Occurrence of Squamous Cell Carcinoma in Sheep From a Farm in São Paulo State, Brazil

Abstract

The occurrence of squamous cell carcinoma in sheep on a farm in São Paulo state, Brazil, is reported. The flock, composed by Suffolk, Santa Inês, Poll Dorset and Ile de France breeds is managed intensively. All the ewes were clinically examined and papillomas and tumoural lesions were observed only in the Ile de France breed. Histopathological findings (HE) revealed invasive squamous cell carcinoma in the vulval labia. Negative contrast electron microscopy did not find viral particles in papillomas and tumoural lesions. The clinical study revealed occurrence of squamous cell carcinoma in July/99, January/00 and July/00, respectively, 6.0% (3/50), 4.2% (2/48) and 4.3% (2/46). The incidence from July/99 to January/00 and from January/00 to July/00 was, respectively, 2.1% (1/48) and zero (0/46). Despite all the breeds being managed together, only the Ile de France presented lesions. This lead us to consider that the susceptibility may be associated to racial factors, because all the animals are submitted to the same environmental, sanitary and management conditions. Solar radiation may be the factor that induces the development of squamous cell carcinoma, because Ile de France animals have a unpigmented perineum that is poorly covered by wool and is exposed to solar radiation in the tropical climate.