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.     

Sensitivity patterns to house dust mites and forage mites in atopic dogs: 150 cases

This study investigated intradermal test reactions to extracts of six species of mites in 150 dogs with atopic dermatitis. At least one positive reaction was seen in 120 animals (80%). Dermatophagoides farinae attracted the highest number of positive reactions (108 dogs, 90% of dogs and 72% of atopic dogs showing positive reactions). Positive reactions to other mites were not uncommon, with many dogs testing positive for Dermatophagoides pteronyssinus (32% of dogs tested), Acarus siro (35%), Tyrophagus putrescentiae (30%), Glycyphagus domesticus (27%) and Lepidoglyphus destructor (23%). Sensitivity to D. farinae alone occurred commonly (57% of cases), but multiple sensitivities were seen frequently with the other mites. Cases of sensitivity to only one mite were also seen: D. pteronyssinus (five cases), T. putrescentiae (one case) and G. domesticus (one case). Further studies are needed to appreciate more clearly the precise role played by the different species of mite in canine atopic dermatitis.     

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.     

Effects of propofol-induced sedation on intradermal test reactions in dogs with atopic dermatitis

We compared the effect of propofol and saline control on intradermal test reactions in dogs with atopic dermatitis undergoing outpatient intradermal testing (IDT). Nineteen dogs were used in this clinical study. Patients were randomly allocated to receive either intravenous (IV) propofol or IV 0.9% saline, and IDT was performed on the right or left (randomized) lateral thorax. One investigator, unaware of the treatments, interpreted all IDT results. Injection sites were analysed using a subjective and objective method. A value of P or= 1+ on all dogs, significantly more positive sites were apparent during propofol sedation than during saline administration. In addition, the greater number of individual dogs experiencing more positive reactions >or= 1+ during propofol sedation was significant. When subjectively analysing reactions >or= 2+, the greater number of positive reactions and the greater number of dogs with more positive reactions observed during propofol treatment was not significantly different from the saline control. When analysed objectively, the greater number of positive reactions observed during propofol sedation was not significant. A greater number of dogs had higher subjective scores and larger objective measurements during propofol sedation compared with saline administration. In summary, propofol sedation was associated with an overall greater number of positive IDT reactions compared with the saline control. Although not always significant, this difference should be considered when choosing propofol for skin testing dogs with atopic dermatitis.     

Atopy patch test reactions in high-IgE beagles to different sources and concentrations of house dust mites

Protocols for atopy patch testing (APT) were evaluated on six high-IgE dogs sensitized to house dust mites (HDM) using various concentrations and sources of HDM. Two sources of HDM were compared: Heska slurry and four concentrations of Greer HDM. Saline was used as a negative control. Patches were removed after 48 h and the sites evaluated at 0, 6, 24, 48, 72 and 96 h for erythema, macules, papules and pustules. Each sign was scored from 0 to 3 (0 = absent and 3 = severe). Total score was used for analysis. Mean total scores significantly increased for both Greer and Heska HDMs from 6 h, peaking at 48 h for G100 (100 mg mL(-1)), G300 and G668, and at 72 h for Heska and G31.25. Across all times, Heska HDM scores were significantly higher than those of G31.25 with the largest difference at 96 h. Heska scores, however, were significantly lower than those of other Greer concentrations (G100, G300 and G668) particularly at 96 h. No reactions were noted at saline sites. It is concluded that Greer-HDM at 100 mg mL(-1) is the most suitable concentration for APT in dogs because it induces reactions comparable if not higher than more concentrated HDM preparations.     

Quantitation of house dust mites and house dust mite allergens in the microenvironment of dogs

OBJECTIVE: To quantitate the density of Dermatophagoides farinae and D pteronyssinus and concentrations of house dust mite (HDM) allergens (Der f 1, Der p 1, and Group 2 allergens) in the indoor microenvironment of dogs. Sample Population-50 homes in Columbus, Ohio. PROCEDURES: n each home, samples of dust were collected from 3 locations in which dogs spent most time. Whenever possible, the species of mites collected was identified. Mite density (mites/g of dust) was assessed, and allergen concentrations were assayed by standardized ELISAs. Relative humidity and temperature in each home were monitored during a 5-day period. Characteristics of homes and sample sources were evaluated. RESULTS: Dust samples from all 50 homes contained > or = 1 HDM allergen; Der f 1 and Der p 1 were detected in 100 and 74% of homes, respectively. Fifteen homes had HDMs; compared with D pteronyssinus, D farinae was found more commonly (14/15 homes) and at a higher density. Basements, homes without central air-conditioning, and dog beds that were > or = 1 year old had high HDM allergen concentrations. Homes with > or = 2 microg of Der f 1 or Group 2 allergens/g of dust or > or = 100 mites/g of dust were significantly more likely to have a maximum relative humidity > or = 75%. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate the presence of HDMs and HDM allergens in the specific microenvironment of dogs in homes. Factors associated with high levels of exposure were identified, which may be associated with increased risk for sensitization and development of atopic diseases.     

