Dermatology - pruritus and allergy Flashcards
What is the itch scratch cycle?
When the mechanical effect of scratching temporarily stops the sensation of pruritus
The itch then gets worse from the self trauma
What can help to stop the sensation of pruritus?
Interleukins
eg. cytopoint is a interleukin 31 monoclonal antibody
What are flare factors?
Influences to the perception of pruritus
What are some examples of pruritus?
Microbial overgrowth/infection
Fleas
Dry skin
Sweating/moist skin
Psychological factors
What are some visual signs of pruritus in animals?
Licking, rolling, nibbling, pulling hair
Can look like grooming
What is a common dermatological hypersensitivity in horses?
Culicoides hypersensitivity -sweet itch
When does culicoides hypersensitivity usually occur?
April to october
Where does culicoides hypersensitivity usually occur?
Mane, tail, lateral neck
What drugs can you give for culicoides hypersensitivity?
Permethrin or cypermethrin
Antiinflammatories - antihistamines and glucocorticoids
What causes canine atopic dermatitis?
Genetically inherited inflammatory syndrome
Familial inheritance
What is canine atopic dermatitis typically associated with?
Antigen specific IgE antibodies to environmental allergens
When do signs of canine atopic dermatitis usually occur?
From 1-3 years
Rare before 6 months or after 6 years
Mostly indoors
Where does pruritis usually affect?
Face, feet, groin and axillla
What are the primary dermatological signs from canine atopic dermatitis?
Erythema and papules
What are common secondary infections from canine atopic dermatitis?
Bacterial
Malassezia infection
What diagnostic criteria are specific to canine atopic dermatitis?
Pruritus is glucocorticoid responsive
Pruritus is major or only signs
Front feet and concave aspect of pinnae are affected
Ear margins are not affected
What is a desensitising treatment of canine atopic dermatitis?
Allergen specific immunotherapy
What is allergen specific immunotherapy?
Subcut injections to desensitise to environmental allergens
What topical treatment is there for canine atopic dermatitis?
Glucocorticoids
Cyclosporin
Apoquel
Cytopoint
Antihistamines
What is the name for food allergy?
Cutaneous adverse food reaction
What are the clinical signs of cutaneous adverse food reaction?
Mimic atopic dermatitis
Pruritus
Otitis externa, bacterial infections alongside
How do you diagnose cutaneous adverse food reaction?
Use hydrolysed diet, or home cooked novel protein for 8 weeks
Then rechallenge with original diet
What is the clinical presentation of pyoderma?
Intraepidermal pustules - often broken open
Epidermal collarette - caused by peripheral spread of lesions
What are common underlying disorders causing pyoderma?
Ectoparasites
Allergy - atopic dermatitis
Endocrinopathies eg. hypoadrenocorticism, hypothyroidism
What is deep pyoderma?
When infection spreads into the dermis
What is the treatment of choice for pyoderma?
Clip coat, remove scale, crust
Topical therapy - chlorhexidine 10 min soak 2-3 times weekly
What should you do if pyoderma reoccurs?
Culture and sensitivity of intact pustule
Good for antibiotic resistance eg. MRSP (same as MRSA)
What is an equine microbial infection in the epidermis of the feet?
Dermatophilosis (mud fever)
What does dermatophilosis (mud fever) cause?
Pain (rather than pruritis)
Matted hair
Crusts, erosions
Fissuring
Lameness in horses
What is to note about dermatophilosis?
It is zoonotic
Not the same as dermatophytosis
How do you diagnose dermatophilosis?
Take smears from underside of crusts
Will show gram positive bacteria with branching filaments - ‘tram track appearance’
How do you treat dermatophilosis?
Remove predisposing factors eg. moisture, biting insects, abrasive pasture
Clean area with chlorhexidine
3-5 day course of penicillin
What is dermatophilosis called in large animals?
“Mycotic” dermatitis - but not fungal
What is malassezia?
An opportunistic lipid-dependent yeast pathogen normally found in ear canal, chin and interdigital areas of dogs
What are predisposing factors for malassezia?
Skin folds creating moisture
Allergic/bacterial skin disease
What are the clinical signs of malassezia?
Severe pruritus
Oily scale, malodour
Ventral distribution - feet, face, skin folds, perianal region
Otitis externa
How do you diagnose malassezia?
