Dermatology Flashcards
Atopic Dermatitis
- allergic (inappropriate) reaction to environmental allergens
Atopic Dermatitis (Causes)
- allergens gain access to body by resp. or percutaneous route
- hypersensitivity via IgE antibodies
- loss of barrier function
Atopic Dermatitis (Loss of Barrier Function)
- abnormal lipid layer in stratum conreum
- decreased epidermal filaggrin
Allows for: - allergen penetration
- staph spp. and malassezial “stick to the stratum corneum
- water loss
Atopic Dermatitis (Signalment and Clinical Signs)
Dogs:
- Age 1-7 years,
- no sex predilection
- pruritis, erythema, rarely small papules, feet face axilla ears conjunctiva (front end disease)
Cats:
- no age or sex predilection
- facial head neck pruritis, miliary dermatitis (fleas most common cause), eosinophilic granuloma complex, self-induced alopecia
Atopic Dermatitis (Secondary Infections)
- Dogs > Cats
- Staph and Malassezia infections
Atopic Dermatitis (Diagnosis)
- History - seasonal, <7 years old
- Clinical Signs - pruritis, feet face axilla ears
- Rule Outs - food allergy, ectoparasites
Classic (seasonal, typical lesions), Semi-classic (non-seasonal or non-typical lesions), and Not classics (rule outs fail)
Atopic Dermatitis (Hyposensitization)
- intradermal testing (IDT)
- serologic testing
Common Allergens for Atopic Dermatitis
- house dust mites
- house dust
Pyoderma
- pus producing bacterial infection of the skin
Pyoderma ( Reasons for increased frequency)
- canine stratum corneum is less effective barrier to prevent bacterial infection
- lack of ostial plug in entrance of canine hair follicle
Top 3 canine skin pathogens
- Staph pseudintermedius (most common)
- Staph schleiferi (uncommon in dogs, > in cats)
- Staph aureus (uncommon in dogs and cats)
T/F: all staph species can develop methicillin resistance
T
Predisposing Factors for Pyoderma
- pruritis -> self-trauma
- environment
- dec immune function
- endocrinopathy
- infectious dz
- inflammatory dz
- hair follicle dz
- cornification disorders
Diagnosis of Pyoderma
- inflammatory skin disease
- evidence of bacterial invasion/ proliferation
- response to antimicrobial therapy
Acute Moist Dermatitis
- Surface Pyoderma
- ‘hot spot’, pyotraumatic dermatitis
- caudal manifestations usually flea allergy dermatitis
Intertrigo (skin fold pyoderma)
- Surface Pyoderma
- moist areas created w/in skin folds
- either breed related or obesity
- common d/t change in temp, pH, humidity, and frictional microtrauma
Mucocutaneous pyoderma
- Surface Pyoderma
- often around lips and peri-oral
- occurs around muco-cutaneous jxns
Impetigo
- Superficial Pyoderma
- non-follicular pustules
- often less haired areas
- > puppies and immunocompromised
- inguinal regions
Superficial folliculitis
- Superficial Pyoderma
- follicular pustules –> collarette
- circular hair loss, scale
Deep folliculitis and furunculosis
- Deep pyoderma
- pyotraumatic derm on the head/ neck
- any hemorrhage evidence means that it’s deep
Cellulitis
- deep pyoderma
- bacterial infection of skin and deeper tracts
Feline Pyoderma
- same species as dogs
- can present w/ miliary dermatitis (pinpoint rash), papules, scale, and collarettes
When to do culture and sensitivity testing
- <50% reduction in lesions w/in 2wks of abx therapy
- new lesions still develop 2 wks or > after starting abx therapy
- cocci after 6 wks, rods on cytology
- Sample intact pustules*
Tier 1, 2, 3 abx
Tier 1 - no risk factors for antimicrobial drug resistance are present
Tier 2 - post culture and sensitivity
Tier 3 - never use
Treatment of Pyoderma
- surface and superficial can get topical alone (chlorhexidine)(treat for 7 days post-clinical cure)
- Abx (start with tier 1)
T/F: previous abx therapy elevates the risk of mrsa to about 1/3
T
Most important flea species
- Ctenocephalides felis (Most common in all of small animal)
- Ctenocephalides canis
Flea Life Cycle
- Egg
- Larva (feed on organic matter, flea feces, dried blood)
- Pupa (adult emerges in response to CO2, warmth, vibrations)
- Adult
Flea Allergy Dermatitis
- hypersensititivyt to flea saliva
- most common type of allergy in both dogs and cats
Canine FAD: - caudal half disease
- any breed, season, age
Feline FAD: - miliary dermatitis anywhere on the body (esp head and neck)
Diagnosis of Fleas
- history
- flea comb
- location of itch (particularly for dogs)
Fleas (treatment)
- you can either go oral or topical formulations
- topical formulations require the animal to not be swimming all that much or washed a lot
- oral has faster time to kill
2 types of treatments for fleas
- Insect growth regulators
- -> juvenile hormone analog
- -> chitin synthesis inhibitors - Adulticides
Fleas (topical products)
- most topical shave about the same speed of kill
- avoid pyrethroid/ pyrethrin products in felids d/t neuro toxicity
Revolution Plus
- Selametin + Sarolaner
- selamectin activtes glutamate gated chloride channels
- must be over 8 weeks of age
Frontline
- Fipronil
- Binds GABA receptors and blocks transfer of chloride
- do not use in rabbits or hedgehogs
Advantage-multi
- imidacloprid w/ moxidectin
- binds post synaptic nicotinic receptor - blocks impulse transmission
- useful in canine and feline demodeicosis
