A Retrospective Evaluation of Equine Cutaneous Lesions Diagnosed in Southern Brazil

Abstract

Background: Cutaneous lesions in horses are common, accounting for approximately 50% of all neoplasms of this species, and can cause irritability, pruritus and predispose to secondary infections. Studies have provided information of frequency of cutaneous neoplasms in horses, but few included non-neoplastic lesions. The aim of this study is to identify the frequency of cutaneous lesions in horses diagnosed in Southern Brazil, through a retrospective study and identification of the anatomic location of the lesion, the breed, gender and age of the animals affected.Materials, Methods & Results: A retrospective study on skin lesions in horses using the database of the Veterinary Pathology Laboratory located in Southern Brazil was carried out from January 2000 to February 2013. Cases were searched for and selected by diagnosis, considering age, breed, gender, location and time of occurrence. The most common lesions included sarcoid, exuberant granulation tissue, squamous cell carcinoma (SCC), pythiosis, habronemiasis, melanoma, papillomatosis and Culicoides hypersensitivity. The most affected age range for sarcoid was animals from 1 to 5 years of age and for SCC was over 15 years of age. There was a positive association between sarcoid occurrence and being female and between SCC and habronemiasis and being male. Sarcoid, exuberant granulation tissue, pythiosis and habronemiasis most frequently involved the limbs, while SCC affected the urogenital and ocular systems and melanoma affected the tail. Pythiosis, habronemiasis, Culicoides hypersensitivity and nodular collagenolytic granuloma had seasonal occurrences. Sarcoid, exuberant granulation tissue and SCC were the most commonly diagnosed lesions. Sarcoid affected mostly younger animals, while SCC commonly affected older animals. Habronemiasis and Culicoides hypersensitivity occurred mostly during the spring and summer, while pythiosis most often presented during autumn and winter.Discussion: The frequency of neoplastic lesions in the present work was similar to other studies. Among horse skin neoplasms, sarcoid is the most common, as was observed in this study. Sarcoid primarily affects young animals and most of these have an age range between one and five years, which was also noted and supported by statistical analysis. EGT is the most common non-neoplastic lesion in the skin of horses, most commonly in the limbs. The high frequency described may be related to a higher genetic predisposition or due to the employment of these horses in intensive work. SCC is the second most common skin neoplasm and often affects older horses, as it was observed. Urogenital tract and males were the most affected location and gender. Due to their ventral location, smegma may be a more likely etiology. It was observed a lower frequency of pythiosis and this may be due to the geographical location of the laboratory, where economy it is not based on livestock or rice farming, which can predispose animals to stay in stagnant water. Cutaneous habronemiasis is often diagnosed during warm months that have high biting insect activity, as observed here, where 75% of the cases occurred during the spring-summer. Differential diagnoses of nodular collagenolytic granuloma and habronemiasis was based not only on the presence of the parasite but also on the morphologic features of the lesion. Culicoides hypersensitivity is the most common and severe allergic condition in horses distributed worldwide because of the favorable weather conditions for the reproduction of the insect. In this study, 75% of the cases occurred during the spring-summer. Lesions are usually multiple, as it was observed in 50% of the cases.