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.     

Diagnostic testing of dogs for food hypersensitivity

Thirteen food-allergic dogs were studied to evaluate the efficacy of feeding a commercially available egg and rice diet, intradermal skin testing, and serologic testing by ELISA for diagnosing and/or characterizing food hypersensitivity. Feeding of a home-cooked whole lamb meat and rice diet for 3 weeks, followed by challenge with each dog's regular diet, served as the standard for diagnosing food hypersensitivity. Each dog underwent provocative testing with 6 individual ingredients to determine as many of its dietary allergens as possible. Prior to skin testing and serologic testing by ELISA, most dogs had been recently exposed to the offending diet and subsequently manifested clinical signs of allergy. All dogs that tolerated the aforementioned commercial diet were exposed to it for at least 7 weeks; 84.6% of food-hypersensitive dogs ate the commercial diet with impunity. Of the 2 reactors to the commercial diet, only 1 became pruritic in response to provocation testing with chicken eggs. Low sensitivity and high specificity were found for skin testing and the ELISA, indicating a lack of true- and false-positive reactions. Neither the positive nor negative predictive values adequately predicted positive and negative reactions, respectively, for either test. On the basis of these results, the commercial diet, skin testing, and anti-IgE ELISA cannot replace an owner-prepared food elimination diet for food hypersensitivity testing in dogs.     

The study of canine atopic dermatitis involving the isolation of dogs

Twenty-seven pruritic dogs were used in this study. When a hypoallergenic diet was fed to these 27 dogs for six weeks, none of the dogs showed improvement of the pruritus. These dogs had a history and clinical signs of atopic dermatitis (AD) as defined by Prelaud's diagnostic criteria. Subsequently, the 27 dogs were isolated for observation for two weeks in the hospital. In the isolation room in the veterinary clinic, cages and tableware were all stainless steel, and carpet was not used. A hypoallergenic diet was continuously fed to the 27 dogs for two weeks, during which time they were kept in the isolation room. PVAS (Pruritus Visual Analog Scale) was performed prior to starting the isolation, at the start of the study and 2 weeks after starting the isolation. In 17 dogs (63%) the pruritus improved in the isolation room. A statistically significant reduction (p < 0.01) of PLS (Pruritus liners score) was recorded 2 weeks after isolation. It was hypothesized that the 17 dogs whose pruritus improved in the isolation room had AD caused by an environmental antigen that was not present in the isolation room. Pruritus of the remaining 10 dogs (37%) did not improve. For 6/10 dogs, the intradermal allergy testing was positive for an environmental antigen. For 4/10 dogs, the intradermal allergy testing was negative for all environmental antigens. Dogs for which sensitivity to an environmental antigen was not identified were thought to have atopic-like dermatitis.     

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

Adverse food reaction (AFR) is a common differential diagnosis for pruritic dogs. The only way to diagnose AFR is an elimination diet of 6-8 weeks with a protein and a carbohydrate source not previously fed. In humans, patch testing has been shown to be a useful tool to diagnose food allergies. In veterinary medicine, serum food allergen-specific antibody testing is widely offered to identify suitable ingredients for such diets. The aim of this study was to determine sensitivity, specificity, negative and positive predictability of patch testing with and serum antibody testing for a variety of common food stuffs. Twenty-five allergic dogs underwent an elimination diet and individual rechallenge with selected food stuffs, food patch testing and serum testing for food-antigen specific IgE and IgG. Eleven clinically normal control dogs only were subjected to patch and serum testing. The sensitivity and specificity of the patch test were 96.7 and 89.0% respectively, negative and positive predictability were 99.3 and 63.0%. For IgE and IgG the sensitivity was 6.7 and 26.7%, specificity were 91.4 and 88.3%, the negative predictive values 80.7 and 83.7% and the positive predictive values were 15.4 and 34.8%. 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. We 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 AFR.     

Validity of skin testing for diagnosis of food allergy in dogs.

