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BVM3 Skin > Superficial Fungal Skin Disease > Flashcards

Superficial Fungal Skin Disease Flashcards

1
Q

What is this?

A

Dermatophytosis

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2
Q

What kind of organism is fungi? How does it intake nutrients? How do they reproduce? What do the cell walls contain?

A
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3
Q

What are the 3 morphological forms of fungi?

A
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4
Q

What is Malassezia?

A

Species of yeast - a unicellular budding fungus

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5
Q

Define “dermatophytosis”

A

Infection of hair, claw or stratum corneum by a fungus of the arthorodermataceae family

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6
Q

How are dermatophytes classified? List the classifications

A

Based on ecology
Zoophilic - affect higher animals
Geophilic -adapted for soil habitation
Anthropophilic - adapted for infection of man

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7
Q

What is the dermatophyte species primary affecting cats?

A

M. canis

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8
Q

What is the dermatophyte species primarily affecting cattle?

A

T. verrucosum

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9
Q

What species are adapted for infection of horses?

A

T. equinum
(M. gypseum, M. canis)

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10
Q

What is (by far) the most prevalent species of dermatophyte (US and UK)?

A

M. canis (US and UK)
T. mentag (US and UK)
M. gypseum (US)

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11
Q

What types of animals are predisposed to dermatophytosis?

A

Young animals
Long haired cats predisposed
High incidence of M. canis in Yorkshire terriers
High incidence of sylvatic dermatophytosis in Jack Russels

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12
Q

What does “sylvatic” mean?

A

Picked up from wild animals

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13
Q

How does dermatophytosis cause disease?

A

Contact with infected hair or squame
Adherence of conidia to corneocytes
Germination of spore

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14
Q

What parts of the skin (layers of epidermis) does fungus invade and what kind of host response does it cause?

A

Invasion between or through corneocytes of stratum corneum or hair (exoprotein production)
Host inflammatory/immunological response

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15
Q

What is this?

A
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16
Q

What is this?

A
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17
Q

How common is dermatophytosis in dogs?

A

Uncommon
If it looks like ringworm, its probably staphylococcal folliculitis

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18
Q

Can you tell what this lesion is just by looking?

A

No - cannot tell without sampling

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19
Q

What are the top differentials for this patient?

A

Dermatophytosis (ringworm)
Demodicosis

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20
Q

Describe this lesion. What are the top differentials?

A

Dermatophytosis (diagnosed in this case on microscopy - found fungus)
Epithelial lymphoma

Well distributed inflammatory plaques with scaling and patchy hair loss

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21
Q

What is this lesion? Describe this lesion.

A

Kerion - lesion that develops as a result of ringworm, fungus and cutaneous bacteria mixing with
Nodular, bloody puss-filled lump

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22
Q

What is this type of lesion called (shape)? What is it caused by?

A

Annular lesion (circular with healing center) caused by ringworm (cat)

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23
Q

Describe the clinical signs associated with dermatophytosis
How are clinical signs often hidden by animals?

A

Clinical signs are variable
Circular/annular lesions with scaling/crust/erythema (advancing) and alopecia
Diffuse scaling
Nodules/Ulceration
Asymptomatic (carriers)

Can be hidden by long hair (need to either clip or check under the hair coat for full extent of lesions)

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24
Q

What is this lesion? How is it contracted? How do you know?

A

Sylvatic dermatophytosis (from wildlife source)
Note - Jack Russell Terrier (rodent hunters) - interact with wildlife often

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25
Q

What is the name of the species of dermatophytosis contracted from hedgehogs (pictured)

A

Dermatophytosis caused by T. erinacei (hedgehog)

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26
Q

How does sylvatic dermatophytosis often present?

A

Folliculitis/Furunculosis

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27
Q

What is unusual about M. persicolor dermatophytosis?

A

Does not invade the hair follicle/hair shaft (no folliculitis, no furunculosis, just causes scales)

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28
Q

What do you need to make sure to do after clipping one animal before clipping another with the same tools?

A

Need to make sure to disinfect the clippers to not transfer skin conditions from one animal to another

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29
Q

Which disinfectant is particularly good for fungi?

