Diagnosis and management of food allergy and intolerance in dogs and cats

SUMMARY This paper reviews food allergy and intolerance in dogs and cats. Adverse reactions to ingested food components can affect many systems and can produce signs involving the skin, gastrointestinal tract, respiratory tract and central nervous system, and these clinical signs are reviewed. Most basic food ingredients have the potential to induce an allergic response, although most reactions are caused by proteins. In particular, dogs and cats can become sensitive to cow's milk, beef, fish or cereal. Food allergy and intolerance is rare in dogs and cats, although the incidence in practice is difficult to establish. Clinical signs are quite variable, depending on the individual response, although the major clinical sign is pruritus. Diagnosis can be difficult, as there is no single test available to help the clinician to confirm or refute the presence of food sensitivity. Diagnosis is based on dietary investigation in the form of elimination diets and test meals. Elimination diets for dogs include lamb, chicken, rabbit, horse meat and fish as sources of protein, with rice or potatoes. Successful elimination diets for cats include lamb, chicken, rabbit or venison, with rice. Improvement in clinical signs while on the elimination diet is suggestive of food allergy. The diagnosis should be confirmed by feeding the original diet, with the development of clinical signs within 7 to 14 days of feeding.     

Double-blind evaluation of two commercial hypoallergenic diets in cats with adverse food reactions

The aim of this study was to evaluate two commercially available selected-protein-source diets as maintenance diets in cats with dermatological manifestations of adverse food reactions. Twenty cats with a confirmed adverse food reaction were tested in a double-blind manner. An adverse food reaction was diagnosed when, after recovery with a home-cooked elimination diet, the signs relapsed after a challenge with their previous dietary components, and re-disappeared on a second elimination diet period. Hereafter the cats were blind and randomly challenged with two commercial hypoallergenic diets. Relapse of the clinical signs was seen in eight cats (40%) on a lamb and rice diet and in 13 cats (65%) on a chicken and rice diet (P>0.05).Neither one of the commercial diets was as effective in controlling the skin problems as the home-cooked elimination diet. The study confirms that commercial hypoallergenic diets are adequate for maintenance.     

Gastroscopic food sensitivity testing in 17 dogs

Seven of 17 dogs with gastrointestinal signs and suspected dietary intolerance had positive responses to gastroscopic food sensitivity testing (GFST). Five of the non-responders and six of the dogs that responded to GFST were successfully treated with dietary control alone. The seventh dog that responded to GFST had an ileal adenocarcinoma and did not survive to follow-up. Local reactions to GFST included mucosal oedema, mucosal hyperaemia and gastric hyperperistalsis and systemic reactions consisted of hyperventilation and retching. The character of the responses to GFST is consistent with a type 1 hypersensitivity reaction to the food antigen, suggesting that IgE may mediate dietary sensitivity in some dogs. Positive responses to GFST may, therefore, demonstrate gastric mucosal hypersensitivity to food antigens and be useful in formulating therapeutic diets; negative responses need to be interpreted with caution. The limitations of the procedure are that it requires a videoendoscopy system, may significantly add to general anaesthetic time and will only detect immediate reactions.     

Lymphocyte blastogenic responses to food antigens in cats showing clinical symptoms of food hypersensitivity

Three cats were diagnosed as having food hypersensitivity by food elimination and oral food provocation tests. Twelve allergenic food ingredients were identified by oral food provocation test in the 3 cats. Of the 12 food ingredients, 9 offending food antigens were shown to be positive in a lymphocyte stimulation test; however, none of them were positive in antigen-specific IgE testing, and only four food antigens were positive in intradermal testing. The stimulation indices in the lymphocyte stimulation tests for the 9 food ingredients were found to be decreased after the cats were fed elimination diets. The present study demonstrates that the lymphocyte stimulation test reflects an immunologic reaction involved in food hypersensitivity and can help identify allergenic food ingredients in feline food hypersensitivity.     

