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No. 99: Sanitary survey of production areas in Løgstør Bredning

Larsen, M.M., Jakobsen, H.H., Göke, C., Hendriksen, N.B., Rømer, J.K., Mohn, C. & Schultz, A.C. 2017. Sanitary survey af produktionsområder i Løgstør Bredning. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 128 s. - Teknisk rapport fra DCE - Nationalt Center for Miljø og Energi nr. 99.


According to the Regulation for food products of animal origin (Europa Parlamentets og Rådets Forordning (EF) Nr. 854), microbiological classification of production areas for live bivalve mollusks etc.[1] and the associated sampling plan are required to be based on a so-called ‘sanitary surveys’. A sanitary survey is an assessment of the interactions between potential sources of microbial pollution, climate conditions and oceanography in the area. The EU Commission guidance for making a sanitary survey formed the basis for this report. However, in certain cases, the Danish practice for microbiological sampling frequency and classification made previously on the basis of this, as described in ‘muslingebekendtgørelsen’ is summarized in Appendix 13.

The report covers production areas (P)16, P33, P34, P35, P36, P37, P38 and P39 in Løgstør Broads. These production areas coincide currently with the algae area A6. For editorial reasons, the production areas are regarded under one term “Løgstør Broads’, knowing that the production areas also include other bordering geographical areas. The covered production areas within Løgstør Broads are marked as A6

The report recommends a microbiological sampling plan consisting of re­commended selected sampling points and sampling frequencies for individual production areas. It is further discussed whether merging of production areas into fewer production areas could be considered in the future. This merge would then reduce the number of sampling points, without compromising food safety.

The report is supported by public assessible data from monitoring of microbiological contamination in Løgstør Broads, where the concentration of E. coli is determined in samples of mussels, etc. taken at fixed sampling points.

The Danish monitoring of production areas for live bivalve mollusks offers generally a solid set of historical data of E. coli concentrations in clams etc. collected from the positions where mussels have been harvested in the past in Løgstør Broads. The key data set used is the classification of production areas based on samples taken during the past 10 years (2007-2016). Within this data set, 99.2 % of a total of 908 samples contain E. coli A level (<230 E. coli/100 g), and 0 % of a total of 350 samples contain Salmonella.

In summary, the sanitary survey of Løgstør Broads identifies an area that in general is a microbial homogeneous, stable and microbiologically clean area, and only rare occurrence of critical microbial contamination were found.

Summary of recommended sampling program

Based on an assessment of sources and transport routes for microbiological contamination (sanitary survey) verified against historical microbiological data in Løgstør Broads, a recommended microbiological monitoring programme is recommended for each of the production areas in Løgstør Broads

In each of the recommended monitoring programmes, proposals for a sampling location, classification status (preliminary or permanent) and a sampling plan are outlined.

Based on the results from the sanitary survey of the producing areas, supported by the historical data set of the number, frequency and E. coli concentration in samples, the production areas P33-P39 are deemed suitable for permanent classification with a proposed future sampling frequency of at least 8 samples per year over a continued period of three years. Furthermore, production area P16 is given an initial classification for the first six-month period of the calendar year. That is, analyses of 8 samples per year are required until the area can be upgraded to permanent classification. However, P16 remains unclassified during the months July through December due to lack of historical data during the past three years.

The report is divided into main chapters which provide a summary of identified microbiological contaminants. The main chapters take the starting point in appendix 2-10. Appendix 11 is a detailed review of all historical microbiological data from mussel monitoring consisting of the fishery’s own-check and the Danish Veterinary and Food Administration’s[2] verification projects of the industry´s microbial monitoring. It is decided that a so-called ‘shoreline survey’ is unnecessary because all possible sources of sanitary contamination are described in the sewage plans for the cities in the area, the beach water quality monitoring and in the analyses of the Ministry of Environment and Food under the auspices of the Water Framework Directive.

[1] Include live bivalve mollusks, echinoderms, tunicates and gastropods.

[2] Fødevarestyrelsen