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CHAPTER 11 - CONTROL OF MARINE BIOTOXINS

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Shellfish areas on both the Atlantic and Pacific coasts of Canada have been affected by marine biotoxins. The toxins are produced by certain species of naturally occurring microscopic algae that bloom under favourable hydrographic conditions. Filter-feeding molluscan shellfish accumulate the toxins when utilizing toxic algae as a food source. The consumption of toxic shellfish can lead to illness and even death. The toxins do not kill the shellfish nor cause any discernible changes in the appearance, smell or taste of shellfish that would alert consumers of toxicity. As hydrographic conditions become less favourable, the bloom subsides and with time, shellfish rid themselves of toxin and are once again safe to eat.

Any filter feeding bivalve can acquire the toxins, and in Canada, many species of clams, oysters, mussels and scallops have been affected. The rates at which toxins are accumulated and eliminated varies with species. Also, animals that feed on bivalves may become toxic, and toxins have been detected in lobsters, crabs, and whelks and other predatory gastropods.

Canadian shellfish have been contaminated with three types of biotoxins: Paralytic Shellfish Poison (PSP), Amnesic Shellfish Poison (ASP) and Diarrhetic Shellfish Poison (DSP). The toxins are named for the most notable symptom they cause, i.e., paralysis, amnesia and diarrhea, respectively. No deaths have been recorded for DSP, but deaths have resulted from PSP and ASP intoxications.

Programs to monitor biotoxin levels and control the harvesting of toxic shellfish have been established. The Canadian Food Inspection Agency (CFIA) is responsible for collecting and analysing shellfish samples, and making recommendations for the opening and closing of shellfish areas to the Department of Fisheries and Oceans (DFO) which implements and enforces closures.

11.1 Program responsibilities and Reporting

The CFIA is responsible for overall program implementation while the Regional Inspection Divisions manage specific programs within their geographic limits, in cooperation with DFO Fishery Officers responsible for enforcement and patrol.

Reports of all activities are centrally maintained at the Regional level. Because of the risk of serious illness and death, reports of suspected cases of poisoning are closely investigated. A Consumer Complaint Record (Annex 11A) is required to be completed for each person who may have been involved. Any incident is to be reported to the Regional Director, CFIA by telephone and followed as soon as possible with a detailed report, including a Consumer Complaint Record.

11.2 Sampling of Harvesting Areas

Each Fisheries Region has established sampling stations and frequencies to monitor changes in PSP and ASP.

DSP testing will only occur in suspect harvesting areas or as a result of consumer complaints where symptoms would indicate possible DSP intoxication. If no DSP related illnesses occur within a year of initial testing, an area would not remain defined as suspect and sampling could be discontinued.

The toxicity levels in shellfish vary depending on the location of the actual sampling site. It is important that sampling sites for monitoring toxicity levels be carefully chosen after a thorough analysis of toxicity score data.

The following conditions must be considered in site selection:

1. accessibility to the site at all times of the year;
2. the supply of shellfish available in a localised area;
3. a location which can be readily identified or marked; and
4. assessment of the site by past records of toxicity.

In order to maintain reliability of bioassay results, the period of time between the digging of shellfish and extraction should be uniform and limited. Each sample must be properly identified with the area of digging, the species, the date of digging and the sampling officer's name. Samples should be stored at refrigerated temperatures 2 ^o to 7 ^oC (35 ^o to 45 ^oF) until extracted.

In the case of aquaculture operations, samples may be collected at the establishment if the same standards of continuity and sample handling are maintained.

Regions should have in place a monitoring program to adequately monitor marine biotoxins. As levels begin to rise, sampling frequency is to be increased in accordance with the speed of the rise to ensure timely closure. Areas that have been closed are to be monitored on a regular basis but with increased frequency as PSP scores decline toward acceptable levels. The objective is to ensure that shellfish areas are closed when:

1. PSP toxin levels reach 80 µg/100 g and are opened only when toxin levels are consistently below 80 µg/100 g;
2. ASP toxin levels reach 20 µg/g and are opened only when toxin levels are consistently below 20 µg/g; and
3. DSP chemical analysis gives okadaic acid and/or DTX-1, singly or in combination, of less than 1 microgram per gram (µg/g) of digestive tissue (equivalent to approximately 20 µg/100g soft tissue) and are opened only when consistently below this level.

Should departures from the scheduled sampling and/or analyses occur, due to weather conditions, absence of staff, diversion of sampling/analytical resources to areas of higher concern, then factors such as previous toxic history, harvesting activity and other supporting results should be considered and documented in a derogation report for the justification in not closing an area.

In addition to normal sampling, when certain species are used for canning (e.g., butter clams in British Columbia) a special Harvesting License (Annex 11B) is required, and the shellfish must be tested for PSP prior to release for sale.