A

Hypochlorite bleach

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30
Q

What is this?

A
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31
Q

What are these 2 conditions? Describe the lesions? How do they differ? Why is it so easy to get them mixed up?

A

Left - severe inflammatory lesions with relative central healing and advancing border of inflammation at the periphery
- Condition worsens with steroids
Right - involvement of nasal planum, presence of studded crusts
- Condition improves with systemic prednisone

Tendency for facial dermatophytosis to be misdiagnosed as autoimmune disease (like pemphigus)

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32
Q

What are these 2 conditions? How can you tell? Describe the lesions
How do you finally diagnose these lesions?

A

Left - circular lesions with peripheral rim of inflammation/crust and central post-inflammatory hyperpigmentation
- Not ringworm, but rather Pyoderma
Right - ring-like lesion with ring of scale, but less defined. Also has post-inflammatory central hyperpigmentation
- Ringworm!

Needs to be tested to differentiate

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33
Q

What are your top differentials for this patient?

A

Dermatophytosis (ringworm)
Superficial staphylococcal pyoderma

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34
Q

What is interesting about this fungal lesion in this cat?

A

Very little-to-no inflammation
Fungi adapted in cats (should be on differentials list)

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35
Q

How is an infection coming from within vs. from the environment going to differ in symmetry of the lesions?

A

From within is usually symmetrical lesions
From the outside (landing on the skin) not expected to be asymmetrical

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36
Q

What is the name for this lesion? Describe what is happening here.
What is your job to figure out as the veterinarian?

A

Pseudomycetoma - nodule with sinus tracts and tissue grains/sulfur grains (yellow grains)
Fungus gets into the fat (Aberrant)
Job as vet is to figure out what is causing this (could be bacteria, fungi, neoplasia, etc.)

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37
Q

How is dermatophytosis diagnosed?

A

Based on demonstrating fungi in host tissue through:
- Skin scrapings/hair plucks
- Wood’s lamp
- Fungal culture
- Skin biopsies
- PCR (newer option)

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38
Q

What is this microscopically demonstrating?
What is this an immediate diagnosis of?

A

Fungal spores in hair shaft (commonly produced on external aspect of the hair)
Immediate diagnosis of ringworm

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39
Q

Based on these sensitivity statistics, is light microscopy diagnosis of fungal infection worth doing?

A

While sensitivity is ~50% for experienced pathologists and <50% for “common” practitioners, it is still worth doing because when you do diagnose based on microscopy it is a definitive diagnosis
Can always send out for more sensitive testing if you are unsure

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40
Q

How can you improve the sensitivity of microscopy? What is a (minor) issue with fluorescence microscopy?

A

Fluorescence microscopy - add weight to potassium hydroxide, look under UV microscopy, fungi glow green
Much easier! But not routinely found all over the world

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41
Q

How does a woods lamp work? Where on the body does fungi fluoresce under the wood lamp? What lighting do you need for wood’s lamp to work? Which species of fungi does not fluoresce with wood’s lamp?

A

HAIR - Wood’s lamp turns fungi apple-green on haircoat
Irrelevant on skin as debris can turn green
Must have darkened room, lamp needs to be warmed up

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42
Q

What should you do to diagnose fungi if wood’s lamp examination is negative, but you still suspect dermatophytosis?

A

Trichophyton spp. of veterinary importance do not fluoresce
Need to follow up with culture

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43
Q

How sensitive is wood’s lamp for isolating dermatophytosis in cats/dogs (Ex. M. canis)

A
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44
Q

What is the most sensitive test you can use for diagnosing dermatophytosis?

A

Culture

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45
Q

How do you perform fungal culture? How and where do you send the sample?

A
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46
Q

What is the typical fungal culture medium? Why is cycloheximide added in? Why is chloramphenicol added in?

A

Sabouraud’s dextrose agar - typical culture medium
Cycloheximide added in to inhibit growth of other fungi in environment
Chloramphenicol added in to inhibit growth of bacteria

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47
Q

At what temperature and how long do you incubate fungal culture?

A
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48
Q

At what intervals do you receive a report about fungal culture growth?

