Epidemiological, clinical and anatomopathological characterization of nasal rhinosporidiosis in a horse

Abstract

The objective of this study is to describe the clinical, epidemiological and anatomopathological aspects of a case of nasal rhinosporidiosis in a horse in the Northeast of Brazil. A 15-year-old female horse of mixed breed presented a nodule in the mucosa of the right nasal septum. Surgical excision was performed and sent for histopathological examination. Macroscopically, the nodule had an irregular and reddish surface, and when cut it was soft, whitish, and polypoid in shape. Microscopically, myriads of sporangia with endospores inside were observed in the lamina propria, morphologically similar to Rhinosporidium seeberi in various stages of maturation. The structures were also evidenced and marked by periodic acid Schiff (PAS), Grocott methenamine silver (GMS) and toluidine blue. The diagnosis of rhinosporidiosis was made based on macroscopic aspects and confirmed through histopathological examination. The presence of myriads of sporangia measuring 115 to 220 µm, containing endospores in its interior allowed the diagnosis. Although rhinosporidiosis is considered rare in Brazil, in the Northeast region there are descriptions of the disease in humans, suggesting that the disease in animals occurs and has possibly not been diagnosed. Therefore, it is important to include it as a differential diagnosis of diseases that affect the nasal cavity of horses in the region and that present similar lesions.