Patch testing of experimentally sensitized beagle dogs: development of a model for skin lesions of atopic dermatitis

In humans with atopic dermatitis (AD), the epicutaneous application of allergens (atopy patch tests or APT) to which the patients are sensitized often results in the development of inflammation resembling that of spontaneous skin lesions. Dogs are affected with a natural homologue of human AD, but information on the induction of positive patch testing reactions is limited. The objectives of this pilot study were to determine the nature and cellular dynamics of inflammation occurring after APT in dogs hypersensitive to house dust mite and flea allergens. Laboratory Beagles were sensitized experimentally to Dermatophagoides farinae house dust mites (two dogs), Ctenocephalides felis flea saliva (one dog) or both (two dogs). Two other dogs served as nonsensitized controls. Both allergens and saline were applied epicutaneously. Macroscopic evaluations and skin biopsies were performed at 4, 24, 48 and 96 h after starting allergenic challenge. Biopsies were evaluated histologically and immunohistochemically with a panel of monoclonal antibodies specific for canine leucocyte antigens. Positive macroscopic reactions consisted of erythema, oedema and induration, and they occurred between 24 and 96 h after allergen application. Macroscopic and microscopic APT reactions developed only whenever serum IgE was present against tested allergens. Microscopically, positive APT was associated with epidermal hyperplasia, Langerhans' cell hyperplasia, and eosinophil and lymphocyte epidermotropism. Dermal inflammation was mixed and arranged in a superficial perivascular to interstitial pattern. Numerous IgE+-CD1+ dendritic cells and gamma-delta T-lymphocytes were observed. Macroscopically and microscopically, APT reactions in these experimentally sensitized animals resembled those seen in lesional biopsy specimens of dogs and humans with spontaneous AD. Therefore, APT in hypersensitive dogs provides a relevant experimental model to investigate the pathogenesis and treatment of both canine and human AD skin lesions.     

Dermatophagoides mites in house dust as an allergen source in atopic dogs

Thirty dogs with a clinical diagnosis of atopy were skin tested with 58 allergens including an aqueous house dust mite extract and a crude house dust extract. Sixty percent of the dogs had positive skin reactions to both the house dust mite and house dust antigens. In atopic dogs, house dust mites appear to be an important allergen source in house dust extracts but are not the only major source.     

Canine atopic dermatitis: a retrospective study of 266 cases examined at the University of California, Davis, 1992-1998. Part I. Clinical features and allergy testing results

The medical records of 266 dogs diagnosed as having atopic dermatitis were reviewed. Statistical data were evaluated referable to breed predilections, clinical signs and positive reactions to allergens. Positive reactions were most common to house dust mites (more common with clinical signs in the fall) followed by moulds (more common with clinical signs in the fall and spring). Dogs with positive reactions to moulds, trees or cultivated plants were more likely to have skin and ear yeast infections. Dogs with positive reactions to cultivated plants were more likely to have otitis externa and pedal lesions. Positive reactions to house dust were more common in dogs with early onset of signs and in those tested early in the disease. Dogs had more positive reactions to weeds when allergy tests were performed in the summer and fall. Positive reactions to flea antigen were highly correlated with the clinical diagnosis of flea allergy dermatitis.     

Reactivity to intradermal injection of extracts of Dermatophagoides farinae, Dermatophagoides pteronyssinus, house dust mite mix, and house dust in dogs suspected to have atopic dermatitis: 115 cases (1996-1998)

OBJECTIVE: To compare reactivities to intradermal injection of extracts of Dermatophagoides farinae, Dermatophagoides pteronyssinus, house dust mite mix, and house dust in dogs suspected to have atopic dermatitis. DESIGN: Retrospective study. ANIMALS: 115 dogs. PROCEDURES: Records of all dogs suspected to have atopic dermatitis that underwent intradermal testing between October 1996 and July 1998 were reviewed. Reactivities to intradermal injection of crude mixed house dust mite (1:25,000 wt/vol) and crude house dust (25 PNU/ml) extracts were compared with reactivities to intradermal injection of individual extracts of D farinae and D pteronyssinus (1:50,000 wt/vol). RESULTS: Ninety dogs were confirmed to have atopic dermatitis including 61 of the 69 dogs with positive reactions to either or both of the individual house dust mite extracts. Intradermal testing with the mixed house dust mite extract had sensitivity of 75%, specificity of 96%, and accuracy of 83%. Intradermal testing with the house dust extract had sensitivity of 30%, specificity of 93%, and accuracy of 56%. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that use of crude mixed house dust mite and crude house dust extracts for intradermal testing in dogs is not as accurate a method of determining house dust mite hypersensitivity as is the use of individual D farinae and D pteronyssinus extracts mainly because of the high percentage of false-negative results. Extracts of individual house dust mites are recommended for intradermal testing of dogs suspected to have atopic dermatitis.     

