Prevalence of positive reactions in intradermal and IgE serological allergy tests in dogs from South Australia, and the subsequent outcome of allergen-specific immunotherapy.

OBJECTIVE: To determine the prevalence of positive allergen reactions in intradermal and IgE serological tests in dogs presenting to a dermatology referral centre in South Australia and the clinical efficacy of subsequent allergen-specific immunotherapy. DESIGN: Retrospective study. METHODS: Results from 108 intradermal allergy tests, 25 IgE serological assays and immunotherapy outcomes in 37 dogs were retrospectively analysed. Immunotherapy outcomes were determined as excellent, good, modest or failure using a global assessment of efficacy matrix which incorporated pruritus scores, lesion severity, medication requirements, and owner and clinician opinion. RESULTS: The most common positive reactions in intradermal allergy tests were Red clover (59%), Dermatophagoides farinae (29%), Tyrophagus putrescentiae (28%), Yellow dock (25%) and Malassezia pachydermatis (24%). In the IgE serological tests, Yorkshire fog grass (40%), Yellow dock (36%), Kentucky bluegrass (36%) and T. putrescentiae (36%) were the most commonly reported positive results. The outcome of allergen-specific immunotherapy was judged to be excellent in 20% of dogs, good in 15%, modest in 18% and a failure in 47%. CONCLUSION: As has been reported in other geographical areas, environmental mites and plant pollens frequently gave positive reactions in allergy tests in South Australia. However, the prevalence of individual allergen reactions differed between intradermal and IgE serological tests, with M. pachydermatis being identified as a common cause of hypersensitivity in intradermal tests but not in IgE serological assays. Immunotherapy was judged to be a beneficial treatment in 35% of dogs but was essentially unsuccessful in 65%.

The immunopathogenesis of staphylococcal skin infections - A review.

Staphylococcus aureus and S. pseudintermedius are the major causes of bacterial skin disease in humans and dogs. These organisms can exist as commensals on the skin, but they can also cause severe or even devastating infections. The immune system has evolved mechanisms to deal with pathogenic microorganisms and has strategies to combat bacteria of this type. What emerges is a delicate "peace" between the opposing sides, but this balance can be disrupted leading to a full blown "war". In the ferocious battle that ensues, both sides attempt to get the upper hand, using strategies that are comparable to those used by modern day armies. In this review article, the complex interactions between the immune system and the organisms are described using such military analogies. The process is described in a sequential manner, starting with the invasion itself, and progressing to the eventual battlezone in which there are heavy casualties on both sides. By the end, the appearance of a simple pustule on the skin surface will take on a whole new meaning.

Pilot study of the effect of individualised homeopathy on the pruritus associated with atopic dermatitis in dogs.

Twenty dogs with confirmed atopic dermatitis were treated with homeopathy. In the first phase of this pilot study, all of the dogs were treated by a veterinary homeopath with individualised remedies prescribed on the basis of the dog's cutaneous signs and constitutional characteristics. The response to treatment was assessed by scoring the severity of pruritus from 0 to 10 on a validated scale. The dogs were evaluated at monthly intervals for at least two months. In 15 cases, the owners reported no improvement following homeopathic treatment. In the other five cases, the owners believed that the homeopathic treatment was associated with a substantial improvement, and reported reductions in pruritus scores ranging from 64 to 100 per cent. These five dogs were selected for the second phase of the study, in which homeopathic remedies were tested against placebos in a randomised and blinded trial. In one of these dogs, atopic dermatitis resolved completely and so this dog could not participate in phase 2; another dog was euthanased because of status epilepticus before phase 2 could be started. In the remaining three cases, the owners correctly distinguished between the placebo and homeopathic remedies, and reported reductions in the pruritus score of 0, 0.2 and 0.8 following placebo treatment and 4.3, 2.4 and 3.0, respectively, following the remedy.

Dermal arteritis of the nasal philtrum: surgery as an alternative to long-term medical therapy in two dogs.

Two dogs were presented with dermal arteritis of the nasal philtrum associated with repeated episodes of bleeding. Described treatment for this condition consists of long-term, usually life-long medication with various combinations of immune suppressant and anti-inflammatory medication. This paper describes a novel surgical approach to the condition that induced long-term remission in both cases.