One hundred suspected allergic dogs were skin-tested with 9 food extracts, in addition to other inhalant and insect allergens. Forty-eight of the dogs had +2 or greater intradermal reactions to 1 or more food extracts at concentration of 1,000 protein nitrogen units/ml. Thirty of the food extract-positive dogs were fed a restrictive hypoallergenic diet. Of these 30 dogs, 3 improved, then allergy signs worsened when they were challenge-exposed with the original diet. Fifty-two dogs did not have skin test reactivity to any of the 9 food extracts. Of these 52 dogs, 35 were fed a restrictive diet. Six improved, then allergy signs worsened when dogs were challenge-exposed with the original diet. Skin-testing with selected allergenic food extracts was not useful in identifying food-sensitive dogs.     

Food hypersensitivity in 30 dogs

Food hypersensitivity was diagnosed in 30 dogs. Clinical signs varied, with pruritus (97%), erythema (50%), and papules (37%) being the most common. Diagnosis was based on resolution of clinical signs when the dogs were fed a restricted ("hypoallergenic") diet, and recurrence of signs when fed their original diet or other foods. No age, breed, or sex predilection was noticed. None of the owners could relate the onset of clinical signs with a recent change in diet. Seven dogs had concurrent fleabite, inhalant, intestinal parasite, or insulin hypersensitivity.     

Lymphocyte blastogenic responses to inciting food allergens in dogs with food hypersensitivity

Lymphocyte blastogenic responses against food allergens in dogs with food hypersensitivity were evaluated in this study. Eleven dogs with food hypersensitivity, based on food elimination and oral food provocation tests and allergic responses to food allergens, were examined by various tests such as intradermal testing, antigen-specific IgE testing, and lymphocyte blastogenic responses. The number and kinds of food allergens identified as positive by these tests were compared with the offending food allergens that were found in an oral food provocation test. In 9 (82%) of the 11 dogs with food hypersensitivity, there was close agreement for positive allergens between the results of lymphocyte blastogenic responses and oral food provocation test; however, there was little agreement for intradermal and IgE testing of the positive allergens with those of the oral food provocation test (11% and 31%, respectively). In the 9 dogs, the stimulation indices of lymphocyte blastogenic responses increased to 2.0-10.1 upon food provocation but decreased significantly to 0.7-1.4 upon feeding the elimination diet until clinical signs disappeared. These results indicate that lymphocyte blastogenic responses may fluctuate because of exposure to offending food allergens in dogs with food hypersensitivity. Lymphocytes reactive to food allergens may play an important role in the pathogenesis of food hypersensitivity in dogs.     

Erythema multiforme possibly triggered by food substances in a dog

A 5-year-old female border collie presented with erythematous skin lesions at the axillae, groin, mucocutaneous junctions, and pinnae. Biopsy revealed lymphocytic interface dermatitis with hydropic degeneration of basal cells and keratinocyte apoptosis. Based on gross and histological features, diagnosis of erythema multiforme was made. The disease was resolved by treatment with azathioprine, prednisolone, and a hypoallergenic diet. Finally, the skin lesion was controlled without drug therapy but recurred easily every time commercial foods except the hypoallergenic diet were used, suggesting that food substances triggered this outbreak.     

Evaluation of the clinical and allergen specific serum immunoglobulin E responses to oral challenge with cornstarch,corn, soy and a soy hydrolysate diet in dogs with spontaneous food allergy

