Production of killed vaccine from Streptococcus sp. and its application in sea bass (Lates calcarifer)

Abstract

Fish with an average length of 3.0-4.0 inches vaccinated with formalin-killed vaccine of Streptococcus sp. either by intraperitoneal injection and immersion methods had a survival rate of 100% indicating that the vaccine is safe to be used with sea bass. The highest efficacy was received when the vaccine containing bacterin at 2.50x1010 CFU/ml. Injection of vaccine together with adjuvant (CFA) was highly effective against Streptococcus sp. infection. The relative percent survival (RPS) of fish injected with vaccine alone and vaccine plus adjuvant were 100 (10 days post vaccination), 54.06 and 92.29 (20 days post vaccination) and 31.58 and 73.68 (30 days post vaccination) respectively. The fish which received vaccine by hyperosmotic immersion showed higher resistance to the disease than by direct immersion with the RPS of 30.77 and 71.80 (10 days post vaccination), 9.75 and 70.73 (20 days post vaccination) and 7.14 and 16.67 (30 days post vaccination) for direct immersion and hyperosmotic immersion, respectively