An outbreak of scuticociliatosis in cultured common dentex (Dentex dentex) in Turkey

In this study, Miamiensis avidus (syn. Philasterides dicentrarchi) was identified by molecular tools as the causative agent responsible for a disease outbreak in cultured common dentex (Dentex dentex). The outbreak occurred in May when the water temperature was 18 degrees C in a commercial fish farm located in Aegean Region of Turkey. Fifteen moribund cultured common dentex juveniles (10-15 g in weight) were selected from indoor circular tanks of the hatchery and examined. The disease signs in all sampled fish included hemorrhaging on various body surfaces, dorsal fin rot induding skin depigmentation, accumulation of ascitic fluid due to a hyperaemic liver and consequent distended abdominal cavity and an enlarged spleen. Light microscopic examination revealed that the skin of diseased fish was heavily infected with ovoid-shaped, highly motile ciliates, of which some encompassed multiple erythrocytes in their cytoplasm, when observed HE-stained histological sections. The ciliate was identified as Miamiensis avidus by both partial 18S ribosomal RNA (18S rRNA) and cytochrome c oxidase subunit I (COX1) genes sequence analysis, while morphological characterisation was not done. In addition, Vibrio sp. were isolated from the liver of five moribund fish, however this was considered a secondary infection since only one-third of the fish were affected. To our knowledge, this is the first-report of scuticociliatosis caused by Miamiensis avidus in cultured common dentex.