Adverse Food Reactions In Canines

Adverse food Reaction by definition

An adverse food reaction is any clinically abnormal response attributed to the ingestion of food or food additive. Adverse food reactions are categorized as either food allergies or food intolerance reactions. As the headline of the article indicates this essay will be only talking about food allergies . The difference between these two types is based on an immunologically immolated response, which occurs in food allergy. Therefore, food allergy can be defined as an immunologically mediated adverse food reaction to food unrelated to any physiological effect of the food or food additive.

How the Immunophysiology system works under normal physiological conditions

The immune system is linked to adverse food reactions in the body by causing an allergic reaction. An allergic reaction occurs when the immune system overreacts to a harmless substance known as an allergen. These antibodies travel to the cells that release the chemicals and cause different symptoms.There are two basic pathways to remove pathogens; one is the natural immunity in which pathogens are removed by cellular and humoral elements. These are not antigen-specific but can react immediately. The second type of immunity requires the production of highly specific and very effective antibodies or immune cells against the non-self material. The response can be either cellular or humoral also in this case. This type is called acquired or specific or adaptive immune response. Materials triggering the immune response are called antigens. The specific defence molecules produced against these antigens are the antibodies (proteins either dissolved or bound to cells). Antigens are identified as non-self entities and are removed by the defence reactions of the body; the recognition of these foreign entities is due to the fact that the immune system produces immunoglobulins against almost an unlimited number of possible antigen structures by gene rearrangement.

The prevalence of dogs with lymphocyte proliferative responses to food allergens in canine allergic dermatitis

Another way of identifying adverse food reactions in dogs is to examine the correlation between the results of lymphocyte proliferative test (LPT) specific to food allergens and allergic skin diseases in dogs. An investigation was conducted on allergic skin diseases in different dogs. Of the animals investigated, more than 75% cases had positive reactions in LPT specific to food allergens. Of these 97 dogs, 67 animals were diagnosed with canine atopic dermatitis (CAD), some dogs do not have IgE antibodies due to environmental allergens(Favrot et al. 2010) Some dogs underwent elimination diet trial based on the test results and all of them showed improvement in the pruritus (severe itching of the skin, as a symptom of various ailments.) Therefore, we conclude that LPT is an effective diagnostic test for allergic skin disease. Results of the lymphocyte test are useful in the identification of food allergens for the elimination diet trial. IDST or allergen-specific IgE test is neither sensitive nor specific enough to diagnose food allergy (Paterson et al., 1995) Allergic skin diseases in dogs can be broadly classified into the following two groups: atopic dermatitis and food allergy. Canine atopic dermatitis (CAD) can be diagnosed either by intradermal skin test (IDST) or the presence of allergen-specific immunoglobulin E (IgE) to environmental allergens in the serum in combination. Over the years, the diagnosis of a food allergy is often challenging. Clinical symptoms of food allergy overlap with those of CAD . . so we end up with the question that “ is there a relationship between canine atopic dermatitis and cutaneous adverse food reaction ? There’s at least a subset of dogs with cutaneous adverse food reactions due to IgE mediated food allergy (Olson et al.2000;Guildford,1993;deWeck,1996). however, the vast majority of dogs suffering from cutaneous clinical signs of food allergy show neither igE mediated hypersensitivity nor any other immunologic mechanism. Therefore, it is believed that the disease should be referred to as cautious adverse food reaction. The relationship between CAD and adverse food reaction is unclear. young age at onset of the disease, pruritus of the ears , axillae , inguinal and distal limbs , a frequent occurrence of otitis , recurrent secondary bacterial and malassezia infection are typical features common to both AD and cutaneous adverse food reactions. 13 - 30 % of dogs with cutaneous adverse food reactions have concurrent AD (White et al., 1986). On the other hand, 30 % ( or according to newer studies , less) of dogs with AD exhibit concurrent adverse food reactions (Criep, 1968;Chamberlain,1974;Chamberlain,1978). However, despite high prevalence of CAD in dogs with cutaneous adverse food reactions, it is concluded that there is insufficient evidence supporting the association between CAD and cutaneous adverse food reaction.

• The incidence of environmental allergen- and food allergen-positive cases: (a) The upper and lower bars indicate thenumbers of cases with allergen-specific Immunoglobulin E (IgE)-positive canine atopic dermatitis (CAD) and those that were negative (non-CAD), respectively, to environmental allergens. The black bar indicates the number of cases that showed positive reaction to food allergens in the lymphocyte proliferation test (LPT), (b) Food allergens identified by the LPT, (c) Changes in pruritus score in 12 dogs between before and after food elimination test.

