Submitted to: Annual Meeting World Aquaculture Society
Publication Type: Abstract Only
Publication Acceptance Date: February 27, 2003
Publication Date: May 19, 2003
Citation: KLESIUS, P.H., EVANS, J.J., SHOEMAKER, C.A. EFFECTS OF SUBLETHAL DISSOLVED OXYGEN STRESS ON BLOOD GLUCOSE AND SUSCEPTIBILITY TO STREPTOCOCCUS AGALACTIAE IN NILE TILAPIA, OREOCHROMIS NILOTICUS. ANNUAL MEETING WORLD AQUACULTURE SOCIETY. 2003. Technical Abstract: The stress effects of sublethal dissolved oxygen (DO) exposures on blood glucose levels and changes in susceptibility to Streptococcus agalactiae infection in Nile tilapia (Oreochromis niloticus) were determined using the OneTouch ® Ultra blood glucose monitoring system. One hundred fish were monitored for temporal changes in blood glucose concentrations before, during and after exposure to £ 1 mg/l DO for 24 h. In additional experiments, fish were exposed to optimal DO or sublethal DO. After exposure, fish were administered 9.5 ´ 101 CFU or 7.5 ´ 102 CFU of S. agalactiae (infected) or tryptic soy broth (TSB) (uninfected) by intraperitoneal (IP) injection. Blood glucose (30.7 ± 1.31 mg/dl) was found to significantly (P >0.001) increase (121 ± 7.41 mg/dl) in response to sublethal DO exposure. Fish exposed to low DO after infection with S. agalactiae at 9.5´ 101 CFU or 7.5 ´ 102 CFU had significantly higher mortality rates of 27 and 80%, respectively, as compared to fish exposed to optimal DO. None of the fish exposed to optimal DO died due to streptococcal infection after challenge with either dose. These increases in susceptibility as a result of sublethal DO exposure could be explained by the stress response. Impairment of innate resistance of tilapia to S. agalactiae may be the result of the stress response to the sublethal DO exposure.