Dermatophytosis Flashcards
(39 cards)
1
Q
What are the most common dermatophytes that affect dogs and cats?
A
- Microsporum canis
- Microsporum gypseum
- Trichophyton mentagrophytes
- Microsporum persicolor
2
Q
What are the most common dermatophytes that affect horses?
A
- Trichophyton equinum
3
Q
What are the most common dermatophytes that affect cattle?
A
- Trichophyton verrucosum
4
Q
What are the most common dermatophytes that affect pigs?
A
Microsporum nanum
5
Q
What is the reservoir for Microsporum canis?
A
cats
6
Q
What is the reservoir for Microsporum gypseum?
A
soil
7
Q
What is the reservoir for T. mentagrophytes?
A
rodents, rabbits, pocket pets
8
Q
What are the predisposing factors for dermatophytosis?
A
- lack/decreased grooming
- presence of microtrauma
- excessive hydration/maceration
- warm temp and humidity
- lack of sun exposure
- strong cell-mediated immunity
9
Q
What are the breed and age predispositions in dogs and cats for dermatophytosis?
A
- Breeds:
- white Persians and Himalayan
- asymptomatic carriers
- terriers
- white Persians and Himalayan
- Age:
- young animals are predisposed
- sick and emaciated animals are predisposed
10
Q
What are the cutaneous signs of dermatophytosis in dogs and cats?
A
- Extremely variable
- always included in differentials for cats
- absent to moderate pruritus
- erythema/alopecia
- crusting/scaling/pustules
- miliary dermatitis (cats)
- dermal nodules/plaques
- muzzle and feet most affected
11
Q
What are the cutaneous signs of dermatophytosis in horses?
A
- most common dermatophyte = T. equinum
- direct and indirect transmission
- infected tack and grooming equipment
- follicular pustules
- variable sized annular alopecic areas
- severe scaling, crusting, pustules, ulcers, pruritus
- saddle and tack regions
- urticaria-like lesions
12
Q
What are the cutaneous signs of dermatophytosis in cattle?
A
- Most comomon dermatophy = T. verrucosum
- most common in confined cattle
- circular, alopecic areas
- severe scaling, crusting, and suppuration
- pain and pruritus - variable
13
Q
Describe kerion
A
a well-circumscribed nodular mass
14
Q
What are your differentials for dermatophytosis?
A
- parasitic dz
- allergies
- pemphigus foliaceus
- keratinization defects
15
Q
Describe the Wood’s lamp diagnostic test
A
- positive in 50% of M. canis/equinum strains
- Tryptophan metabolites
- good screening test
- NON-specific!
16
Q
How do you diagnose dermatophytosis?
A
- Clinical approach: hx and PE
- Diagnostics:
- Wood’s lamp
- Trichogram (hair pluck)
- Fungal culture
- Skin biopsy/histopathology
17
Q
Describe the Trichogram diagnostic test
A
- mineral oil
- KOH/NaOH preparation
- microscope setting
- low condenser
- low light
- low objective
18
Q
How should you store fungal cultures and how often should you check them?
A
- upside-down
- in the dark
- room temp: 30 degrees C
- check daily
19
Q
What is the MacKenzie technique?
A
- useful for feline asymptomatic carriers
- use collected hairs from bristles or cut bristles and place them onto media
20
Q
What stains should you use for tape preps?
A
- Lactophenol Cotton Blue
- Polychromatic Multiple Stain
21
Q
What are three important principles in treatment of both small and large animal infections?
A
- elimination of infection from host
- prevention of further dissemination of infective spores
- spores can survive up to 18 mo
- removal of infective spores already in the environment
*healthy animals can self-cure in 12-17 wks
22
Q
What are you therapeutic options for dermatophytosis?
A
- systemic tx
- topical tx
- environmental tx
treat ALL in contact with animals!
23
Q
What are options for topical therapy?
A
- Ketoconazole
- Miconazole
- Chlorhexidine
- Lyme sulfur
24
Q
How often should rinses be performed for dermatophytosis treatment?
A
twice weekly
- lime sulfur dips
- enilconazole
- ^ these two dry hair coat
- accelerated hydrogen peroxide rinse
25
What are examples of systemic therapy for dermatophytoses?