From the B graph above showed that soybean was the most significant cause of food allergy (p < 0.01, Fig. 2b) among the food allergens that induced an increase in LPT against the food allergen. This was followed by rice, potato, and wheat. Corn and milk also cause an increase in LPT against the food allergen. From the chi square it is evident that the two best meats with the lowest cases were the catfish and turkey, egg yolks also had a low amount of cases in the LPT.

== Evaluation of hydrolysed diets in dogs ==; In this study 14 Maltese x Beagle dogs were examined; they were chosen as they were known to have clinical hypersensitivity to corn and soy. In the first 12 months of their life, the dogs were fed a diet (Diet 1) containing chicken, corn, barley and soy (Jackson et al., 2003). After this time baseline data was collected and each dog was given a cutaneous clinical score (CCS), which evaluated erythema, excoriations and evidence of infection (Jackson et al, 2002). According to Saunders Comprehensive Veterinary Dictionary (2012), erythema and excoriations are recognised by redness of skin and superficial abrasions, resulting in removal of some skin particles, due to scratching.

Next over a period of 5 days Diet 2, consisting of duck and rice, was integrated and eventually replaced Diet 1. During the time the dogs were fed Diet 2 each of them was challenged orally with corn, soy and corn starch allergens. Each allergen was administered twice with a 24 hour interval, and between the different allergens there was a number of rest days (Jackson et al., 2003). As stated by Cave (2006), an allergen is an antigen which can bind to specific immunoglobin E (IgE) antibodies on the surface of cells and thus elicit mast cell degranulation. An oral challenge is when food containing known allergens is consumed under medical conditions with the aim of diagnosing or ruling out that specific food allergy (Boyce et al., 2010). These challenges are considered to be ‘the gold standard’ test in regard to diagnosis of food allergies as they show a clear ‘yes or no’ result (Niggemann., 2009). After each allergen was tested the CCS was re-evaluated and serum was collected via jugular venepuncture and analysed. If the CCS had increased by a minimum of 50% from its previous score, the animal was concluded to have had an adverse reaction. In order to keep variables to a minimum the CCS examination was carried out by the same person each time, and to prevent being influenced, the previous scores were not available to the examiner. The serum IgE was measured using ELISA- enzyme-linked immunosorbent assay (Jackson et al., 2003).

Intradermal skin testing was performed on day 0 (Diet 1) and on day 83 (Diet 2). Intradermal skin testing is used by veterinarians to look for allergen specific IgE antibodies (Olivry et al., 2007). The positive control was a monoclonal antidog immunoglobulin E, while the negative control was saline. Soy and corn allergens were used, and every dog was given three 10-fold dilutions. 20 minutes after administration the diameters of the reactions were measured. The result was said to be positive if it was greater than or equal to 50% of the positive control.

The animals continued Diet 2 for a total of 147 days and similarly to before, Diet 3 was then incorporated over several days and then fed exclusively up until day 160 when the trial ended. Diet 3 was a hydrolysed soy protein canine diet, a hydrolysed protein is one which is broken down into its peptides (Jackson et al., 2003). The main aim of a hydrolysed diet is to eliminate existing allergens and therefore stop immune recognition in an individual already sensitized to the intact protein. A further aim could also be to disturb the protein to a level where no antigens have the ability to cause an immune response and therefore leading to sensitisation of an individual which is not previously sensitized (Cave., 2006).

The results of the trial showed that all treatments effected CCS. The corn, soy and corn starch from the oral challenges all caused a significant increase in the CCS. While Diet 2 alone caused a statistically signicant reduction in CCS at all time points evaluated. 21% of dogs had an adverse reaction to corn starch, 71% to corn and 78% to soy. In addition to this there was also a significant increase in soy-specific and corn-specific IgE concentrations observed between the samples taken on day 0 and on day 83. The initial oral challenge with corn starch caused a signicant increase in the mean IgE concentration and this increase was sustained during the entire challenge period. It was realised there is a positive statistically signicant correlation between the cutaneous clinical scores and corn-specic serum IgE. There is also a second positive correlation between the serum allergen-specic IgE and total IgE, concentrations. Finally, after the introduction of Diet 3 most of the dogs which had adverse reactions to soy and corn showed no increase in cutaneous clinical score (Jackson et al., 2003).