Importance of house dust and storage mites in canine atopic dermatitis in the geographic region of Galicia, Spain

Sensitisation to mites is frequent in atopic dogs. The main mite genus involved in canine atopic dermatitis is Dermatophagoides. The importance of storage mite allergens in dogs has been controversial. The aim of this study was to evaluate the sensitisation rates against storage mites (Lepidoglyphus destructor and Tyrophagus putrescentiae) and house dust mites (Dermatophagoides farinae and D. pteronyssinus) in atopic dogs from Galicia, a highly humid and temperate region of Spain, using a FcepsilonRIalpha-based immunoglobulin E (IgE) in vitro test. The study was performed on 95 dogs suffering from atopic dermatitis and presenting detectable specific serum IgE levels: 91.6% of the dogs tested positive for storage mites, whereas sensitisation to house dust mites was detected in 87.4%. These results indicate the importance of storage mites in this specific geographic area.     

Comparison of intradermal testing and serum testing for allergen-specific IgE using monoclonal IgE antibodies in 84 atopic dogs

OBJECTIVE: To compare an ELISA measuring serum allergen-specific IgE with intradermal skin testing in canine atopic dermatitis. PROCEDURE: Eighty-four dogs with the clinical diagnosis of atopic dermatitis underwent intradermal skin testing and serum testing for allergen-specific IgE. Tests were performed in a blinded fashion. Positive reactions were compared and the sensitivity and specificity of the serum test (using intradermal skin test as the standard) were determined overall and for individual allergen groups (grass pollens, weed pollens, tree pollens, house dust mites and fleas). RESULTS: The sensitivity of the ELISA overall was 90.4%. Evaluating the individual allergen groups, the sensitivity for dust mite hypersensitivity was 95.1%, for fleas 85.4%, for tree pollens 84.3%, for grass pollens 95.1% and for weed pollens 96.4%. The specificity was 91.6% overall, for dust mites 96.3%, for fleas 92.7%, for tree pollens 95.2%, for grass pollens 94% and for weed pollens 80.7%. CONCLUSION: The evaluated ELISA seemed reliable for the diagnosis of atopy in practice and can be recommended as a screening test prior to intradermal skin testing or for use in dogs when immunotherapy is not a therapeutic option.     

House dust and forage mite allergens and their role in human and canine atopic dermatitis

This article reviews the literature regarding the role of house dust and forage mite allergens in canine atopic dermatitis. The presence of immunoglobulin E (IgE) to these mites, especially to Dermatophagoides farinae, is common in both normal and atopic dogs. Exposure of dogs to the different mites is described both in the direct environment and in the coat of animals for house dust mites and in the food for forage mites. Allergens causing allergic disease in dogs seem to be different from those in humans. Dogs seem to react to high molecular weight allergens, compared to the low molecular weight group 1 and group 2 proteases that are commonly implicated in humans with atopic diseases. Despite numerous published studies dealing with this subject, a number of questions still need to be addressed to better understand the exact role of these mites in the pathogenesis of canine atopic dermatitis and to improve the quality of the allergens used in practice.     