- don’t use in birds - maxidectin is ok but imidacloprid is toxic
Bravecto
- Fluralaner
- oral or topical
- well tolerated for cats
- avoid in dogs w/ seizure history
Oral Products
- quicker to kill than topicals
- often easier to administer
- should be given with a meal
Isoxazolines
- oral product
- inhibits GABA gated chloride channels
- CNS signs have been reported anecdotally
- Nexgard, Simpirica, Credelio, Fluralaner,
Nexgard
- Afoxolaner
- oral chewable
- useful against fleas and ticks (also off label demodex and sarcoptes)
- given via soy protein
- avoid in animals w/ seizure history
Simparica
- Sarolaner
- good for fleas and ticks (also off label for demodex and sarcoptes)
- avoid in animals w/ seizures
- Revolution plus contains Selamectin + Sarolaner
Capstar
- nitenpyram
- kills adults fleas, 100% w/in 6 hrs
- can be given orally every 23-72 hours
Environmental Treatment
- vacuum and throw away bag
- do not steam clean carpets
Hyposensitization treatment for Atopic Dermatitis
- 70% of dogs that improve do so w/in 4-6 months
- Injections q48hr x 1 month, then once weekly
- Oral b.i.d. continually
- cats = dogs
Atopic Dermatitis (Rx)
Systemic:
- corticosteroids, antihistamines, psychotropic agents, EFAs, cyclosporine, oclacitinib, lokivetmab
Topicals:
- steroids, barrier aids
AD (Corticosteroids)
- pred/ prednisolone/ methylprednisolone
AD (Antihistamines)
Dogs = Cetirizine, diphen, dyroxyzine, chlorpheniramine Cats = Chlorpheniramine
AD (EFAs)
- Omega 3
- Omega 6
- steroid-sparing, but may take > 3 months
AD (Cyclosporine)
- inhibits T cell activation
- Atopica
- ok to test for allergies while receiving
- ok to hyposensitize while receiving
Side Effects: Anorexia, vomiting (store in freezer to avoid), diarrhea, papillomas, pyoderma, hypertrichosis, gingival enlargement
How to avoid vomiting w/ cyclosporine
- keep in freezer
- give with food
- pair with cerenia
AD (oclacitinib)
- Apoquel
- JAK stat 1 inhibitor
- mediator of IL 31
- only approved in dogs
AD (Lokivetmab)
- Cytopoint
- antibody targeting IL31
- not useful in cats
malassezia pachydermatitis (dogs)
- yeast organism, normal inhabitant of skin
- waxy brown exudate: skin or proximal claws, erythema interdigitally or under tail
- usually secondary to AD or food allergy
malassezia pachydermatitis (cats)
- sometimes associated w/ AD
- generalized - look for systemic disease
malassezia pachydermatitis (Diagnosis)
- by cytology via acetate tape preparation or skin scrapings
Anti-Yeats Rx: Systemic
- Terbinafine
- Ketoconazole (not in cats, and not w/ ivermectin)
Advantages of Topical Therapies
- can be sole or adjunctive treatments for numerous skin conditions
- relatively cheap compared to oral medications
- direct delivery of a specific ingredient to the skin surface
Downsides of Topical Therapies
- may be time-consuming
- risk of topical reactions
- risk of systemic absorption
Agent vs Excipient
Agent: active ingredients
Excipient: inactive ingredients. often include the vehicle (primary excipient used to carry the agent)
Shampoos
- minimum contact time of 10 minutes
- use veterinary products - canine skin is more basic
Conditioners
- contain cationic surfactants –> bind to damaged, negatively charged hair shafts
Rinses/ Dips
- concentrated solutions or powders mixed with water- do not rinse off afterwards
Wipes
- easy to use
- can only cover small surface areas
Mousses
- basically a foam formulation-
- do not rinse off after use
- can contain alcohol - sting
Keratolytic vs Keratoplastic
Lytic - remove excess scale
Plastic - reduces scale production
avg epidermal turnover rate is 21 days
Moisterizing Agents
- Emoolients - lipid based to improve skin barrier function
- Humectants - non-oily hydrscopic agents to attract water
Chlorhexidine
- positively-charged bisbiguanide compound –> binds to negatively-charged bacterial cell walls
- antifungal at 3% concentration or greater
Benzoyl Peroxide
- antibacterial, kertolytic, degreasing follicular flushing
- human concentrations are too strong and will damage the skin (only use 2.5-5%)
- indications: superficial pyoderma, comedones, +/- demodicosis
Ethyl Lactate
- antibacterial, astringent, cooling
- breaks down to lactic acid and ethanol
Sodium Hypochlorite
- bactericidal, fungicidal, sporicidal, and virucidal
- dilute to 1:10-20 with water and spot-test
Mupirocin
- topical antibiotic
- mostly gram-positive activity
- excellent for resistant Staph pyoderma
Silver Sulfadiazine (SSD)
- extensive broad spectrum activity - very useful for pseudomonas aeruginosa
Imidazoles
- antifungals
- interfere with the production of ergosterol
- Indications: dermatophytosis, malassezia dermatitis
Lime Sulfur
- antifungal, antiparasitics, keratolytic, keratoplastic, anti-pruritic
- Indications: dermatophytosis and most ectoparasites
- does not treat demodex or fleas **
- will stain every surface yellow-green
Tris-EDTA
- antibacterial, antifungal, anti-biofilm
- very good for ear cleaning since it is non-ototoxic
Tacrolimus
- inhibition of calcineurin –> inhibition of T-cell proliferation/ activation
- expensive
Trifexis
- milbemycin/ spinosab
- kills heartworm, fleas, intestinal worms
- > 8 wks of age
- don’t give with ivermectin
