الفهرس 
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Abstract
Salinity and Temperature Extremes Effects On Pathogenicity Of Vibrosis In Cultured Seabass
Vibriosis is one of the devastating bacterial diseases affecting marine fishes, crustaceans and bivalves causing high mortalities with severe economic losses worldwide. Family Vibrionaceae contain 45 species of Gram-negative that live in a wide range of aquatic environments. In our study, a total number of one hundred and fifty (150) of cultured sea bass (Dicentrarchus labrax L.) were collected from private fish farms in Mathalath-El Diba region–Domitte city at Domitte governorate, Egypt during different seasons (December of 2016; January of 2017; February of 2017; June of 2017; July of 2017 and August of 2017).
The weights, number of fish every months and water temperature as well as salinity. Fish 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, postmortem (PM) lesions and bacteriological examinations.
Results of heavy metal concentrations (mg/L) in water samples comparison with permissible levels clear that the Cadmium (Cd) levels were higher in some water samples over the permissible level so that it considered toxic for fish.
Cadmium levels follow this order: Aug. 2017 > July 2017 > June 2017 over the permissible level. Lead (Pb) levels were higher in Aug. 2017> July 2017 > June 2017 > over the permissible level. Mercury (Hg) levels were higher in Aug. 2017 > and July 2017 than the permissible levels. Moreover, Iron (Fe) levels were higher in all water samples over the permissible level. Moreover, Iron levels follow the following order: Aug. 2017; July 2017; June 2017; Feb. 2017; Jan. 2017 and Decemb. 2016.
Results of clinical examination of infected sea bass (Dicentrarchus labrax L.) show severe hemorrhagic patches at the body and severe hemorrhages at base of pectoral fins. Moreover, hemorrhages at the operculum and around the eye some naturally examined sea bass showing darkening of skin color and with opacity of the eye and necrotic tissue overhead and petechial hemorrhages on the opercular region.
Results of Postmortem (PM) examination showing hemorrhages at gills; others show serous ascetic fluid tinged with blood, while the others show congestion of different degrees on the liver of examined fish. Some naturally examined broodstock sea bass has petechial hemorrhages distributed on liver surface and extended to the gastrointestinal tract leads to gastroenteritis.
The data showed that the high incidence of V. anguillarum, V. harveyi, V. vulnificus, V. alginolyticus and V. fluvialis was higher in gills than; liver than; Kidneys and lowest in Spleen during Decemb. 2016; Jan. 2017; Feb. 2017; June 2017; July 2017 and Aug. of 2017 in naturally infected sea bass respectively. Moreover the data revealed that the V. anguillarum, V. harveyi, V. vulnificus, V. alginolyticus and V. fluvialis increased in different organs with increase of temperature and salinity. On the other hand the V. harveyi was not isolated except in June 2017; July 2017 and Aug. of 2017 which is the warmness months all over the years.
Histopathological results of internal organs of naturally infected sea bass with different Vibrio species showed that Spleen had sever fibrosis and hemosiderin-phages and sever fibrosis and hemosiderin-phages. Liver showed congested portal vein, accumulation of bile pigment and coagulative necrosis of hepatocytes with the bile duct hyperplasia, increased connective tissue around bile duct and coagulative necrosis of hepatocytes.