11.3 Sampling from Processing Plants

As an additional safety measure samples are periodically taken for toxin analysis from plants processing shellfish. Shellstock shippers, shucker-packers and other registered shellfish plants are monitored and the following enforcement policy is applied.

a) Where a shellfish sample collected from a plant shows a PSP level > 80 µg/100 g, and/or an ASP level > 20 µg/g, and/or DSP chemical analysis gives okadaic acid and/or DTX-1, singly or in combination, of > 1 microgram per gram (µg/g) of digestive tissue (equivalent to approximately 20 µg/100g soft tissue), the production lot should be detained if still available at the plant. If the lot is unavailable the inspector should consult with his/her supervisor on the need for a possible product recall. Any recalls should follow the appropriate CFIA Food Emergency Response Manual requirements. National Headquarters (National Manager, Product Inspection, and National Manager, Aquaculture and Shellfish Inspection) is to be advised with Regional recommendations and actions taken.

b) Recent results from the suspect harvest area should be reviewed and additional harvest area samples taken, if necessary, to determine if toxin levels have exceeded allowable limits. If limits have been exceeded then the area should be closed immediately.

c) Until such time as samples from the suspect harvest area are analysed, all production lots (originating from the suspect area) from all plants should be detained and sampled.

d) Should the harvest area samples be acceptable and there are no additional high results in samples from other plants, all efforts would be re-directed at the original plant. Detention and sampling shall continue at the original plant until three consecutive lots are shown to have less than 80 µg/100 g PSP or less than 20 µg/g ASP or DSP chemical analysis gives okadaic acid and/or DTX-1, singly or in combination, of less than 1 microgram per gram (µg/g) of digestive tissue (equivalent to approximately 20 µg/100g soft tissue).

e) If, throughout the fishing season there are five occurrences at a plant in which production had to be placed under detention as a result of lots being > 80 µg/100 g PSP or > 20 µg/g ASP, or DSP chemical analysis gives okadaic acid and/or DTX-1, singly or in combination, of > 1 microgram per gram (µg/g) of digestive tissue (equivalent to approximately 20 µg/100g soft tissue), consideration will be given to taking further enforcement action under Section 10 of the Fish Inspection Act.

Note: For the purpose of this section each consecutive lot should be indicative of a "normal day's production". This would be equivalent to an average of the last 14 days' production.

In connection with in-plant toxin sampling, sea scallop processing deserves special mention. The adductor muscle of the sea scallop (Placopecten magellanicus) is free from toxin, however, the gonads and roe may be toxic. The marketing of sea scallops with roe attached is not permitted in the Bay of Fundy. In addition, all lots of sea scallops harvested in the Gulf of St. Lawrence, Northumberland Strait, George's Bank and other areas, and which are packed whole or with roe attached, are sampled for toxicity content prior to release for market. To ensure adequate control of this problem, fish processing plants must, prior to packing any scallop whole or with roe on, obtain special permission from the CFIA.

Note: The purple-hinged rock scallop (Crassedoma giganteum / Hinnites multirugosus) accumulates PSP toxin in the adductor muscle.

11.4 Sample Priority

To ensure the timely analysis of samples, a system has been established to assist laboratory personnel in determining priorities for toxin analyses. The system is based upon immediate analysis of product that may go directly to the consumer.

Priority 1 - These are samples from a suspected illness, approved areas where toxicity may be increasing, samples that were delayed in analysis and from detained shellstock or fresh shucked product shipments. Samples are shipped by the most rapid means possible, are analysed immediately upon receipt and results are reported by telephone with mail or fax follow-up.

Priority 2 - These are samples from approved areas where levels are stable, closed areas which are showing changes, commercial lots of frozen products or heat-processed canned meats. Samples are shipped by regular means and are analysed within 24 hours of receipt.

Priority 3 - These are samples for research purposes, shipped by regular means and fitted into laboratory workloads.

11.5 Standards Applied and Procedures for Controlling Harvesting

A PSP toxin level > 80 µg/100 g, or ASP toxin level > 20 µg/g, or okadaic acid and/or DTX-1, singly or in combination, > 1 microgram per gram (µg/g) of digestive tissue (equivalent to approximately 20 µg/100 g soft tissue) in a sample, will require the area from which the sample is taken to be closed. The area may be re-opened only when three consecutive acceptable values are obtained during a minimum period of 14 days, i.e., 1^st sample on day 1 and the 3^rd sample no earlier than day 14. Test results must contain < 80 µg/100 g PSP or < 20 µg/g ASP or okadaic acid and/or DTX-1, singly or in combination, of < 1 microgram per gram (µg/g) of digestive tissue (equivalent to approximately 20 µg/100g soft tissue). In the past, grid samples taken at the end of the 14-day period have been found effective in some areas in reducing the likelihood of product having unacceptable biotoxin levels reaching the marketplace.

A closure or opening is implemented in the following manner.

1. Where mouse bioassay or chemical analysis results indicate an opening or closure is required, an order is prepared, under the Management of Contaminated Fisheries Regulations, for the signature of the Regional Director General (DFO) (see Appendix VII for details).
2. A news release is issued to local media. Departmental staff, fishermen's associations and shellfish processors are notified by telephone. All normal access points to the area are prominently posted with closure signs specifying the area affected or, closure signs are removed in the case of an opening.
3. Patrols are arranged to ensure effective closure.

As the canning process reduces PSP toxin, licences may be issued to harvest clams and mussels under the following specific criteria and conditions.

Soft shell clams and mussels (Atlantic) may be harvested when PSP toxin levels exceed 80 µg/100 g and are less than 160 µg/100 g.

Butter clams on the West Coast may be harvested and canned, subject to the following conditions, when the PSP toxin levels (µg/100 g) are:

• > 300 to < 500 ....... entire siphon must be removed
• > 80 to < 300 .........distal half of the siphon must be removed
• < 80 ........................black tip of the siphon must be removed.