Quantitation of house dust mites and house dust mite allergens in the microenvironment of dogs

OBJECTIVE: To quantitate the density of Dermatophagoides farinae and D pteronyssinus and concentrations of house dust mite (HDM) allergens (Der f 1, Der p 1, and Group 2 allergens) in the indoor microenvironment of dogs. SAMPLE POPULATION: 50 homes in Columbus, Ohio. PROCEDURES: In each home, samples of dust were collected from 3 locations in which dogs spent most time. Whenever possible, the species of mites collected was identified. Mite density (mites/g of dust) was assessed, and allergen concentrations were assayed by standardized ELISAs. Relative humidity and temperature in each home were monitored during a 5-day period. Characteristics of homes and sample sources were evaluated. RESULTS: Dust samples from all 50 homes contained > or = 1 HDM allergen; Der f 1 and Der p 1 were detected in 100 and 74% of homes, respectively. Fifteen homes had HDMs; compared with D pteronyssinus, D farinae was found more commonly (14/15 homes) and at a higher density. Basements, homes without central air-conditioning, and dog beds that were > or = 1 year old had high HDM allergen concentrations. Homes with > or = 2 microg of Der f 1 or Group 2 allergens/g of dust or > or = 100 mites/g of dust were significantly more likely to have a maximum relative humidity > or = 75%. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated the presence of HDMs and HDM allergens in the specific microenvironment of dogs in homes. Factors associated with high levels of exposure were identified, which may be associated with increased risk for sensitization and development of atopic diseases.     

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.     

Pilot investigation of a model for canine atopic dermatitis: environmental house dust mite challenge of high-IgE-producing beagles, mite hypersensitive dogs with atopic dermatitis and normal dogs

Although canine atopic dermatitis (cAD) is common, few models are available. The aim of this study was to evaluate high-IgE beagles epicutaneously sensitized to house dust mite (HDM) as a possible model for cAD. Six high-IgE beagles were environmentally challenged with HDM using various doses and protocols. Similar challenge protocols were used in positive and negative control dogs: three dogs with naturally occurring cAD and positive intradermal skin test (IDT) to HDM and three normal dogs without history of skin disease and negative IDT to HDM. All high-IgE beagles and all atopic dogs developed severe cutaneous lesions and pruritus after challenge. Lesions were erythematous papules and macules in contact areas such as face, ears, ventral abdomen, groin, axillae and feet. They were first visible after 6 h and increased in severity over time. No normal dog developed pruritus or lesions. Biopsies of representative lesions in the high-IgE beagles were taken for histopathology and immunohistochemistry. There was superficial perivascular dermatitis with mononuclear infiltrates and spongiosis. Lymphocytes and eosinophils accumulated in small epidermal micro-abscesses with hyperplasia of epidermal IgE-bearing dendritic cells. These findings suggest that this colony of high-IgE beagles develops a dermatitis that clinically, histopathologically and immunologically resembles the naturally occurring canine disease. It is also concluded that this modality of challenge is not irritating to normal dogs but induces flare-ups in hypersensitive atopic dogs.     

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.     

Tolerability and clinical efficacy of oral immunotherapy with house dust mites in a model of canine atopic dermatitis: a pilot study

Atopic dermatitis (AD) is a chronic, life‐long disease. In humans, immunotherapy (IT) is the only treatment that can alter the course of AD. Oral IT is appealing owing to the ease of administration and the potential for increased compliance. The purposes of this study were to investigate the tolerability, clinical efficacy and effects on allergen‐specific IgE of oral IT using a canine AD model. Thirteen atopic beagles sensitized to house dust mites (HDMs) were randomly divided into two groups. One group received daily oral doses of HDMs while the other group received vehicle only for 7 months. The investigator evaluating the dogs was blinded to the allocation of treatments. Prior to and after 2 and 7 months of IT, dogs were challenged daily with HDMs for 3 days concurrently, and clinical signs were scored using a modified Canine Atopic Dermatitis Extent and Severity Index (CADESI). Prior to and at completion of oral IT, serum was collected for measurement of allergen‐specific IgE. Oral IT was well tolerated, and no adverse effects were noted. Analysis of variance showed no significant effect of time, group and group × time interaction for CADESI scores. In addition, there were no significant differences in allergen‐specific IgE levels. In conclusion, it appears that oral administration of HDMs is well tolerated in these atopic beagles but that this protocol was not sufficient to induce clinical improvement. Further, longer‐term studies will be necessary to explore the potential of oral IT in veterinary medicine.     

Determination of antigenic proteins of housedust mites in 90 dogs suffering from atopic dermatitis

Housedust mites, Dermatophagoides pteronyssinus (D. pteronyssinus) and Dermatophagoides farinae (D. farinae), are the important causative agents of allergic diseases in human and animals. By using 165 dogs suffering from atopic dermatitis (AD), serum levels of immunogloblin E (IgE) antibody against 25 kinds of allergen including housedust mites were determined. Housedust mites were the most frequent allergen against which 90 of the 165 allergic dogs (54.5%) by IMMUNODOT assay. With the further analysis of immunoblotting assay in the 90 dogs sensitized with housedust mites, antigenic proteins of housedust mites recognized by IgE antibodies were with the apparent molecular masses of 15, 76, 90, 98, and 170-kD. Among them, the 15-kD protein that might be identical to Group 2 antigens (Der f2, Der p2) was prominently observed (52/90). This study indicates that about a half of dogs with AD were sensitized to housedust mites, suggesting that Group 2 antigens of housedust mites may be a major allergen in canine AD.     

