Aquatic species, amphibians, reptiles, birds, mammals, and humans are all at risk of ingesting toxic algae, which are present in freshwater, brackish water, and marine ecosystems.
Some algae toxins are powerful enough to result in human poisoning cases after eating, and cases of death are also documented.
Phytotoxins, which are organic dangerous chemicals that create a variety of highly hazardous compounds, are the name given to the toxins produced by algae and cyanobacteria.
Although it hasn't been shown to far, it is possible that the ability to generate hazardous substances evolved as a means of protecting organisms from predators.
Phycotoxins such saxitoxin, gonyautoxin, okadaic toxin, brevetoxin, ciguatoxin, domoic toxin, palytoxin, and tetrodotoxin are produced by marine algae (dinoflagellates), yellow-brown algae (diatoms), and blue-green algae (cyanobacteria).
These poisons kill many aquatic creatures and are hazardous to people, producing gastrointestinal problems, algal pollution, and aquatic animal deaths.
The breakdown of enormous amounts of algae beneath shallow water reduces the oxygen supply, which kills fish.
Fish are poisoned by algae such Prymnesium parvum and the dinoflagellates Gymnodinium veneficum, Gymnodinium brevis, and Gonyaulax monitala.
The dinoflagellates Gonyaulax catenella and Gonyaulax tamarensis are responsible for human shellfish poisoning.
When they devour this toxic algae, many non-poisonous fish turn poisonous, and the chain is continued by humans eating herbivorous fish and shellfish.
In addition to contaminating drinking water used for food and feed production, these poisonous algae also directly harm people and animals.
Similar to how azaspiracid shellfish poisoning (ASP) is caused by 12 azaspiracid analogues, neurotoxic shellfish poisoning (NSP) by brevetoxins, and ciguatera fish poisoning (CFP or Ciguatera) by ciguatoxin, gambiertoxin, and maitotoxin, different types of food poisoning are caused by various sources and types of toxicity.
Others include saxitoxins, DA derivatives, okadaic acid, and dinophysistoxins-related paralytic shellfish poisoning (PSP), amnesic shellfish poisoning (ASP), and diarrhoeal shellfish poisoning (DSP).
Less well known toxins include those from golden algal toxins, karlotoxins, Pfiesteria toxins, pectenotoxins, and yessotoxins.
Red tides are brought on by phycotoxins such as dinoflagellate blooms, cyanotoxins, and harmful algal blooms (HAB).
In addition to two lipid-soluble toxins (hemolytic and neurotoxic) that have an impact on the lives of freshwater and marine creatures, dinoflagellate cells also contain chlorophylls a and c.
Dinoflagellates called gonyaulax are red and give the water a reddish tint because they reproduce quickly and produce pigment that turns from brown to red.
Dinoflagellates create toxins that can lead to respiratory paralysis and digestive issues.
In the majority of cases of seafood poisoning, the brevetoxin results in a neurological issue.
Toxins produced by Diatoms
Diatoms, sometimes referred to as phytoflagellates, are yellow-brown algae that inhabit brackish ponds and estuaries.
A yellow-brown alga called Prymnesium parvum includes the chlorophylls a, c, and e as well as a toxin that prevents oxygen from passing through the fish gill membrane.
This toxin is thermolabile and contains a strong hemolytic agent that can harm seafood and humans and cause digestive and respiratory issues.
Fish poisoning has been a major issue and a source of financial loss for commercial farms throughout many nations.
Toxins produced by Cyanobacteria
Blue-green algae are another name for cyanobacteria, and the species Nodularia spumigena is responsible for the toxin generation that causes food poisoning in humans.
Freshwater and brackish waters are home to the bacteria Nodularia spumigena and Microcystis aeruginosa, which harm cattle.
Common species that generate heat-stable neurotoxins including anatoxin-a, which is poisonous to many animals, are Anabaena circinalis and Anabaena flos-aquae.
Jumping movements, abdominal breathing, convulsions, lacrimation, salivation, urine, and diarrhoea are the clinical signs of these poisons.
Aphanizomenon spp., Anabaena spp., Cylindrospermopsis spp., Lyngbya spp., Caulerpa spp., Schizothrix spp., and Planktothrix spp. are more species of cyanobacteria that produce toxins.
Some toxins, which are produced by bacteria linked to algae, infect fish, making them hazardous to both the fish themselves and the animals that eat them. Inside the fish's body, microorganisms make poisons from the food they consume that may be linked to algae.
Route of exposure to Algal Food Poisoning
Consuming infected seafood items including contaminated clams, mussels, scallops, oysters, and other shellfish is the main exposure route.
Saxitoxin is produced when pufferfish are consumed, whereas ciguatera is produced by huge reef fish like barracuda and grouper.
It is also known that Karenia brevis's brevetoxin, which causes airborne poisons, may be inhaled.
People living close are irritated by this airborne poison, which may be prevented by using particle filter masks.
The foetus and newborn babies are also severely harmed by ciguateratoxins and maitotoxins, which are transferred by sexual contact.
These poisons can be passed from mother to child through the placenta and through breast milk transmission.
Through direct skin contact or ingesting tainted water, several cyanobacterial toxins can infect people.
Those who work on boats and in the fishing industry are at a greater risk of contamination.
Toxicokinetics of Algal Toxins
When lipophilic and hydrophilic algal toxins are ingested by the digestive and respiratory systems, their metabolism happens quickly.
Within seven days of exposure, the acute inhalation of the brevetoxin toxicokinetics begins. It is absorbed in the lungs and dispersed throughout the body by blood flow.
Toxins build up in the liver, gut, and skeletal muscle whereas they are hardly detectable in the blood, brain, and fat.
For up to a week, about 20% of toxins can be found in the lung, liver, and kidney before slowly spreading throughout the body.
The blood-brain transporter cannot be penetrated by domoic acid, which is taken orally and transferred to other body parts via the blood.
This toxin carries dangers and the potential for compromised renal function along with higher blood serum concentrations.
Humans use glucuronidation, a detoxification process that turns xenobiotics into water-soluble metabolites, to break down saxitoxin.
After saxitoxin metabolism, the toxins are eliminated by urine and faeces and are still present in the pancreas, liver, brain, adrenal glands, thyroid glands, cerebrospinal fluid, stomach, spleen, liver, and other organs.
The microcystins are carried into the liver from the blood in the gastrointestinal tract, where the cyanobacterial toxins are absorbed.
Microcystins can stay in the liver for up to 6 days, but only for roughly 24 hours in the kidney.
Acute and chronic toxicity
Within minutes to 24 hours after eating infected seafood, gastrointestinal signs and symptoms appear.
Breathing problems, tingling and numbness in the peripheral nervous system, hallucinations, memory loss, erratic blood pressure, and heart arrhythmia are among the symptoms.
Depending on the specific condition and dosage concentration, the sickness might persist anywhere from a few hours to several months.
The cells and tissues of the organs are affected by chronic toxicity, although its exposure has not been well researched.
Control and clinical management of Algal Food Poisoning
Within three days of the disease, medical care that assists in alleviating acute symptoms as well as preventing chronic ones must be given.
Repeated treatments with activated charcoal or diluted bicarbonate solution for stomach emptying and decontamination to stop vomiting and diarrhoea are necessary if symptoms return.
For treating symptoms including weariness and paresthesias, doctors advise using atropine and amitriptyline.
If the symptoms are minor, fluid treatment, bed rest, and no hospitalisation are advised.
The best saxitoxin therapy involves ventilator support and artificial breathing.
Action levels have been set by the US Food and Drug Administration (FDA) to implement the HACCP plan and stop dangerous items from reaching consumers.
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