Keeping shellfish safe

A new metrology-based test is now facilitating the worldwide acceptance of a far more efficient, accurate and sensitive method of detecting toxins in shellfish.

Shellfish poisoning is a much greater problem than the odd bout of illness caused by eating toxic shellfish at a beach barbecue; it is a significant public health, environmental and economic issue for New Zealand and its $256m shellfish aquaculture industry.

In response to increasing international concern around the widely varying results of testing laboratories around the world, the new method for the testing of marine toxins in shellfish has now been validated for worldwide acceptance in a project led by Laly Samuel for the IRL-initiated Virtual Institute for Metrology in Chemistry and Biology (VIMC), in collaboration with independent Nelson-based research organisation the Cawthron Institute.

Marine toxins are natural compounds produced by phytoplankton in the water, which shellfish consume to live. Neurotoxic shellfish poisoning (NSP) is a syndrome caused by the consumption of shellfish contaminated with a class of these natural toxins, called brevetoxins.

Since the 1950s, the testing of shellfish around the world has been via mouse bioassay, a laborious process involving mice of specified body weight and the use of large amounts of chemicals which can be dangerous and difficult to handle in the laboratory.

There is no standardised mouse bioassay protocol and the test is not validated, which means results can vary considerably depending on the mouse being tested.

The Cawthron Institute became the first laboratory in the world to replace the NSP mouse bioassay in 2004 when the New Zealand Food Safety Authority (NZFSA) approved an analytical chemistry technique called LCMS. This is a powerful technique used for many applications and has very high sensitivity and specificity for detecting and identifying toxins.

However, in order to be accepted as a worldwide standard the method had to be validated, says Cawthron’s technical manager, Paul McNabb.

“Apart from ethical issues, this method has one main property which the previous assay doesn’t have — the ability to be validated and verified. This is very significant for international trade because in a trade dispute over a mouse bioassay result it can’t be established whether or not the result is wrong.

Whereas if the test being used is based on metrology,it can be established through scientific investigation why something that may have been certified as safe here in New Zealand has produced a different result in another country.

“IRL’s Measurement Standards Laboratory recognised the need for validation and felt it was an important issue where New Zealand could make a significant impact globally. It was something they were prepared to invest in and, rather than try to duplicate everything, they contracted the outcome to us.”

Helen Smale, executive officer of the Marlborough Shellfish Quality Programme, an organisation owned and operated by industry to manage regulatory requirements under the Animal Products Act, says that the new method is already making a significant difference.

“Cawthron and IRL have done a brilliant job in making the LCMS method available to us as a management tool. It has revolutionised the management process as the results are available sooner, are more accurate and more sensitive than the bioassay tests. The industry has been eager to move away from the bioassay testing and this is another step towards that goal.”

The newly validated LCMS system has prompted researchers at the USFDA (US Food and Drug Authority) to support its use as a total replacement for NSP mouse bioassay around the world.

Robert Dickey, supervisor chemical hazards research unit, USFDA, says that the international scientific community as a whole, and the USFDA in particular, are very excited about these alternative method developments.

“We are even more excited with the prospect of finally implementing this move away from live animal testing to protect public health. Such developments will also dramatically improve the international acceptability of import/export certifications for global trade.

“As an international collaborative effort, we must move away from live animal testing where it is manifestly and demonstrably unnecessary and indeed inferior to alternative methods. It is past time that support be granted to this final transition to modern public health protection measures.”