Submitted to: European Association of Fish Pathologists
Publication Type: Abstract Only
Publication Acceptance Date: June 4, 2007
Publication Date: September 17, 2007
Citation: Klesius, P.H., Shoemaker, C.A., Evans, J.J. 2007. Immersion vaccination of newly hatched and sex reversed nile tilapia (oreochromis niloticus) using a streptococcus iniae vaccine. page 92. European Association of Fish Pathologists. 13th EAFP International Conference on 'Disease of Fish and Shellfish' 17th-21st September, 2007 Grado, Italy. Technical Abstract: The objective of this investigation was to assess immersion Streptococcus iniae vaccination of newly hatched and sex reversed Nile tilapia fry against S. iniae. Nile tilapia (Oreochromis niloticus; 0.01 g wet weight; 160,000 fish/1500 L) were immunized by bath immersion using a 1/500 dilution of modified S. iniae vaccine for 2 min with aeration at a Florida tilapia hatchery. The fish were sex reversed with oral administration of 17-beta-methyltestosterone (MT) in their starter feed for 28 d and then shipped (0.3-0.4 g wet weight) to a Minnesota tilapia producer. The male fish (about 90%) were immersion boostered with the vaccine using a 1/500 dilution for 2 min at 35 d post vaccination. The fish (15 g) were again boostered 34 d later. After 7 d post secondary booster, 150 fish (23 g) were shipped to the USDA laboratory in Alabama and stocked into 57 L aquaria. No mortality was reported during the immunizations and transport. After 7 d acclimation, 20 immunized fish were cohabitated with 20 TSB-immunized calcein-marked fish in 4 separate 57 L aquarium (Klesius et al. 2006. Fish and Shellfish Immunol. 20:20-28) and challenged with 1 x 106 or 1 x 107 CFU S. iniae/fish in duplicate aquaria. The S. iniae vaccine relative percent survival (RPS) 14 d post challenge was 68.2 and 47.4 when challenged with 1 x 106 CFU/fish and 78.5 and 91.7 when challenged with 1 x 107 CFU/fish. Streptococcus iniae was cultured from 34% of 50 immunized fish sampled from the farm. Aeromonas hydrophia was obtained from 40% of the 50 sampled fish. No bacteria were cultured from 18% of the fish. The farm reported healthy and actively feeding fish with greatly reduced mortality from S. iniae. A specific antibody response was measured following vaccinations and appeared to be directly related to the protective immune response against S. iniae. The results indicate that immersion immunization using diluted S. iniae vaccine in newly hatched tilapia followed by sex reversal and immersion boosters was efficacious against S. iniae. Efficacy of Streptococcus iniae vaccine in Nile tilapia following immersion immunizations of newly hatched and sex reversed fry and fingerlings. Aquarium CFU/Fish challenge1 Cumulative mortality in vaccinates/controls RPS 1a 1 x 106 6/19 68.2 2a 1 x 106 10/19 47.4 3b 1 x 107 3/14 78.5 4b 1 x 107 1/12 91.7 120 vaccinates and 20 control (TSB immunized) were cohabitated in a single aquarium and challenge with S. iniae by IP injection.