P-44 The presence of dust mite species in the environment of dust mite-sensitized atopic dogs

The importance of pollen allergies in dogs with atopic dermatitis in South America has not been determined. Local allergists and pallinologists have performed a few studies evaluating pollen counts in Buenos Aires throughout the year. Those studies helped the author in choosing a pollen allergen panel for intradermal testing based on local allergens. One-hundred-sixty dogs with atopic dermatitis were tested intradermally during a 3-year period, using 30 individual allergens including house dust mites, moulds, trees, weeds and grasses. The most important pollen allergens in terms of positive reactions were Platanus acerifolia (32 dogs), Fraxinus Americana (11 dogs), Cynodon dactylon (13 dogs), Ambrosia tenuifolia (26 dogs), Artemisia spp. (16 dogs), Plantago lanceolata (21 dogs), Chenopodium spp. (16 dogs) and grass pollen (29 dogs). Other pollens on the panel were less important. A correlation between pollination season and atopic dermatitis symptoms was determined. A few dogs were only positive for pollen and not for house dust mites. The incidence of pollen allergies in canine atopic dermatitis in South America must be determined in order to select an adequate panel for the area and for its main cities, and to exclude those allergens that are irrelevant locally. Special individual cases might be further tested, if necessary, with other allergens upon plant identification in the patient's environment. The findings encourage more investigation in this area, and suggest that allergen-specific immunotherapy with tree, weed and grass pollen should be considered.
Funding: Self-funded.     

Prevalence and features of canine atopic dermatitis in Hungary

Medical records of 600 dogs diagnosed with atopic dermatitis were reviewed and evaluated with reference to history, geographical distribution, breed predilection, clinical signs and positive reactions to allergens as determined by intradermal skin testing (IDT) manufactured by Artuvetrin Laboratories. In 66.6% of dogs, the age of onset of atopic dermatitis was between 4 months and 3 years. Dogs living in the garden suburb of Budapest were more sensitive to house dust mites, fleas and moulds, and dogs from the western part of Hungary were more sensitive to weeds than to other allergens (p < 0.01). Positive reactions were most common to Dermatophagoides farinae followed by human dander. The breed distribution found in the present study was consistent with that reported in the literature, except for the breeds Hungarian Vizsla, Pumi, French bulldog, Doberman Pinscher and Bobtail which were over-represented among atopic dogs compared to the breed distribution of the general dog population of a large city in Hungary. Breeds with verified adverse reaction to food were Cocker spaniels, French bulldogs, Bullmastiffs, Bull terriers, St. Bernards, Tervurens, West Highland White terriers and American Staffordshire terriers (p < 0.05). The clinical signs of atopic dermatitis and their occurrence are in accordance with the data described in the literature.     

Validation of a novel epicutaneous delivery system for patch testing of house dust mite‐hypersensitive dogs

Background – Patch tests with allergens are used for the evaluation of cellular hypersensitivity to food and environmental allergens in dogs and humans with atopic dermatitis. Viaskin is a novel allergen epicutaneous delivery system that enhances epidermal allergen capture by immune cells. Objectives – To compare the use of Viaskin and Finn chamber patch tests in dogs hypersensitive to mite allergens. Methods – Empty control or Dermatophagoides farinae house dust mite‐containing Viaskin or Finn chamber patches were applied to the thoracic skin of six mite‐hypersensitive Maltese‐beagle crossbred atopic dogs. Lesions were graded 49 and 72 h after patch test application, and skin biopsies were collected after 72 h. Overall microscopic inflammation, eosinophil and T‐lymphocyte infiltrations were scored. Results – Positive macroscopic patch test reactions developed at five of six Viaskin application sites and four of six Finn chamber application sites. Median microscopic epidermal and dermal inflammation, as well as eosinophil and CD3 T‐lymphocyte dermal scores were always higher in biopsies collected at Viaskin than at Finn chamber sites. Microscopic inflammation scores were significantly higher after mite allergen‐containing Viaskin compared with empty patches, but this was not the case for mite‐containing Finn chambers compared with control chambers. Scores obtained using Viaskin were not significantly different from those obtained using Finn chambers. Macroscopic and microscopic scores were significantly correlated. Conclusions and clinical importance – In mite‐allergic dogs, Viaskin epicutaneous delivery systems appear to induce stronger allergen‐specific inflammation than currently used Finn chamber patch tests. Consequently, Viaskin patches might offer a better alternative for screening cellular hypersensitivity to food and environmental allergens.     

