Prospective study of bacterial overgrowth syndrome in eight dogs.

Eight dogs with cutaneous lesions, clinical signs and cytological findings compatible with bacterial overgrowth syndrome were compared with four healthy dogs. The affected dogs were treated for 28 days with 30 mg/kg/day cephalexin. The results showed that the syndrome was a superficial cutaneous disorder characterised by marked pruritus, greasy seborrhoea, offensive odour, erythema, lichenification, hyperpigmentation, excoriations and alopecia involving principally the ventral aspect of the body, but no papules, pustules, epidermal collarettes or crusts; it was caused by overgrowths of Staphylococcus intermedius all over the body surface. Histopathological findings included a superficial, perivascular, hyperplastic and spongiotic dermatitis with a mixed inflammatory infiltrate, but no lesions suggestive of a true pyoderma. In the affected dogs, anti-staphylococcal immunoglobulin G levels were high, but anti-staphylococcal immunoglobulin E levels were low, suggesting that staphylococcal hypersensitivity is not the underlying pathogenic process. The antibiotic treatment improved the condition of all the dogs, but five of the eight had an underlying allergic skin disease.

The prevalence of immediate and delayed type hypersensitivity reactions to Microsporum canis antigens in cats.

Spontaneous recovery from Microsporum canis infections in cats is thought to be dependent on the development of a competent immune response. The purpose of this study was to determine the prevalence of positive delayed type hypersensitivity reactions in cats with and without dermatophytosis. Four groups of cats were intradermally skin tested with M canis extract and test sites were evaluated both subjectively and objectively at 0, 24 and 48 h after injection. Delayed intradermal testing (IDT) reactions were absent in cats not exposed to dermatophytosis (n=20); infected-recovered cats (n=38 culture negative lesion negative and n=43 lesion negative but culture positive) had significantly larger IDT reactions than unexposed cats and cats that were still actively infected (n=18). Based on the results of this study, IDT with M canis extract can be used to assess the cellular immune response of cats with dermatophytosis.

IgE reactivity and cross-reactivity to Japanese cedar (Cryptomeria japonica) and cypress (Chamaecyparis obtusa) pollen allergens in dogs with atopic dermatitis.

The natural occurrence of Japanese cedar (Cryptomeria japonica) pollinosis has been reported in dogs with atopic dermatitis. However, the reactivity to Japanese cypress (Chamaecyparis obtusa) pollen allergens in these dogs has not been reported. The present study was designed to investigate the reactivity to Japanese cypress pollen allergens in dogs sensitized to Japanese cedar pollen allergens. In 19 dogs with specific IgE to C. japonica pollen allergen, we measured the specific IgE to C. obtusa pollen allergen and examined the reactivity to the allergen by intradermal test. Of the 19 dogs, 18 had specific IgE to crude and purified major allergens (Cha o 1) of C. obtusa pollen. Most of the dogs showed a positive reaction to C. obtusa pollen allergens in the intradermal test. Allergenic cross-reactivity between Cha o 1 and Cry j 1 (a major allergen in C. japonica pollen) was observed by the ELISA inhibition method. Dogs sensitized to Japanese cedar pollen allergens demonstrate reactivity to Japanese cypress pollen allergens.

The ACVD task force on canine atopic dermatitis (III): the role of antibodies in canine atopic dermatitis.

Although an important pathogenic role for IgE is established in the case of allergic asthma and rhinitis in man, its role in atopic dermatitis is less clear. There are many studies where allergists and immunologists have provided evidence in favour of such a role, whereas dermatologists are less than convinced. In dogs, however, there is an abundance of clinical evidence implying that atopic dermatitis is antigen driven, and recent studies suggest that there may be a role for IgE, not only in the effector pathway, but also in antigen capture. Although an IgG response often accompanies an IgE response in dogs with atopic dermatitis, there is little evidence in support of a pathogenic role in respect of the former isotype.

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 (XII): the relationship of cutaneous infections to the pathogenesis and clinical course of canine atopic dermatitis.

