Wednesday, October 9, 2013

Local Biotoxins and Toxic Bacteria

Written September 30, 2013, published in October 2013, all photos by Kathleen Sayce

With the next razor clam season approaching, this is a good time to review biotoxins and bacteria that are health hazards. First, a historical perspective:  Commercial razor clam digger Ed Chellis routinely dug hundreds of pounds of razor clams per tide, 1930-40s. He said the clam cannery kept pigs and chickens to eat the leftover clam parts. Sometimes the chickens and pigs walked funny or staggered around for days, and sometimes they all died. He did not take clams home for his family when the animals fell ill. 
Bottom line:  Biotoxins have been here for a long time. 

Prorocentrum species are associated with biotoxins in some areas. This genus is common in local waters. On the south coast of Washington, it has not been associated with water-borne toxins. 


At the top of the list of locally common toxins is Paralytic Shellfish Poisoning (PSP), caused by saxitoxin, which is produced by species in the dinoflagellate genus Alexandrium, other dinoflagellates, cyanobacteria, and at least one species of pufferfish. Shellfish may store these toxins to reduce predation; it remains in animal tissues for weeks to years. Poisoning occurs by eating the shellfish. Saxitoxin is water soluble, and is heat and acid-stable, which means that cooking makes no difference to its toxicity.  Alexandrium species are seen regularly along the Pacific Northwest coast, and are common in local waters during warm weather, spring through fall.  Otters, seals and whales have died from high doses of PSP. 

The symptoms of PSP appear soon after eating, and include tingling or burning of lips, tongue and mouth, or other skin surfaces (face, neck, arms, etc.), nausea, vomiting, abdominal pain, diarrhea, shortness of breath, dry mouth, a choking feeling, confused or slurred speech, and loss of coordination. Cooking does not affect this biotoxin. I once took a bite of steamer clams that were high in PSP; it felt like fireworks went off in my mouth. I spit them out, rinsed my mouth and dumped the meal; my mouth was numb for a few minutes. 

In extreme cases of PSP poisoning, respiratory arrest shuts down the breathing system, hence the word paralysis in the name. Recently campers on the Olympic Peninsula ate PSP-contaminated mussels, and after one mouthful, one of them went into full respiratory arrest. His companions gave him mouth to mouth until help arrived, and he recovered. If people survive the initial poisoning event with respiratory support, they usually make a full recovery.

Pseudo-nitzschia species produce domoic acid, and locally were responsible for many closures in the 1990s in local waters. 


Amnesiac Shellfish Poisoning (ASP) is caused by domoic acid, a small protein produced by diatoms in two genera, Pseudo-nitzschia and Nitzschia. Domoic acid concentrates in fat cells as it moves up the food chain from diatoms to zooplankton, shellfish, crabs and small fish to larger fish; this is called bioconcentrating. Birds, marine mammals and humans are neurologically affected by ASP. Domoic acid is unaffected by heat or other food preparation methods, and can persist in animal tissues for years following large blooms. This biotoxin may be a relatively recent arrival, reaching the West Coast after WWII in ballast water on commercial ships. In some years it has been a dominant species outside the surf zone in local waters. 

Symptoms of ASP show up some hours to days after eating shellfish, and include gastric upset (nausea, vomiting, diarrhea) followed by neurological problems (headache, seizures, dizziness and other symptoms). Death can result; in survivors the most serious problem may be short term memory loss. Recovery from this is so slow that the memory loss is effectively permanent. 


Diarrhetic Shellfish Poisoning (DSP) is generally not life threatening, though profoundly uncomfortable to victims. Caused by okadaic acid, and found in two genera of dinoflagellates, Prorcentrum and Dinophysis, the result is diarrhea, which begins within an hour of consumption and lasts about one day. No fatalities have been recorded from known cases of DSP. These dinoflagellates are common in local waters each summer, but are rarely dominant in blooms. 

Dinophysis species are common summer phytoplankton in local waters. This dinoflagellate genus causes DSP in warmer waters, such as in Florida. 


Cyanotoxins are a group of biotoxins produced by cyanobacteria, and include some of the most potent neurotoxins on the planet, found in both freshwater and saltwater. Following exposure, the most common form of death is by respiratory failure. There are many other impacts; cyanotoxins can kill from just skin contact or inhaled fumes as blooms decay. Animals of all kinds can be killed, fish included, and humans. 

Cyanobacteria are widespread; blooms often occur during warm weather in areas where there are high concentrations of nutrients, such as at wastewater treatment plants or lakes. If you see water (particularly freshwater) so thick with plankton growth that it appears to be filled with light green to reddish liquid paint, stay out of the water, and keep your dog out too––it's likely to be full of cyanobacteria. 


