotton Blue''' enhances visualisation. One may see, septate hyphae or spores in the stratum corneum, keratin layers and in hair follicles. Perifolliculitis, folliculitis or furunculosis, epidermal hyperplasia and intracorneal microabscesses may also be seen.
+
*Hot, humid environment predisposes to infection
  
−
'''Sabouraud's Dextrose agar''' containing cyclohexamide and chloramphenicol can be used to culture the dermatophyte at room temperature for a month.
+
*More common in young animals
  
−
A '''biopsy''' can also be taken and examined histologically. Signs will include epidermal hyperplasia (hyperkeratosis, parakeratosis, acanthosis) and inflammation.
+
*Produce proteolytic enzymes to penetrate surface lipid
  
−
== Treatment  ==
+
*Fungal hyphae invade keratin -> break into arthrospores
  
−
The affected animal should be isolated and precautions should be taken to prevent human infection, such as wearing gloves. Hair should be clipped around the skin lesions.
+
*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
  
−
[[Antifungal Drugs]]:
+
==Pathogenesis==
  
−
[[Antifungal Drugs#Griseofluvin|'''Griseofulvin''']] is the best method of systemic treatment, however it can be expensive and prolonged oral treatment may be required. Griseofulvin is no longer licensed for small animals but has been used for many years with useful results. The treatment is continued for 2 weeks after clinical and mycological cure. Griseofulvin is teratogenic and contra-indicated in pregnancy. Haematological side effects have been reported, including neutropenia in [[FIV]]-positive cats. Owners handling tablets must wear gloves.
+
*Epidermal hyperplasia ([[Skin Glossary - Pathology|hyperkeratosis, parakeratosis, acanthosis]]) and [[:Category:Inflammation|inflammation]]
  
−
'''Itraconazole''' is now licensed for cats in the U.K. (Itrafungol, Janssen). The manufacturers suggest 3 cycles of therapy, one week on, one week off, reflecting the lipophilic properties of the drug that leads to its persistence in the stratum corneum. Laboratory infection models of ''M. canis'' infection in kittens have shown that griseofulvin and itraconazole have comparable efficacy.
+
*Superficial perivascular dermatitis -> exocytosis (migration through epidermal layers) -> intracorneal microabscesses
  
−
Apply '''topical therapy'''. Topical therapy alone is unlikely to shorten the course of disease because the agents do not penetrate into infected hairs. However, it does assist in removal of surface organisms and reduces environmental contamination. '''Enilconazole''' (Imaverol) is licensed for use in dogs and should be applied every three days, in conjunction with systemic therapy. Fatal idiosyncratic reactions have been reported in cats treated with enilconazole. A miconazole + chlorhexidine shampoo (Malaseb, VetXX) is helpful in cats and dogs, and is licensed in the former species for use in conjunction with griseofulvin.
+
*Exocytosis -> folliculitis -> furunculosis
  
−
Monitor treatment by repeat cultures.
+
*Highly variable lesions
  
−
== Image Gallery ==
+
*Normal -> eruptive nodular -> [[Dermatophytic Pseudomycetoma|pseudomycetoma]] -> onychomycosis
 +
 
 +
*Secondary invasion by ''[[Staphylococcus aureus]]'' and [[:Category:Staphylococcus species|''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 [[:Category:Inflammation|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]]
 +
 
 +
==Image Gallery==
  
 
{| align="center"
 
{| align="center"
−
|-
+
|<gallery>Image:Dermatophyte arthrospore hair root.jpg|<center><p>'''Dermatophyte arthrospores on a hair root'''</p><sup>Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath</sup></center>
−
| <gallery>Image:Dermatophyte arthrospore hair root.jpg|<center><p>'''Dermatophyte arthrospores on a hair root'''</p><sup>Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath</sup></center>
 
 
Image:Dermatophyte mycelium in skin.jpg|<center><p>'''Dermatophytosis mycelium in skin'''</p><sup>Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath</sup></center>
 
Image:Dermatophyte mycelium in skin.jpg|<center><p>'''Dermatophytosis mycelium in skin'''</p><sup>Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath</sup></center>
 
Image:Dermatophyte skin KOH.jpg|<center><p>'''Dermatophyte in skin using a KOH mount'''</p><sup>Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath</sup></center>
 
Image:Dermatophyte skin KOH.jpg|<center><p>'''Dermatophyte in skin using a KOH mount'''</p><sup>Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath</sup></center>
Line 61: Line 136:
 
Image:Dermatophytosis dog foot.jpg|<center><p>'''Dermatophytosis lesion on a dog's leg'''</p><sup>Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath</sup></center>
 
Image:Dermatophytosis dog foot.jpg|<center><p>'''Dermatophytosis lesion on a dog's leg'''</p><sup>Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath</sup></center>
 
Image:Dermatophytosis in a horse.jpg|<center><p>'''Dermatophytosis in a horse'''</p><sup>Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath</sup></center>
 
