الفهرس 
coverOnly 14 pages are availabe for public view
 |  | from | 59 |  |  |
| | | from | 59 | | |
Abstract
The disease is mainly caused by specific strains of Vibrio in L. vannamei shrimp both in hatcheries and in grow-out cultures however, this is the first time that is isolated from L. vannamei shrimp. The present work aimed to study the following items in L. vannamei; Water quality and bacteriological analysis of water in rearing of L.vannamei during hatchery and growout stage at Wadi-mariout - Borg El-Arab city at Alexandria and Domitte governorate. Clinical sign and gross pathology of naturally infected L. vannamei; biochemical and physiological characteristics of different Vibrio species by different bacteriological methods were recorded. Sensitivity test of different Vibrio species and Histopathological studies in hepatopancreas of experimentally infected L. vannamei with V. harveyi .
In our study, a total number of two hundreds pieces of diseased shrimp of Litopenaeus vannamei samples (100 samples) were collected from hatchery and (100 samples) collected during growout stages from both Alexandria and Domitte region the average body weight. Shrimp were transported a live to the laboratory of the department of poultry and fish diseases, Faculty of Veterinary Medicine, Alexandria university. The freshly dead fish specimens were subjected to full clinical and bacteriological examinations. Also, four hundred postlarvae of L. vannamei for measurement of pathogenicity and control of Vibrio harveyii infection were used.
* The results revealed that the :
1) The levels of dissolved oxygen, nitrite (NO2) and unionized ammonia (NH3) in all tested water samples were higher than the Permissible limits during grow out stage in both Borg El-Arab, Alexandria province and Mathalath El-Diba Domitte province than hatchery stage in the same place.
2) Increase of total plate count (TPC) in all tested water samples during aquaculture farm stage in both Borg El-Arab, Alexandria province and Mathalath El-Diba Domitte province than hatchery stage in the same place, while is more increase in Mathalath El-Diba than Borg El-Arab. On the same manner the total presumptive vibrio count (TPVC) was increase in all tested water samples during aquaculture farm stage in both Borg El-Arab, Alexandria province and Mathalath El-Diba Domitte province than hatchery stage in the same place, while is more increase in Mathalath El-Diba than Borg El-Arab .
3) Clinical signs and gross pathology of infected L. vannamei during hatchery stage are lethargic, anorexic and swim near the surface and edges of ponds . They display degrees of pink to red colouration of the appendages and body surface . The gills may be yellow to pink. Gill fouling and tail rot are common among infected L. vannamei obtained from hatchery Borg El-Arab, Alexandria province. Infected L. vannamei during growout stage appear pale red while their tail fans become bright red (red tail) . They are soft shelled, lethargic and anorexic. Apart from the white, turbid appearance of the hepatopancreas and/or midgut was recorded .
4) After culture on media and biochemical reactions, Results indicated that (36) naturally infected L. vannamei out of (200) were found to be infected with Vibrio species. The Vibrio species was summarized as; V. anguillarum (1, 2), (2, 3), V. vulnificus (2, 2), (3, 6), V. harveyii (2.3), (1, 4), V. fluvialis (0, 1), (0, 1) and V. alginolyticus and (0, 0) isolates during hatchery stage and growout stage in Borg El-Arab, Alexandria province respectively (1, 2) isolates during hatchery stage and growout stage in Mathalath El-Diba Domitte province respectively.
5) PCR method used for detection of the most prevalent bacterial serotype among all bacterial serotypes (V. vulnificus and V. harveyi) and used V. harveyi for experimental infection .
6) The results of the sensitivity of different Vibrio isolates to different antimicrobial revealed that the ciprofloxacin is the most susceptible antibiotics to different isolated bacteria . On the other hand the other tested antibiotics appeared as resistant to all tested bacterial isolates.
7) Experimental infection of postlarvae of L. vannamei with V. harveyii and in vivo biocontrol by Bacillus spp. results revealed that :
a) B. subtilis improvement of relative percentage survival against V. harveyi.
b) B. subtilis improvement of immune indices of shrimp such as respiratory burst activity, and phenoloxidase as compared with the control group . The RBA activities and PO feed-treated groups were significantly higher than those of the control group.
c) Histopathological findings of hepatopancreas of experimentally infected L vannamei with V. harveyii showing acute sloughing of tubular epithelial cells and haemocyte infiltration of hepatopancreas; haemocyte infiltration; haemocyte infiltration, bacterial colonization; Epithelial cells, intratubular bacterial colonization, and haemocytic infiltration; Hydropic degeneration .