Efficacy of Polymerase Chain Reaction in Diagnosis of Saproleniosis in Oreochromis Niloticus

Abstract

The present study was carried out on 100 cultured Nile tilapia (O. niloticus) of different ages were collected from farms of Central Laboratory for Aquaculture Research (Abbassa, Abou Hammad, Sharkia, Egypt) during period from late November, 2014 to march, 2015. The collected fish samples were studies for presence of fungal infection. Fish were clinically showed respiratory manifestation, erratic movement, loss of equilibrium, off food and also showed whit to gray patches of filamentous mycelium “cotton like” on fish skin, around head, dorsal and caudal fins, gills, on the muscular layer and eye causing unilateral or bilateral eye opacity. Internally, the diseased fish showed, pale gills, dark and enlarged liver, kidney and intestine free from any food. The collected samples were suspected to mycological and biochemical identification which initially suggestive of Saprolegnia spp . The tradionally identification was supported by using Polymerase Chain Reaction (PCR) which very important rapid and accurate method to identify Saprolegnia from other water mold. Also, in this study, the antifungal effect of ethanolic extract of Ruta graveolens( natural herbal plant) on Saprolegnia was studied in vitro by disk and well diffusion methods. Further by trials, iodine was an effective antifungal disinfectant for infected fish.