SFPA Guidance Document for Inspecting LBM Purification Centres.

Transcription

1 SFPA Guidance Document for Inspecting LBM Purification Centres. Ref: Regulation (EC) 853/2004 Annex III Section VII Additional Reading via FAO website: Scope: This guidance document aims to clarify and standardise procedures for Sea Fishery Protection Officers inspecting and approving LBM purification systems. It outlines what are considered best practices in the operation of LBM purification systems and may also be used as a guide to industry. Definition: Depuration (purification) is a process by which shellfish are held in tanks of clean seawater under conditions which maximize the natural filtering activity and results in the expulsion of intestinal contents. The depuration process in Ireland involves placing shellfish from B Classified production areas into a purpose made tank which is then filled with clean seawater. In Ireland, Seawater is mainly treated by ultraviolet (UV) disinfection, and is then recycled through the system providing optimum temperature, salinity and oxygen levels for the shellfish to function normally and expel faecal contamination to produce shellfish of A Class microbiological standard which can be eaten raw or lightly cooked without risk to public health. Depuration is effective in removing many faecal bacterial contaminants from shellfish, however as currently commercially practised, it is less effective at removing viral contaminants such as norovirus* *Additional purification requirements are required to reduce norovirus levels in high risk shellfish at high risk periods (See High Risk Species) Specific Legislation Requirements: Structural 1. The location of premises on land must not be subject to flooding by ordinary high tides or run-off from surrounding areas. 2. Tanks and water storage containers must meet the following requirements: (a) Internal surfaces must be smooth, durable, impermeable and easy to clean. (b) They must be constructed so as to allow complete draining of water. (c) Any water intake must be situated in a position that avoids contamination of the water supply. 3. In addition, in purification centres, purification tanks must be suitable for the volume and type of products to be purified. Hygiene 1. Before purification commences, live bivalve molluscs must be washed free of mud and accumulated debris using clean water. 2. Operation of the purification system must allow live bivalve molluscs rapidly to resume

2 and to maintain filter feeding activity, to eliminate microbiological contamination, not to become re-contaminated and to be able to remain alive in a suitable condition after purification for wrapping, storage and transport before being placed on the market. 3. The quantity of live bivalve molluscs to be purified must not exceed the capacity of the purification centre. The live bivalve molluscs must be continuously purified for a period sufficient to achieve compliance with the health standards of Chapter V (Freshness and viability and Biotoxins) and microbiological criteria 2073/ Containers used to hold live bivalve molluscs in purification systems must be of a construction that allows clean seawater to flow through. The depth of layers of live bivalve molluscs must not impede the opening of shells during purification. 5. Should a purification tank contain several batches of live bivalve molluscs, they must be of the same species and the length of the treatment must be based on the time required by the batch needing the longest period of purification. 6. No crustaceans, fish or other marine species may be kept in a purification tank in which live bivalve molluscs are undergoing purification. ULTRA VIOLET IRRADIATION Ultra-violet (UV) treatment of seawater is the most common means of disinfection process for purification systems in Ireland. Low-pressure lamps have been applied most commonly in depuration systems and the main output of such lamps should be in the UVc region (200 to 280 nm; peak microbiocidal wavelength 254 nm) for disinfection purposes. A single lamp unit consists of a tube in which the UV lamp is contained within a quartz sleeve with the seawater passing down the space between the tube and the sleeve. UV unit manufacturers will specify the maximum flow rates that can be used with the units, and the makers of UV lamps will specify likely lifetimes for UV lamps to maintain 80% efficiency. NB UV disinfection rapidly diminishes in effectiveness when transmission is reduced by: a. Turbid water. b. When algal or dirt build up on quartz sleeves which are not cleaned properly. c. When the recommended lifespan of the bulbs are exceeded. Good Practice Guidelines The depuration or purification process of LBMs will only begin after the shellfish resume their filtration activity. Prior to loading: Prior to loading shellfish into trays or tanks, all mud, stones and weed must be cleaned and removed. Empty shells, crabs, and gaping shells must be removed Loading: Shellfish must be loaded into the trays or tanks at a density that allows them to open and resume filter feeding. The level of water above the shellfish should also be sufficient to ensure that the shellfish remain immersed throughout the entire period of depuration. Disturbance: It should be noted that shellfish are sensitive animals and if disturbed directly by the effects of cascades, aeration or operator handling during the purification cycle, will cease to filter effectively. A primary requirement for avoiding recontamination during depuration is the operation of a batch all-in/all-out system, with no more shellfish being added to the system once the depuration cycle has been started. This is necessary to prevent partially depurated shellfish being re-contaminated by the material excreted from freshly introduced shellfish. It also prevents settled faecal material being re-suspended during the addition of further shellfish.