Image:Dermatophytosis in a horse.jpg|<center><p>'''Dermatophytosis in a horse'''</p><sup>Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath</sup></center>
−
Image:Microsporum canis.jpg|<center><p>'''''Microsporum canis'''''</p><sup>Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath</sup></center>
+
Image:Microsporum canis.jpg|<center><p>'''Microsporum canis'''</p><sup>Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath</sup></center>
−
Image:Microsporum canis macroconidium.jpg|<center><p>'''''Microsporum canis ''macroconidium'''</p><sup>Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath</sup></center>
+
Image:Microsporum canis macroconidium.jpg|<center><p>'''Microsporum canis macroconidium'''</p><sup>Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath</sup></center>
−
Image:T.mentagrophytes.jpg|<center><p>'''''T. mentagrophytes'''''</p><sup>Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath</sup></center>
+
Image:T.mentagrophytes.jpg|<center><p>'''T.mentagrophytes'''</p><sup>Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath</sup></center>
−
Image:Microsporum canis dysgonic.jpg|<center><p>'''''Microsporum canis'' dysgonic at 3 weeks'''</p><sup>Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath</sup></center>
+
Image:Microsporum canis dysgonic.jpg|<center><p>'''Microsporum canis dysgonic at 3 weeks'''</p><sup>Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath</sup></center>
−
Image:Microsporum equinum.jpg|<center><p>'''''Microsporum equinum'''''</p><sup>Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath</sup></center></gallery>
+
Image:Microsporum equinum.jpg|<center><p>'''Microsporum equinum'''</p><sup>Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath</sup></center></gallery>
 
|}
 
|}
  
−
{{Learning
+
[[Image: Microsporum canis lesions.jpg|100px|thumb|right|<small><center>''Microsporum canis'' alopecia and scaling lesions (Courtesy of Bristol BioMed Image Archive)</center></small>]]
−
|Vetstream = [https://www.vetstream.com/canis/Content/Disease/dis00124.asp Dematophytosis in dogs]
+
[[Image: Ringworm dog.jpg|100px|thumb|right|<small><center>Ringworm in a dog (Courtesy of Bristol BioMed Image Archive)</center></small>]]
−
|flashcards = [[Dermatophytosis - Flashcards|Dermatophytosis Flashcards]] <br>[[Small Animal Dermatology Q&A 08]]<br>[[Small Mammals Q&A 20]]
+
[[Image: Trichophyton mentagrophytes dog.jpg|100px|thumb|right|<small><center>Trichophyton mentagrophytes in a dog (Courtesy of Bristol BioMed Image Archive)</center></small>]]
−
}}
 
−
 
 
−
 
 
−
{{Chapter}}
 
−
{{Mansonchapter
 
−
|chapterlink = http://www.mansonpublishing.co.uk/book-images/9781840760491_sample.pdf
 
−
|chaptername = Ringworm
 
−
|book = Sheep Medicine
 
−
|author = Philip R. Scott
 
−
|isbn = 9781840761498
 
−
}}
 
−
 
 
−
== References ==
 
−
 
 
−
Foster, A, and Foll, C. (2003) '''BSAVA small animal dermatology '''(Second Edition) ''British Small Animal Veterinary Association''
 
−
 
 
−
Merck &amp; Co (2008) '''The Merck Veterinary Manual''' (Eighth Edition) ''Merial''
 
−
 
 
−
Nelson, R.W. and Couto, C.G. (2009) '''Small Animal Internal Medicine '''(Fourth Edition)'' Mosby Elsevier.''
 
−
 
 
−
Quinn, P.J., Markey, B.K., Carter, M.E., Donnelly, W.J., Leonard, F.C. (2007)''' Veterinary Microbiology and Microbial Disease '''''Blackwell Publishing''
 
−
 
 
−
Radostits, O.M, Arundel, J.H, and Gay, C.C. (2000) '''Veterinary Medicine: a textbook of the diseases of cattle, sheep, pigs, goats and horses''''' Elsevier Health Sciences''
 
  
−
Tilley, L.P. and Smith, F.W.K.(2004) '''The 5-minute Veterinary Consult''' (Third Edition) ''Lippincott, Williams & Wilkins.''
+
*Caused by [[Fungi|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 ([[Skin Glossary - Pathology|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
  
−
+
==Test yourself with the Dermatophytosis Flashcards==
−
{{review}}
 
  
−
==Webinars==
+
[[Dermatophytosis_-_WikiBugs|Dermatophytosis Flashcards]]
−
<rss max="10" highlight="none">https://www.thewebinarvet.com/dermatology/webinars/feed</rss>
 
  
−
[[Category:Expert_Review]] [[Category:Dermatological_Diseases_-_Dog]] [[Category:Dermatological_Diseases_-_Cat]][[Category:Dermatological_Diseases_-_Horse]][[Category:Dermatological_Diseases_-_Cattle]][[Category:Dermatological_Diseases_-_Sheep]][[Category:Cutaneous_Mycoses]]
+
[[Category:Fungi]]
−
[[Category:Zoonoses]]
+
[[Category:To_Do_-_Parasites]]

Revision as of 20:25, 17 August 2010


 This article is still under construction.


General

Trichophyton mentagrophytes in a dog - Courtesy of Bristol BioMed Image Archive
  • 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

  • Superficial perivascular dermatitis -> exocytosis (migration through epidermal layers) -> intracorneal microabscesses
  • Exocytosis -> folliculitis -> furunculosis
  • Highly variable lesions
  • 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

Further Links

Image Gallery

  • Dermatophyte arthrospores on a hair root

    Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath

  • Dermatophytosis mycelium in skin

    Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath

  • Dermatophyte in skin using a KOH mount

    Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath

  • Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath

  • Ringworm on a human arm

    Wikimedia Commons

  • Dermatophytosis in a dog

    Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath

  • Dermatophytosis in a cow

    Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath

  • Dermatophytosis in a chicken

    Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath

  • Dermatophytosis lesion on a dog's leg

    Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath

  • Dermatophytosis in a horse

    Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath

  • Microsporum canis

    Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath

  • Microsporum canis macroconidium

    Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath

  • T.mentagrophytes

    Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath

  • Microsporum canis dysgonic at 3 weeks

    Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath

  • Microsporum equinum

    Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath
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)
  • 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

Test yourself with the Dermatophytosis Flashcards

Dermatophytosis Flashcards

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