J. Vet. Sci. (2002), 3(4), 335-341 J O U R N A L O F Veterinary Science Allergens Causing Atopic Diseases in Canine Hwa-Young Youn, Hyung-Seok Kang, Dong-Ha Bhang, Min-Kue Kim, Cheol-Yong Hwang* and Hong-Ryul Han Department of Internal Veterinary Medicine, College of Veterinary Medicine and School of Agricultural Biotechnology, Seoul National University, Seoul 151-742, Korea Received J une 18, 2002 / Accepted December 2, 2002 Abstract12) is one type of the allergy. In man, the term atopy is used to describe a triad of asthma, hay fever, and atopic dermatitis Canine atopic skin disease is se asonal or som etim es (AD). In pets, atopy historically described a pruritic dermatitis non-seasonal im m une-me diated skin disease w hich associated with the inhalation of pollen, fungal, or environ- occurs com monly in Kore a. The definite clinical sign mental allergens. However, in dog, the respiratory route of is system ic pruritus, e specially on periocular parts, exposure is the subject of investigation although the external ear, interdigit spaces and lateral flank. For exposure through the skin in man has reliable evidences[8, diagnosis of this derm atitis, com plete history taking 11]. Canine atopic dermatitis (AD) is a common skin disease follow ed by intraderm al skin test and serum in vitro in dogs[14, 17]. In dogs, atopy is considered to be an IgE test needs to be pe rform ed. Allergen selection for hereditary clinical hypersensitivity state or an hereditary, the diagnosis and treatm ent of atopic derm atitis reagin mediated hypersensitivity to inhalant allergens[26]. should be varied geographically. In this study, w ith But, no genetic markers have been found for the disease[10]. intraderm al skin te st(ID ST) the prevalence of atopic Among the four types of hypersensitivity, anaphylactic or disease and w hat allergens are involved in are immediate type Ⅰ hypersensitivity reactions are of importance researched. Allerge ns use d for IDST included 26 in relation to atopy[17]. In animals with atopy, exposure to allergen extracts from six alle rgen groups: grasses, an allergen causes production of Immunoglobulin E(IgE) trees, w eeds, m olds, epiderm al allergens and environ- and directed against that allergen; on subsequent exposure, m ental allergens. The num ber of allergens w as 42 in an allergic reaction occurs. Allergen specific IgE attaches to w hich the positive and negative controls are the surface of mast cell, thus causing it to degranulate and included. The m ost comm on positive allergen reaction release mediators of inflammation[1]. w as the house dust mite s on ID ST(22/35, 63%). The The breed predisposition for atopic disease has been othe r positive allergen reactions w ere to flea(3/35, mentioned in Lhasa apso, miniature schnauzer, pug, Sealyham 9%), m olds(1/35, 3%), house dusts(2/35, 6%), fe athers terrier, Scottish terrier, West Highland white terrier, the (1/35, 3%), cedar/juniper(1/35, 3%), tim othy grass(1/35, wire haired fox terrier, cairn terriers and the golden 3%) and dandelion(1/35, 3%). In this study, the m ost retriever[22, 23, 26] and Cocker spaniel, setters, Labrador prevalent allergen causing atopic dermatitis in dogs retrievers, and German shepherd dogs which are common in Korea w as the house dust mite s follow ed by the breeds in Korea have also been described[12, 25]. flea. The most common clinical signs include a history of seasonal or nonseasonal pruritus, otitis externa, recurrent Key w ords : canine atopic disease, intradermal skin test and chronic inflammatory dermatitis especially in the axillary, (IDST), allergens, house dust mites. inguinal, and flexor skin surfaces, r ecur rent bacterial infections, face rubbing and/or foot licking and chewing. But Introduction the signs of canine atopy are usually seasonal in the beginning, often become non-seasonal with time, and occasionally Allergy is an altered state of immune reactivity and atopy are non-seasonal from the start[17]. The allergens involved in the pathogenesis of canine atopy include house dust mites ＊Corresponding author: Cheol-Yong Hwang (HDM), house dust, molds, weeds, trees, grasses, epithelia and Department of Internal Veterinary Medicine, College of Veterinary arthropods[15, 19]. Some allergens are ubiquitous in the Medicine and School of Agricultural Biotechnology, Seoul National environment (e.g. house dust); however, many other clinically University, Seoul 151-742, Korea Tel : +82-2-880-8685, Fax : +82-2-880-8682 important allergens vary with respect to season, climate, E-mail : [email protected] and/or geographic region. What is important in one geographic 336 Hwa-Young Youn, Hyung-Seok Kang, Dong-Ha Bhang, Min-Kue Kim, Cheol-Yong Hwang and Hong-Ryul Han region or country, may not be important in another[14, 