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Canine Atopic Dermatitis: Update and Current Insights on Desensitization
- 2025/02/12
- 再生時間： 19 分
- ポッドキャスト
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サマリー
あらすじ・解説
Canine atopic dermatitis (CAD) is a common and complex inflammatory skin disease in dogs, requiring a thorough understanding for accurate diagnosis and effective management. This overview focuses on the diagnostic process, treatment options, and specifically, allergen-specific immunotherapy (ASIT), a critical area for veterinary dermatologists. Diagnosing CAD is challenging, as no single definitive test exists. A structured, multi-faceted approach is essential, encompassing three key steps: ruling out other skin conditions, carefully interpreting the dog's history and clinical signs, and performing allergy testing. The first step involves excluding other potential causes of itching (pruritus) and skin lesions. Diagnostic tests include flea combing to identify flea infestations, skin scrapings to detect parasites like sarcoptic mange (scabies) and demodicosis (Demodex mites), and skin cytology to identify secondary bacterial infections (often Staphylococcus pseudintermedius) and yeast overgrowth (Malassezia pachydermatis). Treating these secondary infections is crucial as they can worsen pruritus and complicate the diagnosis. A trial treatment for sarcoptic mange might be necessary if strongly suspected but not confirmed. Elimination diet trials are required for non-seasonal pruritus or digestive signs to rule out food allergies. Next, a detailed interpretation of the dog's medical history and clinical signs is paramount. Pruritus, manifesting as scratching, licking, rubbing, or head shaking, is the hallmark symptom. Common areas affected include the face, ears, abdomen, armpits, groin, perianal region, and paws. However, lesion distribution can vary by breed. Assessing the seasonality of pruritus aids in identifying potential allergens. The Favrot criteria can assist in diagnosis. Chronic CAD often leads to secondary lesions like excoriations, hair loss, lichenification (thickened skin), hyperpigmentation, and crusts. Once CAD is suspected, allergy testing can identify responsible allergens for ASIT. Available tests include intradermal testing (IDT) and serological tests (specific IgE assays). IDT involves injecting small amounts of allergens into the skin. Serological tests measure allergen-specific IgE antibodies in the blood. Results must be interpreted within the context of the dog's history and clinical signs. Cross-reactions between allergens, like dust mites and storage mites, can occur. A positive test doesn't automatically indicate clinically relevant hypersensitivity; tests should identify allergens contributing to CAD, not diagnose environmental allergies. ASIT is currently the only treatment capable of inducing tolerance to CAD-triggering allergens. It involves progressively administering allergen extracts via subcutaneous injections to modulate the immune response. The goal is to increase regulatory T cells (suppressing the allergic response) and shift the antibody profile from IgE to IgG. Allergen selection for ASIT relies on skin or serological test results, along with the dog's history and clinical presentation. Extract composition and potency vary by manufacturer, so selecting a reliable source is crucial. ASIT begins with an induction phase, increasing doses over weeks, followed by a maintenance phase with regular injections (typically every 3-4 weeks). Doses and frequency are adjusted based on the individual dog's clinical response. Studies show ASIT efficacy in 51-64% of cases. A recent retrospective study found approximately 60% of dogs with CAD had a 50% or greater improvement after ASIT. Treatment efficacy shouldn't be evaluated before 12 months. Improvement is classified as excellent, good, or poor. Regular re-evaluations improve ASIT outcomes. Sublingual immunotherapy (SLIT), administering allergen extracts under the tongue, is another ASIT option showing promise in both humans and dogs. It may be more convenient. Intralymphatic immunotherapy, showing interest in humans, is also being explored in veterinary dermatology. Research is exploring modified allergens, adjuvants, and encapsulated molecules to enhance ASIT's efficacy. Several factors influence ASIT's success. Regular re-evaluations improve outcomes, emphasizing communication between veterinarian and owner, and understanding the disease and treatment. Systemic glucocorticoid (corticosteroid) use during ASIT is linked to poorer responses; minimizing long-term corticosteroid use, especially in the first 9 months, is preferable. The impact of ciclosporin and oclacitinib is less clear. Clinically relevant allergen selection, considering the patient's presentation and environment, is essential. Individual responses to ASIT vary, requiring dose or frequency adjustments. Common canine allergens include pollens, dust mites, molds, and animal dander. Cross-reactions are possible, such as between dust mites and storage mites. Cat allergens include dander, saliva, and albumin. Cross-sensitization between species is possible, but ...
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