Elucidating the dynamics and transmission potential of the aquatic pathogen Renibacterium salmoninarum in Rainbow trout: 21st International Conference on Diseases of Fish and Shellfish

Alejandra Villamil Alonso, Giulia Zarantonello, Niccolò Vendramin, Lone Madsen, Tine Moesgaard Iburg, Argelia Cuenca

    Publikation: KonferencebidragKonferenceabstrakt til konferenceForskningpeer review


    Introduction: Renibacterium salmoninarum (Rs) is a facultative intracellular bacterium and the aetiologic agent of bacterial kidney disease (BKD). This chronic infection is associated with severe mortality in salmonid fish worldwide. Rainbow trout (Oncorhynchus mykiss), the main species farmed in Denmark, is highly susceptible to Rs although the mechanisms of transmission and the chronic state of the infection are not yet fully understood. The disease represents one of the main health challenges in Recirculating Aquaculture systems (RAS).Methodology: Our study aimed to characterize disease kinetics and host survival through in-vivo cohabitation at 6°C and 12°C in RAS. Rainbow trout shedders were intraperitoneally injected with Rs (1x109, 1x108 cells dose-1) or saline water (control), and subjected to survival analysis during 12 weeks post-infection (wpi). Naïve fish were put in cohabitation with shedders to assess the transmission potential and bacterial kinetics through qPCR of bacterial DNA and environmental DNA (eDNA) extracted from fish kidney and water samples, respectively.Results: All challenged groups were susceptible to Rs, but only the shedders experienced reduced survival due to BKD. Reduced survival began at an earlier stage at 12°C, and the probability of surviving until the end of the trial was 16.10%, 5%, and 0% for the groups injected at low dose at 12°C, high dose at 12°C, and high dose at 6°C, respectively. Infection by cohabitation was established within 2 weeks, and abundance of bacterial transcripts was significantly higher at 4 wpi in the kidney of sampled fish in all infected groups. Interestingly, water eDNA analyses revealed bacterial shedding at its highest at 3 wpi and detected the bacteria at late infection sampling points. Moreover, Rs was reisolated in SKDM media from fish kidney samples also at the latest stage of infection at 6°C.Conclusion: Our results provide information on disease progression and transmission potential of BKD and insights into the chronic state of the infection. Here we also confirm the possibility to detect Rs in RAS at different infection stages. Overall, this study defines an infection model of Rs in rainbow trout, essential to further explore the underlying mechanisms of pathogenicity of the bacterium.
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    StatusUdgivet - 2023