University, Gillette researchers develop field test to detect shellfish poisoning

welchlanieLR.jpg A new testing procedure could soon turn the tide against incidents of paralytic shellfish poisoning, or PSP. The test will also allow shellfish harvesters and growers to easily test their catches for the deadly toxin in remote areas.

In Kodiak late last month, aquaculture specialist Ray RaLonde of the University of Alaska’s Marine Advisory Program and researchers from Gillette Biotech were scheduled to unveil a PSP field test kit they’ve invented, and instruct people on how to use it.

fishfactor.jpg Kodiak Island is an appropriate place to introduce the new technology, as the region has the dubious distinction of being the "PSP Capital of the World." Whereas the allowable limit of PSP is 80 micrograms per 100 grams of tissue, shellfish around Kodiak have contained as much as 19,600 micrograms.

"A concentration that high will deliver a lethal dose by consumption of only a single small mussel," RaLonde said.

Other areas showing worrisome, albeit much lower, levels of PSP are along the southern shores of the Aleutian Chain, in Southeast Alaska near Ketchikan and near Juneau. According to the U.S. Department of the Interior, the occurrence of PSP has severely affected development of clam fisheries throughout Alaska, where an estimated 50 million pounds are available each year for harvest.

PSP comes from a single-celled algae that produces the toxins as a normal byproduct. Shellfish, and some crabs, feed on the algae and can accumulate PSP toxins to dangerous levels. PSP is estimated to be 1,000 times more toxic than cyanide, and symptoms appear soon after consuming toxic shellfish. So far, at lease 24 molecular forms of PSP toxins have been identified, "and we’re still counting," RaLonde said.

Collectively, the toxins are termed saxitoxins, named after the common butter clam, Saxidomus giganteus, where they were originally extracted and identified. Butter clams are particularly notorious, because they can hold the PSP toxin for two years. The toxins block movement of sodium through nerve cell membranes, and stop the flow of nerve impulses. This results in the symptoms of PSP, which include numbness, paralysis, disorientation and even death.

There is no antidote for PSP, and all cases require immediate medical attention. In Alaska, more than 172 cases of PSP have occurred since the 1970s, although the state Department of Epidemiology estimates that only one in seven cases is reported. Two deaths from PSP have occurred in recent years, both on Kodiak.

Currently, the only federally approved test for PSP involves injecting a serum made from ground up shellfish tissue into a mouse. The level of toxicity is determined by how long it takes the mouse to die. In Alaska, testing of all shellfish is done through the Department of Environmental Conservation at a single lab in Palmer.

State funding provides only for the testing of commercially harvested products, and there is no mandate or funding to test beaches for recreational harvests. The only beaches officially certified in Alaska are on Kachemak Bay and Cook Inlet, where harvests of razor clams and shellfish sent in by aquatic farmers are tested regularly.

PSP episodes in Alaska tend to be seasonal, occurring most often during late spring and summer. According to a paper by RaLonde, "Paralytic Shellfish Poisoning: The Alaska Problem," shellfish become toxic when environmental conditions, such as changes in salinity, warming water temperature and increased nutrients and sunlight, enable the poisonous cells to rapidly reproduce, causing a toxic bloom. In time, the water may take on a fluorescent reddish color referred to as a red tide.

But that can often be a misnomer. RaLonde said: "In Kodiak, for example, we have never seen a red tide that’s caused the toxicity. You don’t see the massive amounts of cells, but the ones that are there are highly toxic. A bloom may come and go quickly, but the shellfish are contaminated."

RaLonde said that in 1997, funding by the Alaska Science and Technology Foundation enabled Gillette researchers to discover which kinds of PSP toxins are found in Alaska, and they developed fabricated antibodies that link to the toxin.

"The antibody has a color tag, and when you mix the toxic serum with the antibody, the color shows the level of toxicity. It’s a yes/no test, the product either passes or it doesn’t," he said.

People will need some training to use the field kit properly, as it involves grinding and heating shellfish tissue, and the test protocol must be followed exactly. RaLonde said: "There are limitations, but it has great potential. I look at it as a good monitoring tool to screen locations, or find patterns of toxicity occurring in a certain area. Finally, you don’t have to send samples into a lab for testing. You can do right here."

Rock music attracts fish

The Internet site WorldCatch reports that a new survey reveals that fish love listening to the Rolling Stones. Fishermen reportedly have found that playing classic tracks of the Stones and ZZ Top attract large schools of fish. On the contrary, female voices tend to send the fish flying.

WorldCatch said that according to the magazine Boating, the sounds of Alanis Morissette and Dionne Warwick "send the fish swimming off in a panic."

Kodiak-based free-lance writer Laine Welch can be reached via e-mail at ([email protected]).

Updated: 
07/09/2001 - 8:00pm

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