Efficacy of a killed Streptococcus iniae vaccine in tilapia (Oreochromis niloticus)

Tilapia (Oreochromis niloticus) were vaccinated intraperitoneally (IP) at m ean weights of 25 and 100 g with killed Streptococcus iniae vaccine compose d of whole cells and concentrated, extracellular products (greater than 2 k Da). At 30 days post vaccination, the groups of vaccinates and non vaccinat es were IP challenged and monitored daily for clinical signs and mortality for 60 days. Vaccination reduced mortality 91.3 percent and prevented errat ic swimming, hemorrhagic exophthalmia and ocular opacity, immunized 25g til apia had relative percent survival (RPS) of 95.3 and 100 g tilapia had RPS' s ranging from 84.2 to 94.7.