Testing for food-specific antibodies in saliva and blood of food allergic and healthy dogs

Establishment of clinical criteria for the diagnosis of adverse food reactions in dogs with atopic dermatitis

BACKGROUND

Diagnosis of canine adverse food reactions (AFRs) is based on vague criteria, such as '>50% improvement' during elimination diet trial (EDT) followed by 'deterioration' during provocation test (PT).

OBJECTIVE

The objective of the study was to use predefined criteria to evaluate response during EDT [i.e., Owner Global Assessment of Treatment Efficacy (OGATE) = good-to-excellent] and relapse during PT [i.e., Owner Global Assessment of Challenge Deterioration (OGACD) = moderate-to-severe and/or >100% increase of lesional (Canine Atopic Dermatitis Extent and Severity Index, 4th iteration, CADESI-04) and/or of pruritus (pruritus Visual Analog Scale, PVAS) scores].

ANIMALS

Twenty-nine dogs with atopic dermatitis.

MATERIALS AND METHODS

An extensively hydrolysed diet was fed to all dogs followed, in seven of 11 nonresponders, by a second home-made novel-protein EDT. Dogs responding to either EDT were challenged with their previous diet.

RESULTS

Thirteen (44.8%) dogs were diagnosed with AFRs: at the end of EDT, their OGATE was good (9 of 13; 69.2%) or excellent (four of 13; 30.8%), and both CADESI-04 (46.7%) and PVAS (71.1%) had decreased significantly; at the end of PT, OGACD was moderate or severe in 12 of 13 (92.3%) dogs, and both CADESI-04 (127.9%) and PVAS (181.8%) had increased significantly. Of the 16 dogs without AFRs, 6 (37.5%) responded to the commercial (n = 5) or home-made (n = 1) diet [OGATE = good (three of six) or excellent (three of six)], with significant concurrent reduction of CADESI-04 and nonsignificant reduction of PVAS, yet they did not relapse during PT.

CONCLUSIONS AND CLINICAL RELEVANCE

The proposed (predefined) criteria for the evaluation of response during EDT and deterioration during PT seem reliable and are easily applicable in clinical practice and research.

Detection of allergen-specific antibody-secreting cells in dogs by ELISPOT

Current laboratory tests are unable to distinguish healthy from allergic dogs. Unlike serum antibody responses, circulating antibody-secreting cells (ASC) are temporarily induced after each contact with the antigen. These ASC can be identified using ELISPOT and the observation of allergen-specific ASC might correlate with the causative allergens in dogs with an allergic dermatitis. In this study, blood was sampled from six privately-owned allergic dogs and six non-allergic laboratory beagles to determine the frequency of circulating allergen-specific ASC for common allergens. Blood IgE+, IgA + and IgG + cells were magnetically isolated to determine the number of allergen-specific ASC with ELISPOT for Dermatophagoides farinae, Dermatophagoides pteronyssinus, Alternaria alternata, birch, timothy grass, wheat, cow's milk, bovine, chicken and lamb meat. For IgA and IgG, allergen-specific spots were observed, however for IgE, no spots were detected for any of the allergens. ELISPOT could not differentiate allergic from non-allergic dogs. When the responses to the different allergens were compared, more IgA ASC for D. pteronyssinus were observed compared to some of the other allergens which was statistically significant for the non-allergic dogs and approached significance in the allergic dogs. These findings indicate that ELISPOT can be used to identify circulating allergen-specific IgA- and IgG-secreting cells. The technique did however not detect allergen-specific IgE ASC and was unable to distinguish allergic from non-allergic dogs. Only a small number of studies have studied allergen-specific IgA in dogs. The finding that dogs have higher numbers of D. pteronyssinus-specific IgA ASC points out that apart from IgE and IgG, it might be interesting to include IgA measurements for certain allergens to analyse the complete spectrum of both the protective and pro-allergic antibody responses.

Assessment of the clinical accuracy of serum and saliva assays for identification of adverse food reaction in dogs without clinical signs of disease

OBJECTIVE

To assess the clinical accuracy of 2 serum-based assays and 1 saliva-based assay for detection of adverse food reaction (AFR) in dogs without clinical signs of disease.

ANIMALS

30 healthy client-owned dogs.

PROCEDURES

Dog owners completed an online survey to collect comprehensive information about their pets' diet history. From each dog, serum and saliva samples were obtained and submitted for AFR testing by means of 3 assays that assessed the immunoglobulin response to 24 foods. Assays A and B measured food allergen-specific IgE concentrations in serum, whereas assay C measured food allergen-specific IgA and IgM concentrations in saliva. Descriptive data were generated, and Fisher exact tests were used to assess the respective associations between positive test results and specific food ingredients to which dogs were exposed.

RESULTS

Assays A, B, and C yielded positive results for 26, 18, and 30 dogs, respectively. All dogs had positive results for at least 1 assay. The median (range) number of foods or ingredients to which dogs tested positive was 10.5 (0 to 24) for assay A, 1 (0 to 13) for assay B, and 12.5 (4 to 22; IgM) and 3 (0 to 24; IgA) for assay C. Positive test results were not significantly associated with prior food exposure.

CONCLUSIONS AND CLINICAL RELEVANCE

Saliva and serum assays for AFR often yielded positive results for apparently healthy dogs and are not recommended for clinical use. Elimination diet trials remain the gold standard for diagnosis of AFR in dogs.