Abstract
The study was designed with the aims of determining the fish parasites metacercariae on Elibrahimiyah Canal (from River Nile) in Assuit governorate and tests the effect of freezing on the viability of parasite on Nile Tilapia “Oreochromis niloticus”. 620 of Nile Tilapia were caught from Elibrahimiyah Canal, samples measured, weighed, and then efficiently inspected of the skin, gills, internal organs, and musculature grossly and microscopically with and without stain. Positive parasitism’s fish stored under freezing condition below -4°C to -7°C for about 7 days to measure the effect of freezing on its viability. The total prevalence rate of Clinostomum spp. and Euclinostomum ardeolae metcercaria infection in Nile Tilapia were about 40/620 (6.45%) totally as following; 10/620 (1.61%) and 30/620 (4.84%) for Clinostomum spp. and Euclinostomum ardeolae metcercaria infection respectively. Macroscopic and Microscopic Examination of Euclinostomum ardeolae metacercaria and Clinostomum spp. declared their shape in details. In addition to the inhibition effect of freezing on the Viability of Euclinostomum ardeolae and Clinostomum spp. metacercaria. The susceptibility of man to yellow grub increases the medical importance of examination of Oreochromis niloticus in Assiut governorate although, the evident of it in Nile tilapia belonging to Elibrahimia Canal are rarely. Prevention of metcercariae requires avoidance of introduction of the parasite snails and aquatic birds and alteration of the water environment. More attention should be given to the fish parasites among Elibarahimia canal. The effectiveness of freezing to kill viable metcercaria including the freezing temperature and period needed to freeze the fish tissue.

Key words: snails, Euclinostomum ardeolae, Clinostomum spp., metacercaria., zoonosis, freezing.