The objective of this study was to u se risk assessment to determine the biosecurity risk associated with Viral encephalopathy and retinopathy (VNN) introduction and spread in Mediterranean seabass production, and to identify the control measures to manage the risks.
Biosecurity plans for prevention of introduction and further spread of disease pathogens involve knowledge on risk assessment of disease hazards in the region, likelihood of introducing the infectious agent into the production system, epidemiology and transmission routes, critical points for introduction and control. VNN was identified as the most important disease of seabass in the western, central, eastern and southern Mediterranean areas in terms of production and economic impact due to factors such as the high mortality and morbidity by literature, survey, and expert opinion.
A group of 10 experts consisting of fish health specialists, veterinarians, biologists, and epidemiologists were asked to provide their opinion regarding disease hazards, likelihoods of disease introduction and spread in the Mediterranean seabass. Expert knowledge elicitation (EKA) approach was used to elicit expert opinion and perform the risk assessment . Risk matrix was used to present the overall risk estimates by integrating the numerical scores for the likelihood of disease introduction and the economic consequences. The experts to identify the points at which VNN introduction and spread could occur and be prevented. At each action point, experts gave a weight for potential biosecurity measures concerning its feasibility and effectiveness for controlling VNN
The main risk pathways differ by type of production for which the likelihoods of introduction are similar for hatchery and pre-growing, but different from the likelihoods for on-growing. Intake of water, live fish and eggs, vehicle transporting live fish, human, equipment, and high-risk purchasing were identified by the experts as the risk pathway for all types of production. This illustrates a clear recommendation to encourage focusing on introductory risk.
The economic consequences of VNN depend on the type of production of the facility. The consequences of VNN introduction were regarded most devastating in economic terms for hatcheries and pre-growing units and the risk estimate was in general high or very high for these productions. For on-growing the risk estimates were regarded medium to high. Measures to comply with introduction entail requirements of reliable health certificates and quarantining newly acquired fish upon arrival. The measures for disease management entail removing dead fish daily, preventing direct contact between quarantined fish and the other fish on the facility, separate water flow between quarantined fish and the other fish on the facility, and follow-up investigation of disease outbreaks.