Lecture 11 2/24/25 Flashcards
What is the most common clinical sign in allergy conditions?
steroid-responsive pruritus
What are the characteristics of type 1 hypersensitivity?
-IgE mediated
-onset within one hour
-example is anaphylaxis
What are the characteristics of type 2 hypersensitivity?
-IgG or IgM cytotoxic mediation
-onset within hours to days
-example is hemolytic anemia
What are the characteristics of type 3 hypersensitivity?
-immune complex mediated
-onset within 1 to 3 weeks
-example is serum sickness
What are the characteristics of type 4 hypersensitivity?
-T cell mediated
-onset within days to weeks
-example is rash
What is the pathomechanism of flea dermatitis?
type 1 and type 4 hypersensitivity to flea saliva that results in a generalized allergic reaction
What is the clinical presentation of flea dermatitis in dogs?
-pruritis
-affected tail base area
-self-induced alopecia from itching
-papules
What is the clinical presentation of flea dermatitis in cats?
-pruritis
-affected tail base area
-self-induced alopecia from itching
-miliary dermatitis at head and neck
-indolent ulcer
How is flea dermatitis diagnosed?
-typical clinical presentation
-flea comb to detect flea dirt
-treatment response
What is the treatment for flea dermatitis?
-anti-pruritic drugs
-flea prevention
-flea control in environment
What are the important components of treating the environment for fleas?
-there are no insecticides to kill pupa
-vacuuming can physically remove pupa
-should repeat environmental treatment after one month to kill newly hatched fleas
What is canine atopic dermatitis?
hereditary, generally pruritic, predominantly T cell driven inflammatory skin disease involving interplay between skin barrier abnormalities, allergen sensitization, and microbial dysbiosis
What is the clinical presentation of canine atopic dermatitis?
-chronic pruritus
-skin inflammation/erythema
-typical distribution of lesions
Where do the lesions typically distribute in canine atopic dermatitis?
-face
-ears
-axilla
-groin
-flexural area, especially elbow folds
-feet
How is canine atopic dermatitis diagnosed?
-clinical diagnosis
-rule in via signalment, history, and clinical signs
-rule out other pruritic skin dz
-no specific tests
Why is allergy testing not routinely done to diagnose canine atopic dermatitis?
too easy to get false positive and false negative results
What are the Favrot’s criteria for diagnosing canine atopic dermatitis?
to rule in AD:
-age at onset < 3 years old
-mostly indoor pet
-corticosteroid-responsive pruritus
-chronic or recurrent yeast infections
-affected front feet
-affect ear pinnae
to rule out other mimicking dz:
-non-affected ear margins
-non-affected dorso-lumbar area
**all of these things occur in AD
What should be the suspected cause of skin dz based on age at onset?
-less than 1 year: ectoparasites or food allergy
-1 to 3 years: canine atopic dermatitis
-adult: other pruritic skin dz, food allergy, major environmental changes/allergies
How does response to corticosteroids rule canine AD in or out?
-corticosteroid-responsive pruritis is indicative of AD
-pruritus non-responsive to corticosteroids is often not AD
-non-responsiveness to corticosteroids could also be AD complicated by secondary infection
How does age impact the thought process regarding chronic/recurrent skin infection?
-this condition is often seen in young dogs with AD
-older dogs could have endocrine dz leading to chronic/recurrent infection
Why is it important to determine whether the itch or the skin infection came first?
-itching prior to skin infection indicates AD
-skin infection prior to itching indicates causes other than AD
What can be done when an owner is unsure whether the itch or skin infection came first?
treat the infection first and evaluate whether the itch remains despite the skin infection resolving
How does seasonality impact differentials for pruritic skin dz?
-seasonality indicates AD caused by pollen OR flea allergy
-non-seasonality indicates AD caused by house dust mites or food OR other pruritic skin diseases
-non-seasonality with seasonal exacerbation indicates AD caused by pollen AND house dust mites or food
What causes this clinical distribution?
scabies
What causes this clinical distribution?
demodicosis
What causes this clinical distribution?
flea allergy
What causes this clinical distribution?
atopic dermatitis
What are the characteristics of otitis externa?
-occurs in nearly half of AD cases
-AD can be a primary cause leading to secondary infection
-AD can predispose dogs to otitis externa and perpetuate the disease
How is scabies ruled out?
-clinical presentation
-pinnal-pedal reflex
-superficial skin scraping
-treatment trial with isoxazolines
How is flea dermatitis ruled out?
-clinical presentation
-flea comb + flea dirt
-treatment response
How is demodicosis ruled out?
-clinical presentation
-deep skin scraping
