Submitted to: Aquaculture
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/17/2005
Publication Date: 6/1/2006
Citation: Shoemaker, C.A., Vandenberg, G.W., Desormeaux, A., Klesius, P.H., Evans, J.J. 2006. Efficacy of a Streptococcus iniae modified bacterin delivered using Oralject TM technology in Nile tilapia (Oreochromis niloticus). Aquaculture 255, 151-156. Interpretive Summary: Streptococcus iniae is one of the most significant Gram-positive bacterial pathogens of cultured and wild fish worldwide. Estimates of economic losses in the United States alone exceed $10 million annually. Vaccines have been developed however, delivery is by injection. Injection delivery is difficult due to stress of handling each fish and the labor cost associated with the injection of each fish. A strategy to mass deliver vaccines to fish is desirable. We worked with a company from Canada (under a non-funded cooperative agreement) that developed an oral delivery strategy to deliver vaccines to fish and other animals. The results indicated that oral delivery of the patented ARS S. iniae vaccine incorporated in this delivery system was effective. Oral delivery of the S. iniae vaccine will provide a non-stressful, less labor intensive method of mass vaccination to tilapia.
Technical Abstract: This study evaluated the potential to orally deliver a previously developed Streptococcus iniae vaccine in tilapia using Oralject™ technology. This technology was developed to administer bioactive compounds to monogastric animals, and has been shown to be effective for delivery of a variety of antigens in numerous fish species. Two different formulations containing two doses of vaccine (four treatments) were fed to tilapia (4 tanks of 25 fish each) for one (Oralject-1 and Oralject-2 each containing 2 X 109 cells/g of feed) day (am and pm to satiation) or five (Oralject-1 and -2 each containing 2 X 108 cells/g of feed) days (once daily to satiation). The incorporated vaccine was a patented lyophilized modified bacterin (US Patent No. 6,379,677 B1). A positive control treatment [intraperitoneally (i.p.) injected S. iniae vaccine] and a negative control treatment (i.p. injection of tryptic soy broth, TSB) were included. Mean percent intake indicated that tilapia fed for one day (twice to satiation) the Oralject-1 consumed significantly (p < 0.05) more feed than fish fed Oralject-2 (4.05 vs. 3.21 %, respectively). Fish fed for five days either commercial feed or Oralject-1 or -2 also showed differences in feed intake; on most days, fish consumed significantly less (p < 0.05) Oralject-2 (~ 1%) than the commercial diet or Oralject-1 (~2.5 %). Tilapia were challenged 23 days post vaccination by i.p. injection of 1 X 106 CFU S. iniae/fish. Mean percent mortality was 47.5 (± 7.5) in the TSB-immunized challenged tilapia and was significantly higher (p < 0.001) than in all immunized groups. No mortality occurred in the i.p. vaccinated tilapia. Mortality ranged from 17.5 to 31.25 in the Oralject™ treatments. Relative percent survival was 100 % in the i.p. vaccinated tilapia and 63.1 % in the most effective Oralject-vaccine-treated group. The results suggest that oral delivery of the lyophilized S. iniae vaccine using Oralject™ technology provided protection against streptococcal disease. These data validate an initial proof-of-principle for oral vaccination of tilapia using S. iniae in the Oralject™ system.