Assessment of exotic fish disease introduction and establishment in the United Kingdom via live fish transporters.

Abstract

Live fish transporters returning empty from mainland Europe may mechanically introduce exotic pathogens and parasites to the UK. A qualitative risk assessment approach was adopted to investigate the likelihood of introduction and establishment in rainbow trout farms of viral haemorrhagic septicaemia (VHS), infectious haematopoietic necrosis (IHN) and Gyrodactylus salaris via this route. A scenario tree was developed and estimates made for the likelihood of each step based on a review of the available information. The level of uncertainty associated with each step was qualitatively assessed. The likelihood of a lorry becoming contaminated with any of the 3 hazards was only greater than negligible if the lorry made movements between farms in mainland Europe. In these circumstances, the overall likelihood of introduction and establishment was extremely low (would occur very rarely), extremely low to negligible and very low (would occur rarely) for VHS, IHN and G. salaris, respectively. A high level of uncertainty existed due to the lack of data on farm-level prevalence, minimum infectious dose (of the viral hazards) and the large variability in duration and conditions of transport. A telephone survey of live fish transporters found that cleaning and disinfection practices after return to the UK were implemented. Currently, no UK-based transporters make movements between farms in mainland Europe. Thus, the likelihood that UK-owned transporters may become infected is negligible. Changes in the way in which UK-based live fish transporters operate in mainland Europe need to be monitored and development of a code of practice to minimise the risk of disease introduction considered.