Immunoallergological profile atopic dogs from two regions of Portugal

Abstract

Introduction and Objectives Canine atopic dermatitis (cAD) was recently redefined as a “hereditary, typically pruritic and predominantly T- cell driven inflammatory skin disease involving interplay between skin barrier abnormalities, allergen sensitization and microbial dysbiosis”. This definition high-lights the importance of a multimodal approach in the management of this disease, where the allergen-specific immunotherapy has a relevant role. The assessment of the sensitization profile in atopic dogs can be done by intradermal tests (IDT) and/or determination of allergen-specific immunoglobulin E (sIgE) in serum. The selection of tested allergens should be based on the prevalence of the allergens in a specific geographical region and on the immunoallergological profile of the patients living in each area. Similar to human allergic patients, the most common allergens implicated in cAD are house dust mites, but in dogs Dermatophagoides farinae appears to be the most prevalent allergen involved in cAD worldwide. The main objective of this study is to evaluate whether there are different sensitization rates for a panel of environmental allergens, assessed by IDT, among atopic dogs living in two regions of Portugal.

Material and Methods A total of 24 atopic dogs were selected from dermatology consultations in two different regions of Portugal: 12 from the Center and 12 from Alentejo. The diagnosis of cAD was made through the most recent guidelines from the International Committee on Allergic Diseases of Animals, which include evaluation of historical and clinical features; rule out other skin conditions with clinical signs resembling cAD; control of secondary bacteria and/or fungal infections; and assessment of skin reactivity by IDT and/or determination of sIgE in serum. All the 24 selected atopic dogs performed IDT by inoculation of 23 commercial environmental allergen extracts, which includes house dust and storage mites, grass pollens, tree pollens, weeds pollens, fungi and epithelia.

Results All dogs from the Center region presented at least a positive skin test. One of the 12 dogs selected from Alentejo region presented negative IDT for all the allergenic extracts used, probably a clinical case of the so-called canine atopic-like disease. In both groups of dogs, the highest sensitization rate was recorded for house-dust and storage mites allergens, followed by grass pollen and fungal species. All patients with positive IDT to fungal species also presented, at least, a positive skin test for dust-mites. Only two dogs testing positive for pollen extracts did not test positive for mites. Twenty-one of the 24 atopic dogs tested showed, at least, a positive IDT to mites. The sensitization rate to dust and storage mites was in the following decreasing order: Euroglyphus maynei (13), Acarus siro (12), Dermatophagoides farinae and Lepidoglyphus destructor (11), and Tyrophagus putrescentiae (10). A significant difference was found between the sensitization rate and the country region for Dermatophagoides farinae (p=0.004). The patients from the Center region showed nine positive IDT to Dermatophagoides farinae, while the sensitization to this mite was just found in two dogs from the Alentejo region. Conclusions In this study, the highest sensitization rate observed was to house dust and storage mites as has already been demonstrated in other European countries. Euroglyphus maynei was the mite with the highest rate of positive IDT in this study population. Patients living in the Center of Portugal showed a sensitization rate significantly higher to Dermatophagoides farinae when compared with the atopic dogs from Alentejo. These results can be explained by a geographical variability of that mite species prevalence – according to the acarological map of Portugal, Dermatophagoides farinae is more abundant in the Portuguese homes in the central coastal region of the country than in the southern interior area. This study shows the relevance of evaluating IDT results for each region. By adjusting the panel of allergens to test, we can obtain more reliable IDT results, promoting a better response to allergen-specific immunotherapy. Future enlarged studies are needed to evaluate possible geographical variabilities for other allergen species, like fungi and pollens.