RISK ASSESSMENT OF CAMPYLOBACTER SPECIES IN SHELLFISH - IDENTIFYING THE UNKNOWN

Shellfish are frequently contaminated by Campylobacter spp, presumably originating from faeces from gulls feeding in the growing or relaying waters. The possible health effects of eating contaminated shellfish were estimated by quantitative risk assessment. A paucity of data was encountered necessitating many assumptions to complete the risk estima te. The level of Campylobacter spp in shellfish meat was calculated on the basis of a five-tube, single dilution MPN and was strongly season -dependent. The contamination level of mussels (<1/g) appeared to be h igher than in oysters. The usual steaming process of mussels was found to completely inactivate Campylobacter spp so that risks are restrict ed To raw/undercooked shellfish. Consumption data were estimated on th e basis of the usual size of a portion of raw shellfish and the weight of meat/individual animal. Using these data, season-dependent dose-di stributions could be estimated. The dominant species in Dutch shellfis h is C. lari but little is known on its infectivity for man. As a wors t case assumption, it was assumed that the infectivity was similar to C. jejuni. A published dose-response model for Campylobacter-infection of volunteers is available but with considerable uncertainty in the l ow dose region. Using Monte Carlo simulation, risk estimates were cons tructed. The consumption of a single portion of raw shellfish resulted in a risk of infection of 5-20% for mussels (depending on season; 95% CI 0.01-60%). Repeated (e.g. monthly) exposures throughout a year res ulted in an infection risk of 60% (95% CI 7-99%). Risks for oysters we re slightly lower than for mussels. It can be concluded that, under th e assumptions made, the risk of infection with Campylobacter spp by ea ting of raw shellfish is substantial. Quantitative risk estimates are highly demanding for the availability and quality of experimental data , and many research needs were identified. (C) 1997 IAWQ. Published by Elsevier Science Ltd.