Efficacy of 0.5% Tretinoin in the Treatment of Equine Aural Plaques

BACKGROUND: Equine aural plaques are a benign form of auricular papillomatosis caused by equine papillomavirus. Despite the efficacy of 5% imiquimod cream, a marked local reaction is frequently observed during therapy, often requiring sedation before application. HYPOTHESIS/OBJECTIVES: The aim of this study was to evaluate the efficacy and potential adverse effects of 0.5% topical tretinoin in the treatment of equine aural plaques. We hypothesised that tretinoin would be effective, with fewer adverse effects compared to imiquimod. ANIMALS: The study included 10 horses of both sexes, aged between 7 months and 15 years, diagnosed with unilateral or bilateral aural plaques (totalling 17 ears). MATERIALS AND METHODS: This was a controlled clinical trial. Three horses underwent a pilot study, in which only one ear per animal was treated to allow for intra-animal comparison, while the remaining seven horses received treatment in both ears. Lesions were classified into three groups based on the percentage of the inner auricular surface affected. Treatment was performed with 0.5% topical tretinoin once daily until lesion stabilisation or resolution. Lesion characteristics, treatment response, adverse effects and recurrence were evaluated. RESULTS: Sixty-five percent of the ears exhibited an improvement of > 50% following treatment. On average, maximal lesion resolution occurred within 52.8 days (range 6-74 days). None of the horses exhibited severe sensitivity during the treatment period, allowing for ear manipulation throughout the study. CONCLUSIONS AND CLINICAL RELEVANCE: The topical application of 0.5% tretinoin cream proved to be an effective and safe treatment for equine aural plaques. Further studies with a larger sample size and long-term follow-up are recommended to optimise treatment protocols.