Submitted to: International Veterinary Vaccines and Diagnostics Conference
Publication Type: Other
Publication Acceptance Date: May 1, 2000
Publication Date: July 23, 2000
Citation: KLESIUS, P.H., SHOEMAKER, C.A., EVANS, J.J. DEVELOPMENT AND USE OF MODIFIED LIVE EDWARDSIELLA ICTALURI VACCINE AGAINST ENTERIC SEPTICEMIA OF CATFISH. 2nd INTERNATIONAL VETERINARY VACCINES AND DIAGNOSTICS CONFERENCE. POSTER PRESENTATION. 2000. Technical Abstract: Enteric septicemia of a catfish (ESC), caused by Edwarsiella ictaluri, is responsible for over $60 million in annual losses to the catfish industry in the United States. In previous studies, we demonstrated that cell mediated immunity (CMI) and killing of E. ictaluri by macrophages was responsible for protective immunity. Passive transfer of immune antibodies failed to protect catfish against ESC. The objective of this study was to develop a modified live E. ictaluri vaccine that would provide protective CMI. We used rifampicin to attenuate an E. ictaluri isolate. The modified live E. ictaluri did not cause ESC in susceptible catfish. However, the E. ictaluri was able to enter and persist in the catfish resulting in acquired CMI to ESC. Safety of the E. ictaluri was shown at 2 X 107 colony forming units / mL of bacteria following immersion exposure to the vaccine strain for 60 minutes. No mortality or reversion to virulence occurred following five serial in vivo passages. Efficacy of the modified live E. ictaluri vaccine was demonstrated in 14 day to 9 months old channel catfish. This protective immunity was demonstrated at 21 days post vaccination following 2 to 10 minute immersion exposures in water containing the vaccine. This vaccine is licensed for use in 9 days old channel catfish fry and is being produced by Intervet, Inc. under the label AQUAVAC-ESC'.