Authors: Vendrell, D.; Balcázar, J. L.; Ruiz-Zarzuela, I.; de Blas, I.; Gironés, O.; Múzquiz, J. L.

We studied the safety and efficacy of an inactivated vaccine (Ichtiovac-Lg) against Lactococcus garvieae in rainbow trout (Oncorhynchus mykiss). In an initial dose-response experiment to test safety, we injected 50 rainbow trout weighing 30–40 g with a double dose of vaccine (0.2 ml) intraperitoneally. We observed these fish three times a day until day 50 post-vaccination when they were killed to evaluate visceral reactions, adhesions and intraperitoneal absorption. Survival was 100% in both the treatment and control groups and no significant differences were found in percentage of severe adhesions and pigmentation of peritonea and viscera. In a second trial, we injected 50 rainbow trout weighing 30–40 g with 0.1

Our results clearly demonstrate that under our experimental conditions the intraperitoneal vaccination using oil adjuvants in rainbow trout showed some moderate intra-abdominal lesions while major lesions showed lower prevalence, which are considered acceptable by European Pharmacopoeia. Intraperitoneal vaccination 1 month before intraperitoneal experimental challenge with L. garvieae was quite successful: the RPS was 94% (94% survival of the 50 vaccinated trout versus only 4% survival of the controls).