A

2 weeks (or sooner) - interim report to tell us if there is something growing
4 weeks - full assessment (final report)

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49
Q

How long after starting fungal culture is growth typically evident?

A

5 - 10 days after starting culture

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50
Q

How is fungal culture assessed? What methods are preferable for assessing fungi (vs bacteria)?
What kind of lab should you make sure to use for testing?

A

For fungi preference is to assess phenotype, gross colony and microscopy rather than biochemical testing/MALDITOF (commonly used for bacteria)
Use reputable mycology lab!!!

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51
Q

What is this? What is it used for?

A

Denman brush - good way of doing brush culture, particularly looking for asymptomatic carriers or animals with widespread lesions to inoculate SDA plates

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52
Q

What is this? How is it produced? What is this used for in the laboratory? What IS produced by dermatophytes on the animal instead?

A

Macroconidia - ONLY produced in laboratory culture
Spores never produced by dermatophytes in an animal
ONLY used for laboratory identification
Hyphae and spores are produced on an animal

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53
Q

What is saprobic macroconidia? How is this different from macroconidia produced by dermatophytes in culture?

A

Saprobic macroconidia found in cytology specimens from animals with inflammatory skin disease (skin allergic reaction)
Produced by SAPROBIC FUNGUS (decomposer) and NOT ringworm

54
Q

Label these fungal cultures from left to right

A

Left - medium before culture
Left/middle - saprobic fungus, no color change
Right/middle - color change LATE (carbohydrates produced by saprobic fungi)
Far right - EARLY color change (indicates dermpatophytosis)

55
Q

How does dermatophyte test medium indicate dermatophytosis (color change)?
What color change/what stage of culture + what color colony = dermatophyte present?

A

Test medium turns red (red phenol indicator) in response to dermatophytes utilizing protein to make alkaline metabolites, which turns the medium a red color
EARLY color change + white colony = dermatophyte

56
Q

How else can the color change be delayed or altered/negatively affected?

A

Incorrect temperature (low)
Heavy saprobic growth = red change
Delayed observation (lab error)

57
Q

What is seen in this image?

A

Translucent hyphae within the hair
Extending spores all around the hair shaft

58
Q

What is the red arrow pointing to?

A

Hyphae within the stratum corneum

59
Q

What is the red arrow pointing to?

A

Branched hyphae within the scale

60
Q

What can you see on this deep skin scraping?

A

Deep in the dermis
Hair shaft with hyphae and spores (red arrows)
Surrounded by plasmacytic infiltrate (host trying to get rid of the fungus, blue arrows)

61
Q

What are the benefits of using PCR to diagnose dermpatophytosis? What is the typical turnaround time?

A

2-3 days turn-around
High sensitivity and specificity
Use for something that is high risk of zoonosis or highly contagious

62
Q

Is PCR necessary? What is important IN ADDITION to culture when diagnosing dermatophytosis?

A

No - not if you do proper Wood’s Lamp and fluorescence microscopy, followed up by culture when suspicious of negative result on the former 2 steps

63
Q

How long does it take the adaptive immune system to work to control dermatophytosis?

A

Lesions may resolve as a consequence of adaptive immunity in 1-4 months

64
Q

What are the important factors regarding zoonoses that need to be communicated to clients? Why is treatment of dermatophytosis NECESSARY when it comes to zoonotic potential?

A

Public health risk
Offer client counseling/advice
Potential for litigation - need to treat/give advice and KEEP NOTES
Refer human to their own health care provider

65
Q

What is this an example of? What is the major zoonotic risk in this photo?

A

Trichophyton dermatophytosis
HAIRBAND on student’s wrist in close proximity to hair follicle dermatophyte infection - NOT GOOD

66
Q

Should you use steroids to treat dermatophytosis?

A

NO NO NO
CONTRAINDICATED IN THIS CONDITION
Risk making things MUCH worse
Blocks inflammatory response (adaptive immunity) which leads to eventual recovery

67
Q

Should you simply await resolution of dermatophytosis in small animals?

A

No, not in small animals

68
Q

What is the best environmental decontaminant for dermatophytosis infections?

