Affiliation:
1. PHARMAQ AS, 0275 Oslo, Norway
2. Pure Salmon Technology, 3241 Sandefjord, Norway
Abstract
Salmonid Rickettsial Septicemia (SRS), caused by the bacterium Piscirickettsia salmonis, is the main reason for antibiotic usage in the Chilean aquaculture industry. In 2016, a live attenuated vaccine (ALPHA JECT LiVac® SRS, PHARMAQ AS) was licensed in Chile and has been widely used in farmed salmonids since then. In experimental injection and cohabitation laboratory challenge models, we found that the vaccine is effective in protecting Atlantic salmon (Salmo salar) for at least 15 months against P. salmonis-induced mortality. However, the protection offered by the vaccine is sensitive to temperature during immunization. Fish vaccinated and immunized at 10 °C and above were well protected, but those immunized at 7 °C and 8 °C (the lower end of the temperature range commonly found in Chile) experienced a significant loss of protection. This temperature-dependent loss of effect correlated with the amount of vaccine-strain RNA detected in the liver the first week after vaccination and with in vitro growth curves, which failed to detect any growth at 8 °C. We found that good vaccine efficacy can be restored by exposing fish to 15 °C for the first five days after vaccination before lowering the temperature to 7 °C for the remaining immunization period. This suggests that maintaining the correct temperature during the first few days after vaccination is crucial for achieving a protective immune response with ALPHA JECT LiVac® SRS. Our results emphasize the importance of temperature control when vaccinating poikilothermic animals with live vaccines.
Reference25 articles.
1. Sernapesca (2023). Informe Sanitario con Información Sanitaria de Agua Dulce y mar Año 2022, Servicio Nacional de Pesca y Acuicultura.
2. Coho salmon syndrome in Chile;Bravo;FHS/AFS Newsl.,1989
3. Isolation of a rickettsiales-like organism from diseased coho salmon Oncorhynchus kisutch in Chile;Fryer;Fish. Pathol.,1990
4. Infectivity of a rickettsia isolated from coho salmon Oncorhynchus kisutch;Garces;Dis. Aquat. Org.,1991
5. Jones, S.R.M. (2019). Characterization of Piscirickettsia salmonis and Salmonid Rickettsial Septicaemia to Inform Pathogen Transfer Risk Assessments in British Columbia, Fisheries and Oceans Canada. Canadian Science Advisory Secretariat (CSAS) Research Document 2019/020.