Potential Tracked for Emerging Biotoxin in Shellfish

by Laurie Schreiber

ELLSWORTH – Oddly, a common biotoxin that causes paralytic shellfish poisoning (PSP) in humans skipped town this year.

But another biotoxin, which causes amnesiac shellfish poisoning (ASP), appears to be gaining a foothold, said scientists with the Department of Marine Resources (DMR) Marine Biotoxin Monitoring Program.

“We have potential for ASP,” Alison Sirois, western Maine biotoxin program supervisor covering the coast from Kittery to Castine, told the DMR’s Shellfish Advisory Council in July.

ASP is caused by the domoic acid that is produced by a phytoplankton called Pseudo-nitzschia.
A critical area for Pseudo-nitzschia this summer has been Frenchman’s Bay and the Schoodic Peninsula, said Sirois.

Domoic acid can accumulate in marine organisms such as shellfish, anchovies and sardines that feed on Pseudo-nitzschia. In mammals, including humans, domoic acid acts as a neurotoxin that causes ASP. There may be gastrointestinal symptoms and, in more severe cases, neurological symptoms.

PSP is caused by a phytoplankton called Alexandrium, which produces toxins that can also accumulate in filter-feeding organisms such as mussels and clams.

The phytoplanktons that cause PSP and ASP are monitored by DMR staff and a volunteer monitoring network along the coast. When monitors see a bloom of Pseudo-nitzschia or Alexandrium, they do a quick field test to see if there’s toxin in the water. If there’s a positive, they conduct another field test on shellfish in those areas.

A subsequent lab test using high-performance liquid chromatography (HPLC) determines the amount of toxin in the shellfish. If a certain regulatory level is exceeded, the DMR closes the area to shellfish harvesting.

In April, the DMR announced it upgraded its testing techniques to the HPLC method for most species of bivalve shellfish, such as clams, mussels and oysters.

The monitoring program is important because the shellfish industry is one of Maine’s most valuable marine sectors. By July, the DMR had imposed a precautionary closure for ASP in Frenchman’s Bay. This happened at the same time the DMR put in place a flood closure for the entire Down East region, from mid-Penobscot Bay to the Canadian border, due to early-summer torrents of rain.

This was not the first time Maine has seen ASP, Sirois said. “Historically, we’ve had a few episodes,” she said. “Last year, we closed twice precautionarily. We tested the shellfish and they were below the regulatory limit.”

Still, she said, “We’re seeing ASP more, empirically. We’re seeing an increase at this time of year.”

With regard to PSP-causing Alexandrium, however, 2013 was “a very low, weird, anomaly year,” she said.

Early signs of Alexandrium generally appear in western Maine in April, then it spreads eastward for the next few months.

It’s difficult to say why Alexandrium took a break and Pseudo-nitzschia is showing up more, Sirois said.

“There are a lot of researchers out there asking those questions,” she said. “This fall, we’ll have a better sense of, oceanographically, what went on, but I think it’s probably environmental parameters.”

The Pseudo-nitzschia season seems to be similar to Alexandrium, with the potential addition of August through October.

“We are still figuring it out,” Sirois said.
“I think we’re actually in some Pseudo-nitzschia situations in some areas,” she told the council. “So we’re monitoring and we’re working with the volunteers, who are critical.”

Sirois told the council that she and others from both the DMR and Bigelow Laboratory of Ocean Sciences in East Boothbay have been investigating new chemical methods for monitoring biotoxins in shellfish.

Although ASP is not prevalent in Maine, said Sirois, “we need to think about the future. We have potential for ASP.”

According to the DMR, the Marine Biotoxin Monitoring Program uses standards outlined in the National Shellfish Sanitation Program to monitor levels of Alexandrium (commonly called “red tide”) and other marine biotoxins.

When toxin is found at levels near or above where human illness may occur, closures to the harvest of shellfish areas are implemented. Maine has historically had high levels of PSP during the warmer periods of the year. Shellfish samples are collected statewide between March and October and evaluated at the two laboratories – Boothbay Harbor for the western portion of the state, and Lamoine for the east.

Also in April, the DMR announced it was changing its sampling strategy to create regional mussel closures during the height of the biotoxin season and maintain exception areas for wild and recreational mussel harvest. The exception areas were determined with the help of harvesters, Sirois said. The regional mussel closures were implemented on May 15.

“At the end of this fall, we want to come back to you and present how the season went,” Sirois told the council. “The good thing about the mussel closures was, we didn’t have all these schizophrenic closures in weird parts of the coast. It was more, just, ‘Okay, make sure the exception areas are clear,’ and if we did start to see scores go up, we could go back. So I feel it was more predictable for the industry because they could count on the fact the mussel closure was in place and, if there weren’t any changes, it was a little less chaotic.”

Sirois said she’d like input from the industry about whether communication from the DMR was adequate. There were a couple of instances when biotoxin levels exceeded regulatory limits, but the areas were already closed, so the DMR didn’t send out an email, she said.

“That’s something we can talk more about, if it worked for everyone,” she said.

Another public health issue for the shellfish industry, said DMR Public Health Bureau director Kohl Kanwit, is increasing incidences of a bacteria called Vibrio.

“Vibrio is an issue in a lot of states. It’s become an increasing issue with the warm water,” Kanwit said.

Several species of Vibrio can cause foodborne infection. It is usually associated with raw or undercooked seafood. It also occurs naturally in the environment and, under certain conditions with warmer water temperatures, there is increased risk, particularly in shellfish aquaculture areas, said Kanwit.

There have been several outbreaks of Vibrio-related illnesses in Massachusetts and New Jersey, she said. The U.S. Food and Drug Administration would be reviewing the DMR’s growing area program, she said.

In other business, shellfish advisors said they would prefer to criminalize clam-digging without a town license. Digging without a license is now a civil penalty.

It used to be a criminal offense, but was changed to civil to expedite the court process.

Municipal shellfish warden Lewis Pinkham of Milbridge said shellfish wardens don’t have enough power to enforce civil penalties. “As far as I’m concerned, it was the wrong thing to do,” Pinkham said of the switch to civil. “Now, people can set up a payment plan, and if they don’t pay, we have to wait for months or a year. As far as I’m concerned, this has just frigged us up.”

“It is a frig for a warden,” said harvester Joe Porada of Hancock. “He gives a ticket, and they don’t really have to pay.”

“I think for municipal violations, it does make sense on the commercial end, because the person is knowingly going and harvesting shellfish without a municipal license,” said Denis-Marc Nault, a shellfish program supervisor who covers the southern towns from Eliot to Old Orchard Beach, and eastern towns from Milbridge to Calais.

Digging in closed areas remains a criminal violation, Nault noted.

Porada and others said they knew of several people who have been digging clams without a license. They would apparently be selling directly to the public rather than to dealers, because dealer transactions are traceable, the council agreed.

“I can’t see them getting a civil violation when they’re blatantly violating the law,” said Porada.
The council voted to take the proposal to the DMR, which would in turn take the matter to the state legislature for a statute change.

“This has been a growing problem that we’ve seen, so yeah, I think this makes sense as a stepping stone,” said Nault.