An open prospective investigation into aetiology in a group of cats with suspected allergic skin disease

Abstract This prospective study evaluated the cause(s) of dermatitis in a series of cats with signs suggestive of allergic skin disease. Twenty cases completed the díagnostic evaluation, which included intradermal skin testing, a rigorous flea-control programme, and a 4-month stabilization period on a restricted protein source commercial diet, followed by rechallenge with the cat's original diet. The most common final díagnoses included flea allergic dermatitis (seven cases), and flea allergic dermatitis together with atopy (seven cases). Three additional cases which did not complete the study were also considered to be atopic. No cases were considered to be primarily associated with food hypersensitivity, an observation supporting previous data indicating this to be a rare cause of allergic skin disease in the cat. These observations emphasize the value of a rigorous flea-control programme as part of the management of many cases of feline allergic dermatitis. Résumé Une étude étiologique prospective a été réalisée dans une population de chats suspects de dermites allergiques. Des tests cutanés intradermiques ont été réalisés ainsi qu'un contrôle antipuce rigoureux et un régime d'élimination, faisant appel à une alimentation du commerce restreinte en protéines pendant 4 mois, suivi par une réintroduction de l'alimentation initiale du chat. Le díagnostic le plus fréquent est la Dermite par Allergie à la Piqûres de Puce (DAPP) (7 cas), une DAPP associée à une atopie (7 cas). Trois cas supplémentaires sont atopiques. Aucun cas n'est en rapport avec seulement une allergie alimentaire. Cette observation montre que l'allergie alimentaire est une cause rare de dermite allergique chez le chat. Ces observations confirment par ailleurs l'intérêt d'un contrôle antipuce rigoureux dans la gestion thérapeutique des dermites allergiques du chat. [O'Dair, H.A., Markwell, P.J., Maskell, I.E. An open prospective investigation into aetiology in a group of cats with suspected allergic skin disease (Etude étiologique prospective ouverte dans une population de chats suspects de dermite allergiques). Veterinary Dermatology 1996; 7 : 193–202.] Resumen Este estudio prospective evalúa la(s) causa(s) de dermatitis en un grupo de gatos con sintomas sugestivos de dermatosis alérgica. Se evaluó el díagnóstico de veinte casos, incluyendo pruebas cutáneas intradérmicas, programa riguroso de control de pulgas y un periodo de cuatro meses de estabilización con una dieta comercial con fuente de proteina restringida, seguido de una re-exposición a la dieta original del gato. El díagnóstico final más frecuente fue de dermatitis alérgica a las pulgas (siete casos) y dermatitis alérgica a las pulgas con atopia (siete casos). Tres casos más que no completaron el estudio fueron también considerados atópicos. Ninguno de los casos fue considerado estar principalmente asociado a una hipersensibilidad alimentaria, lo que apoya hallazgos previos indicativos de que este tipo de hipersensibilidad es poco frecuente en el gato. Estos hallazgos resaltan la importancia de un programa rigurosos de control de pulgas en el protocolo de manejo de muchos casos de dermatitis alérgica felina. [O'Dair, H.A., Markwell, P.J., Maskell, I.E. An open prospective investigation into aetiology in a group of cats with suspected allergic skin disease (Investigacion prospectiva abierta de la etiologia en un grupo de gatos sospechosos de dermatosis alérgica). Veterinary Dermatology 1996; 7 : 193–202.] Zusammenfassung Diese prospektive Untersuchung wertete die Fälle von Dermatitis bei einer Reihe von Katzen aus, die Symptome aufwiesen, welche auf eine allergische Hautkrankheit deuteten. Zwanzig Fälle wiesen eine vollständige díagnostische Untersuchung äuf, die intradermale Hauttests, striktes Flohbekämpfungsprogramm und eine viermonatige Stabilisierungsphase mit einer kommerziellen Diät mit begrenzten Eiweißquellen, gefolgt von einer Provokation mit dem bisher üblichen Katzenfutter, beinhaltete. Die häufigste endgültige Diagnose bestand in Flohbißdermatitis (sieben Fälle) und Flohbißdermatitis zusammen mit Atopie (sieben Fälle). Drei weitere Fälle durchliefen die Studie nicht vollständig, wurden aber als atopisch angesehen. Kein Fall wurde primär in Verbindug mit Futtermittelhypersensibilität gesehen, eine Beobachtung, die frühere Daten unterstützt, die dies als seltene Ursache bei allergischen Hautkrankheiten der Katze nennt. Diese Beobachtungen betonen die Bedeutung des genauen Flohbekämpfungsprogramms als Teil des Management vieler Fälle von allergischen Hautkrankheiten bei der Katze. [O'Dair, H.A., Markwell, P.J., Maskell, I.E. An open prospective investigation into aetiology in a group of cats with suspected allergic skin disease (Offene prospektive Untersuchung über die Ätiologie bei einer Gruppe von Katzen mit Verdacht auf allergische Hautkrankheiten). Veterinary Dermatology 1996; 7 : 193–202.]     

