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Abstract
The present study was planned to investigate streptococcosis in
cultured and wild Nile tilapia. The studies were carried out on 160 Nile
tilapia. The clinical picture was darkening of skin, opacity in the eye,
haemorrhages in different parts of body with presence of detached scales.
20 bacterial isolates of Streptococcus faecalis were detected. The
prevalence was high in summer season (44%) than winter (8%) to gain
total prevalence (18%) all over the year. Kidney was the most common
organ where44.4% of Streptococcus species were located. The antibiogram
revealed that the isolates were sensitive to oxytetracycline and
chloramphenicol, and resistant to ampicillin, erythromycin, nalidixic acid,
neomycin, streptomycin, kanamycin and sulphaltrimethoprim.
Experimentally infection with Streptococcus faecalis caused nearly the
same clinical signs found. The mortalities were observed among fish
infected by dipping in the bacterial suspension with skin scrafication and
by intraperitoneal injection.
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