Saltwater cholera or Vibrio gastroenteritis is caused by Vibrio species that live in saltwater. In our area, Vibrio parahemolyticus grows in warm saltwater, most abundant in late summer to early fall. Live shellfish held in waters warmer than 20 C (68 F) often have increased numbers of V. parahemolyticus. During cool summers and cool weather cycles, this bacterium is not usually a problem in our area, but when it's warm, then Vibro bacteria can be very abundant. On the east coast, a man died last week from wading in water with high concentrations of  Vibrio vulnificus. He had no skin lesions or cuts, but still took in enough toxins from this bacteria to shut down his internal organs. 

During El Nino-Southern Oscillation Events (ENSO), as for many years during the 1980-1990s, whenever warm subtropical waters reach our coast, Vibrio thrives. It has caused widespread closures in the past. When shellfish are undercooked or served raw, contaminated shellfish cause Vibrio gastroenteritis, or on the skin, infect open wounds and cause septicemia. As with other choleras, hydration support is important; choleras of all kinds can be deadly. Vibro gastroenteritis is a problem anywhere shellfish live in too-warm water. 

E. coli:

Fecal coliform bacteria, Escherichia coli, or E. coli, is found in mammals and birds, and is a common bacterium of human digestive tracts; it is not free-living. E. coli cells can persist for days to weeks in freshwater, but survive less than 48 hours in salt water. Contamination of salt water comes about due to failing septic systems, or from high rainfall events that overflow municipal sewage treatment ponds, or surface flushing of water from livestock areas, or areas of high wildlife concentrations. Normal run off from streams with exposure to oxygen, sunlight and salt water cause E. coli cells to die in estuaries and ocean waters. But high concentrations can occur, and shellfish do take up the bacteria. If raw or undercooked shellfish are consumed when concentrations are high, E. coli causes gastric illness and death. Areas near outfalls from sewage treatment plants are off limits year round due to this bacterium.

Regular sampling helps establish trends. It's common for particular shellfish beds to be closed for a few days after high rainfall events (more than 2 inches of rain per 24 hours) to let the shellfish clear their tissues.  Shellfish growers regularly sample their shellfish, and pay for the samples to be checked by Washington Department of Health. This is a chronic problem for inland marine waters, estuaries and rivers far more than for ocean beaches. Local closures of parts of Willapa Bay are common, for a few days each year, in specific areas. It's also a problem for freshwater rivers, and is one of the main reasons why it's unsafe to eat freshwater shellfish that are wild-harvested from local rivers.

We can all help keep our local waters clean by keeping our septic systems and municipal water treatment plants in optimal operating condition. For private septic systems, this means clean-out and inspection every 3-5 years. For municipal systems, stormwater runoff from streets should be separated from sewage, and inflows from cracks and breaks in sewage collection systems should be repaired to reduce the volume of water that flows to treatment plants during storms and when groundwater levels are high. 

There are two biotoxins, not yet known from our area, that live in the tropics: 


Neurotoxic Shellfish Poisoning (NSP) is caused by brevitoxins, which are produced by Karevia brevis (a dinoflagellate formerly known as Gymnodinium breve and Ptychodiscus brevis), a common component of harmful algal blooms in warm waters. Gastric and neurological illness follows consumption of contaminated shellfish. Some people have been hospitalized with NSP, though no fatalities have been reported. NSP is common  in the Gulf of Mexico and around Florida, where it causes spectacular red tides in salt water. Species of Gymnodinium have been seen here in warm years. 


Ciguatera is a group of toxins produced by Gambierdiscus toxicus, a dinoflagellate of tropical and subtropical waters. Unlike plankton species, Gambierdiscus lives on corals and other reef surfaces, where it is eaten by herbivorous fish. Ciguatera bioaccumulates when those fish are in turn eaten by predatory fish.  This group of toxins include ciguatoxin, maitotoxin, scaritoxin and palytoxin.  These toxins are odorless, tasteless, heat-resistant and unaltered by cooking. Predatory fish at the top of the food chain around tropical reefs are most likely to bioaccumulate ciguatera There are both gastrointestinal and neurological effects; death is fairly common and long term neurological problems may persist for decades. Ciguatera is not yet known from this area. 


When Washington Departments of Health and Fisheries and Wildlife announce beach closures during razor clam season, know that these agencies are monitoring for several toxic species. They close beaches and commercial shellfish beds to protect public health. Most harmful species are more common in warm weather, so spring through fall closures are more likely. The occasional biotoxin will pop up in mid to late fall, or even in midwinter, even in cold wet years. In ENSO years, all bets are off. Biotoxins can appear at any time during these years and persist for months to years. 

Messages go out on regional television stations and radio when closures are announced, including to newspapers and other media. The state agencies post seasons and closures for beaches throughout the state at While no one wants a clam season to be shut down suddenly, these closures come about because one of several biotoxins or bacteria has appeared, and is rising in concentration.