Desenvolvimento de um método esfoliativo para diagnóstico de placa aural em equinos e investigação do potencial de carrapatos como vetores de papilomavírus

Abstract

Aural plaque is a viral dermatological disease that affects the ear region of equines. It is caused by various papillomaviruses and presents characteristics of depigmentation and keratinization of the inner ear, which can present as punctiform or coalescent lesions.These lesions generate economic losses for horse breeders due to the commercial depreciation of the affected animals, limiting participation in some shows, competitions, and auctions. Currently, the diagnosis of these lesions relies primarily on the collection of a biopsy followed by polymerase chain reaction (PCR), the test with the highest diagnostic sensitivity for the virus. A biopsy involves using a 6- to 8-mm-diameter punch, from which a fragment of the affected tissue is removed for examination. Subsequently, the biopsied area requires daily wound care until completely healed. In this study, we used a 2-mm dermatological curette to curette the inner ear of clinically evaluated horses with aural plaques. Subsequent PCR analysis was performed, along with histopathological analysis and collection of ticks from the region. These were analyzed by PCR to investigate their relationship with papillomavirus transmission. One hundred and one clinically diagnosed aural plaque lesions were collected from 79 animals of different breeds, coats, ages, and husbandry systems located in the Uberlândia region of Minas Gerais. The results showed no statistically significant difference between the methods (p > 0.05). The exfoliative method presented sensitivity and specificity equivalent to biopsy for the EcPV1 (84.2%), EcPV3 (100%), and EcPV6 (71.4%) genotypes, with emphasis on EcPV3, which obtained excellent agreement. Coinfections were detected in 43% of the samples, the most common being between EcPV1 and EcPV6 (40.2%) and between EcPV1 and EcPV4 (25.3%). 100% of the ticks were Dermacentor nitens and tested positive for EcPV1. Coinfections occurred in 30% of the parasites, with a predominance of the combinations EcPV1 and EcPV6 (23.3%) and EcPV1 and EcPV4 (3.3%). These findings suggest that although the detection of viral DNA in ticks does not prove biological transmission, the results indicate a strong association between the presence of these ectoparasites and EcPV infection in horses.