3 Purification Process: Foam collecting on the surface of the water is indicative of actively purifying shellfish and is not a problem Post Purification: During depuration, contaminants are excreted as part of the digestive process predominantly in the form of mucoid faecal strands which must be allowed to settle to the bottom of the depuration tank. Once settled, re-suspension of this faecal matter must be avoided as this may lead to its re-ingestion by the filter-feeding shellfish. At the end of the cycle seawater in the system should be slowly drained down below the level of the shellfish before they are removed. This prevents turbulence caused by removal of trays of shellfish immersed in water leading to the possible re-suspension and re-ingestion of faecal material in neighbouring shellfish. Protein foam which can contain some faeces can develop on the surface of the water in recirculation systems. After draining down, this material may be deposited on the shellfish. This should be rinsed off with potable fresh water. At the end of each cycle, the remaining 10% water, which will be heavily contaminated, must be discarded and the bottom of each tank thoroughly cleaned at the end of the cycle, as this is where the shellfish faecal material containing the contaminants will be concentrated. Immersed Storage In order to comply with the Legislative Hygiene requirement i.e. for purified LBMs to remain alive in a suitable condition after purification for wrapping, storage and transport before being placed on the market, and to avoid contravening legislation prohibiting re-immersement of Live Bivalve Molluscs in water that could cause additional contamination, Purified Live Bivalve Molluscs are allowed to be maintained in immersed storage in clean seawater of at least water from A classified areas or seawater that has been re-circulated through the UV purification system. Validation of Purification System. FBOs operating purification systems must conduct validation testing to prove the effectiveness of their purification system. The recommended method of validation is by testing contaminated LBMs pre purification and post purification via the ISO TS tube three dilution method expressed as MPN E.coli/100grams shellfish flesh, with a limit of 230MPN/100grams of flesh and intervalvular fluid. Specific Parameters The depuration or purification process of LBMs will only begin after the shellfish resume their filtration activity. In order to ensure rapid resumption of filter feeding activity, and effective purification, the following are the minimum recommended parameters that Purification centres should adhere to: 1. Minimum depuration period: Mussels >36hours Oysters > 42hours 2. Salinity >20% <35% 3. Temperature >8 C <18 C 4. Dissolved oxygen levels Minimum 50% with a recommended level of 70%

4 Record keeping Records should be complete and accurate, legible and available for inspection. As required by Regulation (EC) 2073/2005: 1. Post purification testing of LBMs for the presence of E.coli (MPN method) 2. Post purification testing of LBMs for the presence of Salmonella (absence in 25g) Additional records: 1. Results of microbiological tests on purification system water entering the purification tanks 2. Validation Test results: Microbiological tests on pre and post purified live bivalve molluscs 3. Dates and quantities of live bivalve molluscs delivered to the purification centre and corresponding Shellfish Registration Document Numbers. 4. The times of filling and emptying of purification systems (purification times) 5. Dispatch details of consignments after purification. 6. Seawater temperature 7. Seawater salinity 8. Flow rates 9. Tank cleaning 10. UV usage. The hours of UV usage should be recorded and the specified likely lifetimes for UV lamps to maintaining 80% efficiency should not be exceeded. 11. UV Quartz sleeve cleaning. 12. Have records of all mortalities been maintained? (FBO should be using mortality record template provided by MI). Has notification been given to the Fish Health Unit of the Marine Institute where these mortalities were unexplained and could be associated with the presence of a mollusc disease? (Note: Inspecting officer should highlight any discrepancies to notifications@marine.ie) High Risk Species and Norovirus Purification. Viruses (Norovirus) are a major microbiological risk associated with consumption of sewage contaminated Oysters during certain times of the year mainly from December to March. Oysters from A classified production areas often have high levels of Norovirus. Trials conducted by the Microbiological department of the Marine Institute of Ireland have demonstrated that correctly operated Depuration Systems operated at higher temperatures and for a prolonged period combined with careful pre- harvesting practices can significantly reduce Norovirus levels in shellfish to levels which do not pose risk to public health.

5 The following are the recommended Depuration Periods and Temperatures for the removal of Norovirus Contamination from Oysters without adversely affecting the shellfish quality. Recommended Minimum temperature for the removal of Norovirus from Oysters; 15 C Optimal Temperature for the removal of Norovirus from Oysters; 17 C Recommended Minimum Depuration Period; 96 hours Purification Centre Recommended Check List: Reg 853/2004 Annex II Section VII. 1. System: Requirement Comments Tanks: Are the internal Surfaces smooth, durable, impermeable and easy to clean? Are the tanks constructed so as to allow complete draining of water? Is there an even flow through of water through the system? How are individual Tanks identified? Clean seawater in use for purification? Are there any sources of external contamination? Is the recirculation even (no dead spots) and through the UV system? Are the trays raised off the base of the tank? On completion of Purification, are the bottoms of tanks thoroughly cleaned out and remaining 10% discarded? How often is water changed? Comments & Notes: 2. Shellfish: Requirement Comments Are Shellfish Registration Documents available where necessary? Who supplied shellfish? What is classification of the shellfish?

6 What was biotoxin status of the Bay? Date Biotoxin status assigned? Are the shellfish clean, alive and healthy? Are the shellfish fully immersed? Do shellfish appear to be filtering? Is mixing of species evident/batches? In order to avoid recontamination is an all in/ all out batch system used? (No shellfish added once a purification cycle commences) Are shellfish rinsed in potable water after drain down? Comments & Notes: Measurements: Recommended Criteria Comments How long is the depuration Period? (Mussels>36hrs) (Oysters >42hrs) What is the Salinity measurement? (>20% < 35%) What is the temperature of the water in the tank? (>8 <18 ) What is the dissolved Oxygen%? (>50%) What is the recorded UV Lamp usage? How often is water changed in the system? Comments & Notes: Records: Full written specification available for any purification system in use.

7 Maintenance records of UV system/other equipment available Post purification E.coli results Post purification Salmonella results Results of microbiological tests on purified water entering the purification tanks Validation Test results: Microbiological tests on pre and post purified live bivalve molluscs Dates and quantities of shellfish delivered to the purification centre and corresponding Shellfish Registration Document numbers Dispatch details of consignments after purification. Purification Times per species Seawater temperature. Seawater salinity. Tank Cleaning UV Usage, and record of UV quartz sleeve cleaning Comments & Notes: High Risk Species and Norovirus Purification. For control of Norovirus contamination in Oysters from December to March Temperature > 15 C Depuration Period >96 Hours? Norovirus test results Comments and Notes: Signed:

8 Name of Inspecting Officer: Date: