Submitted to: Biologicals
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/11/2011
Publication Date: 9/30/2011
Citation: Shoemaker, C.A., Lafrentz, B.R., Klesius, P.H. 2011. Vaccination of sex reversed hybrid tilapia (Oreochromis niloticus X O. aureus) with an inactivated Vibrio vulnificus vaccine. Biologicals. 39:424-429.
Interpretive Summary: Tilapia production is estimated at more than 2 million tons and tilapia is an important source of protein in the US and worldwide. Loss due to disease impacts global food security and this study provides a tool for prevention of disease loss in tilapia aquaculture. Recently, Vibrio vulnificus, a Gram-negative bacterium with a requirement for salt, has been emerging as a pathogen of economically important farm raised fish. The objectives of this study were to characterize an isolate of V. vulnificus using biochemical and molecular methods, develop a disease challenge model, and determine the ability of a formalin inactivated whole-cell vaccine to protect tilapia against V. vulnificus. The V. vulnificus isolate we recovered from a sick tilapia was a biotype 1, 16S rRNA type B and vcg type C (i.e., typical of strains found in shellfish with the ability to infect humans), yet was vvhA type 2 that points to environmental strains (i.e., typically less virulent for people). Results of repeated vaccine trials demonstrated the formalin inactivated whole cell vaccine developed using the characterized V. vulnificus strain isolated from tilapia was able to protect against virulent disease. The developed vaccine may provide a means of preventing infections in tilapia caused by diverse isolates of V. vulnificus.
Technical Abstract: Vibrio vulnificus causes disease in economically important aquaculture raised fish and is an opportunistic human pathogen. This study reports on the isolation of V. vulnificus from diseased hybrid tilapia (Oreochromis niloticus X O. aureus) cultured in a North American water reuse facility. Our objectives were to characterize the isolate using biochemical and molecular methods, develop a disease challenge model, and determine the ability of a formalin inactivated whole-cell vaccine to provide protection against V. vulnificus. The V. vulnificus isolate recovered was biotype 1, 16S rRNA type B, vcg type C, and vvhA type 2 and caused disease in tilapia held in static salt water (1.5 g/l sea salt). Fish vaccinated with the formalin inactivated whole-cell vaccine responded to vaccination as measured by agglutinating antibody titer (titers from vaccinated fish ranged from 32-64 and titers from non-vaccinated fish ranged from 4-8). In two trials, vaccinated tilapia exhibited relative percent survival (RPS) of 73 and 60 % following homologous isolate challenge. In two additional trials, vaccinated tilapia exhibited RPS values of up to 88 % following challenge with a heterologous isolate, and the use of a mineral oil adjuvant enhanced protection. This vaccine may provide an effective means of preventing infections caused by biochemically and genetically diverse isolates of V. vulnificus.