AQUATIC ANIMAL DIAGNOSTICS, PATHOGENESIS AND APPLIED EPIDEMIOLOGY
Location: Aquatic Animal Health Research
Title: GROWTH RESPONSE AND ACQUIRED RESISTANCE OF STREPTOCOCCUS INIAE-RECOVERED NILE TILAPIA, OREOCHROMIS NILOTIUCS
Submitted to: Annual Eastern Fish Health Workshop
Publication Type: Abstract Only
Publication Acceptance Date: November 30, 2005
Publication Date: February 3, 2006
Citation: Shoemaker, C.A., Lim, C.E., Aksoy, M., Welker, T.L., Klesius, P.H. 2006. Growth response and acquired resistance of Streptococcus iniae-recovered Nile tilapia, Oreochromis niloticus. 31st Annual Eastern Fish Health Workshop. Charleston, SC. p. 55.
The growth performance and acquired resistance of Streptococcus iniae-recovered Nile tilapia was determined. Tilapia were challenged with three doses of S. iniae (8.8 x 103, 8.8 x 104 and 8.8 x 105 CFU/fish for low, medium and high challenge, respectively). Groups of non-injected and tryptic soy broth-injected fish were maintained as controls. Significantly (P < 0.05) higher mortality (45.0 %) occurred in the high challenge treatment than in the low challenge treatment (29.6 %). The medium challenge group had mortality of 36.3 %. The S. iniae-recovered tilapia used to assess growth performance were selected from survivors without clinical signs of disease. Fish were randomly stocked at 30 fish per 57-L aquarium in triplicate and fed to apparent satiation for 8-weeks. No differences were detected in weight gain, feed intake, feed efficiency ratio or survival between S. iniae-recovered tilapia and the control treatments following the 8-week performance trial. Following the 8-week feeding study, the tilapia were challenged with 1 x 106 CFU/fish of S. iniae to assess acquired immunity. Mean cumulative mortality was significantly higher (P < 0.05) in the control treatments (41.7 % and 43.3 %) than in the low, medium and high challenge treatments (7.4, 3.3 and 8.3 %, respectively). The results suggest that S. iniae-recovered tilapia not showing overt disease signs gained acquired immunity and performed as well as non-infected tilapia.