Page 200 - WSAVA2017
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An Urban Experience
stronger among related allergens. For example, goat, bison, buffalo, water buffalo and antelope are ‘exotic’ but would not be novel compared to lamb or beef. Cross- reactions in dogs include beef & lamb; and chicken, duck & turkey. Mammalian and avian foods don’t cross-react.
Choosing a diet for a diet trial
Diets can be home cooked or a commercially prepared dried or tinned foods. However, identifying novel foods is hard. Owners may not remember or be aware of what’s been fed, and may not be aware of all the ingredients in foods, treats and supplements. Recipes vary and some ingredients may not be listed. Undeclared proteins have been found in up to 80% of tested foods.
Food allergen serology and patch testing
Serology tests are widely used but only two are validated. The Avacta Sensitest® IgE ELISA has a positive predictive value (PPV) of ~30% and negative predictive value (NPV) was ~80% - i.e. for every three dogs with a positive IgE titre only one is allergic to that food, and for every five negative dogs four are not sensitised to that allergen and it would be suitable for a food trial. The Cynodial® test uses Western blots of whole diets rather than individual proteins. The PPV is ~79% and the NPV is ~78%. Therefore these tests should not be used to diagnose a food allergy, but may identify suitable ingredients for diet trials.
Patch testing
Patch testing with food extracts is more accurate –
the very high NPVs make reactions highly unlikely. However, low PPVs limit the significance of positive tests. Carbohydrates are less reliable than proteins and the results from commercial foods are poor. They are also difficult and time consuming to perform.
Home cooked diet trials
These are regarded as the ‘gold standard’. However, it is often difficult to find suitable cost-effective and available foods. These are also difficult and time consuming to prepare and are not balanced for long term feeding (or
in animals with specific nutritional requirements). Minced and processed meat should be avoided, as the contents can’t be guaranteed.
Single protein diets
There is now a variety of single protein, single carbohydrate complete dried and tinned diets. They are often marketed as ‘hypoallergenic’ but are only so if the animal does not react to any of the ingredients. These are easy to prepare, balanced and palatable but the exact ingredients may be unknown (e.g. colourings, flavourings, preservatives, and other carbohydrates, proteins and fats) and it may not be possible to find a diet that contains a novel ingredients.
Hydrolysed foods
Hydrolysis reduces the proteins to <5-10KDa, theoretically rendering them non-immunogenic. However, partial hydrolysation leaves larger (potentially allergenic) fragments. Contamination during manufacture and inclusion of fats and other nutrients could also be a problem. Canine IgE has been shown to bind to maize starch synthase 1 and other proteins (15-60 kD) in three hydrolysed foods (Royal Canin Anallergenic, Purina HA and Hill’s z/d Low Allergen). The degree of hydrolysis is important – up to 20% of dogs sensitized to chicken and soy reacted to a partially hydroysed diet (Royal Canin Hypoallergenic). Where possible, therefore, try to avoid source proteins to which an animal has been exposed.
In contrast, ELISA inhibition is much less with a fully hydrolysed diet (Royal Canin Anallergenic) than with non- or partially hydrolysed chicken meal and comparable
to negative controls. In addition, this diet provoked
much fewer and milder reactions in chicken-sensitized dogs than Hills z/d (chicken liver hydrolysate) and was comparable to home-cooked novel diets in a trial of 69 dogs with pruritus.
Palatability varies, so it’s worth trying different foods (e.g. Royal Canin Anallergenic [chicken feathers & maize starch], Purina HA [soy & maize starch] and Farmina UltraHypo [fish & rice starch]) and/or adding some novel cooked foods to improve the taste.
Grains and glutens
Owners are often very concerned over grains and glutens. Maize, rice and wheat proteins are highly digestible. Allergies to wheat glutens occur but gluten specific reactions are rare (most commonly in Irish setters and Border terriers).
Managing food trials
The keys to a successful diet trial are communication and support. Important points include: explaining the need for the trial and the process; managing expectations; getting family and friends on board; and explaining how strict the trial must be. Diaries or treatment logs are very useful. Things to watch out for include: flavoured medications, toothpaste, treats and scraps, hidden ingredients, eating faeces, discarded and dropped food, and ‘empty’ bowls. It is important to provide a treat options – e.g. bake the kibble or tinned food into treats, make liver cakes, and dry exotic meats (e.g. kangaroo or ostrich) into jerky.
Compliance can be helped by allowing short courses of glucocorticoids or oclacitinib for 3-5 days at the owners’ discretion to manage pruritus. It’s also important to manage infections and ectoparasites during food trials.

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