A

Hypochlorite bleach - wipe all surfaces which animal comes into contact with frequently

69
Q

Does a full body clip work for controlling dermatophytosis?

A

Yes! Controversial, but it will remove a lot of the infected hair and allow topical treatments to work better

70
Q

What are the topical therapy options for dogs/cats and cattle/horses?

A
71
Q

What are the systemic therapy options available? Which of these is licensed for cats?

A

Itraconanazole - given week on, week off for ~6 weeks, lipophilic
Griseofulvin - rarely used now

72
Q

Which of these represents dermatophytosis? What does this say about the necessary targets for anti-fungal therapy?

A

Topical only adjunct in treatment of dermatophytosis (need systemic), while topical treatment will work well for Malassezia (yeast) as it is only located on the surface

73
Q

How effective is T. verrucosum vaccine for cows? What kind of vaccine is this?

A

Bovilis Ringvac very effective - Live attenuated vaccine

74
Q

Why is a live attenuated vaccine not available for use in cats/dogs? Why is it OK to use in a farm setting?

A

Not advisable to allow a zoonotic/contagious fungi into a home where animals and pets are in close contact
OK on the farm where biosecurity measures exist

75
Q

What is this?

A

Malassezia pachydermatis

76
Q

On what animals is Malassezia yeast typically found?

A

Birds and mammals

77
Q

What is the lipid dependent vs. non-lipid dependent species of Malassezia?

A

Lipid-dependent - M. furfur (formerly only described in humans)
Non-lipid dependent (but also lipid dependent) - M. pachydermatis (important in dogs/cats)

78
Q

What is a common condition of the ears that is associated with Malassezia in dogs? What other area of the body does Malassezia frequently target?

A

Otitis Externa - red, waxy ears, brown gunk
Malassezia dermatitis - red, saliva-stained itchy paws

79
Q

What kinds of Malassezia will you typically grow from cats vs. dogs?

A

Dogs - pachydermatis
Cats - all the ones in purple + pachydermatis

80
Q

Which animals are these species of lipid-dependent Malassezia common in?

A
81
Q

Is M. pachydermatis a commensal on healthy dogs?

A

YES - part of normal skin flora
Toe webs, lip folds, ears

82
Q

How does M. pachydermatis cause disease?

A

Opportunistic pathogen, multiplies and cause disease

83
Q

What is evident in this photo?

A

Stratum corneum (silver stain) biopsy sample of epidermis with black peanuts of Malassezia

84
Q

How is the transitional mantel zone of the skin affected by climate and how does this affect the growth of Malassezia?

A

When its cold/dry, not a good environment for yeast to proliferate
When its very hot/humid, body is basically an incubator for yeast and it can proliferate
Might see seasonal variation with climactic changes depending on where you practice

85
Q

What else can influence how Malassezia proliferates?

A

Host chemistry can also influence Malassezia proliferation as well as interaction with bacteria

86
Q

What underlying issue (condition) predisposes dogs to Malassezia?

A

Atopic dermatitis (underlying allergy)

87
Q

Is it possible for dogs to develop allergy to Malassezia? How does this happen?

A

Already allergic dogs develop an allergy to Malassezia, which is part of the commensal flora in a healthy dog

88
Q

Define “Ichthyosis” - Are these puppies usually itchy? How do they become itchy?

A

Congenital ichthyosis is a skin condition in which the outer layer of the skin does not form properly and results in scaling.

Not usually itchy - Scaling disorder allows Malassezia organisms to opportunistically proliferate folds

89
Q

How do folds predispose to the development of Malassezia overgrowth?

A

Malassezia fungi like damp, warm places (folds of skin, underneath sheeps wool, etc)

90
Q

Which cat breeds are predisposed to Malassezia growth?

A

Devon rex and Sphynx cats

91
Q

What is one of the paraneoplastic effects of pancreatic tumors in cats (skin)?

A

Pancreatic paraneoplastic alopecia

92
Q

What type of tumor can cause associated exfoliated dermatitis? What is the treatment protocol for these cats?

