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Paralytic Shellfish Poisoning
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A recent Whidbey News-Times headline proclaimed,
“Red Tide closes Penn Cove
beaches to recreational shellfish harvesting.” According to Kathleen
Parvin, of the Island County Health Department, the offending organism was
Alexandrium catenella.
It is somewhat confusing to call this situation a “red tide” because the
water was not discolored and did not appear abnormal in any way. In
contrast, there was another so-called “red tide” in July in which the water
turned orange. In that case, a completely harmless organism (Noctiluca) was
the cause. Occurrence of dangerous “red tides” are more accurately called
harmful algal blooms and the toxic substance itself is a marine biotoxin.
What do we know about this Alexandrium catenella?
As it turns out, this is an interesting little critter. Alexandrium
catenella is a dinoflagellate or single celled organism that uses two
whip-like tails (flagella) to swim. It lives in the waters of Puget Sound
as a natural part of the plankton. At times it exists as cysts in a resting
state. When conditions of water temperature, nutrient levels, etc. become
favorable, it can quickly convert to an active swimming state and begin to
multiply. In this state, it can form little chains that are said to
undulate through the water like a snake. The organism contains a toxic
substance called a saxitoxin.
Our shellfish, including clams, mussels, and scallops draw in water through
their siphons and filter out plankton including this organism and other
zooplankton that have already fed on it. As they absorb the nutrients from
the plankton, they also absorb the saxitoxin. It accumulates in their
tissues and levels of it build until they reach a point where it can be
toxic or even lethal to birds, marine mammals, and humans. Crabs can also
harbor the toxin.
The saxitoxin is very potent. Gram for gram, it is considerably more toxic
than strychnine and is only slightly less toxic than the neurotoxin found in
cobra venom. Saxitoxins block the flow of nerve impulses in warm blooded
animals and when ingested in toxic amounts, can quickly cause neuromuscular
symptoms ranging from numbness and tingling sensations in the face, mouth,
and extremities to paralysis of the muscles controlling the respiratory
system leading to death.
What is the history of this toxin?
Here in Island County, we have volunteers who collect shellfish
specimens and send them to the state health department for testing. Jim
Simpson, who happens to be a Beach Watcher, is one of our citizens who has
been doing this for about five years.
Jim collects specimens at Ala Spit, on the north end of Whidbey
Island. He says he goes out every two weeks from April to October and
collects about 88 mussels (Mytilus edulis).
Mussels are used for two reasons. First of all, they show the toxin earlier than some other species.
Secondly, it causes less damage to the beach to make frequent collections of
mussels than it would if he had to dig the beach up looking for clams. The
number of mussels collected is to make sure a specific amount of meat is
obtained. If littleneck clams were used, it would only take about 40 of
them.
Jim puts the mussels in a zip lock bag with a frozen gel pack.
He then fills out a form, packs it all up in a shipping container, and takes
it to Oak Harbor to be shipped to the state health department via UPS. The
state department of health tests the mussels then immediately gets any
necessary warnings on the Marine Biotoxin Hotline.
Jim says he would like to find someone to give him a hand with
this as a back up. Kathleen Parvin, from the Island County Health
Department, says she would also like more folks to help collect shellfish for
the studies. She’s particularly interested in finding folks living on
private beaches who would be willing to do this. She stresses that it’s a
serious commitment. If you would like to learn more about this, please give
her a call at the health department [(360) 679-7350].
Another Beach Watcher involved in this program is Sam Taniguchi.
Sam collects shellfish specimens on Camano Island. Kathleen Parvin says that
he is such a dedicated volunteer that when UPS was unable to operate
recently, Sam drove specimens clear to Seattle so the testing could be done.
If you would like more information about shellfish testing in
Island County, check out the Island County Marine Resources Committee website at
www.islandcountymrc.org
where you will find a summary of the program
presented on August 1, 2001 by Ms. Parvin entitled
“Healthy Foods from Healthy
Waters: Shellfish and Public Health in Island County”. The "link" to the summary is
included in the Minutes for August 1, 2001.
How can I find out if shellfish are safe to eat?
Kathleen Parvin says that it is never safe to assume the water
and shellfish are safe from the paralytic shellfish poisoning toxin.
To find information about beach closures, call the Marine Biotoxin Hotline at
1-800-562-5632. Web sites with information about PSP include
http://www.doh.wa.gov/ehp/sf/biotoxin.htm and
http://www.doh.wa.gov/Topics/Red_Tide.htm.
- Mary Jo Adams
This page was created on October 14, 2001 Island County/WSU Beach Watchers Phone: (360) 679-7391; 321-5111 or 629-4522, Ext. 391 |