Pruritis In Dogs Flashcards
Causes of pruritis
Allergic: atopic derm, food allergy, urticaria, drug reaction
Ectoparasites: scabies, mites, Cheyletiella, lice
Infectious: bacteria, fungi
Neoplasia: cutaneous lymphoma
Canine atopic dermaitis
Genetically predisposed inflammatory and pruritic skin disease with characteristic clinical features, associated with most commonly IgE antibodies to environmental allergens
Breeds predisposed to CAD
Golden retrievers, WHWT, GS, cocker spaniels, boxers, frenchies
Vary between countries and continents
Defect of CAD
Multi factorial disease. Defective skin barrier
Allows absorption of allergens through epidermis
Pathogenesis of CAD
Could be
-overactive immune system
- failure to regulate immune system
Regulatory T cells
Tregs- keep the immune system balanced so every chance for assault isn’t a dramatic shift but better managed
Characteristic clinical features of CAD
- Pruritis
- Alopecia
- Excoriation
- Erythema
- Hyperpigmentation
- Lichenificiation
- Recurrent otitis externa
- Recurrent bacterial /yeast skin infection
Common locations for CAD
Face, eyes, throat, ears, armpits, axillary stomach, paws
Distribution of similar clinical signs - CAD
Sarcoptic mange and demodicosis have the closest distribution
Sarcoptic mange: ears, hocks, elbows and axillary stomach
Demodicosis: under eyes, chin, splotchy dispatch on legs and paws
Perianal pruritis
Similar % seen in dogs with CAD and food allergy
Clinical signs for both - only itchy near anus no where else
Role of IgE in CAD
- Percutaneous penetration of allergens
- Langerhans cells (APC) capture allergens
- APC presents processed allergens to naïve T lymph to LN
- Naive t lymph stimulated into Th2 whcih secrete IL-4,5,13
- B cells stimulated become plasma
- Plasma produce IgE antibodies in the circulation
- IgE bind to surface of mast cell (sensitization stage)
- Re-exposure to allergen = cross link w IgE bound to mast
- Mast cell degranulate & release inflammatory mediators (histamine, serotonin, eosinophil chemo tactic factor)
Favrots criteria
Guidelines for CAD
1. <3yrs
2. Mostly indoor (eh)
3. Corticosteroid responsive pruritis
4. Chronic or recurrent yeast infections
5. Affected front feet
6. Affected pinnae
7. Non-affected ear margins
8. Non-affected Dorso-lumbar area
DX CAD
The clinical DX is only given AFTER ruling out pruritic diseases via serum allergy test and intradermal test
Other pruritic diseases
1. Ectoparasites, scabies, Cheyletiellosis
2. Infection
3. Cutaneous adverse food reaction (food allergy)
Tx approach for recurrent skin or ear infections
Skin/ear infection —> recurs after successful treatment —> investigate underlying cause
- allergic disease: parasite, endocrine, chronic steroids
- no underlying: idiopathic recurrent pyoderma
CAD DX
Seasonal pruritis —> canine AD
NON seasonal pruritis —> canine ad? Or food allergy? —> elimination diet trial —> no response —> canine AD
Elimination diet trial
ONLY reliable method to rule in/out food allergy
Serum allergy test is NOT reliable method to diagnose food allergy
Proteins are likely allergen
GI signs +/- but does not rule out food allergy
Hydrolyzed diet
Does not contain intact proteins - only peptides
Allow skin to reset. Diagnosis of food allergy is confirmed when pruritis resolved via elimination diet—>relapse on old diet —> resolve with hydrolyzed diet
Duration of elimination diet
5weeks: 80% of dogs w food allergy can be diagnosed
8 weeks: >90% of dogs w food allergy can be diagnosed
Management and prognosis is usually good
CAD management
Cannot be cured - life long therapy
1. Allergen specific immunotherapy
2. Cyclosporine/ciclosporin
3. Oclacitinib (apoquel)
4. Lokivetmab (cytopoint)
5. GC’s
6. Antihistamine
Pros and cons of ASI
Allergen specific immunotherapy -
Ideal Tx in dogs, injection of allergens to de sensitize
Serum tests can help ID for injections
Works in 50-70% of dogs show 50% improvement
May take up to 12 months
Pros and cons of cyclosporine (ciclosporin)
Advantages:
Highly effective long term treatment (80%)
Cons:
Expensive, 4wk to see benefit
Pros and cons of oclacitinib
Pros:
Highly effective, rapid speed, cheaper than cyclosporine
Pros and cons of lokivetmab
Antibody that neutralized interleukin-31, pruritogenic cytokine in dogs
Convenient - injection last 4weeks, up to 70% respond, rapid speed of action
Cons: expensive
Pros and cons of GC’s
Pro:
Highly effective Tx, rapid speed, cheapest drug
Cons:
MANY adverse effects
Long term Tx of CAD w GC’s is NOT recommended unless other Tx fails
Pros and cons of Antihistamines
Pro:
Cheap, no major ADR
Con:
Ineffective as sole therapy in most CAD