Effect of diets differing in fat content on chronic diarrhea in cats

Background: Fat‐restricted diets have been advocated for dogs with diarrhea for many years. Recommendations for cats with diarrhea have varied between low‐fat and high‐fat diets, but there have been no published studies to support either recommendation. Objectives: The objective of this study was to compare the clinical responses of cats with chronic diarrhea to dietary management using either a high fat or a low fat, highly digestible diet. Animals: Sixty pet cats with chronic diarrhea were recruited; 55 cats completed the study. Methods: Randomized, double‐blinded, controlled clinical trial. Upon completion of baseline measures, cats were fed 1 of 2 diets for 6 weeks, during which the owners recorded fecal scores daily using an illustrated fecal score chart ranging from 0 (very watery) to 100 (firm and dry). After 6 weeks, cats were reevaluated by the attending veterinarians. Results: Fecal scores improved significantly, with 78.2% of cats improving by at least 25 points on the 100‐point scale or having a final fecal score of at least 66. Over one third of the cats developed normal stools. There were no differences in clinical responses between the diets. Clinical improvement was noted within the 1st week, and maximized within 3 weeks. Conclusions and Clinical Importance: These results show that dietary management can be helpful in cats with chronic diarrhea, but dietary fat content does not appear to affect the outcome. Cats that do not respond within 3 weeks should be evaluated further.     

The nutritional management of gastrointestinal tract disorders in companion animals

Dietary protein, carbohydrates, fats and fibre have marked influences on gastrointestinal tract function and dysfunction. This article reviews the nutritional management of common gastrointestinal disorders in companion animals and introduces some of the current areas of research including probiotics, prebiotics, protein-hydrolysate diets, immunonutrition and dietary fibre.

Nutritional management of oesophageal disease revolves around varying the consistency of the diet and feeding the animal from an elevated container. Provision of bowel rest remains the mainstay of the management of acute gastroenteritis but food-based oral rehydration solutions are a useful adjunct. The recommended diet for chronic small bowel diarrhoea is a highly digestible, hypoallergenic, gluten-free, low-lactose and low-fat diet with modest amounts of fermentable fibre. The use of probiotics in the management of diarrhoea in companion animals has not yet been shown to be beneficial. It is likely that prebiotics will prove more effective than probiotics in the prevention of enteropathogenic infections.

Approximately 50% of cats in New Zealand that suffer from chronic idiopathic vomiting or diarrhoea will respond to a novel-protein-elimination diet and approximately 30% meet the diagnostic criteria for food sensitivity. Growing evidence supports the use of protein-hydrolysate diets in the management of inflammatory bowel disease and further advances in immunonutrition are expected. The dietary management of colitis should include a hypoallergenic diet with a fermentable fibre source.

Manipulation of the diet provides clinicians a powerful therapeutic strategy to be used alone or concurrently with drug therapy in the management of gastrointestinal disorders.     

The nutritional management of gastrointestinal tract disorders in companion animals

Dietary protein, carbohydrates, fats and fibre have marked influences on gastrointestinal tract function and dysfunction. This article reviews the nutritional management of common gastrointestinal disorders in companion animals and introduces some of the current areas of research including probiotics, prebiotics, protein-hydrolysate diets, immunonutrition and dietary fibre. Nutritional management of oesophageal disease revolves around varying the consistency of the diet and feeding the animal from an elevated container. Provision of bowel rest remains the mainstay of the management of acute gastroenteritis but food-based oral rehydration solutions are a useful adjunct. The recommended diet for chronic small bowel diarrhoea is a highly digestible, hypoallergenic, gluten-free, low-lactose and low-fat diet with modest amounts of fermentable fibre. The use of probiotics in the management of diarrhoea in companion animals has not yet been shown to be beneficial. It is likely that prebiotics will prove more effective than probiotics in the prevention of enteropathogenic infections. Approximately 50% of cats in New Zealand that suffer from chronic idiopathic vomiting or diarrhoea will respond to a novel-protein-elimination diet and approximately 30% meet the diagnostic criteria for food sensitivity. Growing evidence supports the use of protein-hydrolysate diets in the management of inflammatory bowel disease and further advances in immunonutrition are expected. The dietary management of colitis should include a hypoallergenic diet with a fermentable fibre source. Manipulation of the diet provides clinicians a powerful therapeutic strategy to be used alone or concurrently with drug therapy in the management of gastrointestinal disorders.     

Food hypersensitivity in cats: 14 cases (1982-1987)

Food hypersensitivity was diagnosed in 14 cats. Clinical signs varied; pruritus (100%), alopecia (64%), and papules (21%) were the ones most commonly observed. Pruritus was localized principally to the head or to the neck or ear region in 42% of the cats. Diagnosis was made on the basis of resolution of clinical signs when cats were fed a restricted ("hypoallergenic") diet, and recurrence of signs when cats were fed their original diet or other food. The most common allergens (on the basis of dietary challenge exposure) were fish and dairy products. Age or sex predilection was not observed, and 9 (64%) of the cats were domestic shorthairs. Owners could not relate the onset of clinical signs with a recent change in diet. Three cats had concurrent flea bite, inhalant, or flea collar hypersensitivity.     

