TWENTY-FOURTH ANNUAL EASTERN FISH HEALTH WORKSHOP Royal Pavilion Resort, Atlantic Beach, NC MARCH 9-11, 1999 Efficacy Of A Killed Streptococcus iniae Vaccine Craig A. Shoemaker1, Joyce J. Evans2 and Phillip H. Klesius1 1U.S. Department of Agriculture, Agricultural Research Service, Fish Diseases and Parasites Research Laboratory, PO Box 0952, Auburn, AL 36831;2300 Washington Street, Chestertown, MD 21620 Streptococcus iniae, which causes streptococcal disease in tilapia (Oreochromis niloticus) and hybrid striped bass (Morone saxatilis X M. chrysops), is the most important disease agent in water re-use aquaculture systems in the United States. An effective vaccine to S. iniae is desirable and would help reduce the economic loss caused by this bacterium. We have produced a killed toxoid enriched S. iniae vaccine containing whole cells and concentrated extracellular products (greater than 2 kDa). The vaccine was administered to tilapia (mean weights of 25 and 100g) by intraperitoneal (IP) injection. At 26-30 days post vaccination, the groups of vaccinates and non-vaccinates were IP challenged with S. iniae (1 X 108 CFU) and monitored daily for clinical signs and mortality. Vaccination reduced mortality and prevented erratic swimming, hemorrhagic exopthalmia and ocular opacity. Non-vaccinates began dying 1 day post challenge from S. iniae infection. Clinical signs began occuring on day 4-5 post challenge with peak mortality occuring at about the same time. Vaccine administered by IP injection resulted in RPS values of 84 to 100. These results show that the development of an effective S. iniae vaccine for use in tilapia is possible. The intramuscular route of immunization is currently underway to determine the optimal route of vaccination by injection. Return to 24th Annual Eastern Fish Health Workshop Return to Leetown Science Center Home Page