Branchiomyosis in Nile tilapia (Oreochromis niloticus) in Behiera Governorate with Trials for Treatment

A total number of 100 Nile tilapia (Oreochromis niloticus) were collected from Edco private fish farms in Behiera governorate during the period between July and September 2013 and screened for branchiomyces infection. The infected fish were suffering from respiratory distress (resulted from gill tissue damage); gasping air from the water surface, rapid movement of operculum and massive mortality, which resulted in the loss of 90% of the collected fish. Squash preparations from the infected gill tissue revealed brown, broad, branched and non-septated hyphae. On Sabouraud's dextrose agar (SDA) media with 10% duck decoction showed bright white colonies after 2 days which reached its maximum growth 8 days post inoculation. Microscopical examination of stained growth with Lactophenol cotton blue, branched hyphae at their tips were identified which were characteristic for Branchiomyces sp. The causal pathogen was identified as Branchiomyces demigrans, in which the diameter of spores and non-septated hyphae were 4-10 μm and 16-24 μm, respectively. The fungus was confirmed using polymerase chain reaction (PCR). Experimental infection and rei-solation of fungus revealed the same findings of natural infection. Clotrimazole was more effective than clove oil, while using both of them revealed higher lysozyme activity and phagocytic activity. Histopathological examination from naturally and experimentally infected fish gills revealed non-septated hyphae and spores were embedded in between affected gill tissues, which confirmed that the isolated organism was Branchiomyces demigrans