Assessment of cross-reactivity among five species of house dust and storage mites

In vitro cross-reactivity among two house dust (Dermatophagoides farinae, D. pteronyssinus) and three storage (Acarus siro, Tyrophagus putrescentiae, Lepidoglyphus destructor) mites was examined in 20 mite-sensitive dogs with natural occurring atopic dermatitis (group A), 13 high-IgE beagles experimentally sensitized to D. farinae (group B), and five healthy beagles (group C). Intradermal testing (IDT) and serology for allergen-specific IgE demonstrated that co-sensitization for all possible pairs of the five mites was generally 45% or higher among group A dogs. In the same dogs, enzyme-linked immunosorbent assay cross-inhibition results indicated that each one of D. farinae, A. siro and T. putrescentiae was a strong inhibitor of all the remaining mites, whereas D. pteronyssinus was a strong inhibitor of L. destructor. A high number of positive IDT and serology test results for D. pteronyssinus, A. siro, T. putrescentiae and L. destructor were recorded among group B dogs. No conclusive evidence of exposure to these mites was found upon analysis of dust samples from their environment and their food for the presence of mites and guanine. Also, the number of positive test results was generally higher among group B than among group C dogs. Enzyme-linked immunosorbent assay cross-inhibition revealed that D. farinae was a strong inhibitor of D. pteronyssinus, A. siro and T. putrescentiae. Collectively, these results demonstrated extensive in vitro cross-reactivity among house dust and/or storage mites that can explain false-positive results upon testing of dust mite-sensitive dogs with atopic dermatitis.     

Environmental and oral challenge with storage mites in beagles experimentally sensitized to Dermatophagoides farinae

This study aimed to investigate whether challenge with storage mites elicited flare ups of atopic dermatitis (AD) in Dermatophagoides farinae sensitized atopic Beagles housed in a house dust and storage mite-free environment. Atopic Beagles were environmentally challenged with 50 mg of Tyrophagus putrescentiae for three days in a row. Clinical signs were scored before, 6 h after each challenge and then every 24 h for a total of 5 days using a Canine Atopic Dermatitis Extent and Severity Index. Four healthy Beagles, negative on serology and intradermal testing for both house dust and storage mites, were used as controls and similarly challenged. A month after environmental challenge, the atopic Beagles were challenged by the oral route (50 mg of T. putrescentiae for three days in a row) and evaluated as described. Analyses of variance (ANOVAs) were used for comparisons between groups and types of challenges. All atopic Beagles developed erythematous pruritic lesions clinically compatible with AD on the face, pinnae, feet and ventral abdomen after both environmental and oral challenge. Control dogs did not develop dermatitis except for mild pinnal erythema in one dog. In the environmental challenge, ANOVA showed a significant effect of time, group, and group x time interaction, with atopic Beagles showing significantly higher scores than the controls. There were no significant differences in clinical scores after oral and environmental challenge in the atopic group. Cross-reactivity between house dust and storage mites could therefore contribute to flare ups of AD in house dust mite allergic dogs.     

Serum immunoglobulin E against storage mite allergens in dogs with atopic dermatitis

OBJECTIVE: To determine the prevalence of serum IgE against the storage mites Acarus siro, Blomia tropicalis, and Tyrophagus putrescentiae in a population of dogs with atopic dermatitis. SAMPLE POPULATION: Sera from 84 dogs with atopic dermatitis residing in various regions of the United States and Europe. PROCEDURE: Immunoblotting of sera from atopic dogs was used to identify proteins in mite extracts that bound IgE. RESULTS: 94% of the dogs had serum IgE against proteins in extracts of 1 or more of the storage mite species. Ninety-five, 92, and 89% of the storage mite-sensitive dogs had serum IgE against proteins in extracts of A siro, B tropicalis, and T putrescentiae, respectively. Eighty-two percent had serum IgE against at least 1 protein in all 3 species. Most of the major allergens had molecular weights > 80 kd. A greater percentage of the dog sera had IgE against storage mite proteins, compared with proteins of the house dust mites Dermatophagoides farinae and D pteronyssinus. CONCLUSION AND CLINICAL RELEVANCE: Many dogs with atopic dermatitis have serum IgE against many allergens of storage mites. Most of these allergens, like allergens of dust mites, had molecular weights > 80 kd. Storage mite sensitivity in dogs may be as important, if not more important, than dust mite sensitivity.     