Measurement of serum immunoglobulin E (IgE) specific for house dust mite antigens in normal cats and cats with allergic skin disease

The purpose of this study was to determine whether cats with allergic skin disease have significant concentrations of serum Immunoglobulin E (IgE) specific for antigens derived from the house dust mites (HDM) Dermatophagoides farinae (DF) and Dermatophagoides pteronyssinus (DP). Enzyme-linked immunosorbent assays (ELISA) were developed for this purpose. Binding of serum allergen-specific IgE was detected via the use of biotinylated Fc-epsilon receptor alpha chain protein (FcvarepsilonRIalpha). Following optimisation of the assay, serum samples from 59 cats with allergic skin disease and 54 clinically normal cats were screened. Results were expressed as ELISA units per ml (EU/ml) compared to a standard curve. Serological findings were correlated with the clinical presentation of affected cats. Cats with symptoms of feline allergic skin disease were grouped as follows: self-induced alopecia without lesions (group 1), papulocrusting dermatitis (group 2), eosinophilic granuloma complex (group 3), papular/ulcerative dermatitis of head and neck/facial dermatitis (group 4), and a combination of symptoms (group 5). Control normal cats comprised the final group (group 6). The Kruskal-Wallis test was used for statistical analysis. There was no significant difference between groups for DF- and DP-specific IgE concentrations with a p-value of 0.875 and 0.705, respectively. Although the FcvarepsilonRIalpha-based ELISA was able to detect house dust mite-specific feline IgE, the presence of this allergen-specific IgE correlates poorly with the presence of clinical manifestations of allergic skin disease. The results of this study question the clinical relevance of house dust mite-specific IgE in feline allergic skin disease.     

Prevalence of IgG antibodies to Encephalitozoon cuniculi and Toxoplasma gondii in cats with and without chronic kidney disease from Virginia

Kidney disease is a common and serious condition in domestic cats. There are numerous causes of kidney disease including parasitic infection. Encephalitozoon cuniculi is a microsporidian parasite that develops in the kidneys of rabbits and causes chronic renal disease. Little has been reported concerning E. cuniculi in cats and no serological studies on this parasite in cats have been conducted in the United States to date. The present study explored the possibility that E. cuniculi is an unrecognized contributor to the high prevalence of kidney disease observed in cats. A serological survey was conducted to determine the prevalence of IgG antibodies to spores of E. cuniculi in cats with and without a diagnosis of chronic kidney disease (CKD) according to the International Renal Interest Society (IRIS) staging system. Likewise, samples were examined for IgG antibodies to Toxoplasma gondii, a common well studied protozoan of cats. Plasma and sera were obtained from 232 feline patients at the Virginia-Maryland Regional College of Veterinary Medicine teaching hospital. With the investigators blinded to the renal status of test subjects, samples were screened via indirect immunofluorescent antibody assay (IFA). Thirty-six of the 232 cats met the IRIS staging system criteria for CKD. Antibodies to E. cuniculi were found in 15 of the 232 samples, which included 4 of the 36 cats with CKD. Sera from cats serologically positive to E. cuniculi did not react to spores of E. intestinalis or E. hellem when examined in the IFA. Antibodies to T. gondii were found in 63 of the 232 samples, which included 10 of the 36 cats with CKD. The prevalence of antibodies in cats with CKD to either protozoan was not significantly different (P>0.05) from the cats without CKD in the study. Collectively the results do not support the hypothesis that either E. cuniculi or T. gondii play a significant etiologic role in the occurrence or progression of CKD in cats.     