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.     

Presence and density of domestic mites in the microenvironment of mite‐sensitive dogs with atopic dermatitis

This study was designed to investigate the presence and density of domestic mites (DMs) in households with atopic dogs sensitive to these mites (group A; n = 20), in households with clinically healthy, nonatopic dogs (group B; n = 20) and in households without pets (group C; n = 25). Dust samples were vacuum‐collected from the owner mattress (all groups) and dog sleeping area (groups A and B) or living room couch (group C) on four consecutive occasions, reflecting the four seasons of the year. DMs were found, at least once, in 19 of 20 (95%) group A, 13 of 20 (65%) group B and 21 of 25 (84%) group C households. DM numbers per gram of dust were 0–159 (median, 8.8), 0–302 (median, 3) and 0–1473 (median, 6.9) for group A, B and C, respectively. Dermatophagoides farinae predominated in all groups, since it was identified in 60% of group A, 40% of group B and 64% of group C households. Dermatophagoides pteronyssinus was found in 45%, 35% and 48% of households, in group A, B and C, respectively. No differences were found between households with (groups A and B) or without dogs (group C). When considering both sampling sites together, frequency of DM recovery was higher in group A than in group B (P = 0.044). Also, both mite frequency (P = 0.011) and density (P = 0.015) in dog sleeping area were higher in group A than in group B. In conclusion, presence and density of DMs is higher in the microenvironment of mite‐sensitive dogs with atopic dermatitis than in that of clinically healthy nonatopic dogs.     

Sulphido-leukotriene production from peripheral leukocytes and skin in clinically normal dogs and house dust mite positive atopic dogs

Pathogenesis of canine atopy has not been completely elucidated. In humans, sulphido-leukotrienes (s-LT) play a role in atopy, and increased production of s-LT occurs in the skin and peripheral leukocytes after allergen challenge. The study population included 16 clinically normal and 13 atopic dogs. All atopic dogs had in common a positive reaction (4+) to the intradermal injection of house dust mite (allergen of reference). Blood samples and skin biopsies were collected. Sulphido-LT synthesis by peripheral leukocytes after stimulation was measured, and no statistically significant difference was found between clinically normal and atopic dogs. Sulphido-LT concentrations in skin samples from stimulated and unstimulated sites were measured, and no statistically significant difference was detected between clinically normal and atopic dogs or between lesional and nonlesional skin within the atopic group. Clinical signs of atopic dogs were graded by owners and no correlation was found between their severity and cutaneous concentrations of s-LT. In this study there was no increase in s-LT synthesis in atopic 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.     

Comparison of subjective and objective intradermal allergy test scoring methods in dogs with atopic dermatitis

An intradermal allergy test (IDT) is an important diagnostic tool for identifying offending allergens in canine atopic dermatitis. No standardized method of scoring an IDT has been described. The purpose of this study was to determine whether there is a correlation between a conventional, subjective IDT scoring method based on perceived wheal diameter, erythema, and turgor (0-4+) and an objective scoring method based on measuring wheal diameter alone. Thirty-four atopic dogs were skin tested with 68 different allergens. All skin tests were performed according to standard procedures, and any IDT score ≥2+ was considered clinically significant. When the subjective IDT scores were compared with the objective IDT scores in all dogs, there was a moderate level of correlation overall (r=0.457; P <0.0001). The highest level of agreement between subjective and objective scores was noted with the reactions assigned subjective scores of "0" and "2+." Overall, there was a slight level of agreement between subjective and objective scores based on clinical significance (i.e., subjective scores ≥2+; κ=0.20; P <0.0001). In conclusion, the authors believe that the objective scoring method used in this study may provide a point of reference for inexperienced individuals (dermatology residents, veterinarians, technicians) when learning to grade an IDT.     

Intradermal skin test reactivity to histamine and substance P is blunted in dogs with atopic dermatitis

Skin reactivity to intradermal injections (0.1, 0.5 and 1 nm ) of substance P (SP) was evaluated in 20 clinically normal dogs and 20 dogs with atopic dermatitis (AD). Saline and histamine were used as negative and positive controls, respectively. Wheal diameters were measured. Reactions were evaluated for erythema and induration and a subjective score, on a scale from 0 to 4+, was given. Evaluations were performed at 3, 5, 10, 15 and 30 min after the injections. Wheal diameters for histamine and SP injections were significantly smaller in dogs with AD compared with clinically normal dogs. In both groups, reactions to the various concentrations of SP were not significantly different from each other and were always smaller than histamine reactions. Erythema was not seen with SP injections. In addition, subjective scores for SP injections were significantly lower in dogs with AD compared with controls. The results of this study are similar to those reported in human medicine, where a role for SP in AD is proposed and desensitization of receptors to both SP and histamine is hypothesized. Further studies are needed to investigate the role of SP in the pathogenesis of canine AD.