Evaluation of two diets in the nutritional management of cats with naturally occurring chronic diarrhea

Feeding either a highly digestible, moderate-carbohydrate diet or a highly digestible, high-protein, low-carbohydrate diet resulted in significant (P < .05) improvements in fecal scores in 71% of cats with chronic, nonspecific diarrhea. Approximately 58% of the cats improved on either diet, with no significant differences between the two diets regarding the percentage of cats responding or the degree of response. These results suggest that dietary management may be helpful in cats with chronic diarrhea. If cats do not respond within 1 month, an alternative diet should be considered.     

Influence of dietary source of phosphorus on fecal and urinary excretion of phosphorus and other minerals by male cats

Twelve male cats were fed 2 diets that differed in the source of P. In diet 1 (1.4% P), 62.7% of P originated from poultry, meat, and fish meal, and the remainder from other organic ingredients of food. In diet 2 (1.6% P), 63.5% of P was derived from neutral monobasic/dibasic salts, and the remainder from other organic ingredients of the food. The P intake was nearly the same with both diets, but there was a significant (P less than 0.05) difference between diets in the percentage of ingested P that was excreted in the urine (14.7 +/- 5.3% for diet 1; 34.9 +/- 8.4% for diet 2), and in 6-day urinary P excretion (774 +/- 290 mg for diet 1; 2,004 +/- 556 mg for diet 2). The P concentrations in urine samples obtained by cystocentesis after cats ate were significantly (P less than 0.05) higher when cats were fed diet 2 than when those same cats were fed diet 1. Plasma P concentrations increased after ingestion of diet 2, but were unchanged after ingestion of diet 1. Seemingly, urinary excretion of P was markedly influenced by dietary composition. Diets with the same P content have potential for different biologic effects because of differences in availability of P.     

A retrospective analysis of case series using home-prepared and chicken hydrolysate diets in the diagnosis of adverse food reactions in 181 pruritic dogs

The purpose of this retrospective study was to compare home-prepared and chicken hydrolysate diets in the diagnosis of canine adverse food reactions (AFR). Seventy-two dogs were fed home-prepared diets and 109 were fed hydrolysate. Owners chose the type of diet at presentation, and ingredients of home-prepared diets were selected depending on each dog's dietary history. Ectoparasitic infestations and microbial infections were treated during the trials. Cutaneous and gastrointestinal signs and pruritus scores were recorded before starting the diet, 6 weeks into the trials and after provocation with the original diets. AFR was diagnosed if pruritus resolved during the trial and recurred on dietary provocation. The dropout rate was lower for home-prepared diets although not statistically significant (18.1% home prepared; 24.7% hydrolysate, P=0.377). AFR alone was diagnosed in 10 dogs (17%) using home-prepared diets and in 15 (18.3%) fed the hydrolysate. Gastrointestinal problems were more frequent in dogs with AFR than in dogs without AFR (P=0.001). Another 11 dogs (18.6%) in the home-prepared diet group and 20 (24.4%) in the hydrolysate diet group had AFR concurrent with other pruritic diseases, mainly atopy. The similar frequencies of AFR diagnosis in the two groups (P=0.837 AFR; P=0.416 concurrent AFR) indicate that the chicken hydrolysate diet may be a valuable alternative to home-prepared diets in the diagnosis of canine AFR. Prospective cross-over studies are warranted to confirm these findings.     

Evaluation of the immunogenicity of dietary proteins in cats and the influence of the canning process

OBJECTIVE: To characterize the antigen-specific immune response to dietary proteins in cats and evaluate whether there was a qualitative or quantitative difference between the responses to dietary proteins when those proteins were fed unprocessed or as part of a canned diet. ANIMALS: 14 healthy domestic shorthair cats. PROCEDURE: Cats were fed 2 dietary proteins (soy and casein) either as unprocessed aqueous suspensions or as part of canned diets for 21 days. Serum IgG and IgA and salivary IgA were assayed by indirect ELISA, and antigen-specific proliferation of mesenteric lymph node-derived lymphocytes was determined. RESULTS: Robust serum IgG and IgA responses to dietary proteins were elicited, irrespective of the form in which they were fed. Salivary IgA responses to unprocessed proteins were not detected. However, a significant salivary IgA response to the protein isolated from the canned casein diet was observed in cats fed canned casein but not in those fed unprocessed casein. Lymphocyte proliferation to the antigens was slight, and there were no significant differences between groups. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that cats develop robust serum IgG and IgA responses to dietary proteins when fed as either aqueous suspensions or as part of canned diets. For certain proteins, there may be an increase and a qualitative difference in the immunogenicity of canned diets, compared with unprocessed proteins. Canned diets may not be ideal for management of cats with enteritis.     