Dogs and human beings with atopic dermatitis (AD) frequently exhibit concurrent skin infections with Staphylococcus sp. bacteria or Malassezia yeast, and treatment of such infections is an important facet of managing these patients. Staphylococci appear to colonize atopic skin readily, and bacterial products on the skin could augment cutaneous inflammation via immediate hypersensitivity responses to the bacteria, by superantigen-mediated lymphocyte activation, or other non-specific mechanisms. Similarly, skin colonization by Malassezia yeast could contribute to clinical signs of AD; yeast components could induce inflammation via non-specific mechanisms, such as alteration in mediator release, or via antigen-specific hypersensitivity reactions. Clinical and experimental evidence exists that secondary microbial infections can both initiate and perpetuate episodes of AD in dogs and humans, and could even participate in promotion of pro-allergic immunologic responses. Mechanistic details of these complex interactions are under extensive investigation in human beings; only a few observations have been extended to include dog with AD.

The ACVD task force on canine atopic dermatitis (XIV): clinical manifestations of canine atopic dermatitis.

Canine atopic diseases, including those with skin lesions, have been described for many years. Unfortunately, early descriptions often failed to establish definitive guidelines for considering a patient atopic, and criteria for diagnosing atopic dermatitis (AD) have varied from author to author. Larger case-series published from the 1960s to the 1980s suggested that the most common clinical manifestation of AD was pruritus, particularly of the face, ears, paws, extremities, and/or ventrum. It is not always clear that testing to eliminate other differential diagnoses was always carefully performed on patients in early reports; therefore, some descriptions could include patients affected with diseases other than or in addition to AD. Points of consensus regarding clinical manifestations of AD in case-series include the presence of pruritus beginning at a young age, possibly seasonally; and a prominent lesional involvement of the face, extremities, axillae or ventrum. Conflicting information on breed and sex predispositions is present, perhaps representing regional or temporal variability. Clinical reports vary, in regard to the description of lesions seen in dogs with AD. This reflects a possible confusion with lesions of secondary complications, and highlights the fact that the existence and nature of primary lesions of canine AD are not truly known.

The ACVD task force on canine atopic dermatitis (XV): fundamental concepts in clinical diagnosis.

The clinical signs of atopic dermatitis (AD) in man and in dogs are variable, and there is no single physical or historical feature that, if present, indicates the presence of AD. The initial diagnosis of AD is made clinically with the fulfillment of a combination of criteria that are strongly associated with the disease. Several schemes have been proposed in an attempt to define uniform clinical criteria for diagnosing canine AD, but no system is perfect. Once AD is considered as a possible diagnosis, other important differential diagnoses must be methodically eliminated from consideration. As a final step, once the clinician is certain that AD is probable, "allergy" tests may be conducted to provide additional evidence to "substantiate" the diagnosis. It is important to understand that allergy testing, in whatever form, is not appropriately used early in the patient evaluation as a screening test. Rather, it should be reserved, after a firm clinical diagnosis of AD has been made, to implement allergen avoidance schemes or to select allergens to be incorporated in immunotherapy formulations.

The ACVD task force on canine atopic dermatitis (XVI): laboratory evaluation of dogs with atopic dermatitis with serum-based "allergy" tests.

Serum-based in vitro "allergy tests" are commercially available to veterinarians, and are widely used in diagnostic evaluation of a canine atopic patient. Following initial clinical diagnosis, panels of allergen-specific IgE measurements may be performed in an attempt to identify to which allergens the atopic dog is hypersensitive. Methodology for these tests varies by laboratory; few critical studies have evaluated performance of these tests, and current inter-laboratory standardization and quality control measures are inadequate. Other areas where information is critically limited include the usefulness of these tests in diagnosis of food allergy, the effect of extrinsic factors such as season of the year on results, and the influence of corticosteroid treatment on test results. Allergen-specific IgE serological tests are never completely sensitive, nor completely specific. There is only partial correlation between the serum tests and intradermal testing; however, the significance of discrepant results is unknown and unstudied. Variation in test methodologies along with the absence of universal standardization and reporting procedures have created confusion, varying study results, and an inability to compare between studies performed by different investigators.

The ACVD task force on canine atopic dermatitis (XVII): intradermal testing.

Intradermal testing has been practiced for decades in human and veterinary medicine. The primary utility of intradermal testing is in the demonstration of IgE-mediated allergen hypersensitivity. The presence of a positive reaction on an intradermal test is not always indicative of allergy, as it may sometimes be an indication of sub-clinical hypersensitivity. Despite its widespread use by veterinary dermatologists, the usefulness of the intradermal test would be greatly enhanced by the use of standardized allergen extracts and homogeneous criteria for the interpretation of results. Irrespective of these shortcomings, intradermal testing is regarded as a valuable tool in the demonstration of allergen-specific hypersensitivity when performed according to accepted guidelines.

