Marine environment as reservoir of birnaviruses from poikilothermic animals

In this study 51 aquatic birnaviruses were isolated from environmental samples (molluscs, wild fish and sediments) during routine surveys around fish farms located in Galicia (NW of Spain). These viruses were identified as IPN-like viruses based on their physical and chemical characteristics. Furthermore, these isolates were molecular and serologically compared to the reference strains VR-299, Sp and Ab. Although they caused no mortalities in oysters and showed varying degrees of virulence in trout, all isolates were recovered from the inoculated animals, indicating that oysters can become carriers. The results obtained in this study indicate the role of the molluscs, sediments or fish feed as important agents to consider in the epidemiology of birnaviruses.