28th ANNUAL EASTERN FISH HEALTH WORKSHOP April 21-25, 2003 Fish Vaccinology Phillip H. Klesius1, Joyce J. Evans2, and Craig A. Shoemaker1 1Agricultural Research Service, U.S. Department of Agriculture, Aquatic Animal Health Research Laboratories, P.O. Box 952, Auburn, AL 36830; and 2151 Dixon Drive, Chestertown, MD 21620 Vaccination is a safe and effective means to prevent diseases, and to increase the productivity, and the profitability of farmed fish.  Vaccines will be the prime prophylactic measure of the future due to rapidly developing advances in fish vaccine technology.  Currently, killed and modified live vaccines are licensed, and used to prevent bacterial diseases of fish.  Routes of administration of killed and modified live bacterial vaccines are by injection and immersion, respectively.  The duration of protective immunity is dependent on the vaccine type.  The duration of a killed vaccine with or without adjuvants is 6 to 8 months, in contrast to a duration of years for a modified live vaccine.  Humoral or antibody-dependent immunity is stimulated by injection of a killed vaccine, and thus its effectiveness is limited to extracellular pathogens that are susceptible to humoral antimicrobial pathways.  On the other hand, a modified live vaccine produces both cellular, and humoral antimicrobial immunities that can be effective against both intracellular and extracellular pathogens.  In addition to these advantages, modified live vaccines can be administered more cost-effectively to larger populations of fish at a younger age with minimal stress to the vaccinates.  The economics of vaccination is of utmost importance in the production of fish.  For example, the use of AQUAVAC-ESC®, a modified live vaccine for the prevention of enteric septicemia of catfish, has increased the pounds harvested per acre (P <0.02), pounds per 1,000 fish (P<0.05), and the feed conversion ratio (P<0.09) of channel catfish.  Oral, DNA, and recombinant types of vaccines are being researched to determine their potential as licensed vaccine products to determine if they have advantages over killed and modified live vaccine technologies. Return to 28th Annual Eastern Fish Health Workshop Return to Leetown Science Center Home Page