In conclusion this evidence shows that a hydrolysed protein diet can be a long-term management option for dogs suffering with adverse cutaneous reactions to soy and corn.

Food hypersensitivity tests in dogs

Food hypersensitivity in canine is a common disease cased by allergic reactions to various kinds of food antigens, which provokes pruritic skin disease (Rosser EJ Jr. ), diarrhea, and vomiting. It is thought to be mediated by type I or III or IV hypersensitivity(White SD). Type I reactions are always associated with the formation of IgE against food allergens . There is a firm evidence for an involvement of IgG in type II or type III reactions in immune-mediated adverse reactions to food, whereas type IV reactions, which involve T cells, have important roles in disorders such as celiac disease. There is evidence that the natural immune system, which includes complement, Toll-like receptors, and natural immune cells, also mediates immune reactions against certain food components.

Intradermal and antigen specific serum IgE testing showed positive reaction to some food allergens in hypersensitivity of dogs. However, the sensitivity of oral food provocation test is much higher than those mentioned tests. Therefore, non IgE mediated hypersensitivity might be also associated with pathogenesis of food hypersensitivity in dogs ( Shanley et al.,). It was seen that beef antigen is the most common food allergen in dogs, which 60% of dogs with hypersensitivity showed clinical symptoms( Paterson et J. Smith., ) . Other allergens include : chicken, egg, soybean, milk, corn, and wheat ( Sosis EJ et al.,).

Food elimination test followed by oral food provocation test is used for the diagnosis of food hypersensitivity . Serum antigen specific IgE and Intradermal testing are used for identifying allergens that induce IgE mediated reactions in dogs with CAD ( Lessard P et Codner EC.,). The lymphocyte stimulation test is useful for diagnosis of food hypersensitivity in humans. However in this study, the test was used to identify allergens in hypersensitive dogs . It was also used during food elimination and provocation. For this purpose 11 dogs, which were suspected to be hypersensitive based on clinical signs, were used. Lymphocyte stimulation test was performed with 9 kinds of food ingredients ( beef , chicken , mid, egg, rice , wheat , corn, cod, tuna).

the results were as followed: In oral food elimination and provocation test it was seen that, beef was the most common allergen in 73% of dogs. Wheat and rice caused food allergens in 18% of the dogs. Antigen specific IgE against various kinds of food antigens were detected in 31% of the dogs (antigen specific IgE testing). In intradermal testing, strong reactions against food antigens were found in 11% of the dogs and with moderate reactions in 3 dogs against different allergens. Result of intradermal testing and IgE testing shows low correlation due to presence of non IgE mediated mechanism such as type IV hypersensitivity in pathogenesis of food hypersensitivity. In LST test, 82% showed positive reactions. There was a significant increase and decrease of stimulation indices in dogs at provocation and elimination phase respectively. LST was a better test than IgE testing and intradermal due to the fact that the result of LST reflects reactions of both type I and IV hypersensitivity ( Daguillard F., ). Lymphocyte blastogenic to food allergens were increased in dogs with food hypersensitivity indicating the presence of circulating lymphocyte reactive to food antigens in the peripheral blood .

Patch testing and allergen-specific serum IgE and IgG antibodies in the diagnosis of canine adverse food reactions

One of the ways to diagnose adverse food reactions is an elimination diet of 6–8 weeks with a protein and a carbohydrate source not previously fed. In canines, serum food allergen-specific antibody testing is widely used to identify suitable ingredients for such diets. Different studies were done to determine sensitivity, specificity, negative and positive predictability of patch testing with and serum antibody testing for a variety of common food stuffs. In this study allergic dogs underwent an elimination diet and challenged with selected food stuffs, food patch testing and serum testing for food-antigen specific IgE and IgG. Based on these results, a positive reaction of a dog on these tests is not very helpful, but a negative result indicates that this antigen is tolerated well. . From the results we could conclude that patch testing (and to a lesser degree serum testing) can be helpful in choosing ingredients for an elimination diet in a dog with suspected adverse food reaction.

Conclusion

In conclusion it can be seen that there are multiple foods which cause adverse food reactions in dogs, including corn, soy and even beef. From our research we discovered that there are several tests used to diagnose these allergies; such as elimination diets and patch testing as well as immunoglobin E serum detection. We also found that hydrolysed diets can be an effective long-term solution in managing these allergies. Having said this, a huge amount of research still needs to be carried out in regard to treating and diagnosing allergies. Writing this essay gave us an insight into a side of veterinary medicine that we didn’t realise was of such great importance.

References

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