Opisthorchus is a flat parasitic worm, 5-15 mm long, ribbon-shaped with pointed ends, 2-3 mm wide and 0.4-0.6 mm thick. The body of the parasite is covered with three rows of small suction hooks located on the sides of the body and at its anterior end. The serous capsule around the parasite is penetrated by blood vessels and covered with secretions of the parasite from the anal glands.