Bivalent vaccines for sea bass (Dicentrachus labrax) against vibriosis andpasteurellosis

The relative degree and duration of protection against Vibrio anguillarum a nd Pasteurella piscicida in sea bass vaccinated once by immersion at Ig was compared with fish vaccinated by immersion at Ig and revaccinated at 5 g b y immersion or intraperitoneal (i.p,) injection. The vaccines used were bas ed on V. anguillarum (serotype O1) and P. piscicida. The groups of fish wer e challenged with both pathogens separately at 7 weeks and 26 weeks post re vaccination. Sea bass vaccinated by immersion at Ig and again at 5 g by imm ersion or injection, demonstrated a significant level of protection against V. anguillarum lasting for 26 weeks post revaccination. Sea bass revaccina ted by immersion were significantly protected against P. piscicida 7 weeks post revaccination compared with nonvaccinated fish. Failure in killing non vaccinated sea bass during the latter pasteurellosis challenge renders dura tion of protection against P. piscicida beyond 7 weeks post revaccination a s inconclusive. No long-term protection was measured against either pathoge n in the fish vaccinated at 1 g.