Cyanobacterial Toxins and Symptoms

Some cyanobacteria produce toxins that can affect animals and humans.  These toxins have the potential to affect the liver, the nervous system, or exposed skin.  In order to be affected, people, pets or wildlife have to be exposed to the toxin by drinking or playing in water with a toxic bloom.

The following information on toxins and symptoms is organized by cyanobacteria genera that are most likely to occur in Washington lakes.

Anabaena spp.

Anabaena spp. can produce several kinds of toxins, including anatoxin-a, anatoxin-a(s), saxitoxin, and microcystins.  Anatoxin-a affects nerve synapses. It works as a postsynaptic cholinergic nicotinic agonist, which causes a depolarizing neuromuscular blockade.  Anatoxin-a(s), chemically unrelated to anatoxin-a, also affects nerve synapses.  It acts as an inhibitor of cholinesterase leading to a neuromuscular blockade.  Both can cause a “tetanus-like” muscle paralysis.  Anabaena spp. have also been associated with allergic or irritative dermal reactions affecting exposed tissue.

Neurotoxins are notoriously rapid acting poisons.  Onset of symptoms and death to an animal may occur within a few minutes to a few hours, depending on the size of the animal and amount of toxic bloom consumed.  An animal with anatoxin-a toxicosis may exhibit staggering, paralysis, muscle twitching, gasping, convulsions, backward arching of neck in birds, and death.  Experimental animals with anatoxin-a(s) induced toxicosis may exhibit hypersalivation, tremors, muscle twitching, involuntary muscle movement, diarrhea, cyanosis (tongue and mouth lining appear bluish) and death.

Animals with saxitoxin/neosaxitoxin toxicosis may exhibit weakness, staggering, loss of muscle coordination, difficulty in swallowing, labored respiration, complete muscle paralysis, and death.  Humans may also exhibit tingling around the mouth and fingertips, as well as slurred speech.  Hepatotoxins such as microcystins target the liver.  Symptoms include nausea, vomiting, and acute liver failure.  Symptoms may take 30 minutes to 24 hours to appear, depending on the size of the animal affected and the amount of toxic bloom consumed.  Symptoms of microcystin toxicosis include jaundice, shock, abdominal pain/distention, weakness, nausea/vomiting, severe thirst, rapid/weak pulse and death.

Aphanizomenon spp.

Aphanizomenon flos-aquae is known to produce two of the same toxins as paralytic shellfish poison (PSP):  saxitoxin and neosaxitoxin.  A. flos-aquae is also know to produce anatoxin-a.  These toxins are neurotoxins that affect nerve synapses or nerve axons making them incapable of generating a nerve impulse.  They are effective in extremely small amounts.  Only a small amount of toxic bloom needs to be ingested to cause illness or death in animals.

Because neurotoxins are notoriously rapid-acting poisons, onset of symptoms and animal death may occur within a few minutes to a few hours, depending on the size of the animal and amount of toxic bloom consumed.  Animals with saxitoxin/neosaxitoxin toxicosis may exhibit weakness, staggering, loss of muscle coordination, difficulty in swallowing, labored respiration, complete muscle paralysis, and death.  Humans may exhibit tingling around the mouth and fingertips, as well as slurred speech.

Aphanizomenon spp. also produce cylindrospermosin, which targets the liver and other organs. Symptoms of liver toxicosis include nausea, vomiting, and acute liver failure.  Additionally, laboratory studies have shown that cylindrospermopsin may be carcinogenic and genotoxic.

Reports of allergic or irritative dermal reactions of varying severity have been associated with this genera after recreational exposure.

Cylindrospermopsis

Cylindrospermopsis raciborskii can produce several toxic substances, including cylindrospermopsin, which is mainly toxic to the liver but can affect the kidneys, heart and other organs.  Symptoms of liver toxicosis include nausea, vomiting, and acute liver failure.  Laboratory studies have shown that some of the compounds produced by Cylindrospermopsis may be carcinogenic and genotoxic.

Cylindrospermopsis also produces saxitoxin, a neurotoxin.  Animals with saxitoxin/neosaxitoxin toxicosis may exhibit weakness, staggering, loss of muscle coordination, difficulty in swallowing, labored respiration, complete muscle paralysis, and death.  Humans may exhibit tingling around the mouth and fingertips, as well as slurred speech.  Another nerve toxin produced by Cylindrospermopsis is anatoxin-a, which is a neuromuscular agent that can result in muscle cramps, twitching, paralysis, respiratory distress, convulsions, cardiac failure, and death in animals. 

