Submitted to: Aquaculture
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/28/2001
Publication Date: 1/1/2002
Citation: SHOEMAKER, C.A., KLESIUS, P.H., EVANS, J.J. IN OVO METHODS FOR UTILIZING THE MODIFIED LIVE EDWARDSIELLA ICTALURI VACCINE AGAINST ENTERIC SEPTICEMIA IN CHANNEL CATFISH. AQUACULTURE. 2002. 203. 221-227. Interpretive Summary: Enteric septicemia of catfish, caused by a bacteria (Edwardsiella ictaluri) is responsible for US $60 million in losses annually to the farm raised catfish industry. We developed and transferred to industry an effective modified live vaccine (AQUAVAC-ESC) against this disease. The vaccine is currently delivered to young fish by immersion after catfish hatch from the eegg. The vaccine is licenced by Intervet, Inc., Millsboro, DE. In this study, we wanted to determine if the vaccine could be administered to channel catfish eggs (in ovo) at the eyed stage (eyes become visible on larval fish in the egg) prior to the eggs hatching into fry. We hold a US patent [Klesius et al. 2000, Patent No. 6,153,202] on this technology and were able to vaccinate fish eggs safely and successfully with the modified live vaccine following vaccination with a single dose. Successful in ovo vaccination of channel catfish with the modified live E. ictaluri vaccine will be another tool for use in health management plans of catfish producers. In ovo vaccination of fish eggs will allow for the earliest immunization of fish (i.e., in the hatchery prior to exposure to disease agents).
Technical Abstract: Eyed channel catfish (Ictalurus punctatus) eggs were vaccinated by immersion exposure (10 minutes) with either the modified live Edwardsiella ictaluri isolate RE-33 grown in brain heart infusion broth (trial 1) or the lyophilized AQUAVAC-ESC vaccine (trial 2). Trial 1 consisted of vaccinated d(RE-33 E. ictaluri at 1*10**5 CFU/ml) and non-vaccinated (controls) treat- ments with the eyed eggs hatching into fry 4 days following treatment. In trial 2, three treatments were used, single vaccinated, vaccinated and fry booster vaccinated 7 days following initial immunization and non-vaccinated (controls). The vaccination in trial 2 was carried out according to the manufacturers recommendation for use on channel catfish fry (i.e., AQUAVAC- ESC label). Thirty-three (trial 1) and sixty days (trial 2) following vaccination, fish were challenged with E. ictaluri (isolate AL-93-75) at 1*10**7 CFU/ml. In trial 1, the relative percent survival of vaccinates was 87.9; however, data did not fit Amend's criteria. In trial 2, mean percent mortality in the non-vaccinated treatment (controls) (64.2+/-5.8) was significantly higher (p=0.003) than mean percent mortality in the single vaccinated treatment and booster vaccinated treatment (25.8+/-5.1 and 46.7+/-0.8, respectively). Relative percent survival was 59.7 in the single vaccinated treatment and 27.3 in the booster vaccinates. Safety and efficacy of the modified live E. ictaluri vaccine (AQUAVAC-ESC) was demonstrated in eyed channel catfish eggs following single vaccination. Booster vaccination did not enhance vaccine efficacy; however, timing of the booster may have been too soon following initial vaccination of eggs.