STUDIES ON STREPTOCOCCOSIS IN SOME FRESHWATER FISHES IN RELATION TO AQUATIC BIRDS

Abstract

Streptococcosis is the disease which has a considerable attention in recent years among fishes.

In this investigation 720 fishes of various species and life stages 240 from each Nile tilapia (O.niloticus), Nile catfish (C.gariepinus) and Gray mullet (M.cephalus) which were collected from different localities in Egypt in different seasons of the year, as well as I 0 moorhen (Gallinula cholrapus) were subjected to clinical and bacteriological examination to determine the prevalence of streptococcus infection.

Morphological and biochemical identification of the isolated streptococcus species were applied Beside 416 apparently healthy live O.niloticus with average Body weight 50±2 were used for studying the pathogenicity of the isolated streptococci, effect of environment (temperature, and salinity) on the pathogenicity of Str jaeca/is and trials of •treatment of experimentally infected fish by different chemicals and antibiotics according to the results of sensitivity test against Strfaeca/is.

Forty five healthy one day old duckling were used to determine the pathogenicity of streptococcus species isolated from fish to duckling (aquatic birds). Clinical, postmortem and histopathological examination of experimentally infected fish and duckling as well as effect of Strfaecalis on growth performance of 72 fingerlings O.ni/oticus were another objectives. The results of survey revealed that, the percentage or streptococcus infection among examined fishes (21.8%), In C.gariepimts (28.8%) 111 • mullet (20%) and in Tilapia (16.7%). The percentage of infection was highest in Summer (1 0.3%) followed by (6.7%), (3.1 %) and ( 1.8%) in Spring, Autumn and Winter respectively.