Duration of resistance of yellowtail against pseudotuberculosis induced by Pasteurella piscicida ribosomal and formalin-killed vaccines

Many attempts have been made to develop a practical vaccine against pseudotuberculosis, Pasteurella piscicida infection in yellowtail (Seriola quinqueradiata) mainly by using formalin-killed cells (FKC) , but the protection provided by those vaccines was not satisfactory. In a recent study on various inactivated and component vaccines, better protection was afforded by a ribosomal vaccine compared with FKC, although an immersion vaccination with the ribosomal vaccine did not confer any protection. The duration of protection induced by Pasteurella piscicida vaccines has not been investigated so the present study was undertaken to compare durability of resistance induced by the ribosomal vaccine compared with FKC.