EN
The mass incidence of the parasite was detected in Abramis brama (L) from the dam reservoir of the Gródek-Żur electricity works on the Wda river (Bydgoszcz voivodeship). Seven breams weighing 530-1530 g, measuring 29/35-41/49 cm in lenght (longitudo corporis, longitudo totalis). In all fishes there was a strong protrusion of the cornea that showed small white spots, visible with naked eye (Phot. 1). Post-mortem examinations revealed considerable enlargement of the anterior chamber of the eye with small amount of the vitreus and sticky, hazy fluid in the bulbus. The cornea contained numerous metacercariae (Phot. 2); a mass incidence of the latter was also found under the skin, on the head, anterior part of the body, on pectoral fins and on gills. The most charactcristic changes appeared in the cornea, where metacercariae were present in extremely high numbers; they were either single and disseminated of formed large accumulations. Occasionally, the cornea showed canals burrowed by migrating larvae prior to incystation (Phot. 3). On the transversal sections of the cornea there are holes containing encysted metacercariae; laceration of the corneal surface and separation of the tissue layers are visible (Phot. 4). At autopsy, the cornea was friable, which could be seen distinctly from the presence of transversal fissures in the microtome sections (Phot. 5).