Of mice and mussels

Shellfish scientists testing new ways to detect poisons

Posted: Friday, June 05, 2009

For 60 years we have had generations of laboratory mice to thank for shellfish that don't kill us.

Michael Penn / Juneau Empire
Michael Penn / Juneau Empire

The basic recipe: Clean and shuck one oyster, mussel, geoduck or clam. Weigh out 100 grams. Purée into a paste. Boil in diluted hydrochloric acid, like a soup with a particularly pungent broth. Inject into a mouse. Watch. If the sample is tainted, the mouse dies.

The feds require this test for shellfish that's headed to market, to ensure it doesn't have the tiny toxins that cause paralytic shellfish poisoning, or PSP. Symptoms include numbness, paralysis, disorientation and in some cases, death from respiratory failure.

The test is tried and true. But there are better methods on the way, and Alaska scientists at a state laboratory are some of the front-runners in evaluating them.

"When these methods were devised 50 years ago, that was the best they had," said Emanuel Hignutt, a chemist at the state environmental health lab.

Yet Hignutt finds the mouse test, or bioassay, distasteful. It is a common objection. On the other hand, he said, it saves lives. No one in Alaska has died of PSP in several years, partly because of these tests.

But it is inelegant. Preparing the sample and then waiting for the mouse to live or die takes time. The state Department of Environmental Conservation's small environmental health lab in Anchorage can handle only a handful of samples each day. It would be nice to scale it upefficiently.

And it is expensive. One does go through mice with a terminal test like this one. At the Anchorage lab, they don't breed mice, because that's an extra expense, so they get periodic shipments of just the right strain of female mice. They all must be fed and cared for (in a "mouse hotel," each in individual rooms) and tested for other health problems.

A better proverbial mousetrap would involve no mice at all.

"At some point, we're going to get through the red tape and prove we can do it another way, and stop torturing mice, I guess," said Hignutt. "But we have to have a lot of well-intentioned people working on it."

Testing new methods has been a side project for Hignutt and biologist Sara Longan, who runs the biological analysis side of the lab. Pure research is not the lab's primary mission. They test seafood for its clients, shellfish producers and gatherers, under the state's food safety program.

Saxitoxins are small molecules produced by algae that cause PSP. They are why in general, it's unwise to eat the blue mussels carpeting our shores. Cooking and acid do not destroy them. Some shellfish, like butterclams, store the toxins for up to two years.

Alaska scientists have an advantage in the world of PSP toxin detection.

"We have so many shellfish," said Thomas Hathaway, chief of the state lab. "People would like to get more data to evaluate these tests, and they don't have the samples we have up here."

Various non-mouse methods are in the works around the world. Some are already approved in New Zealand and in Europe. But those methods have disadvantages. For example, one Great Britain test requires something like an assembly-line to be efficient and wouldn't work well for Alaska's small lab.

The new test should be cheaper, faster and extremely reliable.

On reliability: A few years ago, Hathaway said, state scientists were helping the Gillette Corp. test an on-the-spot PSP assay, the cautious shellfish gatherer's dream. It was like a pregnancy test, with a pink line for a positive sample, according to Hathaway. But the state withdrew because the results weren't promising.

"You really never want to have a kit that gives you a false negative," he said. The false positive will merely keep someone from a tasty and harmless clam, while the false negative may kill him.

The state is testing two different methods, comparing them to mouse bioassay results for the same samples.

Longan, the biologist, is working on a promising new test called ELISA, or enzyme-linked immunosorbent assay. Under a certain light, special compounds fluoresce if no PSP toxins are present, but less so if they are. The recipe still requires making shellfish purée, but less. It is cheaper, faster, more sensitive than the mouse method, and so far produces no false negatives.

Hignutt is taking a chemist's approach. First, he physically separates all the parts of a sample through a technique called liquid chromatography. Then he runs it through a mass spectrometer, a device that analyzes the weights of each compound of the sample. Each toxin has a characteristic signature. It is proving to be a good way to confirm ELISA's results, Hignutt said.

Food and Drug Administration approval for PSP detection is a long, fine-tuned process, Longan said. The Alaska scientists have been presenting their work at conferences and are hopeful.

"When we present to the shellfish growers, I say, this is interesting. This looks very good. But this can't happen overnight. Don't get too excited," she said.

• Contact reporter Kate Golden at 523-2276 or kate.golden@juneauempire.com.

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