Gloeotrichia
Gloeotrichia echinulata may produce lipopolysaccharides.  Lipopolysaccharides have been implicated as cytotoxins, a group of toxins that are not highly lethal to animals but that may cause skin irritations and outbreaks of gastroenteritis in swimmers.

G.  echinulata may also cause liver damage as a result of continued ingestion.   Bacterial lipopolysaccharides are recognized to be involved in septic shock syndrome, which may increase the impact of other toxins that induce liver injury (that is, the toxicity of microcystin-LR may be increased in the presence of lipopolysaccharides).  Water from a source with a Gloeotrichia bloom may take on an odor as well as a foul taste.

A recent study found that G. echinulata contained microcystins.  However, no animal deaths have been directly associated with this species.

Lyngbya spp.

Some species/strains of Lyngbya may produce toxins (saxitoxins, aplysiatoxins, lyngbyatoxins, and lipopolysaccharides).  In one case, toxins from Lyngbya wollei caused severe skin reactions and respiratory distress in people who were in contact with algae mats in several Florida springs.  Lyngbya mats can produce gasses that cause them to rise to the surface where the wind can push them against shorelines. To date, problems due to Lyngbya exposure have not been reported in Washington state lakes, although Lyngbya was associated with a toxic bloom in Anderson Lake, Jefferson County, in 2006.

Microcystis spp.
Microcystis is a unicellular cyanobacteria that is microscopic in size.  It forms colonies that can turn the water a blue-green color and may form surface scums.  Some Microcystis spp. may produce a family of toxins called microcystins, which are heptapeptides that primarily affect the liver in animals and are known as hepatotoxins.  Researchers suspect these toxins are liver carcinogens, which could prove significant to humans following continuous, low level exposure.

Symptoms may take 30 minutes to 24 hours to appear, depending upon the size of the animal affected and the amount of toxic bloom consumed.  Microcystin toxicosis may include jaundice, shock, abdominal pain/distention, weakness, nausea/vomiting, severe thirst, rapid/weak pulse and death.

Nostoc  

Nostoc spp. are barrel-shaped or spherically-shaped single-celled cyanobacteria.   Cells form filaments that in turn form colonies tangled in a gelatinous mass.  Nostoc colonies may be microscopic or macroscopic.  Akinetes of Nostoc are usually located halfway between the heterocysts (akinetes in Anabaena are usually adjacent to heterocysts).  Some Nostoc spp. produce microcystins, which are hepatotoxic.  This genera is also reported to produce lipopolysaccharides.

Oscillatoria/Planktothrix.* 

Some species of Oscillatoria produce toxins including microcystins and anatoxins.  Oscillatoria is also reported to produce aplysiatoxins, which can cause allergic or irritative dermal reactions in people.

Planktothrix spp. regularly produce microcystin.  Planktothrix populations have been shown to inhibit glycogen metabolism and affect aquatic organism development.  In a German lake, malformations in whitefish eggs and larvae were observed during Planktothrix blooms, and liver lesions were observed in adults. 

Recently, three additional toxins were identified in Planktothrix spp.  Saxitoxin was identified in a Planktothrix bloom in a lake in Italy.   Anatoxin-a was identified in a bloom in a fishing pond in northern Italy.  Oscillapeptin J, a newly identified toxin that affects crustacean grazers, was produced by a Planktothrix sp. in Lake Zurich. 

Hepatotoxins such as microcystins target the liver where they can cause bleeding.  Symptoms include nausea, vomiting, and acute liver failure.  Symptoms may take 30 minutes to 24 hours to appear, depending on the size of the animal affected and the amount of toxic bloom consumed.  Microcystin toxicosis may include jaundice, shock, abdominal pain/distention, weakness, nausea/vomiting, severe thirst, rapid/weak pulse and death.

Animals with saxitoxin/neosaxitoxin toxicosis may exhibit weakness, staggering, loss of muscle coordination, difficulty in swallowing, labored respiration, complete muscle paralysis, and death.  Humans may exhibit tingling around the mouth and fingertips, as well as slurred speech. 

Anatoxins can block the transmission of signals from neuron to neuron and neuron to muscle.  An animal with anatoxin-a toxicosis may exhibit staggering, paralysis, muscle twitching, gasping, convulsions, backward arching of neck in birds, and death. 