* Ketoconazole
* Itraconazole
* Fluconazole
* Terbinafine
* Griseofulvin
26
Describe griseofulvin
* fungistatic
* very cheap
* variable oral absorption
* incr fatty meal
* particle size
* microsize and ultramicrosize
* presence of polyethylene glycol
* **only effective against dermatophytes**
27
What are the side effects of griseofulvin?
* vomiting
* diarrhea
* anorexia
* bone marrow suppression
* Siameses, Himalayans, and Abyssinians
* Monitor CBC, FIV, FeLV and other viruses
* teratogenic
28
Describe ketoconazole
* Fungistatic
* Ergosterol synthesis in fungal cell wall
* Good oral absorption
* incr fatty meal
* decr non-acid gastric environment
* H2 antagonists
* good efficacy against M. canis, T. mentagrophytes, and Malassezia spp.
29
What are the side effects of ketoconazole?
* vomiting, diarrhea, and anorexia
* incr liver enzymes
* interfer w/ steroid synthesis and inhibtion of cytochrome p450 enzymes
* check for drug interactions
* dogs: tolerate ketoconazole fairly well
* cats: anorexia, even at lower dose
* contraindicated in pregnant animals
30
Describe itraconazole
* fungistatic (low dose)/fungicidal (high dose)
* preferred choice for feline fungal infections
* good oral absorption
* incr fatty meal
* very expensive
* residual effect
* accumulation in keratinized tissues
* formultions:
* capsules
* oral suspension
31
What are the side effects of itraconazole?
* uncommon
* GI upset and hepatotoxicity (rarely)
* reversible, dose-dependent cutaneous vasculitis in dogs at higher doses, anorexia
* mild inhibition of the cytochrome p450
* not rx in pregnant animals
* potential for teratogenicity and embriotoxicity
32
Describe fluconazole
* Fungistatic
* bis-triazole antifungal
* expensive
* broad antimycotic spectrum
* side effects appear uncommon
* GI upset
* little hepatic metabolism
* mild inhibition of the cytochrome p450
* Rx in patients w/ hepatic dz
33
Describe terbinafine
* Allylamine derivative
* inhibits squalene epoxidase and prevent ergosterol synthesis
* fungicidal
* residual effect
* accumulates in keratinized tissues
* very few side effects
* vomiting and facial pruritus (cats)
* incr liver enzymes
* **no inhibition of cytochrome P450**
34
Describe immunotherapy for dermatophytoses
* Killed M. canis in cats licensed for prevention and treatment of lesions, but NOT the dz
* **NO efficacy in preventing or providing rapid cure when compared with untreated controls**
* slightly decr severity of initial infection compared w/ controls
* large animals (cattle)
* considerable success in prophylactic or therapeutic use
35
Describe environmental decontamination for dermatophytoses
* water and bleach
* repeat the wash twice in a washing machine
* any materials that cannot be effectively treated should be discarded
* concentrated bleach and 1% formalin are **100% effective**
* ****toxicity
* 1:10 to 1:100 bleach, 1:33 lime-sulfur, and 0.2% enilconazole
36
Describe the triple cleaning technique
* Mechanically removed spores and hairs
* vacuuming and using Swiffer cloths
* Wash and rinse surfaces 3x
* detergent solution
* Disinfect target areas w/ 1:10 bleach
* Twice weekly using this protocol
* Homes were culture negative after one to three cleanings!
37
For what duration should your therapy last for dermatophytoses?
* therapy should include: topical, systemic, and environmental tx
* **no growth on two sequential weekly cultures**
* ****finalized after 14d
* suggested to **keep the cultures for 21d**
* 2 neg cultures 1 mo apart
38
What is the treatment for onychomycosis?
* prognosis for cure is guarded and will take several months (6-12+) if at all
* **itraconazole and terbinafine** are probably best agents for use
* residual effect
* onychectomy may be indicated for resistant/recalcitrant cases or financial concerns
39
Describe dermatophytoses therapies for large animals
* Infections usually self-limiting
* treatment goals:
* shorten course of dz
* limit spread to other animals and humans
* prevent dissemination into environment
* _good preventative medicine program is important part of tx_
* systemic tx = rarely indicated
* topical tx: lime sulfur spray
* treat 2 wks past clinical cure
* separate infected animals
* environmental decontamination
* decr crowding, incr UV light exposure