Food allergen-specific serum IgG and IgE before and after elimination diets in allergic dogs

Serum food allergen-specific antibody testing is widely offered to identify suitable ingredients for diets to diagnose adverse food reaction (AFR) in dogs with allergic skin disease. Antibody concentrations in blood samples obtained during an unsuccessful diet to help in the choice of diet changes may be influenced by the previous diet. The objective of this paper was to measure food antigen-specific IgE and IgG for the most commonly used 16 food antigens before and after an elimination diet. Levels of food-specific serum IgE and IgG antibodies were measured by enzyme-linked immunosorbent assay (ELISA). Dogs had detectable IgE antibodies to beef, pork, lamb and cows' milk; and detectable IgG antibodies to beef, pork, lamb, cows' milk, chicken and turkey. Of 19 dogs with complete data sets, 14 dogs showed clear improvement during diet and in 7 dogs AFR could be diagnosed by deterioration on rechallenge and subsequent improvement on refeeding the diet. Serum was obtained before and 6-8 weeks after beginning such a diet. There was no significant difference in pre- and post-diet levels for any of the individual allergens nor for the total IgE and IgG concentrations of all antigens (P=0.55 and P=0.53 respectively). In these 19 dogs in which an elimination diet was used for the diagnosis of food allergy and in which 14 were probably food allergic and 7 were proven food allergic there were no significant differences in food-specific antibodies before and after an elimination diet of 6-8 weeks.     

Relationship between a plant-based ‘vegan’ pet food and clinical manifestation of multiple nutrient deficiencies in two cats

A topical subject in human nutrition is the steadily growing number of people choosing to limit or completely avoid all animal-derived food products either for moral dilemma, health concerns or both. To meet people's will of applying their dietary choices to their domestic animals, the pet food industry answered by launching on the market some plant-based diets. This leads to concerns about whether these diets are adequately formulated to satisfy the target species nutritional requirements, especially for cats which are still considered strict carnivores. This case report follows a 2-year-old male neutered Main Coon and a 1-year-old female spayed Domestic Shorthair cat, presented to the nutrition service of the University of Toulouse, France. Reason for consultation was lethargy with in anamnesis a recent dietary transition to a plant-based pet food. Dysorexia, lethargy and muscle waste were present at first consultation. Progressive weight loss developed during follow-ups. A macrocytic, non-regenerative anaemia with serum folates below reference were the main clinical features. Analysis of pet food showed multiple nutrients below minimum recommendation at the average daily intake of both cats. Folic acid supplementation improved dysorexia, and subsequent reintroduction of animal-derived ingredients in the diet restored appetite, weight and a normal mentation in both cases.     

Fiber fermentability effects on energy and macronutrient digestibility, fecal traits, postprandial metabolite responses, and colon histology of overweight cats

Considering the different potential benefits of divergent fiber ingredients, the effect of 3 fiber sources on energy and macronutrient digestibility, fermentation product formation, postprandial metabolite responses, and colon histology of overweight cats (Felis catus) fed kibble diets was compared. Twenty-four healthy adult cats were assigned in a complete randomized block design to 2 groups of 12 animals, and 3 animals from each group were fed 1 of 4 of the following kibble diets: control (CO; 11.5% dietary fiber), beet pulp (BP; 26% dietary fiber), wheat bran (WB; 24% dietary fiber), and sugarcane fiber (SF; 28% dietary fiber). Digestibility was measured by the total collection of feces. After 16 d of diet adaptation and an overnight period without food, blood glucose, cholesterol, and triglyceride postprandial responses were evaluated for 16 h after continued exposure to food. On d 20, colon biopsies of the cats were collected under general anesthesia. Fiber addition reduced food energy and nutrient digestibility. Of all the fiber sources, SF had the least dietary fiber digestibility (P < 0.05), causing the largest reduction of dietary energy digestibility (P < 0.05). The greater fermentability of BP resulted in reduced fecal DM and pH, greater fecal production [g/(cat × d); as-is], and greater fecal concentration of acetate, propionate, and lactate (P < 0.05). For most fecal variables, WB was intermediate between BP and SF, and SF was similar to the control diet except for an increased fecal DM and firmer feces production for the SF diet (P < 0.05). Postprandial evaluations indicated reduced mean glucose concentration and area under the glucose curve in cats fed the SF diet (P < 0.05). Colon mucosa thickness, crypt area, lamina propria area, goblet cell area, crypt mean size, and crypt in bifurcation did not vary among the diets. According to the fiber solubility and fermentation rates, fiber sources can induce different physiological responses in cats, reduce energy digestibility, and favor glucose metabolism (SF), or improve gut health (BP).     