24]. D iagnostic Evaluation In Korea, house dust mite is known to be a common and In complete cases history and physical examination were important nonseasonal allergen in humans. This allergen is done in all 35 dogs. All of the pruritic dermatitis that could also the most common in dogs in most countries. But to date, mimic AD were excluded through multiple skin scrapings there are no informations on the prevalence of atopic for the detection of ectoparasites, skin smear for deep dermatitis and what allergen is most common in dogs in Korea. bacterial infection, culture and antibiotics susceptibility test. For the diagnosis and management of an atopic cases, a Food allergic dermatitis was ruled out on the base of dietary detailed history is the most important factor. For identifying restriction trial, of at least 4-week duration followed by the cause of canine atopic dermatitis, two major diagnostic provocative testing in all cases. In most of the cases, the methods have been developed[14, 15]. Both in vivo and in owners exhibited non-seasonal pruritus. vitro methods of allergy testing are available. In vitro testing involves immunoreactant measurement in serum in Intraderm al Skin Testing the allergic reaction. In vivo allergy testing involves the All of steroids, sedatives, immunosuppressants, antihis- induction of a small scale allergic reaction by the intentional tamines and tranquilizers were discontinued for at least 21 exposure of the patient to a minute amount of allergen. days before IDST[17]. A total of 40 aqueous allergenic Intradermal skin test (IDST), as an in vivo test, is still the extracts were selected for IDST that subsequently were gold standard most commonly used and the most reliable allocated into 6 groups (grass, trees, weeds, molds, epidermal methods. But several factors must be considered with false- allergens, environmental allergens). All the extracts were positive reactions to the IDST due to improper technique, obtained from Greer Lab (Lenoir, North Carolina, USA) and irritant test allergens, irritable skin (dermographism), cross- all allergens are aqueous solutions. All these allergens were reactivity among allergens and possible contamination with diluted at the concentration shown to be non-irritant when histamine-like substance in the extracts[15, 16]. False- tested in normal dogs (Table 1) following the indication of negative reaction to the IDST are more problematic and can Greer Lab. All extracts of the grass, trees, weeds were occur for the following reasons; poor injection technique, diluted at a strength of 1000PNU/ml. House dust and house degradation of allergen solutions, immune status of the dog, dust mite extracts are known irritants and so were used at drug interference, inherent host factors, incorrect antigen a strength of 100PNU/ml and 1:5000w/v, respectively. And selection and test done at the wrong time[14]. Therefore, the molds, questionable irritant allergens, were diluted at a IDST combined with in vitro testing for the diagnosis and strength of 250PNU/ml. Histamine phosphate(0.0275mg/ml) management of dogs with AD is recommended[4]. This was used as the positive control and 0.9% normal saline study was performed to investigate what kinds of allergens with 0.1% phenol added was used as the negative control. involved in canine AD determined by IDST in Korea. All dogs were sedated with medetomidine which did not seem to block skin test reactivity in dogs. The skin test was Materials and Methods performed on the lateral flank after shaving or clipping and then gentle cleaning with water-soaked towel. No other Patient Selection chemicals or soothing agent which can affect the IDST were A total of 35 dogs were admitted to Veterinary Medical applied to the part. The injection sites are marked with a Teaching Hospital, Seoul National University, Seoul, Korea water based naming pen, leaving 3 cm between each injection, between 1999 and 2001. Diagnosis of AD was made by a and 0.05ml of each allergen or control solution was injected combination of compatible history and clinical signs along intradermally using a 1ml syringe with a 26 gauge needle. with the presence of one more positive IDST reactions that The diameters of wheal were measured 20 min after correlated well with the patients' history of exposure and injection[17]. The test sites were graded as follows: +++, the seasonality of clinical signs. Table 1. Allergens used in the intradermal skin test in 35 atopic dogs in Korea and allergen dilutions of testing strength extracts Num ber Ae roalle rgen Dilution Source Grass 1 Bermuda 1000PNU/mla Greer 2 Fescue 1000PNU/ml Greer 3 Kentucky 1000PNU/ml Greer 4 Orchard 1000PNU/ml Greer 5 Rye 1000PNU/ml Greer 6 Timothy 1000PNU/ml Greer Allergens Causing Atopic Diseases