The present study was carried out on 500 brain of sheep slaughtered in Cairo abattoirs and reared in different sheep’s farms. The parasitological results revealed that , the incidence of the parasitic affection of the brain was 21 % and including Coenurus cerebralis 9.4%, Oestrus ovis infestation 10.2 % and sarcocystosis 1.4%. Clinically , in coenuriosis , the infested sheep hold their heads on one side and suffered from uni- or bilateral blindness , recummbancy and complete paralysis . The gross examination of the brain infested with C cerebralis , revealed that , the live cysts appears as bladder like cysts with translucent membrane and contained clear fluid and they were found mostly in the cerebellum. While the dead cysts appeared as old calcified grayish white small nodules. Microscopically , the walls of the live cysts of C cerebralis were formed from thick outer connective tissue layer and inner germinating layer carried many scolices . These cysts induced inflammatory reaction in the form of mononuclear and eosinophilic cellular aggregations around their walls. Meanwhile the dead parasitic cysts were represented by focal areas of caseous necrosis and dystrophic calcification which enclosed by thick connective tissue capsule infiltrated with chronic inflammatory cells. Cerebral congestion , perivascular hemorrhage and cerebral encephalomalacia with gliosis, neural degeneration and necrosis of Purkinje cells were also observed . While in O ovis infestation , the infested sheep were clinically emaciated and rub their noses to the ground or the adjacent animals. Grossly , the brain was congested and showed petechiae on the cerebellum, thickening in the meninges with presence of few larvae attached to the brain surface. Histopathologically , congestion , perivascular hemorrhages , cerebral edema , focal encephalomalacia , mononuclear cellular infiltration with neural degeneration and thickening of the meninges were recorded . On other hand , no characteristic clinical signs or gross lesions were observed in sarcocystosis. Microscopically, oval parasitic cysts of sarcocyst filled with PAS positive bradyzoites without any inflammatory reaction were noticed in the examined brain.
Finely , it concluded that , C cerebralis and O ovis infestations of the brain of sheep were accompanied with irritation of the brain tissue resulting in focal encephalomalacia with congestion , hemorrhages and mononuclear inflammatory cellular reaction. While in sarcocystosis no tissue host reaction was recorded in the brain of infested sheep.
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