Impression smears with a dry swab
Or direct slide contact
What does malassezia look like on cytology?
Peanut or foot shape
How do you treat malassezia?
Topical shampoos - chlorhexidine, miconazole
Twice weekly
What are the 4 clinical syndromes of allergic dermatitis in cats ?
Symmetrical alopecia - self induced
Papular/miliary dermatitis
Ulcerative dermatitis - self trauma
Eosinophilic dermatoses - granuloma complex
What can cause miliary dermatitis in cats? Differential diagnoses
Flea bite hypersensitivity
Food allergy
Feline atopic skin syndrome
Ectoparasites
Dermatophytosis
What makes up the eosinophilic granuloma complex?
Eosinophilic ulcer
Eosinophilic plaque
Granuloma
What is an eosinophilic plaque?
A pruritic raised ulcerated plaque-like lesion
Due to allergic skin disease
Usually in younger cats
What often accompanies eosinophilic plaques?
A circulating eosinophilia - lots of eosinophils in the skin
What is the most likely cause of eosinophilic plaques in cats?
Flea allergy
What is an eosinophilic ulcer?
Unilateral or bilateral ulcers on the philtrum of the upper lip
Large, easily recognised
Not usually painful
Need to biopsy to rule out biopsy or infections
What are indolent ulcers?
Same as eosinophilic ulcers
What is the treatment for eosinophilic ulcers?
Just leave untreated if not bothering the cat
Treat the underlying cause
What is an eosinophilic (linear) granuloma?
Idiopathic nodular granulomas
Associated with peripheral circulating eosinophilia
Where are eosinophilic (linear) granulomas found?
In the oral cavity on the tongue, hard palate
On chin and lower lip - ‘pout’
Can also be found on the medial aspect of the forelegs or caudal thighs
Associated with skin grooming pathways
How do you treat eosinophilic (linear) granulomas?
Surgical debulking
Glucocorticoids
But difficult to treat
What are the clinical signs of cutaneous adverse food reaction in cats?
Non seasonal pruritus
Miliary dermatitis
Symmetrical alopecia
What is the equivalent of atopic dermatitis in cats?
Feline atopic skin syndrome
How is best to treat pruritic cats?
Gulcocorticoids - prednisolone
Ciclosporin - expensive
What steroid dose do you give cats for an antiinflammatory effect?
Initial dose 1-2mg/kg/day of prednisolone
What dose do you give cats for an immunosuppressive effect?
Initial dose >4mg/kg/day of prednisolone
What are some side effects of long term glucocorticoid therapy?
PUPD
Weight gain
Diabetes mellitus
Gastric ulceration
Bacterial cystitis
Iatrogenic hyperadrenocorticism
Dermatophytosis
Demodicosis
What is the name for the cat flea?
Ctenocephalides felis
What types of hypersensitivity reactions occur in flea bite hypersensitivity reactions?
Type 1 and type 4
What are cats sensitised to in flea bite hypersensitivity reactions?
Sensitised to the antigenic components of flea saliva
How can you tell if cats have fleas?
Flea excreta - cats are very efficient at removing fleas by grooming
What can you use to treat fleas?
Pymethrin/pyrethroids
Neonicotinoids
Fipronil
Macrocyclic lactones
Isoxazolines
What are some factors that can influence efficacy of flea control?
Formulation
Hair coat length
Bathing/swimming
Use of insecticidal products
Insect growth development inhibitors
What are some mechanical control measures of flea infestation?
Vacuuming - 30-60% of eggs removed
Do not shampoo or steam clean carpets - humidity not good
How do you diagnose sarcoptes scabiei?
Scrape
How do you treat sarcoptes scabiei?
Macrocyclic lactones and isoxazolines
What does chorioptic mange cause?
Pruritus, alopecia, scale crust in large animals
Where does chorioptic mange affect horses?
Lower legs
Where does chorioptic mange affect cows?
Tail base, udder
Where does chorioptic mange affect alpacas?
Tail base
Ventral abdomen
Medial limbs
Ears
How do you treat chorioptic mange?
Treat all affected and in contact animals
Treat environment
How long do you need to treat chorioptic mange for?
6 weeks - two life cycles
How do you treat chorioptes in camelids?
Ivermectin
Fibronil spray
What is a louse infection called?
Pediculosis
How do you treat pediculosis?
Synthetic pyrethroids, macrocyclic lactones
