28th ANNUAL EASTERN FISH HEALTH WORKSHOP April 21-25, 2003 Induction Of Elevated Protective Immunity And Phagocytosis In The American Lobster William. D. Paterson1 and I. R. Keith2 1Paterson Applied Technology, Loretto, Ontario, Canada; 2Charlottetown, Prince Edward Island, Canada The valuable commercial lobster fishery suffers significant annual losses due to disease, especially during the pounded holding periods, characteristic of this industry.  Research progresses to understand this phenomenon toward providing tools to minimize these losses.  In this presentation, stimulated increases in phagocytosis and protective immunity against gaffkemia will be described.  Previously developed procedures to quantify the in vitro phagocytosis of sheep erythrocytes (SRBC) and Aerococcus viridans var homari bacteria by lobster hemocytes were utilized to measure the effect of several stimulants on the level of phagocytosis.  Stimulation of lobsters with Pseudomonas perolens cells or endotoxin resulted in increased phagocytosis.  A lower response was elicited by A. viridans cellular vaccines.  The dynamics of this increased phagocytic response indicated an onset of eight days and duration of about 80 days.  Lack of specificity was shown by   increases in phagocytosis of particles other than those of the stimulant source.  The conference of increased protective immunity against gaffkemia was evaluated in the laboratory using both juvenile and adult lobsters and in the field with adult animals.  A vaccine composed of inactivated A. viridans cells was injected into the ventral sinus of each treated animal.  Protection was evaluated following assessment of gaffkemia mortality caused by injection of graded doses of virulent, viable A. viridans cells.  Significant increases in survival of both juvenile and adult animals resulted following vaccination.  The increase in gaffkemia protection was detected about six days after vaccination of lobsters and lasted for approximately 90 days.  In the field, protective immunity to gaffkemia was assessed in Bay of Fundy lobster pounds using differential banding to distinguish between vaccinates and controls.  Survival recovery data constituted the measure of vaccine performance.  In three trials using different lobster stocks, vaccination increased susrvival by 12.5, 16.7, and 26.2 percent, respectively.  In summary, increased phagocytosis and protective immunity resulted from stimulation or vaccination of lobsters.  Only virulent A. viridans was a potent immunogen.  Return to 28th Annual Eastern Fish Health Workshop Return to Leetown Science Center Home Page