Veterinary dermatology2026; doi: 10.1111/vde.70090

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

de Mattos, FS
·
Conceição, LG
·
Schuartz, YGH
·
Silva, VRM
·
Fidélis, CF
·
Mansur, FC
·
Teixeira, CS
·
Sancler-Silva, YFR
·
Oliveira-Filho, JP
·
Borges, AS
·
Bromberger, CR
·
Filho, JDR
·
Avanza, MFB
·
Silva, JRB
·
Teixeira, RBC

Abstract: 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. Objective: 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. Methods: 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). 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: 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.

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Publication Date: 2026-05-29 PubMed ID: 42215420DOI: 10.1111/vde.70090Google Scholar: Lookup

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Summary

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Overview

This study investigated the effectiveness and safety of 0.5% tretinoin cream for treating equine aural plaques, a benign ear condition caused by papillomavirus in horses.
The researchers aimed to find a treatment with fewer adverse effects than the commonly used 5% imiquimod cream, and found that tretinoin was effective with minimal side effects.

Background

Equine aural plaques are benign lesions on the inner surface of horses’ ears caused by equine papillomavirus.
Existing treatment often involves 5% imiquimod cream which is effective but frequently causes strong local reactions, making application difficult and sometimes requiring sedation.
The need existed for a treatment that is both effective and better tolerated by horses.

Objective

To evaluate whether 0.5% topical tretinoin cream could effectively treat equine aural plaques.
To assess if tretinoin causes fewer adverse effects compared to imiquimod.

Methods

Subjects: 10 horses aged 7 months to 15 years, with 17 affected ears (some horses had unilateral while others had bilateral plaques).
Design: Controlled clinical trial with a pilot study on 3 horses where only one ear was treated for intra-animal comparison, and the other 7 horses treated on both ears.
Lesion classification: Lesions were grouped based on the percentage of the ear’s inner surface involved.
Treatment: 0.5% tretinoin cream applied once daily until lesions stabilized or resolved.
Outcome assessment: Monitoring of lesion size reduction, time to maximal resolution, any adverse effects, and recurrence during follow-up.

Results

Improvement: 65% of treated ears showed over 50% reduction in lesion size.
Time frame: Maximal lesion resolution was reached on average in approximately 53 days, with a range from 6 to 74 days among horses.
Adverse effects: No severe sensitivity or discomfort was observed in any horse; all tolerated ear manipulation throughout the treatment without sedation.

Conclusions

Topical 0.5% tretinoin cream is an effective and well-tolerated treatment for equine aural plaques.
Unlike imiquimod, tretinoin did not cause marked adverse local reactions that hindered treatment.
Larger studies and long-term monitoring are encouraged to refine treatment protocols and confirm lasting benefits.

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APA

de Mattos FS, Conceição LG, Schuartz YGH, Silva VRM, Fidélis CF, Mansur FC, Teixeira CS, Sancler-Silva YFR, Oliveira-Filho JP, Borges AS, Bromberger CR, Filho JDR, Avanza MFB, Silva JRB, Teixeira RBC. (2026). Efficacy of 0.5% Tretinoin in the Treatment of Equine Aural Plaques. Vet Dermatol. https://doi.org/10.1111/vde.70090

Publication

Veterinary dermatology

ISSN: 1365-3164

NlmUniqueID: 9426187

Country: England

Language: English

Researcher Affiliations

de Mattos, Felipe Sperandio

Departament of Veterinary Medicine, Federal University of Viçosa (UFV), Viçosa, Minas Gerais, Brazil.

Conceição, Lissandro Gonçalves

Departament of Veterinary Medicine, Federal University of Viçosa (UFV), Viçosa, Minas Gerais, Brazil.

Schuartz, Ytalo Galinari Henrique

Departament of Veterinary Medicine, Federal University of Viçosa (UFV), Viçosa, Minas Gerais, Brazil.

Silva, Vitória Régia Melo

Departament of Veterinary Medicine, Federal University of Viçosa (UFV), Viçosa, Minas Gerais, Brazil.

Fidélis, Cintia Fernandes

Departament of Veterinary Medicine, Federal University of Viçosa (UFV), Viçosa, Minas Gerais, Brazil.

Mansur, Fernanda Campos

FAMINAS University Center, Muriaé, Minas Gerais, Brazil.

Teixeira, Cristian Silva

Departament of Animal Science, Federal University of Viçosa (UFV), Viçosa, Minas Gerais, Brazil.

Sancler-Silva, Yame Fabres Robaina

Departament of Animal Science, Federal University of Viçosa (UFV), Viçosa, Minas Gerais, Brazil.

Oliveira-Filho, Jose Paes

Department of Veterinary Clinical Science, São Paulo State University (Unesp), school of Veterinary Medicine and Animal Science, Botucatu, Brazil.

Borges, Alexandre Secorun

Department of Veterinary Clinical Science, São Paulo State University (Unesp), school of Veterinary Medicine and Animal Science, Botucatu, Brazil.

Bromberger, Cristiana Raach

Department of Veterinary Clinical Science, São Paulo State University (Unesp), school of Veterinary Medicine and Animal Science, Botucatu, Brazil.

Filho, José Dantas Ribeiro

Departament of Veterinary Medicine, Federal University of Viçosa (UFV), Viçosa, Minas Gerais, Brazil.

Avanza, Marcel Ferreira Bastos

Departament of Veterinary Medicine, Federal University of Viçosa (UFV), Viçosa, Minas Gerais, Brazil.

Silva, José Ricardo Barboza

Departament of Veterinary Medicine, Federal University of Viçosa (UFV), Viçosa, Minas Gerais, Brazil.

Teixeira, Raffaella Bertoni Cavalcanti

Departament of Veterinary Medicine, Federal University of Viçosa (UFV), Viçosa, Minas Gerais, Brazil.

Grant Funding

Finance Code 001 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Fundação de Amparo à Pesquisa do Estado de Minas Gerais
Conselho Nacional de Desenvolvimento Científico e Tecnológico

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