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United States Department of Agriculture

Agricultural Research Service

Title: Duration of Protective Antibodies and Correlation with Survival in Nile Tilapia (Oreochromis Niloticus) Following Streptococcus Agalactiae Vaccination

Authors
item Pasnik, David
item Evans, Joyce
item Klesius, Phillip

Submitted to: Diseases of Aquatic Organisms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 24, 2005
Publication Date: September 5, 2005
Citation: Pasnik, D.J., Evans, J.J., Klesius, P.H. 2005. Duration of protective antibodies and correlation with survival in nile tilapia (oreochromis niloticus) following streptococcus agalactiae vaccination. Diseases of Aquatic Organisms. 66:129-134.

Interpretive Summary: Streptococcus agalactiae infections have been associated with significant morbidity and mortality among freshwater, estuarine, and marine fish species worldwide. Pathogenesis in fish involves septicemia and colonization of numerous organs, and clinical signs appear soon after infection and include depression or excitability, anorexia, 'C'-shaped body posturing, erratic swimming, and death. Considering the economic importance of fish susceptible to S. agalactiae throughout the world, a highly efficacious S. agalactiae vaccine was developed using an extracellular product (ECP) fraction and formalin-killed whole cells of S. agalactiae. A vaccine study was conducted by intraperitoneal (i.p.) injection in Nile tilapia, Oreochromis niloticus, in order to determine the duration of protection and its correlation to antibodies specific for this pathogen. After 47, 90, or 180 days post-vaccination (DPV), the fish were i.p. challenged with 2.0 x 104 colony-forming units (CFU) S. agalactiae per fish to determine the duration of protective immunity. The percent survival in control fish i.p. injected with sterile TSB was 16, 16, and 4% on 47, 90, and 180 DPV, respectively, while the percent survival for the vaccinated fish was 67, 62, and 49%, respectively. The mean specific antibody concentration of the vaccinated fish was significantly higher than the control fish with correlation between the ELISA optical density (OD) and protection. Mean antibody concentration and percent survival significantly increased in the vaccinated fish to 0.115 OD and 67%, respectively, at 47 DPV. Mean antibody concentration and percent survival declined from 0.192 OD and 62% to 0.095 OD and 49% between 90 and 180 DPV, respectively. These results indicate that the specific antibody has a correlation with protection following immunization with S. agalactiae vaccine. Furthermore, the weaker degree of immunity at 180 DPV may be sufficient to protect fish exposed to S. agalactiae in aquaculture production systems.

Technical Abstract: Streptococcus agalactiae is a major piscine pathogen that causes significant morbidity and mortality among numerous species of freshwater, estuarine and marine fish. Considering the economic importance of fish susceptible to S. agalactiae throughout the world, a highly efficacious S. agalactiae vaccine was developed using an extracellular product (ECP) fraction and formalin-killed whole cells of S. agalactiae. A vaccine study was conducted by intraperitoneal (i.p.) injection in Nile tilapia, Oreochromis niloticus, in order to determine the duration of protection and its correlation to antibodies specific for this pathogen. After 47, 90, or 180 days post-vaccination (DPV), the fish were i.p. challenged with 2.0 x 104 colony-forming units (CFU) S. agalactiae fish-1 to determine the duration of protective immunity. The percent survival in control fish i.p. injected with sterile TSB was 16, 16, and 4% on 47, 90, and 180 DPV, respectively, while the percent survival for the vaccinated fish was 67, 62, and 49%, respectively. The specific mean antibody concentration of the vaccinated fish was significantly higher than the control fish with correlation between the ELISA optical density (OD) and protection. Mean antibody concentration and percent survival significantly increased in the vaccinated fish to 0.115 OD and 67%, respectively, at 47 DPV. Mean antibody concentration and percent survival declined from 0.192 OD and 62% to 0.095 OD and 49%, respectively, between 90 and 180 DPV. These results indicate that the specific antibody has a correlation with protection following immunization with S. agalactiae vaccine. Furthermore, the weaker degree of immunity at 180 DPV may be sufficient to protect fish exposed to S. agalactiae in aquaculture production systems.

Last Modified: 7/24/2014