Further validation of a pruritus severity scale for use in dogs.

A scale to assess the severity of pruritus in dogs was further validated. Comparison of the scale with one containing visible numerical markings demonstrated that owners were heavily influenced by the presence of numbers, resulting in a loss of the scale's ability to generate continuous data. The presence of a traditional visual analogue scale was therefore essential. The scale was tested on 713 owners who presented their dogs for veterinary attention. Pruritus scores in 408 dogs with skin disease covered the full range of possible values (0 to 10). In 305 dogs with no skin disease, 90 owners gave a score greater than zero. Comparison of the scores seen in pruritic dogs, and dogs with no evidence of skin disease, allowed a 'normal range' of 0-1.9 to be established. The scale was able to discriminate between conditions typically regarded as pruritic or non-pruritic. When the scale was assessed for its ability to detect changes in pruritus score following treatment, a median reduction of 4.4 points was observed. The scale was also used to determine what magnitude of response owners would expect following treatment of their pruritic dogs. Only 12% would have been satisfied with a 50% reduction, a figure that is typically quoted as a satisfactory response in clinical trials of anti-pruritic drugs. As a result, alternative methods of assessing clinical trials are proposed. This study has shown the scale to be a valuable tool for clinical assessment of patients, and for monitoring treatment responses in clinical trials.

Immunoglobulin G responses in 21 dogs with skin diseases to antigens from different isolates of Staphylococcus intermedius.

The aim of this study was to characterise the immunoglobulin G (IgG) response in 21 dogs with or without pyoderma to antigens from six isolates of Staphylococcus intermedius. The staphylococcal proteins were separated by sodium dodecyl sulphate polyacrylamide gel electrophoresis, transferred electrophoretically on to a membrane and subjected to immunoblotting with the dogs' serum. Gels containing separated proteins from the six isolates revealed 29 to 33 distinct bands with molecular weights ranging from 20 to 230 kDa. All the dogs' sera contained IgG that recognised 12 to 24 bands (mean 17), regardless of whether the dogs had pyoderma. The recognised proteins had molecular weights ranging from 20 to 198 kDa but the majority had molecular weights below 75 kDa. The most intense band in all six isolates had a molecular weight of 28 to 29 kDa. The antibody responses to the six isolates were essentially similar except that there were significantly more bands in the response to isolate 2 than to isolate 6, and occasional differences in the intensity of individual bands. All 21 dogs mounted an IgG response to multiple antigens in S intermedius, which differed only marginally between the six isolates. This lack of variation provides evidence that the host's response to different isolates of S intermedius is not a major factor in canine pyoderma.

Epidermolysis bullosa acquisita in a Great Dane.

Autoimmune subepidermal blistering diseases in dogs were all classified as bullous pemphigoid until 1998. Since then, refinements in reagents and immunological techniques have allowed diseases which are histologically similar but which have a different molecular pathogenesis to be described. This report describes the first case of one such disease, epidermolysis bullosa acquisita, to be documented in the UK. The dog presented with a severe blistering and ulcerative disease affecting the oral cavity, pinnae and distal limbs. The diagnosis was confirmed by histopathology and direct and indirect immunofluorescent demonstration of immunoglobulin G reactivity to basement membrane antigens. Treatment with glucocorticoids, azathioprine, colchicine and an intravenous infusion of immunoglobulins resulted in complete resolution. The drugs were discontinued 12 months after the start of treatment and the dog remained in remission.

Development of an owner-assessed scale to measure the severity of pruritus in dogs.

Assessment of pruritus is critical in dermatological history taking, both for initial diagnosis and for monitoring treatment. Various methods of assessing pruritus in the dog have been described but none have been validated. In this study, four different pruritus scales were initially assessed: a 0-5 numerical scale; a scale containing six categories of pruritic behaviours; a scale with six basic descriptors of severity; and a visual analogue scale with severity descriptions at either end. One hundred and sixteen owners were asked to grade their dog's pruritus with each of the four scales given to them in a randomized order, and asked which they thought was easiest to use, which was most accurate in assessing their dog's pruritus level, and which two scales they would combine to make a superior scale. Pruritus scores from different scales were highly correlated with each other, but scores were significantly higher with the severity and numerical scales compared to the behaviour scale. Based on the clients' responses, a new scale was developed that combined features of the behaviour and severity-based scales with the visual analogue scale. When tested on 166 different owners, 98% thought it was easy to use and accurate in assessing their dog's pruritus level. In 44 dogs, independent scores obtained by two owners were highly correlated (R = 0.8; P < 0.0001), confirming the scale's repeatability. The new scale proved to be an easy and repeatable method for owners to determine the severity of pruritus in their dog.