The ACVD task force on canine atopic dermatitis (XXI): antihistamine pharmacotherapy.

Antihistamines frequently are recommended by veterinary dermatologists for symptomatic treatment of pruritus associated with canine atopic dermatitis (AD), perhaps because of their moderate success in some human patients with AD. A critical review of the literature describing antihistamine use in canine AD reveals that the majority of published, peer-reviewed studies are open, uncontrolled or partially-controlled trials. Such studies vary widely in reported efficacy, from perhaps 0 to 75% of patients, even using the same drug. The few blinded placebo-controlled trials available have failed to confirm efficacy of these drugs to relieve the pruritus of canine AD. Some studies indicate that synergistic effects could occur with concurrent use of essential fatty acid supplements. Consequently, at the time of this writing, there is insufficient evidence to conclude for or against the efficacy of antihistamines for treatment of canine AD. Additional blinded, randomized and controlled trials with larger numbers of patients are necessary to establish which of the antihistamine drugs currently available, if any, are truly efficacious for canine AD. Nevertheless, present clinician consensus suggests that several different antihistamine drugs should be evaluated in sequence, for 7-14 days each, in canine patients with AD.

Commercial dry dog food in the north central United States is not contaminated by Dermatophagoides house dust mites.

Contamination of home-stored cereal grain food products with Dermatophagoides spp. house dust mites (HDM) was reported recently, along with anaphylaxis after consumption of these foods by dust mite-allergic people. We hypothesized that commercial dry dog food could become similarly contaminated, particularly if stored improperly, and could eventually contribute to allergic signs in dogs. Newly purchased bags of dry dog food (n = 30), from a variety of sources and manufacturers, and client samples of dry dog food (n = 50), stored under a variety of conditions, were obtained. Food samples were extracted in aqueous buffer, and extracts were assayed using ELISA for Dermatophagoides group II (Der II) allergen, as a marker for the presence of HDM. Der II allergen was not detected in any of the 30 newly purchased or 50 stored samples tested. Positive control samples consisting of house dust or dog food mixed with house dust, similarly extracted, and Dermatophagoides commercial allergen extract were positive for Der II in the same assay. We could find no evidence of HDM contamination in newly purchased or stored commercial dry dog food in the north central United States.

Analysis of the canine IgE-binding epitope on the major allergen (Cry j 1) of Japanese cedar pollen with anti-Cry j 1 monoclonal antibodies.

In our previous study [Immunology 91 (1997) 161] using monoclonal antibodies (mAbs) specific to Cry j 1, a major allergen in Japanese cedar (Cryptomeria japonica) pollen, we identified five independent epitopes (EP-1-EP-5) on the molecule and found that EP-1 and EP-5 are the predominant allergic epitopes for humans and monkeys, respectively. In this study, we analyzed the epitopes recognized by IgE in the sera of 10 dogs sensitive to C. japonica pollen allergen using an IgE-ELISA inhibition method with these mAbs. The IgE reaction patterns varied among dogs. In eight of the 10 dogs, IgE recognized EP-5 which is a predominant allergic epitope for monkeys with the pollenosis. In four dogs, IgE recognized EP-1 which is a predominant allergic epitope for human patients with the pollenosis. In three dogs, IgE recognized EP-4 which is a heat-stable epitope. EP-5 is a predominant allergic epitope for dogs and some, but not all, dogs have IgE reaction patterns to the epitopes similar to those of humans.

Experimental sensitization with Japanese cedar pollen in dogs.

Japanese cedar pollinosis is a type I allergic disease mediated by immunoglobulin E (IgE) antibodies to Japanese cedar (Cryptomeria japonica) pollen antigen (CPAg). By using 22 dogs consisting of 20 dogs aged 3 months and 2 dogs aged 3 years, immunization was performed by subcutaneous injections of CPAg with aluminum hydroxide gel. Variable levels of CPAg-specific IgE antibody response were detected in 21 of the 22 immunized dogs two weeks after the second immunization. This study provided an experimental sensitization system with CPAg in dogs, which will be useful for further immunological studies on Japanese cedar pollinosis.

In vivo and in vitro tests showing sensitization to Japanese cedar (Cryptomeria japonica) pollen allergen in atopic dogs.

