Alarming the critical times for occurrence of important bacterial problems in cultured Oreochromis niloticus under semi intensive system in Sharkia province [electronic resource].

Includes references.

The study was carried out on 1000 0. niloticus collected from private and governmental semi intensive earth ponds in Sharkia province during disease outbreaks, the examined farms belongs to the Central Lab for Aquatic Research in Abbassa as well as private farms through the seasons of the year 2008. The clinical signs and postmortem lesions of diseased fish were recorded. The results revealed that (420) fish were found to be infected with bacterial agents which means that the prevalence of bacterial diseases was 42% among the examined fish. The isolated and identified bacteria were Aeromonas hydrophila in a percentage (56.67%) and the highest rate of infection was observed in winter season (39.9%), Pseudomonas fluorescence in a percentage (36%) and the highest rate of infection was observed in autumn season (48.8%). Streptococcus spp. in a percentage (19.77%) and the highest rate of infection was observed in spring season (54.2%). Flavobacterium columnaris in a percentage (8.34%) and the highest rate of infection was observed in autumn season (57.1 %). Pathogencity of selected bacterial isolates belonged to Aeromonas hydrophila or Pseudomonas spp. were done through experimental infection via interperitonial and intramuscular routes.

Summary in Arabic.