Requirement for additional treatment for dogs with atopic dermatitis undergoing allergen-specific immunotherapy.

Allergen-specific immunotherapy (ASIT) is one of the main treatments for atopic dermatitis in dogs, but it often requires additional treatments such as antibacterial and antifungal therapy for secondary bacterial and yeast infections, or antipruritic drugs to control the clinical signs or treat the adverse effects of the immunotherapy. Twenty-seven dogs enrolled in a study of ASIT were clinically assessed four times over a period of nine months; their requirement for treatment for secondary bacterial and yeast infections, for the administration of glucocorticoids as additional antipruritic therapy, and for the treatment of any adverse effects of the ASIT were evaluated. Twenty (74 per cent) of the dogs were treated for superficial bacterial pyoderma, 18 (66.6 per cent) required treatment for Malassezia species dermatitis on one or more occasions, eight (29.6 per cent) required treatment for otitis externa due to Malassezia species or bacteria, and eight required glucocorticoids to control their clinical signs. Five (18.5 per cent) of the dogs experienced adverse effects due to the ASIT and two required treatment with antihistamines (H1 receptor antagonists) in order to continue with the ASIT.

Survey of the prevalence, diagnosis and treatment of dermatological conditions in small animals in general practice.

A survey was made of the prevalence, diagnosis and treatment of dermatological conditions in small animals in general practice in the UK. Out of 3707 small animal consultations in general practice that were observed and recorded, 795 (21.4 per cent) involved animals that had a dermatological problem. In dogs and exotic species, pruritus was the most common presenting sign, accounting for 30 to 40 per cent of the dermatological consultations. In cats, cutaneous swellings were the most common presentation (36 per cent). A diagnosis or recommendation for treatment was made on the basis of the presenting clinical signs and physical examination alone in 576 (72 per cent) of the cases, and various diagnostic tests were performed in the other cases. In dogs, parasitic infestations, bacterial infections and neoplasia accounted for the majority of the diagnoses. In cats, parasites and bacterial infections were the most common. In exotic species, parasites accounted for over 80 per cent of the dermatological diagnoses. In dogs, the most common final diagnoses were otitis, pyoderma, anal sac impaction, flea infestation and atopic dermatitis. In cats, abscesses, flea infestation, and otitis were the most common diagnoses. In exotic species, the most common diagnosis was an unspecified mite infestation. Systemic antibiotics were prescribed in 196 cases (25 per cent), systemic glucocorticoids were prescribed in 162 cases (20 per cent) and treatment with an ectoparasiticide was prescribed in 167 cases (21 per cent).

Dermatitis and lymphadenitis resembling juvenile cellulitis in a four-year-old dog.

A four-year-old, entire male toy poodle was presented with a two-and-a-half-week history of ocular discharge progressing to periorbital alopecia, depigmentation, alopecia and ulceration around the muzzle. There was also a haemorrhagic discharge from the ears, pyrexia, lethargy and generalised lymphadenopathy. The clinical, cytological, bacteriological and histopathological findings were consistent with a diagnosis of dermatitis resembling juvenile cellulitis in an adult dog. Glucocorticoid therapy led to rapid resolution of the clinical signs and the dog has remained in remission for two years after cessation of treatment.

T-helper 1, T-helper 2 and immunosuppressive cytokines in canine atopic dermatitis.

