RESUMO
BACKGROUND AND OBJECTIVE: Sessiline ciliates live as eco commensals (low numbers) and parasites (high numbers) on different hosts, like mollusks copepods, mysids and fish. Riboscyphidia ecto-protozoan is moderately pathogenic but high numbers of it on the gills can physically prevent gas exchange. The present study aimed to describe the epizoic ciliates Riboscyphidia found on the Red Sea cultured Asian sea bass and obtain more information on the Epidemiology of the parasite with special references to control and histopathological examination of naturally infected sea bass. MATERIALS AND METHODS: The occurrence of epizoic ciliates on the adult Asian Sea bass. About 100 Asian sea bass were collected by the fishing net at a private marine fish farm at Ismailia governorate and transferred to the hydrobiology laboratory at National Research Centre. A parasitological and histopathological study of epizoic sessile ciliate species was done. ANOVA test was used for Statistical analysis. RESULTS: Riboscyphidia sp. was found and isolated after parasitological examination of investigated adult's Asian sea bass. The prevalence of Riboscyphidiosis was 64%. Sessile ciliates were found on gills, skin and fins. The clinical signs of Riboscyphidiosis were respiratory distress, flashing and off food. Histopathological alterations in naturally infested Asian sea bass were investigated. CONCLUSION: The treatment of choice of Riboscyphidiosis was prolonged immersion by Copper citrate with a dose of 0.56 mg mL-1 for 7 days.