CANINE DIETARY AND ENVIRONMENTAL HYPERSENSITIVITY

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Branden Chambers
5 years ago
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1 CANINE DIETARY AND ENVIRONMENTAL HYPERSENSITIVITY

2 Canine allergens What are the most common canine allergens?

3 Common canine allergens What are the most common canine allergens? Flea allergy dermatitis Environmental allergens (atopy) House dust mites House dust Feathers Mold Weeds, grasses, trees Dietary allergens

4 Types of hypersensitivity reactions Immediate Cytotoxic Cell-mediated Delayed

5 Dietary hypersensitivity

6 Dietary hypersensitivity Can occur anytime (80% < 3 years) Nonseasonal Clinical signs: Cutaneous Pruritus, otitis externa, recurrent pyoderma GI vomiting, diarrhea, scooting, straining, Intermittent blood/mucus

7 Differential diagnoses Environmental allergy Bacterial infection Malassezia infection Ectoparasites Dermatophytosis

8 Most common dietary allergens

9 Dietary hypersensitivity testing 10 week strict hypoallergenic diet trial followed by challenge Low sensitivity/specificity of serum and intradermal allergy testing for food Range from 0 to 14% sensitivity for serum Range from 0 to 10% for IDAT

10 Selecting a trial diet No previous exposure Will not cross-react with previous diets Acceptable to patient Acceptable to owner

11 Types of trial diet Novel protein (commercial) Novel protein (home-cooked) Hydrolyzed

12 What about OTC diets? Fish-based, venison-based, etc Cross-contamination with non-labeled allergens

13 Performing a diet trial Gradually transition to prescription diet Feed prescription diet for weeks Feed nothing but the prescription diet and water Continue treating secondary problems In weeks (if improved), begin challenging

14 Which of these are acceptable? Chewable Rimadyl Flavored toothpaste Heartgard Baby carrots Rawhide Bully sticks Organic broiled free-range chicken breast (just a tiny bit)

15 The prescription diet and water

16 What objections do clients raise? I feed a very good food. But he s never been food-allergic before! His food is grain-free. But he only gets tiny bits of table food. I tried Blue Buffalo Salmon and Potato and it didn t help. But she HAS to have treats! I tried one of those prescription diets for two weeks and nothing changed. But I have 2 young children!

17 Take-home points Diagnose food allergy with diet trial Diet trial must be a prescription hypoallergenic or home-cooked diet Nothing else by mouth for weeks

18 Flea bite hypersensitivity

19 Flea allergy dermatitis Affects up to 50% of dogs with fleas Average age of onset 1-5 years +/- Seasonality Clinical signs Pruritus Lesions

20 Flea allergy dermatitis Diagnosis Flea comb Pattern of pruritus/lesions Flea control trial But my dog CAN T have fleas! My house is very clean! Why do clients say this?

21 Flea allergy dermatitis Treatment ALL the pets Effective product Proper and consistent use Environmental treatment

22 Environmental hypersensitivity

23 Environmental hypersensitivity Atopy: A genetically-predisposed tendency to develop IgE-mediated allergy to environmental allergens. Estimated to affect about 9% of dogs Average age of onset is 1 to 3 years May be seasonal or non-seasonal; 80% eventually have non-seasonal signs

24 IgE-mediated hypersensitivity

25 Other contributing factors Impaired epidermal barrier function Cytokine release from activated mast cells recruits inflammatory cells to area, and infiltrate can persist for days APCs in atopic dogs are more likely to express IgE, and at higher levels, and are more likely to drive an IgE-mediated response Keratinocytes from human atopic patients produce fewer antimicrobial peptides, allowing easier bacterial colonization and infection. They also make more pro-inflammatory cytokines.

26 Clinical signs Pruritus Face, feet, distal limbs, ventrum Lesions Erythema, salivary staining, partial alopecia, papules, pustules, hyperpigmentation, lichenification

27 Most common environmental allergens House dust mites House dust Feathers Mold? Plants

28 Sequelae of atopy Secondary bacterial pyoderma Malassezia skin infections Otitis externa (~50% of dogs)

29 Secondary bacterial pyoderma Allergy to Staphylococcus bacteria? Staphylococcal exotoxins functioning as superantigens May account for significant proportion of clinical signs in atopic dogs Early evaluation and treatment!