Peripheral blood mononuclear cell responses to Dermatophagoides farinae in canine atopic dermatitis

Atopic dermatitis is a chronic inflammatory and pruritic skin disease commonly seen in dogs and humans that is characterised by the presence of allergen-specific IgE. Data from skin tests and serological analysis suggest that the house dust mite Dermatophagoides farinae is the most important allergen in dogs with atopic dermatitis. The aim of this study was to determine if D. farinae specific peripheral blood mononuclear cell (PBMC) responses could be detected in dogs with atopic dermatitis. PBMCs were isolated by the density centrifugation from dogs with atopic dermatitis that were skin test positive for D. farinae, dogs with atopic dermatitis that were skin test negative for D. farinae, and healthy dogs. Cells were cultured with increasing concentrations of the D. farinae extract, no antigen, vaccine antigens or concanavalin A (ConA). There was significantly greater responsiveness of PBMCs from the D. farinae positive dogs than from either the D. farinae negative or healthy dogs (ANOVA, P<0.05). In contrast, no significant differences were observed in the control responses between the three groups. This is the first study to demonstrate that D. farinae specific circulating memory cells are involved in the pathogenesis of canine house dust mite hypersensitivity.     

Sensitization rates of causative allergens for dogs with atopic dermatitis: detection of canine allergen-specific IgE

Allergen-specific IgE serology tests became commercially available in the 1980s. Since then these tests have been widely used to diagnose and treat allergic skin diseases. However, the relationship between a positive reaction and disease occurrence has been controversial. The purpose of this study was to evaluate allergens using a serologic allergy test in dogs with atopic dermatitis (AD). Dogs clinically diagnosed with AD (n=101) were tested using an allergen-specific IgE immunoassay. Among the total 92 environmental and food allergens, house dust and house dust mites were the most common. Several allergens including airborne pollens and molds produced positive reactions, and which was considered increasing allergens relating to the climate changes. The presence of antibodies against staphylococci and Malassezia in cases of canine AD was warranted in this study. Additionally, strong (chicken, turkey, brown rice, brewer''s yeast, and soybean) and weakly (rabbit, vension, duck, and tuna) positive reactions to food allergens could be used for avoidance and limited-allergen trials.     

The clinical effect of environmental control of house dust mites in 60 house dust mite-sensitive dogs

Abstract   The purpose of this study was to evaluate the effects of benzyl benzoate, an acaricide for the control of house dust mites, in 60 house dust mite-sensitive dogs. All dogs showed positive reactions on intradermal skin testing for house dust mites ( Dermatophagoides farinae , Dermatophagoides pteronyssinus ) alone, or house dust mites with storage mites ( Acarus siro , Tyrophagus putrescentiae , Glycophagus domesticus ). House dust samples from the owners' houses were collected and sent to the clinic, where the authors performed a test (Acarex® test) to semiquantify the amount of guanine, a house dust mite product. Treatment with benzyl benzoate was repeated until the house dust samples were negative for house dust mite guanine. After treatment, 29 out of 60 house dust mite-sensitive dogs (48%) showed no skin lesions or pruritus. Moderate results were achieved in 22 dogs (36%), with reduced pruritus and minimal skin lesions, but still requiring medication. In 13 dogs, this involved regular treatment (3–4 times a year) with antibiotics and antiyeast medication, and in eight dogs, immunotherapy was used. One dog was controlled with essential fatty acids as monotherapy and one dog was controlled with immunotherapy and essential fatty acids. In the remaining nine dogs (15%), the pruritus remained the same, and these dogs were controlled with oral corticosteroids. These results indicate that house dust mite elimination is a useful tool in the management of house dust mite-sensitive dogs.     