Atopic dermatitis is a common inflammatory skin disease of humans and dogs. Human atopic dermatitis is associated with T-helper (Th) 2 type responses, although Th1 cytokines are present in chronic lesions. This study used semi-quantitative reverse transcriptase polymerase chain reactions to determine the expression of gene transcripts for immunosuppressive cytokines (transforming growth factor beta [TGFbeta] and interleukin [IL]-10), Th2 type cytokines (IL-4 and IL-6) and Th1 type cytokines (interferon gamma [IFNgamma], tumour necrosis factor alpha [TNFalpha], IL-2 and IL-12) in lesional atopic, non-lesional atopic and healthy canine skin. Canine atopic dermatitis was associated with over-expression of IL-4 mRNA and reduced transcription of TGFbeta compared to healthy skin (ANOVA, p<0.05). Higher levels of IFNgamma, TNFalpha and IL-2 mRNA were seen in lesional compared to non-lesional and healthy skin (p<0.05). There were no significant differences in IL-10, IL-6 or IL-12 transcription. This is the first report to demonstrate that canine atopic dermatitis is associated with over-production of IL-4 and under expression of TGFbeta.

Expression of Th1, Th2 and immunosuppressive cytokine gene transcripts in canine atopic dermatitis.

BACKGROUND: Atopic dermatitis is a common inflammatory skin disease of humans and dogs. Human atopic dermatitis is associated with Th2-type responses, although Th1 cytokines can be identified in chronic lesions. In contrast, tolerance to environmental allergens in healthy individuals is mediated by regulatory T cells. OBJECTIVE: This study examined the expression of the immunosuppressive cytokines TGF-beta and IL-10, the Th2-type cytokines IL-4 and IL-6, and the Th1-type cytokines IFN-gamma, TNF-alpha, IL-2, IL-12p35 and IL-12p40, in canine atopic dermatitis. MATERIALS AND METHODS: RNA was isolated from lesional atopic, non-lesional atopic and healthy canine skin samples. Semi-quantitative reverse transcriptase polymerase chain reactions (RT-PCRs) were carried out using specific primers and one-way analyses of variance used to compare cytokine expression in each group. RESULTS: Canine atopic dermatitis was associated with over-expression of IL-4 mRNA and reduced transcription of TGF-beta compared with healthy skin (P < 0.05). Higher levels of IFN-gamma, TNF-alpha and IL-2 mRNA were seen in lesional compared with non-lesional and healthy skin (P < 0.05). There were no significant differences in IL-10, IL-6, IL-12p35 or IL-12p40 transcription between the three groups. CONCLUSIONS: This is the first report to demonstrate that canine atopic dermatitis is associated with over-production of IL-4. Clinical tolerance in healthy individuals appears to be associated with TGF-beta, although it is unclear if this reflects an active mechanism or simply non-responsiveness of the immune system. Th1 cytokines may be induced by subsequent self-trauma and secondary infections in atopic skin. We believe that these results better characterize spontaneously occurring canine atopic dermatitis. We further propose that this should be investigated as a possible animal model of human atopic dermatitis.

Peripheral blood mononuclear cell responses to major and minor Dermatophagoides allergens in canine atopic dermatitis.

Atopic dermatitis is a chronic inflammatory and pruritic skin disease commonly seen in dogs and humans. Most cases involve hypersensitivity to the house dust mites (HDM) Dermatophagoides farinae and Dermatophagoides pteronyssinus. Human atopic dermatitis is associated with the HDM derived allergens Der f 1 and 2, and Der p 1 and 2. Serological data, however, suggest that a 98/104kD protein is the most important allergen in dogs with atopic dermatitis. The aim of this study was to characterise the specificity of circulating T-cells in canine atopic dermatitis for HDM derived allergens. Peripheral blood mononuclear cells (PBMCs) from dogs with atopic dermatitis that were skin test positive for D. farinae and D. pteronyssinus were cultured with crude extracts of D. farinae, D. pteronyssinus and D. microceras, a 98/104kD allergen purified from D. farinae, Der f 1 and Der f 2. There was significantly greater responsiveness of PBMCs to the D. farinae and D. pteronyssinus extracts compared to the D. microceras extract, and similarly to the purified 98/104kD allergen compared to Der f 1 and Der f 2. The close association between serological findings and PBMC proliferation implies that the 98/104kD HDM protein is a major target of immune recognition and that T-cells also participate in the pathogenesis of canine atopic dermatitis by supporting IgE production.