IgE and IgG antibodies in skin allergy of the horse

In horses, allergies have been characterized by clinical signs and/or intradermal (i.d.) allergen testing. Our aim was to find the first direct evidence that immunoglobulin E (IgE) mediates equine allergy. In addition, we tested the hypothesis that immediate skin reactions in horses can also be mediated by IgG. Anti-IgE affinity columns were used to purify IgE from serum of one healthy horse and three horses affected with summer eczema, an allergic dermatitis which is believed to be induced by Culicoides midges. A modified Prausnitz-Küstner experiment was performed in four clinical healthy horses by i.d. injection of the purified serum IgE antibodies. The following day, Culicoides allergen was injected at the same sites. Skin reactions were not observed in response to allergen alone, and in two horses after stimulation at any previous IgE injection site. However, the other two horses showed an immediate skin reaction at the previous injection sites of IgE obtained from allergic horses. In addition, purified monoclonal antibodies to various equine immunoglobulin isotypes were injected i.d. into six healthy horses. Immediate skin reactions were observed in response to anti-IgE (6/6 horses) and anti-IgG(T) injections (5/6 horses). The specificities of both antibodies for IgE and IgG(T), respectively, were confirmed by enzyme linked immunosorbent assays. The results provide the first direct evidence that IgE mediates classical Type-I allergy in horses and plays a major role in the pathogenesis of summer eczema. The data also suggest that IgG(T) can bind to skin mast cells and might contribute to clinical allergy.     

The immunology of allergic skin disease

The major immunological pathways that lead to the development of allergic skin disorders are described. The current and prospective trends in therapy are discussed in relationship to the stage in the pathogenesis at which they are effective. Résumé. Les voies immunologiques principales qui mènent à l'apparition d'affections dermiques causées par une allergie sont décrites. Les tendances thérapeutiques actuelles et futures sont examinées en fonction du stade pathogénique où elles sont efficaces. Zusammenfassung. Die immunologischen Hauptwege, die zur Entstehung von allergischen Hautstörungen führen, werden beschrieben. Die gegenwärtigen und vorauszusehenden Ent-wicklungen der Therapie werden unter Berücksichtigung des Stadiums in der Pathogenese besprochen, in dem sie wirksam werden.     

Interleukin 4-producing CD4+ T cells in the skin of cats with allergic dermatitis

Lesional skin of cats with allergic dermatitis has a cellular infiltrate and a CD4/CD8 ratio comparable to that in humans with atopic dermatitis. CD4+ helper T cells and in particular cells belonging to the Th2 subset play an important role in disease pathogenesis in humans. We investigated the cytokine pattern of CD4+ T cells in situ, with special emphasis on the putative presence of cells producing interleukin 4 (IL4), in cats with allergic dermatitis. Immunohistochemical procedures were used to determine that CD4+ T cells in lesional and nonlesional skin of cats with allergic dermatitis can produce IL4, as occurs in humans. Lesional and nonlesional skin of cats with allergic dermatitis had significantly more IL4+ T cells (P = 0.001) than did skin of healthy control cats. Double staining indicated that all IL4+ cells were positive for pan-T or CD4 markers. Double labeling for mast cell chymase and IL4 stained primarily different cells. Western blotting demonstrated cross-reactivity between the antibody against human IL4 and a feline recombinant IL4. These results indicate that IL4 is primarily produced by CD4+ T cells and is also present in clinically uninvolved skin, indicating a role in the pathogenesis of allergic dermatitis in cats.     

Advances in methodology for diagnosis of allergic skin disease

Advantages of IDST for diagnosis of atopy and selection of antigens for hyposensitization include the following: 1. The test is widely accepted by clients. 2. The clinician can select individual test allergens based on the patient history and geographic location. 3. It has been the standard for diagnosing atopy in the dog for more than 40 years. Disadvantages of IDST include the following: 1. The test should be performed on a regular basis to maintain reliability. 2. Interpretation of test results is subjective. 3. The test is not standardized on the basis of the examiner, source of the allergen, or reproducibility. 4. There is occasional difficulty in performing the test (e.g., need for sedation). 5. Anaphylaxis is a potential risk. 6. A significant amount of office time is needed to perform the test. 7. Condition of the patient's skin (e.g., lichenification, hyperpigmentation, pyoderma) may preclude its use. 8. There is a possibility of failure to test for appropriate allergens. 9. There may be false-positive and false-negative reactions. 10. Other medications can interfere with the test (e.g., antihistamines, corticosteroids). Advantages of in vitro testing for diagnosis of atopy and selecting antigens for hyposensitization include the following.(ABSTRACT TRUNCATED AT 250 WORDS)     