30 Malassezia dermatitis Malassezia hypersensitivity common in atopic dogs Number of yeast on cytology appears not proportional to severity of clinical signs May account for significant proportion of clinical signs in atopic dogs Early evaluation and treatment!

31 Bacterial or yeast skin infection Diagnosis: Cytology (direct impression, cotton swab, tape prep, superficial skin scraping) 0 No organisms seen on careful examination 1+ Occasional organisms, but have to look carefully 2+ Organisms present in low numbers, but easily detectable 3+ Organisms present in larger numbers and rapidly detectable without difficulty 4+ Massive numbers of organisms, rapidly detectable

32 Differential diagnoses for atopy What conditions commonly cause similar clinical signs?

33 Differential diagnoses Flea bite hypersensitivity Dietary hypersensitivity Scabies Insect hypersensitivity Contact dermatitis Intestinal parasite hypersensitivity Bacterial folliculitis Malassezia dermatitis

34 Diagnosis of atopy Exclusion! ACVD task force (2001): Corticosteroid-sensitive pruritus Erythema of the pinnae Bilateral erythematous pododermatitis of the forefeet Cheilitis Appearance of signs between 6 months and 3 years of age

35 Intradermal allergen testing (IDAT)

36 Intradermal allergen testing (IDAT)

37 In vitro testing

38 Allergy testing in dogs IDAT In vitro Requires drug withdrawal Yes No Requires sedation and clipping Yes No Direct testing of affected organ Yes No Able to perform despite No Yes widespread skin disease Risk of anaphylaxis Yes No Frequent false positives/negatives No Yes

39 Treatment Avoidance Topical therapy Oral therapy (symptomatic) Hyposensitization

40 Environmental decontamination HEPA filter Dehumidify to below 40% Discard old dog beds Frequent rinsing or washing of exposed areas to remove allergen before it can penetrate skin Restoring/maintaining epidermal barrier function

41 Topical therapy Repair skin barrier layer Phytosphingosine Fatty acids Increase patient comfort Glucocorticoids Treat concurrent disease (ie, pyoderma) Antiseptic Antifungal

42 Systemic therapy Essential fatty acids 40 mg/kg of EPA Antihistamines Variety, dose varies with choice Glucocorticoids mg/kg BID Cyclosporine (Atopica) 5 mg/kg SID until effect, then taper to q2-3d Apoquel mg/kg BID for 14 days, then SID

43 Hyposensitization

44 Take-home points Atopy is diagnosis of exclusion Other disease processes can contribute Treatment can include avoidance, symptomatic treatment, treatment of concurrent infection, and hyposensitization

45 References DeBoer DJ Vet Immunol and Immunopath 2001;81(3-4):143. Olivry T et al. The ACVD Task Force on Canine Atopic Dermatitis 2001 Lund EM et al. J. Am. Vet. Med. Assoc., 1999;214:1336 Youn HY et al. J Vet Sci. 2002;3(4):335 Spiegel IB. ACVC Proceedings 2013 Scott DW et al. Small Animal Dermatology. WB Saunders, NY. 5 th ed, Nuttall TH et al. Clin Exp Allergy 2002;32:789 Ong PY et al. NEJM 2002;347:1151 Jutel M et al. Curr Allergy Asthma Rep. 2011;11(2):139 DeBoer DJ et al. Waltham International Science Symposium: Nature, Nurture, and the Case for Nutrition Raditic DM et al. J Anim Physiol Anim Nutr (Berl) 2011;95(1):90 Willis-Mahn C et al. J Am Anim Hosp Assoc. 2014;50(6):383 Jeffers JG et al. JAVMA (2): 245 Hillier A et al, ACVD proceedings 1994 Mueller R et al, Vet Dermatol 1998; 9:167-71

Cutaneous adverse food reactions in the canine patient

Cutaneous adverse food reactions in the canine patient D R. M I C H A E L A. R O S S I, D V M, M N S D I P. A M E R I C A N C O L L E G E O F V E T E R I N A R Y D E R M A T O L O G Y C O A S T A L V E