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Abstract
The present study was planned to investigate the most bacterial
diseases affecting cultured tilapias.
These studies were carried out on 300 tilapias collected
randomly from El. Abbassa Fish Forms, Sharkia Governarate as 75
Oreochromis nilaticus, 75 O. aurous, 75 Sarothredone galilaeus
and 75 Tilapia zlllli.
The present study revealed the follwing :
The highest affected tilapia by bacterial diseases was o.
niloticus while the least affected Tilapia was T. zillii, where the
incidence of infection were 14 , 11.6 , 5.6 and 4.6% in O. niloticus,
O. aurous, S. galilaeus and T. zillii respectively.
1- The most prevealing bacterial diseases affecting tilapias reard
in Abbassa Fish Farm were pseudomonas septicaemia, motile
aeromonas septicaemia, red mouth disease, columnaris disease
and ulcer disease with an incidence of30.5 ,28.7 ,9.2 , 19.4
and 120/0 respectively.
2- In the present study 74 bacterial isolates of Pseudomonas
species were detected and identified as pseudomonas putida,
Ps. Aeruginosa and Ps. fluorescence (60.8% , 32.40/0 and
6.70/0) respectively causing pseudomonas septicaemia.
3- Identification of 52 bacterial isolates of Aeromonas
hyDROPhila causingMAS, and red mouth diseases.
~UMMARY
( 95 )
l- 21 bacterial isolates of Flexibacter columnaris were recovered
from tilapias suffering from columnaris disease.
5- 17 isolates of Vibrio species (Vibrio damsela and Vibrio
metschenikovii) were isolated from ulcered tilapias.
5- The common clinical signs observed on diseased tilapias by
such bacterial diseases were haemorrhages on different parts of
external body surface, exophthalmia, ascitis, fin and tail rot,
dark colour of skin, ulcers with anemic gills in some cases and
congested in other ones.
7- The common postmortem findings in diseased tilapias revealed
presence of yellow ascitic fluid, congested kidneys or pale
colour and enlarged in size. Congested liver to pale colour and
presence of necrotic foci. The spleen was dark and the intestine
was inflamed with corregation in some cases.
8- The pathogencity test revealed that bacterial isolates recovered
from naturally infected tilapia were virulent to apparantly
healthy fish showing nearly the same clinical signs and
postmortem findings observed in naturally infected fishes.
9- The sensitivity test to different antibiotics revealed that all
isolates were sensitive to chloramphenicol and tetracycline but
Vibrio species were sensitive to ampecillin and resistant to
sulphamethoxazole trimethoprim while Ps. species and A.
hyDROPhila resistant to ampecillin and sensitive to
sulphamathoxazole trimethoprim.
JMMARY
( 96 )
. The histopathological studies showed In differnt bacterial
diseases affecting tilapias, showed edema, necrosis,
haemorrhoges and degenerative changes in various organs.