Fourteen dogs with known clinical hypersensitivity to soy and corn were maintained on a limited antigen duck and rice diet until cutaneous manifestations of pruritus were minimal (78 days). Sequential oral challenges with cornstarch, corn and soy were then performed. Subsequently, the dogs were fed a diet containing hydrolysed soy protein and cornstarch. Throughout the study period the dogs were examined for cutaneous manifestations of pruritus and, additionally, serum was collected for measurement of allergen-specific and total immunoglobulin (Ig)E concentrations. Intradermal testing with food antigens was performed prior to entry into the study and after 83 days. A statistically significant clinical improvement was measured between days 0 and 83. Significant pruritus was induced after oral challenge with cornstarch, corn and soy (P = 0.04, 0.002, 0.01, respectively) but not with the hydrolysed diet (P = 0.5). The positive predictive value of the skin test for soy and corn allergy was reduced after feeding a soy and corn free diet. Although increases in soy and corn-specific serum IgE concentrations were measured in individual dogs post challenge they were not statistically significant and could not be used to predict clinical hypersensitivity.     

Evaluation of colonoscopic allergen provocation as a diagnostic tool in dogs with proven food hypersensitivity reactions

OBJECTIVE: To evaluate the colonoscopic allergen provocation (COLAP) test as a new tool for the diagnosis of IgE-mediated food allergy. METHODS: Oral food challenges as well as COLAP testing were performed in a colony of nine research dogs with proven immediate-type food allergic reactions. In addition, COLAP was performed in five healthy dogs. RESULTS: When compared with the oral challenge test, COLAP accurately determined 18 of 23 (73 per cent) positive oral challenge reactions (73 per cent) in dogs with food allergies and was negative in the healthy dogs. CLINICAL SIGNIFICANCE: The accuracy of this new test may be higher than that for gastric sensitivity testing. Therefore, COLAP holds promise as a new test to confirm the diagnosis of suspect IgE-mediated food allergy in dogs.     

Evaluation of Pet‐Related Management Factors and the Risk of Salmonella spp. Carriage in Pet Dogs from Volunteer Households in Ontario (2005–2006)

The purpose of this study was to determine pet‐related management factors that may be associated with the presence of Salmonella spp. in feces of pet dogs from volunteer households. From October 2005 until May 2006, 138 dogs from 84 households in Ontario were recruited to participate in a cross‐sectional study. Five consecutive daily fecal samples were collected from each dog and enrichment culture for Salmonella spp. was performed. A higher than expected number of the dogs (23.2%; 32/138) had at least one fecal sample positive for Salmonella, and 25% (21/84) of the households had at least one dog shedding Salmonella. Twelve serotypes of Salmonella enterica subsp. enterica were identified, with the predominant serotypes being Typhimurium (33.3%; 13/39), Kentucky (15.4%; 6/39), Brandenburg (15.4%; 6/39) and Heidelberg (12.8%; 5/39). Univariable logistic regression models were created with a random effect for household to account for clustering. Statistically significant risk factors for a dog testing positive included having contact with livestock, receiving a probiotic in the previous 30 days, feeding a commercial or homemade raw food diet, feeding raw meat and eggs, feeding a homemade cooked diet, and having more than one dog in the household. In two‐variable models that controlled for feeding raw food, the non‐dietary variables were no longer statistically significant. These results highlight the potential public health risk of including raw animal products in canine diets.     

Food hypersensitivity in a cat

Food hypersensitivity was diagnosed in a 4-year-old Siamese cat. Clinical signs included intense erythema, with alopecia, excoriations, erosions, and crusts involving the ventral portion of the abdomen, inguinal region, medial aspect of each thigh, and cranial and lateral aspects of all 4 limbs. The cat was intensely pruritic. Histologically, there was cutaneous mast cell hyperplasia and diffuse infiltration of eosinophils in the dermis. Blood eosinophilia also was found. Clinical signs resolved after exclusive feeding of a hypoallergenic diet.     