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.

Characterisation of major and minor Dermatophagoides allergens in canine atopic dermatitis.

Atopic dermatitis is a well-recognised chronic inflammatory skin disease of humans and dogs. Most atopic dogs are sensitised to Dermatophagoides mites. The aim of this study was to characterise allergens in different Dermatophagoides species using polyclonal and monoclonal antibodies to canine IgE. Western blots were prepared from crude extracts of D farinae, D pteronyssinus and D microceras, and purified group 1 and 2 allergens under reducing and non-reducing conditions. They were probed with sera from atopic (n = 33) and healthy (n = 27) dogs. There was no significant difference in the sensitivity or specificity between the polyclonal and monoclonal sera in detecting Dermatophagoides -specific IgE. Major allergens common to both D farinae and D pteronyssinus were detected at 97-98 kDa, 103-104 kDa and 134-139 kDa on both reducing and non-reducing blots. Major allergens at 84-85 kDa, 65-69 kDa and 44-45 kDa were only recognised on reducing blots, suggesting that these are fragments of the larger allergens. Only a few sera recognised group 1 or 2 allergens on blots of crude extracts or purified allergens. These results confirm that, in atopic dogs, high molecular weight allergens are the most important Dermatophagoides allergens, rather than the low molecular weight group 1 and 2 proteins.

The ACVD task force on canine atopic dermatitis (IV): environmental allergens.

Numerous environmental allergens have been incriminated in the pathogenesis of canine atopic dermatitis (AD). These include dust and storage mite antigens, house dust, pollens from grasses, trees and weeds, mould spores, epidermal antigens, insect antigens, and miscellaneous antigens such as kapok. In this paper, we review the literature concerning the allergens that have been reported to contribute to canine AD. We conclude that attempts to identify the relevant canine antigens in the past have been plagued by a lack of standardisation of extracts and techniques, and the presence of false-positive and -negative reactions in allergy tests. Until these problems are rectified, it is unlikely that we will be able to provide a list of major and minor antigens for dogs. Hence, we recommend that future studies should be aimed at determining the major patterns of reactivity and cross-reactivity to specific protein allergens within antigenic extracts using electrophoresis and immunoblotting techniques. Once this information becomes available, it may be possible to use a selection of genetically engineered, highly pure antigens for both diagnostic and therapeutic purposes in canine allergy investigations. The use of such antigens will allow standardisation of canine allergy testing and immunotherapy so that the reliability and efficacy of these procedures can be objectively assessed.

The ACVD task force on canine atopic dermatitis (V): biology and role of inflammatory cells in cutaneous allergic reactions.

Numerous inflammatory cells are thought to play a role in the pathogenesis of canine atopic dermatitis (AD) although, in the past, mast cells were considered the most important. However, evidence for this assumption is lacking. In this paper, we review the literature concerning the role of inflammatory cells in allergic reactions and conclude that a complex interplay exists between a wide variety of cell types. Thus, on the basis of the available evidence, the cells that appear to be the most important in the pathogenesis of canine AD are Langerhans' cells and dermal dendritic cells (both responsible for antigen processing and presentation), B-lymphocytes (responsible for reaginic antibody production), allergen-specific helper T-lymphocytes (responsible for cytokine production leading to activation of B-cells and other inflammatory cells) and mast cells (production of inflammatory mediators leading to inflammation).

The ACVD task force on canine atopic dermatitis (VI): IgE-induced immediate and late-phase reactions, two inflammatory sequences at sites of intradermal allergen injections.

Intradermal testing is a common diagnostic procedure used in the evaluation of dogs with suspected atopic dermatitis (AD). To do this, most investigators assess the appearance of wheals that develop at the sites of intradermal allergen injections. However, wheals are rarely seen in dogs with naturally occurring AD. Furthermore, infiltration of inflammatory cells into the injection sites can occur 6-24h later, a phenomenon known as the late-phase reaction. The histological appearance of these late-phase reactions closely approximates that seen in the natural disease, suggesting that they might be more relevant than the immediate reactions. In this paper, we review the literature on immediate and late-phase reactions and re-assess the evidence for using current intradermal testing procedures as a diagnostic test in dogs.