Amaurosis in sheep resulting from treatment with rafoxanide

Amarurosis occurred in sheep on various farms in the Republic of South Africa after treatment with rafoxamide. Histopathological examination revealed a status spongiosus of varying severity in the central nervous system in all the cases, having a predilection for certain areas such as the periventricular area of the lateral ventricles, optic tracts, lateral geniculates and optic fasiculi. The retina was the only ocular tissue affected and lesions observed in the retina included necrosis of nerve cells in the ganglionic layer. In chronic cases of amaurosis this layer showed a complete absence of nerve cells. The possible pathogenesis of the lesions and their differentiation from those found in certain plant toxicoses are discussed.