Small Animal Food and Environmental Allergies

1. Small Animal Food and Environmental Allergies Heather Haskins Emily Mercer

2. Contents • Atopic Dermatitis • Allergic Contact/Inhalant Dermatitis • Food Allergy Dermatitis

3. Atopic Dermatitis • Inherited type I hypersensitivity reaction to environmental allergens

4. What is a type I hypersensitivity reaction? • Allergen contact induces allergen-specific IgE antibody production leading to memory cell hyper reactivity upon reexposure

5. Normal Immune Response

6. Type I hypersensitivity rxn

7. Breeds most commonly affected by Atopic Dermatitis • West Highland white terriers • Wire-haired fox terrier • Cairn terrier • Scottish terrier • English setter • Miniature schnauzer • Lhasa apso • Chinese shar-pei

9. Clinical Signs of Atopic Dermatitis • Pruritis • Self-inflicted excoriations • Salivary staining • Alopecia • Lichenification • Hyperpigmentation • Otitis externa

11. Clinical signs of Atopic Dermatitis • Erythema • Secondary Infections: • Malassezia dermatitis • Serous pyoderma • Hemorrhagic pyoderma

12. Allergic Contact Dermatitis • Type IV hypersensitivity reaction to environmental allergens by direct contact

13. What is a type IV hypersensitivity reaction? • Delayed hypersensitivity reaction mediated by lymphocytes, a cell-mediated reaction

14. Common Contact Allergens • Insecticides in flea collars, sprays, dips • Wood preservatives • Floor waxes • Carpet dyes • Some pollens • Dermatological drugs • Leather products • Paints • House plants

15. Clinical Signs of Contact Dermatitis, Acute Lesions • Affects relatively hairless portions of body • Erythema • Papules • Vesicles which rupture to form crusts

16. Clinical Signs of Contact Dermatitis, Chronic Lesions • Alopecia • Hyperpigmentation • Lichenification • Self-inflicted trauma

17. Atopic Dermatitis • Type I hypersensitivity • Hyperemia,pruritis • Face,nose,eyes,feet, perineum • Foods,pollens,fleas, inhaled allergens • Intradermal testing, immediate response • Eosinophilic filtration, edema • Steroids, antihistamines, hyposensitization Contact Dermatitis • Type IV hypersensitivity • Hyperemia, vesiculation,alopecia,erythema, • Hairless areas • Reactive chemicals • Delayed response on patch testing • Mononuclear cell infiltration, vesiculation • Steroids

18. Diagnosing Atopic and Allergic Contact Dermatitis • Take skin scraping and perform fecal float • IDAT: Intradermal allergy testing • In vitro testing: ELISA, RSAT

19. IDAT Requirements • Animal’s allergy season lasts longer than 3 months • Medical therapy no longer controls the symptoms • Avoidance of allergens is not possible • Animal is young and would benefit from long-term immunotherapy

20. IDAT Test • As a pretest, inject .1ml of 1:100,000 histamine phosphate as the positive control and .1ml of saline as the negative control before performing the full skin test • Read the test 10-15 minutes after making the injections • A red, firm wheal ~15mm in diameter or 4X the size of saline control bleb is adequate positive response to histamine

21. Skin Testing

22. In Vitro Tests:ELISA,RSAT • Useful when IDAT not an option • Commercially available • Sedation is not required • Antihistamines and NSAIDS need not be discontinued • Lesser amounts of serum needed • Lower specificity

23. Treatments • Hyposensitivity immunotherapy vaccines • Corticosteroids • Topicals • Antihistamines • Essential Fatty Acids • NSAIDS

24. Immunotherapy with Hyposensitization • Allergy vaccines are made for individual patients based on either serologic or IDAT results • Goal of therapy: to increase the patient’s ability to tolerate environmental allergens without clinical signs

25. Statistics Associated with Immunotherapy • ~25% improve in 3 months • Another 50% in 6 months • Remaining 25% in 6-12 months

26. Food Allergy Hypersensitivity • Suspect if: non seasonal pruritic lesions, no response to steroids or NSAIDS (dogs), no response to progestational drugs (cats) • Immediate (type 1) and delayed (type 4) food reactions

27. Breeds Most Susceptible to Food Allergy Dermatitis • Miniature schnauzer • Golden retriever • West Highland white terrier • Chinese shar-pei

29. Clinical Signs of Food Allergy Dermatitis • Non seasonal pruritis • Ear canal disease that manifests as pruritis and secondary bacterial and yeast infections • Blepharitis • Generalized seborrhea • Papular eruption

30. Patient with Food Allergy Dermatitis

31. Diagnosing Food Allergy Dermatitis • Only reliable diagnostic test= food elimination diet • Trial diet fed up to 3 months • To confirm that food allergy exists, the patient should be rechallenged with previous food and a relapse of clinical signs must occur

32. Most Frequent Food Allergens (Dogs) • Beef • Chicken • Corn • Wheat • Soy • milk

33. Most Frequent Food Allergens (Cats) • Fish • Chicken • beef

34. Hypoallergenic Test Diet • Feed limited number of food-stuffs • Dogs: 1:1 mix of pinto beans and potatoes • Cats: lamb based baby food, without onion • Prescription diet • Do not give palatable meds such as heart worm preventatives, vitamins

35. Food Allergy Treatments • Home made diets consisting of balance of protein, carbohydrate, vitamins, minerals, and taurine for cats • Commercially available limited-allergen diets

36. Two cases: Theodore and Toby • Theodore “Teddy” • 11 years old • Neutered male • Lhasa apso

37. Teddy’s history of skin problems • Scabies • Fleas • Year round pruritus

38. Teddy’s Therapy • Weekly baths • Steroid therapy during intense flare-ups

39. Toby’s problems • Toby: 1 ½ years, neutered male, black lab/basset hound mix • Chronic yeast infection – otitis externa

40. Toby’s Food Allergy • Hill’s Z/D food elimination diet for 6 months • Hill’s D/D duck and rice diet fed daily • No other treats • Ice cubes

41. Food Elimination Diet • Hill’s Z/D Ultra Low Allergen food • Side effects • Fed for specified period of time

42. Conclusions • Trial and Error • Individuality of each patient

43. References: • The Merck Veterinary Manual 8th edition, Aiello, Mays 1998 Merck & Co. INC. • Veterinary Pathology 6th edition, Jones, Hunt, King 1997 Williams & Wilkins • Saunders Manual of Small Animal Practice 2nd edition, Birchard and Sherding 2000 W.B Saunders Company • Veterinary Immunology 6th edition, Tizard, W.B Saunders Co. 2000