The Significance of Subarachnoid Cerebrospinal Fluids (CSF) in the Development of Metacestode of Coenurus Cerebralis in Sheep with Reference to its Pathological Effect

Five one year-old Rahmani sheep showed nervous signs (circling and pushing their heads against objects). Necropsy showed congested meninges in the cerebellar of case (1). Fluid-filled cysts (1-2 cm diameter) were found in the cerebral subarachnoid space (cases 2& 3). No subarachnoid cysts were seen in 2 cases (4& 5). Microscopically, the affected brain (case 1) displayed oncosphere migrating in the cerebellar subarachnoid space. The oncosphere was partially surrounded by caseous necrosis followed by mononuclears. The underlying cerebellar folia showed necrotic Purkinje cells and disorganized neurons of the granular layer. The metacestode-wall (cases 2& 3) revealed invaginated elongated pouches (scolex-sacs) containing scolices at their bases. The inner lining of those scolex-sacs was corrugated. Each sac was connected via an opening to the subarachnoid cerebrospinal fluid (CSF). Small empty cavities (3-7 mm diameter) were detected in the right cerebral hemisphere of cases (4& 5). Such cavities were surrounded by a zone of caseous necrosis followed by mononuclears and giant cells. Others frequently contained caseated and calcified material. The surrounding nervous tissue showed encephalomalacia. It could be concluded that the CSF is required for the differentiation and growth of the metacestode and the scolices develop from the base of the invaginated outer surface of the metacestode-wall.