Effects of Satureja bachtiarica and Nigella sativa essential oils on the efficacy of lactococcosis vaccine in rainbow trout (Oncorhynchus mykiss)

Abstract

Lactococcosis has been defined as acute septicaemia, which causes economic losses in farmed fish, especially in rainbow trout. This study was done to evaluate the effects of Satureja bachtiarica and Nigella sativa essential oils on the efficacy of lactococcosis vaccine in rainbow trout. A total number of 270 fishes with a mean average of 120 g were obtained; they were randomly divided into nine groups, each with three replicates, after two weeks of adaptation. The groups were: no injection, vaccine only, DMSO injection, vaccine with 50, 100, and 200 microgram ip injection. Two, four, and six weeks after vaccination, serological and haematological parameters were evaluated. At the sixth week, 1.7×107 cfu as LD50 96 hrs of Lactococcus garvieae were i.p injected and the relative survival percentage was calculated. The results indicated that N. sativa essence is effective on the leukocyte population as the highest number of leukocytes were found in fish receiving high concentration of N. sativa. The relative survival rate of the studied fish decreased with decreasing of the N. sativa essential oil concentration, with a significant difference with control groups (P<0.05). However, using S. bachtiarica was not significantly effective on the relative survival rate of fish. The results of this study indicated that N. sativa essential oil can be used as adjuvant for L. garvieae vaccine, since it resulted in increasing leukocytes and the relative survival rate, although S. bachtiarica was not effective on immune parameters of the studied fish.