Small Ani. Med- Pruritic Dog 2 (Lecture 3+4)

jihjong's version from 2016-10-31 23:32

Canine atopic dermatitis (CAD)

Question Answer
what is Canine atopic dermatitis (CAD)?Inflammatory and pruritic skin disease associated with a genetic predisposition to produce IgE against environmental allergens
what are the most common allergens to trigger Canine atopic dermatitis (CAD)?House dust mites, storage mites, Pollens, molds, feline and human dander, insects
what is the most common route allergens take to get into the body in CAD?Percutaneous absorption (so least haired parts of body are most affected bc they absorb the most bc less fur in the way). Allergens are to a lesser degree ingested and inhaled
explain the complex pathogenesis of how CAD happens?Type I hypersensitivity reaction (IgE), Epidermal barrier abnormalities --> Increased adherence of bacteria / yeast = infection
what is the Normal stratum corneum like to help keep allergens out?Ceramides 40-50%, Cholesterol 25-35%, Free fatty acids 10-15% all create a barrier that are like the grout between bricks. When these are disrupted, allergens, pathogens, and TEWL (transepidermal water loss) take place
what is the most common age for CAD to start? Is there a breed predilection? sec predilection?Age of onset: between 6 months and 6 years (70% of dogs develop clinical signs between 1-3 years of age) (whereas a food allergy is much older or much younger!!!) Breed predispositions: boxer, shar-pei, dalmatian, English bulldog, setter, Boston Terrier, Cairn Terrier, Scottish Terrier, WHW Terrier, Yorkshire Terrier, Labrador, GSD. Sex predilections: none
Is CAD seasonal?seasonality is Variable, Many dogs start with seasonal signs that progress to non-seasonal after 2-3 years
what are the primary and secondary lesions of CAD? What is their distribution like?(remember main CS is pruritus) PRIMARY: none or erythema. SECONDARY: red-brown salivary staining, excoriations, self-induced alopecia, papules, collarettes, crusts (2* pyoderma), lichenification (2* Malassezia dermatitis). DISTRIBUTION: face, ears, extremities, paws and abdomen
what are common concurrent conditions you will see with CAD?Otitis externa, conjunctivitis and pyotraumatic dermatitis also common
what is interesting to know about the breed predilections with CAD?diff breeds have diff places on the body where the lesions prefer to be. (See other cards)
where do CAD lesions like to be on frenchies?Armpits and front paws esp. affected
where do CAD lesions like to be on westies?all 4 paws
where do CAD lesions like to be on boxers?paws, and OUTSIDE pinna is more affected than the inside
where do CAD lesions like to be on GSD?Ventral abdomens
how do you dx CAD?history, clinical signs and ruling out other pruritic diseases! That is to say Atopic dermatitis is a diagnosis made by exclusion! The easy to rule out ones are: Sarcoptic mange (scabies), Fleas and flea allergy, Cutaneous adverse food reaction, 2* Bacterial folliculitis, 2* Malassezia dermatitis
Atopic dermatitis--> Treatment of acute flare-ups--> what works? what doesnt work?You can Control pruritus and inflammation (Topical or systemic steroids (prednisone, 0.5-1 mg/kg/24 h), Oclacitinib (Apoquel®) 0.4-0.6mg/kg BID) and you must Identify secondary infections and address them ( topical treatment (chlorhexidine) or systemic antibiotics). Antihistamines are no more efficacious than placebo medications
how effective are antihistamines in the TX of CAD, which is a Type I hypersensitivity in response to environmental allergens?Antihistamines are no more efficacious than placebo medications
what type of hypersensitivity reaction is CAD?Type I
Atopic dermatitis--> Long-term treatment (4)(1) Allergen-specific immunotherapy (Custom-formulated based on intradermal and/or serum allergy test results) (2) Cyclosporine A (Atopica®) – 5mg/kg SID (3) Oclacitinib (Apoquel®) – 0.4-0.6mg/kg SID (4) Improve skin barrier function w topical tx
what are two ways to do Allergy testing?(1) Intradermal skin test (IDAT) (in vivo test) (2) Detection of specific IgEs in serum (in vitro test)
what does Allergy testing tell you and NOT tell you? So when do you actually want to do allergy testing?Identifies of the main allergens causing clinical signs. HOWEVER, **Cannot use allergy testing to make a diagnosis of atopic dermatitis bc Clinically normal dogs can have false positive results on IDAT (skin) and SAT (serum antigen test). Only test if owners want to pursue allergen- specific immunotherapy
how does Allergen specific immunotherapy (ASIT) work?SC inoculation of small quantities of allergens in solution, given weekly to monthly--> Induces a change in the immune response (T-regulatory lymphocytes / IL-10). Success rates around 60-70% cases; results appear usually after one year of therapy. Sublingual immunotherapy given BID; as effective as SC ASIT
what are the STRENGTHS and WEAKNESSES of ASIT (allergen specific immunotherapy)STRENGTHS: Can induce a change in the immune response and “cure” the disease, Very few side effects (itch in some patients), Can combined with other therapies. WEAKNESSES: Low efficacy (especially in very severe cases of CAD), Requires allergy testing, Long time before improvement in clinical signs is noted (results should not be evaluated prior to 9 months), No predictability of results, Lack of standardized, validated protocols, Needs high compliance and time dedication of the owners
how long before ASIT (allergen specific immunotherapy) starts to work?like don't even test if there has been an effect before 9mo. Usually success starts after 1yr immunotherapy
what is Cyclosporine A? how does it work? How good is it for tx CAD?This is an IMMUNOSUPPRESSANT drug and Inhibits synthesis of several interleukins (IL-2) and cytokines (considered immunomodulating agent at low doses). 5 mg/Kg PO SID; 1 month, then reduce the dose (5mg/kg/48h, then 5 mg/kg/72 h) (goal is to reduce dosage to min effective dose to keep them on that dose) High effectiveness in the control of CAD 85% cases, but is Slower acting (14-28 days)
what are common side effects of Cyclosporine A?Side effects common [but mild]: vomiting, diarrhea, anorexia; 10-15% of cases (she said if given with food and frozen, can help prevent some of the GI S/Es)
STRENGTHS and WEAKNESSES of using cyclosporine A as a tx for CAD?STRENGTHS: High effectiveness, almost as effective as steroids, Can be used safely for long term treatment, Very easy to use, previous allergy testing not needed, Can be combined with other therapies. WEAKNESSES: Side effects (15% dogs vomit) Long term side effects not completely assessed, Slight delay in response time, Cost can be a limitation in some big dogs
what is Oclacitinib (Apoquel)? how does it work?Inhibits Janus Kinase 1 (JAK 1) and 3 (JAK 3), Blocking the action of many pro-inflammatory/allergic cytokines incl. IL-31. Disrupts signal transmission at the level of gene transcription
how effective is Oclacitinib (Apoquel) in treating CAD? how long does it take to start working?Highly effective in the control of non-complicated CAD >90% cases. 0.4-0.6 mg/Kg PO BID for 2 weeks, then SID. Fast acting (works in 4 hours – as fast as steroids). DOWNSIDES: Side effects uncommon / unknown. Backordered (limited supplies)
Atopic dermatitis--> what is some SUPPORTIVE THERAPY you can provide? (4)(1) Effective + permanent flea control (2) Effective control of secondary infection (3) Regular bathing to control infection and repair skin barrier function (1-2 times/week) (4) Feed essential fatty acid-rich foods, supplements