Advances in science and risk assessment tools for Vibrio parahaemolyticus and V. vulnificus associated with seafood

Globally, the bacterial species V. parahaemolyticus, V. cholerae and V. vulnificus represent important human pathogens associated with the consumption of seafood. In response to the requests for scientific advice from Codex Committee on Food Hygiene (CCFH), risk assessments for the pathogens V. vulnificus, V. cholerae, V. parahaemolyticus and guidance on methods for the detection of Vibrio spp. in seafood have been conducted and published previously by FAO/WHO Joint Expert Meeting on Microbiological Risk Assessment (JEMRA) (e.g. the 2005 Risk assessment of V. vulnificus in raw oysters (VVRA) and the 2011 Risk assessment of V. parahaemolyticus in seafood (FAO/WHO, 2005a, 2011). In order to provide an update on the state-of-the-art advice regarding risk assessment for V. parahaemolyticus and V. vulnificus in seafood, an expert meeting was convened at Centre for Environment Fisheries and Aquaculture Science (Cefas), Weymouth, the United Kingdom, on 13-15 May 2019. This report is the output of that expert meeting. Raw shellfish products such as oysters and clams are the most common foodborne source of vibriosis; thus this document outlines key areas where recent risk assessment has been carried out with regards to assessing, understanding and reducing potential human health risks in these food commodities. Experts reviewed the draft outputs of the expert meeting in 2010 on the risk assessment tools for V. parahaemolyticus and V. vulnificus associated with seafood. It was agreed that the basic information of pathogenicity (including virulence markers), major factors relevant to the fate of V. parahaemolyticus and V. vulnificus (water temperature and salinity) and other main contents had not changed substantially; however, several new models and methods have become available in the last decade which were worthy of inclusion. In addition, several new developments were discussed, including the emergence of highly pathogenic strains of V. parahaemolyticus, as well as the pandemic spread of associated infections which represented key challenges to the seafood industry, risk managers, clinicians and public health. The expert group considered a number of topics where significant new information had emerged in the last decade (and since the publication of the 2010 meeting workshop draft report). These included (1) recent epidemiological data, (2) approaches on remote sensing-based risk assessment models, (3) improvements to detection and molecular methods, (4) aspects related to best practice for reducing risk, (5) new information on climate change, and (6) demographics; all of which represented key aspects in terms of modulating human health risks associated with these pathogens. Several critical developments in the last decade were subsequently noted by the expert working group: 1) The emergence of highly pathogenic strains, in particular x the Pacific Northwest (PNW) V. parahaemolyticus strain (ST36), which have spread to the East coast of the United States of America, Europe, South America and New Zealand. The pandemic spread of these highly pathogenic strains is of global concern for seafood safety. 2) In response to climate change, there has been a significant geographical spread regarding where seafood-associated vibrio infections have been reported, with a general trend in the poleward spread of V. parahaemolyticus and V. vulnificus cases. Over the last decade in particular, there has been an increase in reported illnesses as well as the geographical spread of foodborne infections associated with these bacteria into regions where reported infections were previously absent. 3) The expert group noted that demographic considerations are also important. Globally, an increased at-risk population, increased population densities in coastal regions and improvements in diagnosis of infections may also have played a role in accentuating reported cases. 4) The expert group identified that a range of new approaches for best practice, such as highpressure treatment, harvesting curfews, relaying and temperature controls appear to offer effective and cost-effective approaches for reducing human health risks postharvest associated with these pathogens. Finally, 5) the expert group identified that a range of new methods, such as those utilising genomics and satellite imagery, provide novel means of complementing approaches outlined in previous risk assessment exercises for these globally important foodborne pathogens. The expert group noted, however, that a range of critical data gaps exist. These include approaches to infer further characterization of strains (for instance serotyping, MLST, genotyping, APPCR, WGS); virulence testing; gene expression levels; strain phylogeny and phylogeography. In particular, the paucity of high quality data from geographically diverse regions (other than the United States of America) probably represents the most pressing limitation for risk assessment efforts in this arena. This work has been greatly facilitated by contributions from experts around the world, with expertise in microbiology, risk assessment, molecular biology, remote sensing, epidemiology and modelling among others.\n