Aero-allergens in canine atopic dermatitis in southeastern Australia based on 1000 intradermal skin tests

OBJECTIVE: To determine the most relevant aero-allergens involved in canine atopic dermatitis in southeastern Australia and provide information about these aero-allergens to the general practitioner. PROCEDURE: Dogs presented to the Animal Skin & Allergy Clinic with history and clinical signs of atopic dermatitis were injected intradermally with 38 different allergens and negative and positive control. Intradermal skin tests in 1000 dogs were retrospectively evaluated. RESULTS: One third of all patients reacted to the house dust mite Dermatophagoides farinae. Allergens reacting in more than 15% of the patients were wheat (Triticum aestivum), sweet vernal (Anthoxanthum odoratum), English couch (Agropyron repens), yellow dock (Rumex crispus), Mexican tea (Chenopodium ambrosioides), plantain (Plantago lanceolata), melaleuca (Melaleuca quinquenervia) and peppercorn (Schimus spp). CONCLUSION: House dust mites are the most common allergens in canine atopic dermatitis in southeastern Australia and D farinae is involved most frequently. However, a number of grass, weed and tree pollens also are involved regularly.     

Atopic dermatitis in Norwegian dogs

Of 122 dogs showing clinical symptoms of atopic dermatitis, 65.6% exhibited immediate skin test reactivity to one or more well defined allergen extracts, when intradermal skin tests were performed. The Prausnitz-Küstner test performed on two non-atopic recipient dogs, with serum from affected dogs, showed that "reaginic" antibodies transferred in serum from all affected dogs remained bound within the skin of the recipient dogs for 192 hours. House dust, house dust mite (D. farinae) and human dander were the allergens which most commonly caused immediate skin reactions and West Highland White Terriers and Boxers were the most affected breeds. Age at onset of clinical symptoms proved to be 1-4 year in 72.2% of the dogs.     

Studies on the role of routes of allergen exposure in high IgE-producing beagle dogs sensitized to house dust mites

The current study aimed to investigate the role played by oral, epicutaneous, and inhalation routes of exposure to house dust mites (HDM). The colony of high IgE-producing beagle dogs has been shown to develop pruritic dermatitis compatible with atopic dermatitis following environmental exposure (EE) to HDM. In crossover experiments, the response to EE was compared to two modified challenges, oral exposure (OE) and snood and muzzle exposure (SME). For OE, HDM were fed daily for 3 days. For SME, ingestion of allergen was prevented but there was inhalation and epicutaneous exposure to all body regions except to one ear. In all experiments, dogs were challenged for three consecutive days, and evaluated before, 6 h after exposure and daily thereafter, for 5 days. After a wash-out period, groups were crossed-over so that each dog was randomly challenged to all three protocols. Clinical scores were analysed using least squares analysis of variance. All dogs developed pruritic dermatitis regardless of the protocol. With OE, lesions developed in the same body regions as with EE although scores were lower. This difference became more evident after the first 3 days when OE scores decreased and EE scores continued to increase. The scores of covered and uncovered ears did not differ with SME. Scores for the remainder of the body were significantly lower than for EE. The development of lesions on covered ears supports the importance of inhalation or a systemic reaction to epicutaneous exposure in other areas. It is concluded that all routes are important and have additive effects, that route of exposure does not determine the distribution of lesions and that continuous epicutaneous exposure probably plays the most important role.     

The prevalence of positive intradermal allergy tests in 114 dogs with atopic dermatitis in the Bangkok metropolis, Thailand

Intradermal allergy tests using 47 selected local aero-allergens were performed on 114 dogs with atopic dermatitis. The subject animals visited the Dermatology Unit at the Veterinary Teaching Hospital of Kasetsart University or the SLV Pet Hospital with chronic pruritus and various skin lesions. Allergen extracts were composed of: 4 house dust and house dust mites, 7 household insects, 24 pollens, 11 mold spores, and Kapok. The prevalence of sensitization to various allergens were as follows: Dermatophagoides farinae (74.56%), Dermatophagoides pteronyssinus (53.51%), house dust (26.32%), American cockroach (Periplaneta americana) (23.68%), Para glass (21.93%) and mixed ants (20.18%). No relationship was noted between the various allergen groups and the location of the skin lesions except for those animals that reacted to pollens which appeared to have be more likely to have lesion affecting the perineum and tail area (p=0.022; OR, 6.429; 95% CI, 1.003-40.292).