Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/1997
Publication Date: N/A
Interpretive Summary: Enteric septicemia of catfish (ESC) is the leading disease of cultured channel catfish and responsible for annual losses of 18 to 20 million dollars. Preventation of ESC is an important objective because treatment of ESC is not effective. Vaccines using killed Edwardsiella ictaluri, the cause of ESC, have not worked. We developed a live ESC vaccination scheme that protects catfish against most but not all isolates of E. ictaluri. Previously, it was believed that catfish immunized with one isolate was protected against all isolates. We demonstrated that this belief was untrue and an ESC vaccine needs to be against the isolates that are predominant in production ponds. Further, we demonstrated that live immunized catfish remained protected against ESC for up to 4 months in water at 18oC. These findings are important to the development of efficacious ESC vaccine.
Technical Abstract: It is generally believed that channel catfish, Ictalurus punctatus, immunized with one isolate of Edwardsiella ictaluri would be protected against different isolates of E. ictaluri. In this study six different isolates of E. ictaluri cultured from fish having enteric septicemia of catfish (ESC) and one isolate from the walking catfish, Clarius batrachus, were evaluated for cross protection. Channel catfish immunized by live exposure against isolate EILO were significantly protected against ESC following challenge with E. ictaluri isolates EILO, ATCC-33202, S-94-1017, S-94-629 and AL-93-75, but not against isolate AL-93-58. Immunization with isolates AL-93-75, EILO, AL-93-58, S-94-1017 and S-94-629 induced protection against AL-93-75. Immunization with isolates ATCC-33202 and S-94-1051 did not induce protection against AL-93-75. Channel catfish immunized with two isolates EILO and AL-93-58 (together) were protected upon challenge with the isolates AL-93-75, EILO, AL-93-58 and S-94-1017. Challenge of EILO and AL-93-58 immunized fish with ATCC-33202 resulted in partial protection. Our results, show that differences exist between E. ictaluri isolates in their ability to induce protective immunity against ESC. Catfish immunized at 26 oC and held at 18oC remain protected against heterologous challenge for four months. These findings are important to the development of efficacious ESC vaccines.