Estudo comparativo de casos de pitiose em equídeos, ruminantes, carnívoros e ave no Nordeste do Brasil.

Abstract

We describe in this thesis four scientific papers that address pythiosis in domestic animals in northeastern Brazil. The first chapter gathers and comparatively describes pythiosis cases in equidae, ruminants, carnivores and birds affected in the northeastern region of Brazil over a 35-year period of diagnosis at the Animal Pathology Laboratory of the Federal University of Campina Grande. During the study period, 13,542 tissue samples from necropsies and biopsies were received. Among these samples, 306 were diagnosed as pythiosis: 195 cases in horses, 75 in sheep, 19 in dogs, 6 in mules, 4 in cattle, 3 in cats, 2 in goats, 1 in a donkey, and 1 in an ostrich. The equidae were the most affected species, with lesions in the skin, mammary glands and nasal cavities. Among ruminants, sheep were the most affected, with cutaneous, nasal and digestive lesions, while cattle and goats had cutaneous lesions. Carnivores developed lesions mainly in the alimentary tract, severe enough to determine the animals' death or euthanasia. The single case in a bird affected the alimentary tract and surgical excision determined remission. For most animals, the disease had a long-term and life-threatening clinical course, except for cattle that had spontaneous healing. The clinical signs were directly related to the location of the lesions, which always presented histological evidence of chronic inflammation associated with intralesional hyphae. The second chapter characterizes the epidemiological, clinical and pathological aspects and the main diagnostic techniques for pythiosis in horses, mules and donkeys. Were received 1,331 tissue samples of equidae, 202 (15.17%) of which were diagnosed as pythiosis. Equidae of both sexes with ages varying from 4 months to 25 years were affected. Most animals were mixed breed (79.7%) and reared in an extensive system (73.26%). The disease occurred throughout the year but the highest incidence (70.29%) was noted after the rainy season. The clinical course was always chronic. The lesions were preferentially located on the limbs and ventral thoracoabdominal wall and characterized by nodules or tumor-like masses with ulcerations and serosanguineous discharge. The cut surface showed fistulous tracts containing kunkers. Histopathology revealed a marked inflammatory infiltrate of eosinophils with multifocal well-defined areas of eosinophil necrosis and collagenolysis and intralesional negativelystained hyphal profiles; in the donkey, a pyogranulomatous inflammatory infiltrate was noted surrounding these areas. Immunohistochemistry for Pythium insidiosum revealed strong immunolabelling of the hyphae. The third chapter describes three cases of pythiosis in cats, characterizing the epidemiological, clinical, and pathological findings. Were received 1,928 tissue samples of cats, three of which were diagnosed as pythiosis. Grossly, the cats showed a multinodular mass in the oral cavity associated with facial deformity (case 1), a large multinodular mass thickening the jejunum wall (case 2), and an ulcerated nodule in the skin at the base of the tail (case 3). Histologically, pyogranulomatous inflammation and necrosis, with intralesional predominantly negatively stained hyphae, were observed in all cases. Immunohistochemistry for Pythium insidiosum revealed strong immunolabelling of the hyphae. The diagnosis of pythiosis was based on the epidemiological, clinical and anatomopathological findings, and was confirmed by immunohistochemistry. The fourth chapter reports a case of esophageal pythiosis in an ostrich, characterizing the epidemiological, clinical, pathological, and immunohistochemical aspects. A 2-yearold female red-necked ostrich presented with a nodular mass in the middle third of the esophagus. Histologically, there was a focally extensive area of necrosis extending from the tunica mucosa to the adventitia. Surrounding the necrotic area were a dense inflammatory reaction composed mainly of granulocytes and macrophages and associated with fibroplasia and neovascularization. In some inflammatory and necrotic areas, there were numerous longitudinal and cross sections of negatively stained hyphae, which were best visualized using Grocott methenamine silver stain. Definitive diagnosis of infection by Pythium insidiosum was confirmed by immunohistochemistry. Pythiosis is an endemic disease in northeastern Brazil. Horses, sheep, and dogs seem to be most commonly affected, but it is important to be aware that the disease can affect other animal species. Veterinary clinicians and pathologists should be familiar with the clinicopathological features of the disease and the wide range of susceptible animal species.