STREPTOCOCCOSIS IN SEABASS (Lates calcarifer Bloch) AND PRODUCTION OF VACCINE AGAINST Streptococcus sp.

摘要

Diseased seabass (Lates calcarifer Bloch) exhibited body darkening, loss of equilibrium, exophthalmia and cloudy of cornea, ascites, pale liver, splenomegaly and hemorrhage in the brain. Gram positive cocci and catalase negative bacteria was isolate from the diseased seabass. They grow well in media with pH range 7 - 9 as well as with 0-30 ppt NaCl. Base on physio - chemical and biochemical characteristic, bacteria were identified as Streptococcus sp. The virulence of these bacteria to juvenile seabass was 1.937 × 10~3 CFU (14 day - LD ). The results from experimental infection found high number of bacteria in various tissues in the initial stages of infection and decline in the later stages. Diseased fish exhibited reduction of hematocrit, hemoglobin, plasma protein as well as red blood cell count. In contrast with white blood cell count was found higher in diseased fish than healthy fish. Histopathological changes of diseased seabass included large number of melano - macrophage infiltrated into liver, spleen and kidney. Necrosis and degeneration were found in various tissue including liver, kidney and brain. Inflammation and granuloma were found in heart and brain tissue. Cell hyperplasia and fusion of lamella were found in gill. Eye was severely effect by bacteria, eye chamber filled with bacteria and inflammative cell as well as vacuolation of retina. Formalin - killed vaccine was prepared and tested in juvenile seabass (3-4 inch in length) by mean of peritoneal injection, immersion and oral administration. All 3 routes of administration were saved to fishes. Fish produced the best respond to 2.5 × 10~(10) CFU / ml vaccines. Injection vaccine plus Complete Freund's Adjuvant (CFA) gave a good rotection against Streptococcus challenge. Combination of immersion vaccine with oral route gave a better protection than single route when compared with the control group.