Anatoxines

Anatoxins are a group of potent neurotoxins produced by certain cyanobacteria, also known as blue-green algae. The term commonly refers to anatoxin-a and anatoxin-a(s), among closely related compounds. Anatoxin-a is a small, highly basic alkaloid that acts as a potent agonist of nicotinic acetylcholine receptors at the neuromuscular junction and in the autonomic ganglia, causing rapid depolarization, fasciculations, paralysis, and potentially death from respiratory failure within hours after exposure. Anatoxin-a(s) is a distinct structural class that inhibits acetylcholinesterase, leading to accumulation of acetylcholine and a cholinergic syndrome.

Occurrence and exposure: Anatoxins are produced by several genera of cyanobacteria, including Anabaena, Oscillatoria, and Microcystis, typically during algal blooms in freshwater systems. They may contaminate drinking water, recreational waters, and aquatic food chains. They are water-soluble and can persist in contaminated waters; cooking does not consistently destroy them.

Health effects: Humans and animals may be exposed through drinking water, swimming, or ingestion of contaminated organisms. Onset is usually rapid, from minutes to a few hours, with symptoms such as dizziness, headache, nausea, vomiting, salivation, muscle twitching, weakness, and in severe cases respiratory failure and death.

Detection and regulation: Cyanobacterial monitoring programs test for anatoxins in water using methods such as ELISA and LC-MS/MS. Health-guideline levels have been established in some countries; management includes reducing bloom exposure and ensuring safe drinking-water practices.

Treatment: There is no widely available antidote. Management is supportive, with airway stabilization and respiratory support as needed.