engleski

Development and pathogenicity of Eimeria dicentrarchi (Apicomplexa: Eimeriidae) in farmed European sea bass

Introduction To our knowledge, so far only 2 coccidia of the genus Eimeria have been reported in European sea bass (Dicentrarchus labrax), namely Eimeria dicentrarchi Daoudi et Marquès, 1987 and Eimeria bouixi Daoudi et Marquès, 1987. Originally, E. dicentrarchi was described as a species that develops in the pyloric caeca epithelium. Following the first report in France, E. dicentrarchi has been reported in several other Mediterranean countries. Although infections are common, little is known about this coccidian species. Material and Methods To gain further insight into its site(s) of infection, development and pathogenicity, the present study analysed 57 European sea bass (16-27 cm long) from a commercial fish farm in the Adriatic Sea for the presence of intestinal coccidia. Fresh preparations of mucus and intestinal scrapings were analysed for infection ; when oocysts were found, histology was performed to determine site(s) of infection. Samples of pyloric caeca, anterior intestine and posterior intestine were fixed in 10% neutral buffered formalin. Fixed material was embedded in paraffin and 7 μm serial sections were prepared. Sections were stained with haematoxylin and eosin, toluidine blue and periodic acid-Schiff stain. Results Oocysts of E. dicentrarchi were found in 7 of 57 (12.3%) European sea bass. Most oocysts in mucus and intestinal scrapings were in the sporulated stage, with smaller numbers of unsporulated and semisporulated oocysts also observed. Histological examination revealed E. dicentrarchi at different developmental stages in all three sections of digestive tract, though most parasites were found in the anterior intestine. Oocysts were localised in the epithelium and only occasionally beneath the epithelium, in the lamina propria. Most meronts and macrogamonts were located in the basal part of enterocytes, while most microgamonts were in the supranuclear region. No gross pathological changes were detected in any of the European sea bass infected with E. dicentrarchi. Most histopathological changes were localised and restricted to individual epithelial cells. Infected epithelial cells were partially destroyed, leading to necrotic changes. The cell membrane of infected cells was damaged. Release of oocysts into the intestinal lumen was associated with complete destruction of microvilli and rupture of the host cell membrane. Vacuolisation of epithelial cells and detachment of the lamina epithelialis from the lamina propria were occasionally observed in infected areas. Conclusion The results of this study provide more information on this eimerian species.

Eimeria dicentrarchi; development; pathogenicity; European sea bass

nije evidentirano