Using both in vivo and in vitro tests, dogs with atopic dermatitis were examined for sensitization with Japanese cedar (Cryptomeria japonica, CJ) pollen allergen. Ten dogs with clinical manifestation of atopic dermatitis were shown to be sensitized to CJ pollen based on the results of intradermal skin test and serum antigen-specific IgE test. In vitro lymphocyte stimulation test showed blastogenic response after stimulation with crude antigen of CJ pollen in all of the 5 cases examined. The peripheral leukocytes showed increased histamine release after stimulation with crude antigen of CJ pollen in 2 cases examined. These data indicate that a proportion of dogs with atopic dermatitis is sensitized to CJ pollen in a cell-mediated manner and show immediate phase reaction of type I hypersensitivity.

IgE-reactivity to major Japanese cedar (Cryptomeria japonica) pollen allergens (Cry j 1 and Cry j 2) by ELISA in dogs with atopic dermatitis.

The present study investigated IgE-reactivity to two major Japanese cedar (Cryptomeria japonica, C. japonica) pollen allergens (Cry j 1 and Cry j 2) in dogs with atopic dermatitis by use of a fluorometric ELISA. The serum samples from 27 dogs that showed IgE-sensitivity to crude C. japonica pollen allergen by ELISA were tested for specific IgE to the two major allergens. All 27 dogs had anti-Cry j 1 IgE, and 10 (37%) had anti-Cry j 2 IgE. Inhibition of binding of dog specific IgE to crude C. japonica pollen allergen was carried out by addition of Cry j 1. When serum samples containing anti-Cry j 1 IgE but no anti-Cry j 2 IgE were incubated with Cry j 1, specific IgE binding to crude C. japonica pollen allergen was almost abolished. These findings suggest that Cry j 1 is a major allergen in dogs.

Domain mapping and comparative binding features of eight dog IgE-specific reagents in ELISA, immunoblots, and immunohistochemistry.

Eight dog IgE-specific reagents including monoclonal and polyclonal antibodies (Ab) and a cross-reactive alpha chain of the human high affinity IgE receptor were mapped to recombinant fragments of the second (IgEf2) and third/fourth (IgEf3/4) domains of the dog IgE heavy chain. In ELISA, five out of eight reagents reacted to solid-phase bound IgEf2, of which two polyclonal Ab bound in addition to IgEf3/4. All Ab which recognized at least one recombinant IgE fragment, also bound to IgE in ELISA, immunoblots, and immunohistochemistry. In contrast, only one monoclonal Ab, that did not bind to the recombinant IgE fragments, reacted with immunoblots of serum and immunohistochemistry. The alpha chain could only be applied to ELISA with serum IgE. Furthermore, there was a wide range of heat-lability of binding reactions. Comparative analysis of available dog IgE-specific reagents enables more in-depth functional studies on IgE-mediated phenomena in dogs, and helps to further establish the dog as an animal model for allergy research.

IgE sensitivity and cross-reactivity to crude and purified mite allergens (Der f 1, Der f 2, Der p 1, Der p 2) in atopic dogs sensitive to Dermatophagoides mite allergens.

The present study investigates IgE-reactivity to crude and purified mite allergens by intradermal skin test (IDST), Immunodot method, and ELISA in atopic dogs sensitive to mite allergens, as well as the allergenic cross-reactivity between Dermatophgoides (D) farinae (DF) and D. pteronyssinus (DP) in dogs by IgE-ELISA inhibition. IDST and Immunodot method for crude mite allergens were performed for atopic dogs and 16 atopic dogs showed sensitivity to mite allergens. Of the 16 dogs, all dogs had anti-DF IgE and 11 had anti-DP IgE. We measured specific IgE to purified major allergens (Der f 1, Der f 2, Der p 1, Der p 2). Of the 16 atopic dogs, six had anti-Der f 1 IgE and seven had anti-Der f 2 IgE. Similarly, of the 16 dogs, six had anti-Der p 1 IgE and seven had anti-Der p 2 IgE. However, eight dogs had no specific IgE to these mite allergens. These dogs may be sensitive to other major mite allergens except Der 1 and Der 2. In the dogs that had both anti-DF and DP IgE, IgE binding to DF was greatly inhibited by DP, and reciprocal inhibition was observed. Based on these data, it appears that there is a strong cross-reactivity between DF and DP in dogs. Similarly, a cross-reactivity between DF and DP in purified allergens was also observed. IDST and Immunodot method are useful methods for the diagnosis of atopic diseases in dogs, and ELISA is a useful method for further investigation of IgE-reactivity for the allergens.