A

Thymoma = thymoma-associated exfoliative dermatitis
Thymic growth is causing scaling disorder
Resolved by:
Thymectomy
1-2 washes with antifungal shampoo to resolve dermatitis

93
Q

What type of tumor can cause associated exfoliated dermatitis? What is the treatment protocol for these cats?

A

Thymoma = thymoma-associated exfoliative dermatitis
Thymic growth is causing scaling disorder
Resolved by:
Thymectomy
1-2 washes with antifungal shampoo to resolve dermatitis

94
Q

What are some predisposing factors which favor yeast? Which of these are common vs. rare?

A

Folds (common)
Climate
Breed
Endocrine disease (rare)
Cutaneous hypersensitivity disorders (~50%)
Primary/Secondary Cornification Defects (hereditary Ex. ichthyosis)
Idiopathic (~35%)

95
Q

Why is it important to find an underlying problem for malassezia dermatitis? What is going to happen with patients for which an answer cannot be found?

A

Animal will continue to relapse unless an answer to underlying issue is found
Concurrent allergies must be treated
Problematic folds must be regularly cleaned or surgically corrected
Genetic issues are a lifelong issue

96
Q

What is this?

A

Symmetrical erythema in the groin of a scotty just starting its journey with lifelong skin issues

97
Q

What is this?

A

JRT with intense erythema and traumatic alopecia from scratching due to intense pruritis
Lichenification of skin markings leading to elephant-like skin appearance = evidence of chronic dermatitis

98
Q

What is the evidence for Malassezia diagnosis in this patient?

A

Umbilical folds with brown gunk = classic Malassezia presentation

99
Q

What is this condition? Why is it different than just redness between the toes? What does the brown gunk indicate?

A

Interdigital Malassezia dermatitis
Just red between the toes indicates allergy
Brown gunk indicates microbe involvement (yeasts)

100
Q

What is this condition a result of?

A

Chronic Malassezia dermatitis (failed diagnosis in early 1990’s)

101
Q

What are the clinical signs associated with Malassezia dermatitis? What is the TOP clinical sign?

A

PRURITIS
Erythema +/- papules
Scaling
Greasy exudation
Hyperpigmentation/Lichenification
Malodour (stinky)

102
Q

What is Paronychia? What are the clinical signs?

A

Inflammatory infection around nail fold
Discoloration of claw
Brown gunk right where the claw comes out of the fold
Causes discomfort/chewing
Crusting

103
Q

What is frenzied facial pruritis? Why the term “frenzied”? What is cheilitis? What are the clinical signs?

A

Frenzied facial pruritis is a very intense itching of the face, typically inflammation does not match the level of crazed itching going on, hence “frenzied”
Cheilitis - inflammation of the lips

104
Q

What are the 3 steps to approach a case of Malassezia? Will counts always be high when testing for Malassezia? What do you do if you have a +ve vs. -ve result after testing?

A
  1. Look for clinical signs
  2. Test for Malassezia (cytology or quantitative culture)
    - Counts may not be high!
  3. If YES –> Initiate trial therapy
    If NO –> Sample more sites using different method, reconsider diagnosis
105
Q

What should you do if after treatment the clinical signs have resolved and all the yeast is gone on recheck testing?

A

Diagnose Malassezia dermatitis
Look for underlying cause

106
Q

What should you do if after treatment if all the yeast is gone, but the clinical signs have only partially resolved?

A

Diagnose Malassezia dermatitis
Treat residual disease + investigate

107
Q

What does an owner need to know about treating a patient with a Malassezia infection? How should you prepare them for treatment steps? What if you are left with atopic dermatitis (uncomplicated) after treating Malassezia? What do you still need to do?

A

Might not take care of all the irritation on the first go
Once Malassezia is gotten rid of, we can be left with uncomplicated atopic dermatitis that still needs to be treated and investigated, as the allergy is predisposing patient to yeast susceptibility

108
Q

What can you conclude if yeast is gone without any clinical treatment?

A

Yeast presence was likely incidental

109
Q

What should you do if clinical response is partial and presence of yeast has only partially improved?

