CASE STUDY ON MASS MORTALITIES IN CAGED CULTURED MONOSEX NILE TILAPIA (OREOCHROMIS NILOTICUS) IN EL-FAYUOM GOVERNORATE, EGYPT.
Walaa T. El-Ekiaby1; Abou El-Atta, M. E.1;
Moustafa, M. S. 1and Lamees S. Abd El-Fattah2
1 Fish Health and Management Department, Central Laboratory For Aquaculture Research, Agricultural Research Center, Egypt.
2 National Institute of Ocheanography and Fisheries.
| Received 5/ 1/ 2014 |
Accepted 27/ 2/ 2014 |
Abstract
A total number of 100 naturally infected monosex Nile tilapia (Oreochromis niloticus) were collected alive with an average body weight 200 ±5g per fish from cages suffered from heavy mortalities in El Rayan valley in El Fayuom Governorate in the period of April to October 2012. The physicochemical analyses of water were recorded. Clinical signs and postmortum findings of naturally infected fish were done.
The bacteriological examination revealed the presence of 160 isolates of Enterococcus fecalis with prevalence 45.6 %. Isolation and identification was done by traditional methods
then confirmed using regular PCR technique which revealed that the isolated bacteria strain was Enterococcus fecalis. Isolates were isolated from fins, skin ulcers, liver, spleen, kidney and brain with percentage of 11.25, 25, 21.25, 15, 18.12 and 9.94% respectively.
Enterococcus fecalis
gave 733 bp product size specific for 16S rRNA. The antibiogram sensitivity test of isolated Enterococcus fecalis showed highly sensitive to Amoxicillin (Ax25) and Penicillin (P10). The experimental infection of Oreochromis niloticus with Enterococcus fecalis was associated with mortality rate 80 % in case of intraperitoneal injection (I/P) while intramuscularly injection (I/M) cause 60% mortality. Histopathological changes were studied.
