Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/13/2000
Publication Date: 6/27/2000
Citation: KLESIUS, P.H., SHOEMAKER, C.A., EVANS, J.J. EFFICACY OF SINGLE AND COMBINED STREPTOCOCCUS INIAE ISOLATE VACCINE ADMINISTERED BY INTRAPERITONEAL AND INTRAMUSCULAR ROUTES IN TILAPIA (OREOCHROMIS NILOTICUS). AQUACULTURE 188 (2000) 237-246 Interpretive Summary: Prevention of fish diseases is best accomplished by vaccination against infectious agents that cause significant economic impact to food fish production systems. The production of many species of food fish cultured worldwide is significantly reduced by a bacterial pathogen called, Streptococcus iniae. Antibiotics are usually ineffective for the control of streptococcal diseases in tilapia, hybrid striped bass and rainbow trout. The purpose of this study was to determine the most effective route of immunizing tilapia against streptococcal disease using streptococcal vaccines that were developed by the laboratory. We found that tilapia were resistant to streptococcal infection after intraperitoneal immunization with both monovalent and polyvalent streptococcal vaccines. Tilapia immunized by the intramuscular route were less effectively protected. The polyvalent streptococcal vaccine appeared to be most effective in providing protection against infection by both homologous and heterologous Streptococcus iniae isolates. The use of a streptococcal vaccine to prevent streptococcal infection of food fish should reduce yearly losses by $100 million, worldwide.
Technical Abstract: We evaluated the effectiveness of Streptococcus iniae vaccines prepared from formalin-killed cells and concentrated extracellular products (greater than 2kDa) of a single isolate of S. iniae (ARS-10) and a combination of ARS-10 + ARS-60 S. iniae isolates in tilapia, for prevention of streptococcal disease. Tilapia were vaccinated by intraperitoneal (IP) and intramuscular (IM) injection of the vaccine or tryptic soy broth (control) and challenged by IP injection with 1 * 10 ** 8 colony-forming units of S. iniae. Tilapia IP immunized with ARS-10 vaccine and challenged with the homologous isolate (ARS-10) had a relative percent survival (RPS) of 45.6%. Tilapia IP immunized with ARS-10 vaccine and challenged with a heterologous isolate (ARS-60) had an RPS of 93.7%. In contrast, we found the RPS was 17.7% in tilapia IM immunized with the ARS-10 vaccine and challenged with the same isolate. Heterologous (ARS-60) isolate challenge resulted in a RPS of 59.5%. IM administration of a vaccine combining ARS-10+ARS-60 isolates provided an RPS of 63.1 against ARS-10 isolate and RPS of 87.3% against ARS-60 isolate in comparison to RPS of 17.7 and 59.5 against ARS-10 and 60 isolates provided by the single isolate ARS-10 vaccine. We found a significant negative correlation between the behavioral and morphological score and RPS. Significantly increased antibody titers were produced by IM immunization of the combined ARS-10 + ARS-60 vaccine. Administration of the single isolate ARS-10 vaccine by IM injection was marginally protective in preventing streptococcal disease caused by homologous and heterologous isolates of S. iniae. The variability seen in the protective ability of a single S. iniae isolate vaccine indicates that antigenic heterogeneity exists in S. iniae.