Bivalent vaccines for sea bass (Dicentrachus labrax) against vibriosis and pasteurellosis

The relative degree and duration of protection against Vibrio anguillarum and 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 by immersion or intraperitoneal (i.p,) injection. The vaccines used were based on V. anguillarum (serotype O1) and P. piscicida. The groups of fish were challenged with both pathogens separately at 7 weeks and 26 weeks post revaccination. Sea bass vaccinated by immersion at Ig and again at 5 g by immersion or injection, demonstrated a significant level of protection against V. anguillarum lasting for 26 weeks post revaccination. Sea bass revaccinated by immersion were significantly protected against P. piscicida 7 weeks post revaccination compared with nonvaccinated fish. Failure in killing nonvaccinated sea bass during the latter pasteurellosis challenge renders duration of protection against P. piscicida beyond 7 weeks post revaccination as inconclusive. No long-term protection was measured against either pathogen in the fish vaccinated at 1 g.