SEA LICE (CALIGUS) INFESTATION AND ITS ROLE IN ENHANCEMENT OF BACTERIAL INFECTION IN SEA BASS (DICENTRARCHUS LABRAX) IN DAMEITTA GOVERNORATE
Mohamed E. Abou Elatta
Fish Health Department, Central Laboratory for Aquaculture Research, Agricultural Research Center, Ministry of Agriculture, Egypt.
|Received 2/ 7/ 2013||
Accepted 15/ 8/ 2013
One hundred clinically infected Sea bass (Dicentrarchus labrax) 80 ±5gm and 15 ±2cm in length were collected from earthen pond from Tri-angular of El Deeba, Damietta Governorate and subjected to clinical, postmortem investigation, haemotological, bacteriological, parasitological and histopathological examination. Also, the physicochemical analysis of water pond holding Sea bass (Dicentrarchus labrax) was recorded. The clinical investigation observed were lethargic, restlessness, cease to food, excessive mucus, nervous manifestation and jumping over water surface infested fishes were rubbed themselves on solid substrate in attempt to dislodge the crustacean parasites which appeared attached to gills, skin & fins rays, head region and buccal cavity. Opaque of skin, diffused hemorrhage scattered on gill cover, around the mouth, pre anal, caudal and pectoral region, mechanical damage of skin, erosion, sometimes reach ulceration of skin were observed. Infested fishes were showed gasping of air, swimming near to water surface and accumulated around the water inlet (High current water). In severe cases, fish was observed with mechanical damage of the skin, erosion, sometimes ulceration. The postmortem finding showed presence of large number of caligus on the body surface, also occurred in oral cavity and under gills cover. In some cases, the gills were pale with brown focci look like marbling appearance, pale liver, congested spleen and kidney. Other cases showed congested liver and enlarged gall bladder and distended with bile. The haemotological finding of infested Sea bass with caligus showed decreasing in PCV, Hb, total protein and calcium while increasing in glucose, ALT and AST. The result of bacteriological examination revealed the isolation of Vibrio alginolyticus and Streptococcus species. V. alginolyticus was isolated with 35% from infested fish with Caligus. V. alginolyticus was isolated with high percent from necrotic skin, gills, liver and kidney respectively while in low percentage from spleen and blood. The pathogenicity of isolated V. alginolyticus was done and recorded. The result of antibiogram revealed that, Florefenicol, Enrofloxacin, Nalidixic acid and Ciprofloxacin were highly effective against V. alginolyticus. The parasitological examination revealed that the crustacean parasites were identified as copepods of Caligus minimus and Caligus carangis, the prevalence of infestation was 100% and the mean number of individuals per host was twenty five. The histopathological finding of infested skin and gills of infested Sea bass (Dicentrarchus labrax) were studied. The trial of treatment by using Ivermectin 1% (Iverzin lotion 1%) 6ml/L for 5 minutes gave a good results in elimination of adult caligus and immuture developmental stages from infested Sea bass (Dicentrarchus labrax) .