Today's Veterinary Practice

JAN-FEB 2018

Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.

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49 JANUARY/FEBRUARY 2018 ‚óŹ TVPJOURNAL.COM CONTINUING EDUCATION environmental or flea allergies, that could fluctuate daily or seasonally and complicate the length of a food trial. To avoid gastrointestinal upset in the first few days of introduction and rechallenge, my clinical experience suggests initially mixing the old and new food (50%/50%) before complete transition to new or old food. Adjunctive treatments for severe skin inflammation, pruritus, ear infections, and superficial pyoderma should be initiated immediately at the start of a diet trial. The treatment should resolve all concurrent clinical signs of pruritus and infection (ears, skin) within 6 to 10 weeks of the diet trial, at which time the symptomatic medications are discontinued, and the patient can be maintained only on the novel food for the following 2 to 3 weeks. The patients are carefully observed during these 2 to 3 weeks; if the clinical signs or pruritus and skin/ear infections do not recur, the patient should be rechallenged with the old diet. A relapse of clinical signs within 14 days of rechallenge is expected in dogs with food allergy, although in most cases, untrained client/ owner observation is used to determine relapse. 1,3 Environment-Induced CAD Allergen Control The most common causes of CAD in my practice are environmental allergens from dust mites and pollens. House dust mite glycoproteins are likely the most common allergens in atopic dogs; therefore, reducing the numbers of mites and their allergens in the household may help alleviate CAD signs. 1,3 Several products are marketed for dust mite allergen reduction; however, only a single uncontrolled study showed the benefit of house dust mite control with an acaricide benzyl benzoate spray (Acarosan Spray, bissell.com ) for reduction of clinical signs of CAD in mite-hypersensitive atopic dogs. 20 Additional controlled studies correlating dust mite allergen reduction and clinical improvement in atopic dogs are needed; these studies should span several months because of the long persistence of mite allergens in the environment. Another measure to theoretically reduce mite allergens involves frequent and thorough pet mattress and environment washing and vacuuming. Allergen immunotherapy The sole causal treatment for environment-induced CAD is allergen immunotherapy (AIT), also known as desensitization or hyposensitization. 1,3 AIT consists of administering gradually escalating quantities of relevant allergens subcutaneously or sublingually ( BOX 5 ) 21-27 until immunologic tolerance to the allergens is established and relapses of CAD clinical signs are prevented. Molecular and cellular mechanisms of AIT include early mast cell and basophil desensitization effects; an induction of interleukin-10-secreting inducible regulatory T and B cells; regulation of IgE and IgG4 production; and inhibition of responses from BOX 4 Considerations for Diet Trials The closer the taxonomic relationship between meat sources, the higher the risk for immunologic cross-reactivity between proteins. 16 In vitro, allergens from chicken, can cross-react with those from other poultry; identical cross-reactivity exists for beef and other ruminant proteins. 16 As the variety of protein sources available in commercial pet foods has expanded and the habit of feeding table scraps has increased, the choice of novel protein sources has become more limited. Hydrolyzed protein diets are used for the diagnosis and management of dogs with food allergies; in these diets, enzymatic hydrolysis is used to convert native proteins into small peptides that are less likely to be allergenic. 15 However, two recent studies found that dogs allergic to soy and chicken experienced flares when fed a hydrolyzed soy or chicken diet. 17 Additionally, in a recent randomized, double-blinded, crossover trial, a hydrolyzed poultry feather diet did not induce pruritus flares in any of 10 dogs with chicken-induced pruritic food allergy, whereas several dogs had flares after eating a hydrolyzed chicken liver diet. 17 Hydrolysate-containing diets are probably best used in dogs with no suspected hypersensitivity to the original source of hydrolyzed peptides. Diet trials should never be performed with "pet store brand" diets because these diets often contain trace amounts of important allergens not listed on the label. 18 Many flavored medications (chewable heartworm prophylactics, flavored antibiotics, and vitamin tablets), especially over-the-counter medications, may contain unwanted/ hidden proteins. All flavored medication should therefore be avoided, including medication packaged in gelatin capsules. Regardless of the diet chosen, compliance is paramount and strict adherence to the prescribed food is necessary.

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