Vitamin K deficiency in cats fed commercial fish-based diets

Clinical signs of vitamin K deficiency have been observed in cats offered two commercial canned diets high in salmon or tuna. Some of the queens and kittens offered these diets had died while survivors had increased coagulation times. Necropsies revealed hepatic and, or, gastrointestinal haemorrhages. Coagulation times of survivors returned to normal after vitamin K therapy. The purpose of this study was to induce a vitamin K deficiency in kittens and determine the dietary requirement. Kittens were offered vitamin K-deficient purified diets containing antibiotics and, or, substances inherent in canned fish diets that may have contributed to the deficiency. Clinical signs of vitamin K deficiency were not observed, even though one purified diet contained only 4 μg K₁/kg diet compared with 60 μg in the commercial tuna diet. Therefore, a minimum vitamin K requirement could not be determined using purified diets; nevertheless, canned commercial diets formulated primarily with fish should contain more than 60 μg K₁/kg diet.     

Nutritional management of gastrointestinal disease

The gastrointestinal (GI) tract is primarily responsible for acquiring and digesting food, absorbing nutrients and water, and expelling wastes from the body as feces. A proper diet and normally functioning GI tract are integral for the delivery of nutrients, prevention of nutrient deficiencies and malnutrition, repair of damaged intestinal epithelium, restoration of normal luminal bacterial populations, promotion of normal GI motility, and maintenance of normal immune functions (eg, both tolerance and protection from pathogens). The amount of food, its form, the frequency of feeding, and the composition of diet each have important effects on GI function and may be used to help ameliorate signs of GI disease. Although both nutrients and nonnutritional components of a diet are important to GI health, they also may cause or influence the development of GI pathology (eg, antibiotic responsive diarrhea, inflammatory bowel disease, dietary intolerance, or sensitivity and/or allergy). The appropriate diet may have a profound effect on intestinal recovery and successful management of chronic or severe GI disease.     

Hydrolyzed protein diets for dogs and cats.

The primary aim of a hydrolyzed protein diet is to disrupt the proteins within the diet sufficiently to remove existing allergens. Published assessment of hydrolyzed protein diets includes physiochemical and immunologic assays as well as nutritional and clinical feeding trials. Potential problems include poor palatability, hypoosmotic diarrhea, and a reduced nutritional value, although persistent allergenicity is the most significant. The primary indications for a hydrolyzed protein diet are use in elimination trials for the diagnosis of adverse food reactions, and the initial management of inflammatory bowel disease. Initial studies of hydrolyzed diet efficacy are encouraging. Consideration of the source ingredients should be given when using hydrolyzed protein diets in elimination feeding trials because antigenic sites may not be fully destroyed.     

Assessment of the neurologic effects of dietary deficiencies of phenylalanine and tyrosine in cats

OBJECTIVE: To determine the neurologic effects of reduced intake of phenylalanine and tyrosine in black-haired cats. ANIMALS: 53 specific pathogen-free black domestic shorthair cats. PROCEDURE: Cats were fed purified diets containing various concentrations of phenylalanine and tyrosine for < or = 9 months. Blood samples were obtained every 2 months for evaluation of serum aromatic amino acid concentrations. Cats were monitored for changes in hair color and neurologic or behavioral abnormalities. Three cats with neurologic deficits underwent clinical and electrophysiologic investigation; muscle and nerve biopsy specimens were also obtained from these cats. RESULTS: After 6 months, neurologic and behavioral abnormalities including vocalization and abnormal posture and gait were observed in cats that had received diets containing < 16 g of total aromatic amino acid/kg of diet. Electrophysiologic data and results of microscopic examination of muscle and nerve biopsy specimens from 3 cats with neurologic signs were consistent with sensory neuropathy with primary axonal degeneration. Changes in hair color were detected in cats from all groups receiving < 16 g of phenylalanine plus tyrosine/kg of diet. CONCLUSIONS AND CLINICAL RELEVANCE: Findings suggested that chronic dietary restriction of phenylalanine and tyrosine in cats may result in a predominantly sensory neuropathy. In cats, the long-term nutritional requirement for phenylalanine and tyrosine appears to be greater for normal neurologic function than that required in short-term growth experiments. Official present-day recommendations for dietary phenylalanine and tyrosine in cats may be insufficient to support normal long-term neurologic function.