Clinical application of a polymerase chain reaction assay for diagnosis of leptospirosis in dogs

OBJECTIVE: To evaluate the use of a polymerase chain reaction (PCR) assay on urine samples for diagnosis of leptospirosis in dogs. DESIGN: Prospective case study. ANIMALS: 132 dogs with clinical signs suggestive of leptospirosis and 13 healthy dogs. PROCEDURE: PCR testing was performed on urine samples to detect leptospiral DNA; results were compared with results of conventional criteria for the diagnosis of leptospirosis. RESULTS: Leptospirosis was diagnosed in 8 dogs via established criteria; all these dogs had positive results of PCR assay, including 1 dog with positive results before seroconversion developed. A positive PCR assay result was also obtained in 16 dogs that did not have a confirmed diagnosis of leptospirosis. In the 8 dogs that had a confirmed diagnosis of leptospirosis, serovars pomona (n = 3 dogs), grippotyphosa (2), canicola (2), and bratislava (1) were identified serologically. The remaining 121 dogs all had a diagnosis other than leptospirosis or were healthy. For PCR testing on urine, sensitivity was 100%, specificity was 88.3%, positive predictive value was 33%, and negative predictive value was 100%. CONCLUSIONS AND CLINICAL RELEVANCE: Positive PCR test results prior to seroconversion may have value in establishing an early diagnosis. Positive results in dogs that had signs consistent with leptospirosis despite failing to meet established criteria for leptospirosis raise questions regarding the sensitivity of serologic testing in diagnosis of leptospirosis. Serovars pomona, grippotyphosa, and canicola were most common.     

Late-phase reactions to intradermal testing with Dermatophagoides farinae in healthy dogs and dogs with house dust mite-induced atopic dermatitis

OBJECTIVE: To determine the prevalence of late-phase reactions to intradermal testing with Dermatophagoides farinae in healthy dogs and dogs with atopic dermatitis and an immediate reaction to D farinae. ANIMALS: 6 healthy dogs and 20 dogs with atopic dermatitis and immediate reactions to D farinae. PROCEDURE: ntradermal tests were performed with D farinae at 1:1,000 wt/vol and 1:50,000 wt/vol concentrations, and skin reactivity was evaluated after 0.25, 6, and 24 hours. Serum D farinae-specific IgE antibodies were assayed. Extent of lesions (atopy index) and pruritus (visual analogue scale) were evaluated in dogs with atopic dermatitis. RESULTS: Late-phase reactions were observed in healthy dogs at 6 hours (n = 2 dogs) and 24 hours (1) with the 1:1,000 wt/vol concentration, and at 6 hours (1) and 24 hours (1) with the 1:50,000 wt/vol concentration of allergen. Late-phase reactions in healthy dogs were only observed in dogs with an immediate reaction to D farinae. Late-phase reactions were observed in 11 of 20 dogs with atopic dermatitis at 6 and 24 hours with the 1:1,000 wt/vol concentration and in 10 of 20 at 6 and 24 hours with the 1:50,000 wt/vol concentration of allergen. There was no difference in mean atopy index, mean visual analogue scale of pruritus, or mean serum D farinae-specific IgE concentration of dogs with a late-phase reaction, compared to dogs without a late-phase reaction. CONCLUSIONS AND CLINICAL RELEVANCE: Late-phase reactions may be observed after an immediate reaction to intradermal skin testing in healthy and allergic dogs but are more commonly observed in dogs with atopic dermatitis.     

Feeding for health

In the last decade there has been increasing emphasis on the role of healthy eating in the prevention of disease. The aim is to make people aware of the need to be more responsible for their own wellbeing. As attention is drawn to improving our diet there is now also greater awareness of the need to apply the same principles to our pets. I intend to discuss the key elements of dietary selection; nutrient content, energy, digestibility and palatability which are to be considered when formulating a healthy feeding regimen. Both physiological and environmental factors affect food intake and often animals' feeding habits will be affected by their owner. Finally, it must be remembered that cats and dogs are individuals and will always have their own particular food preferences. As long as a balanced diet is offered to the animals in sufficient quantities our pets should enjoy long and healthy lives.     