A

Suspect Malassezia dermatitis
Check on compliance of at-home medications (missing doses, incorrect administration, etc)
Extend treatment for longer or with stronger dosage

110
Q

What should you do if there is no clinical improvement or reduction in yeast after treatment?

A

Review compliance of current medications or change treatments
Consider possibility of antifungal resistance

111
Q

How available is antifungal susceptibility testing? Why are the standard methods not suitable for Malassezia?

A

Uncommon - can be done, but unstandardized
Not suitable for Malassezia as it does not grow in RPMI 1640 (medium)

112
Q

Cells from which layer of skin are sampled using sticky tape?

A
113
Q

What method of staining should you use for tape impression?

A
114
Q

What are the visible cells in this image?

A

Squames in the background
Lots of Malassezia yeast

115
Q

Does direct impression work for sampling Malassezia?

A

Not really - not wet enough
Tape works better - needs to be able to stick

116
Q

What are the 2 methods available for quantitative culture of Malassezia?

A
117
Q

What is the ideal culture media used for Malassezia? Which species does this media target?
What is another media that can be used for dogs?

A

Modified Dixon’s Agar - Targets M. pachymderatis
Can also use “Sab” (Sabouraud’s Dextrose Agar) for dogs

118
Q

What is the difference in temperature/times that yeast should be cultured on Modified Dixon’s Agar in cats vs. dogs - why the difference in temperature/time?

A

Dogs - 32-37C for >3 days - looking for pachydermatis (fast growing)
Cats - 32-34C for >7 days - looking for slower growing lipid-dependent yeasts

119
Q

What species of Malassezia is this? Why are there differing colors in colonies?

A

M. pachydermatis - Larger pale yellow/smaller dark colonies are same species, just lots of genetic variation

120
Q

What are the factors which impact significance of Malassezia findings on cytology/sampling? Are all findings of Malassezia significant?

A

Depends on:
- Sampling method
- Anatomical site
- Breed
- Host immune status

121
Q

Is IgE required for sensitivity to Malassezia?

A

No - Immediate (IgE) mediated hypersensitivity is not required for development of severe Malassezia dermatitis
Can be delayed reaction

122
Q

What are the routes of administration for therapies for treatment of Malassezia yeast?

A

Systemic
Topical
(or both)

123
Q

List the systemic options for therapies for treatment of Malassezia yeast

A
124
Q

What is the “strength of recommendation” for the systemic medications used for treatment of Malassezia yeast? What does “strength of recommendation” actually mean?

A

Strength of recommendations just means that there aren’t enough studies to actually prove how good a medication is, but in practice the medication is really good!
Ex. Itraconazole is VERY good - just not enough studies to show WHY

125
Q

Why is ketoconazole (vs. Itraconazole) the go-to medication in north america?
Why is ketoconazole not used much in the UK?

A

Itraconazole is VERY expensive, used in UK
Ketoconazole is more affordable, but lots of side effects

126
Q

Why should you NOT use compounded formulations of “azoles”? What should you know instead?

A

Poor bioavailability (not combined with cyclodextrin - improves intestinal absorption)
Treatment failure
Use proven generic or innovative product

127
Q

What are the topical therapy treatments available for treatment of Malassezia yeast?
What are the strengths of recommendation for each of these treatments?

A

2% miconazole/2% chlorhexidine (Maloseb shampoo)
- A-strong recommendation (2 double blind studies)
3% chlorhexidine shampoo
- B- moderate recommendation (1 double blind study)
Miconazole conditioners
Essential oils (Malacalm)
- C-weak recommendation

128
Q

What is the best product for an itching animal (either from staph or Malassezia)? Why?

A

2% miconazole/2% chlorhexidine (Maloseb)
2 products which target both sources/causes of itching/irritation

129
Q

What is seen here? What organism outnumbers the other?

A
130
Q

What areas of the body are foams/wipes good for?

A

Folds, nails, in-between toes
Local areas of irritation/infection, but not the whole body

131
Q

Why should we be very careful with prescribing generic products containing chlorhexidine?

A

Difficult to add chlorhexidine into a product and retain stability

132
Q

List prevention options for Malassezia?

A

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