Abstract
This study evaluated efficacy of maternal and larval immunisation against Lactococcus garviae infection and on the lysozyme and immunoglobulin (IgM) levels in rainbow trout Oncorhynchus mykiss (Walaum). Forty-eight-day-old larvae (mean weight 96 mg) originating from injected weekly with letrozole and immunised, only immunised and non-immunised parents were experimentally infected with the L. garvieae, and the mortality rate was recorded daily. Larvae were vaccinated by immersion at 58 days post hatch with live L. garvieae (109 cells/mL) for 15 min. Every third day post larvae vaccination, two larvae from each group were collected for analysis lysozyme (by a method based on the ability of lysozyme to lyse the bacterium Micrococcus lysodeikticus) and IgM (by enzyme-linked immunosorbent assay (ELISA)) parameters. Vaccinated and control larvae were tested for protection against L. garvieae 30 days post larvae immunization when the larvae were 88 days old. Larvae were challenged by bath exposure with live L. garvieae (109 cells/mL) for 2 min and monitored for mortality for at least 10 days following challenge. The challenge experiment with L. garvieae showed a significant reduction in larvae from immunised (54.44% ± 0.64%) and injected weekly with letrozole and immunised fish (52.96% ± 0.97%) compared to larvae from control fish (62.96% ± 2.22%). Vaccinated larvae originated from injected weekly with letrozole and immunised parents showed significantly higher lysozyme activity compared to other fish groups. Vaccinated larvae showed significantly less mortality compared to controls. The relative percent survival (RPS) values of larvae from only immunised, injected weekly with letrozole and immunised and non-immunised parents vaccinated with L. garvieae were 67.36% ± 0.9%, 68.05% ± 0.66% and 48.27% ± 2.79% respectively. The results indicate that the effect of maternal immunization rainbow trout against L. garvieae infection by eliciting the immune responses as indicated by an increase in the IgM level and lysozyme activity.
Highlights
Lactococcus garvieae is considered the most important risk factor for the rainbow trout and marine fish industry [1]
The results indicate that the effect of maternal immunization rainbow trout against L. garvieae infection by eliciting the immune responses as indicated by an increase in the IgM level and lysozyme activity
We investigated the effects of endocrine disrupter component (EDC) letrozole on lysozyme and IgM levels after female immunisation of rainbow trout
Summary
Lactococcus garvieae is considered the most important risk factor for the rainbow trout and marine fish industry [1]. The rapidly expanding aquaculture industry incurs a substantial economic loss due to lactococcosis caused by L. garvieae resulting in more than 50% mortality over a period of 3 - 7 days [2]. Iran from 235 cases of streptococcosis among rainbow trout collected from farms of Fars province [3], streptococci were isolated from 99 cases. These isolates were biochemically allocated to Streptococcus iniae and L. garvieae. L. garvieae outbreaks in farmed rainbow trout are described from different parts of Iran [4] [5]. Therapeutic measures are generally ineffective and development of vaccines is essential to control the disease [4] [6]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
