EU: Mouse test has shortcomings

By

Lindsey Partos, SeafoodSource contributing editor, reporting from Paris

Published on
August 27, 2009

European Union food-safety experts on Wednesday acknowledged that the controversial “mouse test” has its shortcomings.

In a statement, a panel of European Food Safety Authority (EFSA) scientists said the mouse bioassay is an inappropriate method to detect the presence of toxins in bivalves, such as oystersclams and mussels. The method’s shortcomings include high variability in results, insufficient detection capability and limited specificity, cited the scientists.

The declaration is sure to please oyster producers, particularly in France’s Arcachon Bay region, who have been subject to multiple harvesting bans this year. They question the method’s reliability, and earlier this week they renewed their call for an alternative method of testing bivalves for toxins.
 
The mouse bioassay is the only European Commission-sanctioned oyster test. For the test, three mice receive an injection containing an extract from the digestive glands of bivalves. If two or three mice die within 24 hours of the injection, the shellfish are considered unhealthy and the area from which they were harvested is closed.

In response to the EFSA opinion, a spokesperson for France’s national shellfish organization, Comité National de la Conchyliculture, told SeafoodSource: “This is an important step forward, but many new questions will arise for the profession.”

In terms of alternative tests, the EFSA scientists said reference methods for detecting marine biotoxins with lower limits of detection (LOD) have “successfully been tested in pre-validation studies.”
 
The scientists’ opinion follows a request from the European Commission to EFSA to assess current EU limits for six different types of toxins in shellfish, known as marine biotoxins, and the testing methods established in EU legislation.

They concluded that eating shellfish contaminated with marine biotoxins from the yessotoxin or pectenotoxin groups at levels permitted in the EU were not considered to pose a health risk. However, the scientists added, people consuming shellfish tainted with toxins from the okadaic acid, azaspiracid, saxitoxin or domoic acid groups may become ill.

For each type of toxin, the scientists established the amount which can be consumed within a 24-hour period without a appreciable health risk, called the acute reference dose. These were then compared with shellfish consumption and occurrence data from a number of EU countries in order to assess the EU limits.
 
The scientists identified 400 grams as a realistic estimate of a large portion of shellfish and used this in assessing current permitted levels of the toxins.

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