Postprandial venous ammonia concentrations in the diagnosis of hepatobiliary disease in dogs

A postprandial ammonia tolerance test (PPATT) was performed on normal dogs and dogs with signs that suggested they may have liver disease. All dogs underwent transcolonic scintigraphy, liver biopsy, or both and were assigned to extrahepatic disease, primary hepatocellular, and congenital portosystemic vascular anomalies (PSVA) groups. Each dog was fed a chicken and rice diet providing 25% of its estimated daily metabolizable energy requirement (MER) as an ammonia challenge. This is practical in patients with liver disease because ammonium chloride administration often causes vomiting or ammonia toxicity. Venous ammonia concentrations were measured before feeding and every 2 hours after feeding for 8 hours. No difference in mean ammonia concentrations between dogs with extrahepatic disease and control dogs was found. Therefore, the specificity of the PPATT was 100%. Dogs with hepatocellular disease showed no change in mean ammonia concentration at any time point, before or after feeding, but sensitivity was greatest when venous ammonia was measured 6 hours after feeding (sensitivity before feeding, 28%, and after feeding, 36%). Among dogs with congenital PSVA, mean ammonia concentrations were higher than the reference range at all time points before and after feeding, and peak mean ammonia concentration occurred 6 hours after feeding. In this group, the sensitivity of the PPATT was 81% before feeding and 91% 6 hours after feeding. This study demonstrates that the measurement of venous ammonia concentration is a useful test to detect congenital PSVA, and the sensitivity of the test may be improved by sampling 6 hours after feeding. The PPATT has poor sensitivity in detecting primary hepatocellular disease.     

Doppler ultrasonographic evaluation of gastrointestinal hemodynamics in food hypersensitivities: a canine model

Chronic enteropathy due to food hypersensitivity is a common complaint in dogs and humans, and definitive diagnosis and identification of offending allergens remains challenging. Doppler waveform analysis of the celiac artery (CA) and the cranial mesenteric artery (CMA) of 8 dogs with proven food hypersensitivity was performed in the fasting state and at 20, 40, 60, and 90 minutes after feeding their regular daily diet, and at 2 and 4 days after feeding 4 different allergens. Resistive index (RI), pulsatility index (PI), and the percentage differences between these measurements were calculated and compared statistically. The maximal decrease in RI and PI after feeding the regular diet was reached at 40 minutes after ingestion in both vessels (CA: RI = -6%, PI = -23%; CMA: RI = -9%, PI = -30%). After this trough, the resistance in both vessels rose nearly to baseline after 90 minutes (CA: RI = -1%, PI = -13%; CMA: RI = -3%, PI = -14%). When fed an allergen-containing meal the percentage changes at the trough were significantly greater (CA: RI = -10%, PI = -32%; CMA: RI = - 14%, PI = -40 %; p < 0.05) compared to those seen after feeding the maintenance diet. Also, RI and PI values were significantly (P < .05) lower at 90 minutes on days 2 and 4 of the challenge period. During the challenge period, dogs did not show overt signs of gastrointestinal disease. Significant postprandial hemodynamic alterations in response to food allergens in dogs with food hypersensitivities can be shown noninvasively with Doppler ultrasound.     

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.     

Effect of acetic acid consumption on clinical laboratory values in the dog

To investigate the influence of food enriched with acetic acid on the clinical, biochemical, electrolyte, blood gas, haematological and urinary variables in the dog, a cross-over study was carried out with periods of approximately 2 weeks involving six healthy, adult dogs. Another objective was to determine the maximum concentration of acetic acid that the dogs found to be palatable. The dogs were maintained on a commercial meat-based food with added acetic acid and/or glucose. The administered acetic acid was increased in stages. All dogs accepted the diet containing acetic acid at a level of 5% of metabolizable energy. Except for a decrease in plasma total protein, none of the variables were significantly affected by acetic acid consumption. Acetic acid feeding did not affect plasma acetate concentration and urinary acetate excretion, indicating that dogs efficiently metabolize ingested acetic acid.