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Abstract
VI-Summary
The present investigation was done to know the common fish pathogens, lation and identification of the streptococcus species by conventional method SDS PAGE, RAPD-PCR analysis. This investigation applied on 1200 fishes O. niloticus and 600 C. garepinus), these fishes submitted to clinical and t mortem examination and showed that The infected fish showed loss of etite, sluggish movement, swimming close to the surface of the water, argic, no escape reflex, darkening of the skin, easily detached and lose of the les, uleer formation, uni- or bilateral exophthalmia, haemorrhage of the eye,
some cases change cloudy and destruct of eye (pop-eye), haemorrhages on the . especially in the base of fins and tail, abdominal distention, inflammation, ngestion of anal opening and may vertebral column deformities. Internally the er is mainly pale or normal in some cases, and the peritoneal cavity filled with cetie fluid and in some cases haemorrhage in intestine, enlarged spleen and arly black, enlarged and congested kidney.
The results of bacteriological examination revealed the presence of 268 ,Streptococcal species isolates. The prevalence was 22.33 %.
A total of 600 clinically diseased 0. niloticus and 600 clinically diseased C. gariepinus fish were examined throughout the year, the percentage of streptococcal infection for O. niloticus was (17.2%). The highest prevalence rate was recorded in summer (31.33%) follow by spring (18 %), follow by autumn (13.33 %) and the lowest percentage was in winter (6 %) . and for C. ’ gariepinus fish the percentage of streptococcal infection was (27.5%). The highest prevalence rate was recorded in summer (54 %), follow by spring (30 %), and followed by autumn (16.67 %) and the lowest percentage was in winter (9.33 %). The percentage of fish from which Streptococcus spp. were isolated (from total infected tilapia) were (39.8%) in Kafr EI-Sheikh, then