NOTE:  The cyanobacteria (Cyanophyta, blue-green algae) are named under the Botanical Code and the Bacteriological Code, leading to some taxonomic confusion. The present status of the nomenclature of the cyanobacteria under the Bacteriological Code is unclear for some taxa, including Oscillatoria and Planktothrix.  Some genera have never been validly published under the Rules of the Bacteriological Code (1990 Revision).  However, some species names have been validly published under the ICBN.  For more information, visit International Journal of Systematic and Evolutionary Microbiology  "A proposal for further integration of the cyanobacteria under the Bacteriological Code."

Other Cyanobacteria and Their Toxins

Anabaenopsis

Anabaenopsis is a filamentous cyanobacteria similar to Anabaena but with terminal rather than filamentous heterocysts.  This genus is mainly distributed in tropical and subtropical regions but also occurs in summer seasons in temperate zone waters.  Microcystin-type toxins have been identified in a species collected in Greece, and Anabaenopsis is suspected of contributing to toxic blooms in Kenya.

Hapalosiphon

Hapalosiphon species are filamentous cyanobacteria with true branches that are often joined to substrates but that can also be found free-floating.  The majority of species grow in stagnant waters, moors, or peaty waters.  Microcystins have been identified in a terrestrial species of Hapalosiphon.  This genus may produce lipopolysaccharides capable of causing skin irritation and gastrointestinal distress.  One species is suspected as the potential cause of avian vacuolar myelinopathy (AVM) that killed bald eagles and American coots in the Southeastern U.S.

Nodularia

Nodularia spumigena is an important marine and brackish water cyanobacteria species that produces nodularin.  This genus occurs in coastal oceans, estuaries, and saline lakes worldwide.  Blooms are often associated with phosphorus enrichment.  Nodularin has a closely related structure to that of microcystin and shows the same hepatotoxic effects through the inhibition of protein phosphatases.  Low-level exposure to these toxins may promote the development of cancer in the liver and other chronic disorders of the gastrointestinal tract.  Allergic or irritative dermal reactions of have been reported for Nodularia after recreational exposure. The first scientific report of Nodularia spumigena toxicity was issued in 1878, and blooms of this species have caused stock deaths in Australia as a result of animals drinking from bloom-infested lakes.

Schizothrix

Some species of Schizothrix may produce aplysiatoxins or lipopolysaccharides.  The primary target organ of aplysiatoxins in mammals is the skin.  Lipoplysaccharides from Schizothrix calcicola contaminated drinking water in southwestern Pennsylvania.

Umezakia

This species was recently identified from a lake in Japan.  A toxic compound identical to cylindrospermopsin was reported for Umezakia natans.  The main target of the toxin in animal studies was the liver.

Additional Information
 

The World Health Organization issued a summary table of cyanobacterial toxins and symptoms.  View the Table (pdf 16 KB) for more information on toxins, their primary target organ and the genera that produce each toxin type.

Glossary

Agonist
A substance that can combine with a cell receptor to produce a reaction typical for that substance.

Akinetes
Akinetes are resting cells capable of surviving long periods of desiccation and cold.

Aplysiatoxins
Agents commonly known for their dermatotoxic activity causing inflammation of the skin.  They are also potent tumor promoters.

Carcinogenic
An agent with cancer-causing properties.

Cholinesterase
An enzyme that catalyzes the hydrolysis of choline esters chiefly at nerve terminals, where it hydrolyzes and inactivates acetylcholine.

Genotoxic
Damaging to DNA and thereby capable of causing mutations or cancer.

Hepatotoxin
An agent that is toxic to the liver.

Hypersalivation
Excessive flow of saliva.

Jaundice
Yellowish discoloration of the whites of the eyes, skin, and mucous membranes caused by deposition of bile salts in these tissues.

Lipopolysaccharides
Any of a group of polysaccharides in which a lipid constitutes a portion of the molecule.

Neurotoxin
An agent that is toxic to nerves or the nervous system.

Synapse
The junction across which a nerve impulse passes from an axon terminal to a neuron, a muscle cell, or a gland cell.

Septic shock syndrome
Shock associated with septicemia caused by gram-negative bacteria.

Toxin
A poisonous substance, especially a protein that is produced by living cells or organisms.

Toxicosis
Systemic poisoning, or a diseased condition resulting from poisoning.

Toxicant
 A poison or poisonous agent.

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