Adverse events in 50 cats with allergic dermatitis receiving ciclosporin

Ciclosporin is an immunosuppressive drug that has been used to treat allergies and other immune-mediated diseases in cats, dogs and humans. Information about the adverse effects of ciclosporin in cats has been limited to smaller studies and case reports. Adverse effects in dogs are mainly gastrointestinal in nature, but humans can also experience hypertension and altered renal function. The aim of this retrospective case series study was to document the occurrence and clinical appearance of adverse events in cats receiving ciclosporin to treat allergic skin disease. The medical records of 50 cats with allergic dermatitis treated with oral ciclosporin (1.9-7.3 mg/kg/day) were reviewed. Adverse events occurred in 66% (33 cats). Adverse events likely to be associated with ciclosporin included the following: vomiting or diarrhoea within 1-8 weeks of receiving ciclosporin (24%), weight loss (16%), anorexia and subsequent hepatic lipidosis (2%) and gingival hyperplasia (2%). Other adverse events less likely to be associated with ciclosporin therapy included the following: weight gain (14%), dental tartar and gingivitis (10%), otitis (4%), chronic diarrhoea (4%), inflammatory bowel disease with indolent gastrointestinal lymphoma (2%), urinary tract infection (2%), cataract (2%), elevated liver enzymes (2%), hyperthyroidism and renal failure (2%) and transient inappropriate urination (2%). Some cats experienced multiple adverse events. Case-control studies are needed to prove cause and effect of ciclosporin with regard to these adverse events.     

Pilot study: prevalence of positive aeroallergen reactions in 10 cats with small-airway disease without concurrent skin disease

The purpose of this study was to determine the prevalence of positive allergen reactions in cats with small-airway disease (i.e. 'feline asthma', 'feline allergic bronchitis', 'feline bronchial disease'). Intradermal skin tests (IDT) and serum immunoglobulin E (IgE) tests were performed in 10 cats with idiopathic small-airway disease and in 10 normal cats without a history of respiratory disease. None of the cats had a history of skin disease or clinical signs of skin disease at the time of testing. Significantly more individual positive allergen reactions were found on serum IgE tests than on IDT in both groups of cats. Affected cats had significantly more individual positive allergen reactions on both tests than unaffected cats. Both IDT and serum IgE tests resulted in more individual positive allergen reactions to weeds, trees, grasses, and/or moulds in affected cats than in normal cats. Significantly more positive allergen reactions to house dust mites were found in affected compared to non-affected cats by IDT but not by serum IgE testing. One unexpected obstacle to inclusion of more affected cats in the study was the concurrent presence or history of suspect or known allergic skin disease. Concurrent allergic skin disease has not been reported in association with small-airway disease in cats. The increased prevalence of individual positive allergen reactions in affected cats may be due to increased immunological reactivity in these cats. Further studies are needed to answer this question and to determine what role, if any, aeroallergens have in the pathogenesis of this complex feline disease.     

Malassezia spp. overgrowth in allergic cats

A series of 18 allergic cats with multifocal Malassezia spp. overgrowth is reported: atopic dermatitis was diagnosed in 16, an adverse food reaction in another and one was euthanized 2 months after diagnosis of Malassezia overgrowth. All the cats were otherwise healthy and those tested (16 out of 18) for feline leukaemia or feline immunodeficiency virus infections were all negative. At dermatological examination, multifocal alopecia, erythema, crusting and greasy adherent brownish scales were variably distributed on all cats. Cytological examination revealed Malassezia spp. overgrowth with/without bacterial infection in facial skin (n = 11), ventral neck (n = 6), abdomen (n = 6), ear canal (n = 4), chin (n = 2), ear pinnae (n = 2), interdigital (n = 1) and claw folds skin (n = 1). Moreover, in two cats Malassezia pachydermatis was isolated in fungal cultures from lesional skin. Azoles therapy alone was prescribed in seven, azoles and antibacterial therapy in eight and azoles with both antibacterial and anti-inflammatory therapy in three of the cats. After 3-4 weeks of treatment, substantial reduction of pruritus and skin lesions was observed in all 11 cats treated with a combined therapy and in five of seven treated solely with azoles. Malassezia spp. overgrowth may represent a secondary cutaneous problem in allergic cats particularly in those presented for dermatological examination displaying greasy adherent brownish scales. The favourable response to treatment with antifungal treatments alone suggests that, as in dogs, Malassezia spp. may be partly responsible for both pruritus and cutaneous lesions in allergic cats.     

Parasitic skin diseases in cats

Parasites are important causes of skin disease in cats. In this article 10 species of parasites (Table 1) will be discussed. In the United Kingdom, the flea is the most important single cause of skin disease in cats. The most common flea found is Ctenocephalides felis, with hedgehog, dog and rodent fleas being found occasionally.