A 4-year-old Rahmani breed ewe was presented for surgery to the Veterinary Teaching Hospital, South Valley University, Egypt with enlargement and protrusion of the eye ball, blepharitis and congestion of the conjunctiva. On examination, a cyst 2.5 cm x 3.5 cm in diameter containing sandy fluid was detected in the perioptic nerve fat. Histopathological examination revealed that the epithelial lining of the conjunctiva was necrotic and severely infiltrated by neutrophils. The underlying connective tissue was oedematous, hyperaemic and severely infiltrated by neutrophils. Desquamation of the corneal epithelium was seen, together with oedema of the stroma. The tissue surrounding the cyst was compressed and the lacrimal glands revealed pressure atrophy. The muscular tissue was atrophied and infiltrated by fat cells. The cyst wall was lined with white scolices protruding from the inner wall. Based on the gross and histopathological characteristics of the cyst observed, the cyst was diagnosed as Coenurus cerebralis. This is the first report of orbital coenurosis in a sheep.

This study consisted in histopathological and immunohistochemical examinations of the central nervous system of 15 sheep suspected of infection with Coenurus cerebralis. The sheep displayed compulsive circling and were submitted for necropsy in 2012–2016. Species identification was made on the basis of the PCR analysis and parasitological examination of the cysts. Coenurus cerebralis cysts were detected only in the cerebral tissue of 13 sheep and in the cerebral and cerebellar tissues of 2 animals. Out of the 33 parasite cysts, most (21.21%) were located in the right and left frontal lobes of the cerebrum. The largest cyst measured 6 × 5 cm and the smallest cyst was 2 × 2 cm in size. The highest and lowest numbers of scolices were 55 and 21, and the number of rostellar hooks ranged between 22 and 30. Histopathological examination revealed the presence of typical parasitic granulomatous inflammatory foci. Immunohistochemical staining showed that most common in the periphery of the parasite cysts were, in descending order by cell number, GFAP, CD163, CD3, and CD79α-positive cells. The study confirms the role of cellular defence mechanisms in the pathogenesis of Coenurus cerebralis infection in sheep.