Finfish and Human Pathogens in Bivalve Molluscs

Bivalve molluscs are an important food source for living beings, humans included. They are obligated filter feeders, that feed on microalgae, bacteria and organic particles present in the aquatic environment. Accordingly, they could accumulate chemical compounds, marine biotoxins, bacteria and viruses, including human and animal pathogens (Molloy et al., 2013; Serratore et al., 2014), influencing the epidemiology of animal and human infectious diseases (Skär & Mortensen, 2007). This topic has been long investigated for human pathogens. On the other hand, poor studies were available for finfish pathogens. The Ph.D thesis, arranged in three chapters, deals with finfish and human pathogens in bivalve molluscs and focus on betanodavirus presence in these invertebrates, on their interaction with the Redspotted grouper nervous necrosis virus (RGNNV), one species of the genus Betanodavirus, and the development of a method to mitigate bacterial and viral contaminations of bivalve molluscs. Betanodaviruses very closely related to those of finfish have been found widely present in bivalve molluscs. The clams were demonstrated able to take up and then shed viable RGNNV into the surrounding environment through faeces and filtered water into the surrounding environment posing a serious risk for susceptible cohabitant fish species. Finally, a novel Manila clam sea water potassium MPS-based disinfection method was set up to mitigate the impact of bacterial and viral contaminations in bivalve molluscs. The obtained results point out the possible role of bivalve molluscs in the transmission of pathogens to finfish and highlight the needing of surveillance and control activities where a close inter-specific contact is present. The proposed novel disinfection method provides good experimental results and could find wide application in fisheries sector after adequate field tests.