Résumé
In the present study, attempts were made to observe the clinical signs of naturally infested Nile tilapia [Oreochromis niloticus] with ectoparasites of the ciliated Trichodina and aquatic leeches [Glossiphonia spp.]. The prevalence of both parasites were 100% and 30%, respectively. The histopathological investigations revealed sever inflammation with inflammatory cells infiltration in skin as well as coagulative necrosis [Zenker's necrosis] and edema of the muscle bundles. Significance of biological control measures using the Bio-clean product [FER Mone-2/3] [a biological mixture of Bacillus thuringiensis var. Kurstaki [BTK] and Beauveria bassiana [B.b]] as a new method to eradicate such parasites was evaluated. The half lethal concentration [LC50] was 85 mg/L/48 hours. The Bio-clean product was safe to treat Trichodina spp. infestation in fish farms at a dose of 25 mg/L. On the other hand, this product was not suitable for treatment of leeches [Glossiphonia spp.] due to its effective dose [40 mg/L] was narrow safety margin