Naturally occurring food toxins
Renuka Patel1, R.V. Singh2, Bhavana Gupta3, Ajay Rai3 , Shreya Dubey1
1M.V.Sc. Scholar, NDVSU, Jabalpur, Madhya Pradesh, India
2 Associate Professor & Head, NDVSU, Jabalpur, Madhya Pradesh, India
3Assistant Professor, NDVSU, Jabalpur, Madhya Pradesh, India
Corresponding Authors Email; renukapatel265@gmail.com
Introduction
Natural toxins are poisonous secondary metabolites produced by living organisms, which are typically not harmful to the organisms themselves but can impact on human or animal health when consumed. Natural toxins produced by bacteria are also of concern. Shiga toxin-producing Escherichia coli is a frequent cause of food poisoning with enormous human health and economic impacts, and rapid and accurate identification is imperative for protection of human health.
Toxins in seafood
1.Toxins involving algae
Consumption of seafood contaminated with algal toxins results in five different syndromes, paralytic, neurotoxic, amnesic, or diarrhetic shellfish poisoning and ciguatera fish poisoning
Paralytic shellfish poisoning-
Paralytic shellfish poisoning (PSP) is caused by the consumption of molluscan shellfish contaminated with heterocyclic guanidines called saxitoxins. Currently, over 21 known saxitoxins are produced by dinoflagellate species from three genera: Alexandrium, Gymnodium and Pyrodinium.
Toxicity is caused by binding of saxitoxins to voltage-dependent sodium channels, which blocks neuronal activity. The primary site of action in humans is the peripheral nervous system.
Symptoms of toxicity include tingling and numbness of the perioral area and extremities, loss of motor control, drowsiness, and incoherence. Ingestion of 1–4 mg saxitoxin has resulted in death from respiratory paralysis.
In the United States, the permissible level of saxitoxin equivalents in shellfish is 80 micrograms/100 grams.
Neurotoxic shellfish poisoning
The dinoflagellate Karenia brevis produces brevetoxins that are lethal to fish, but not to mollusks such as oysters, clams and mussels.
Karenia brevis brevitoxins cause the syndrome known as neurotoxic shellfish poisoning (NSP), which affects sodium transport in the autonomic nervous system and causes inhibition of neuromuscular transmission in skeletal muscle.
NSP symptoms usually occur within three hours of ingesting contaminated shellfish and may include abdominal pain, nausea and vomiting, vertigo, malaise, generalized muscle weakness, ataxia, incoordination, chills, headache, myalgia, a reversal of hot/cold temperature sensation and progressive parasthesias. Dilated pupils, bradycardia and convulsions may occur in cases of severe poisoning. Unlike PSP, no deaths have been reported from NSP.
The FDA has established an action level of 0.8 ppm (20 mouse units/100 g) brevetoxin-2 equivalents.
Amnesic shellfish poisoning (Domoic acid)
Amnesic shellfish poisoning (ASP) is caused by domoic acid produced by diatoms of the genus Pseudo-nitzchia, which are consumed by mussels, scallops, clams and crabs.
The symptoms of ASP are gastroenteritis, dizziness, disorientation, lethargy, seizures and loss of short term memory. Respiratory difficulty, coma and death. Human toxicity has occurred after ingestion of 1–5 mg/kg domoic acid.
Diarrhetic shellfish poisoning
Diarrhetic shellfish poisoning (DSP) is caused by the production of okadaic acid and dinophysistoxins in the dinoflagellates Dinophysis fortii or Prorocentrum lima, which are consumed by mollusks.
Compared to other types of shellfish poisoning, symptoms of DSP are relatively mild, and generally consist of diarrhea, abdominal cramps, nausea, chills or vomiting within 30 minutes to a few hours after consumption of DSP toxins. The FDA has established an action level of 0.2 ppm okadaic acid plus 35-methyl okadaic acid (DXT 1).
Ciguatera poisoning
Ciguatera fish poisoning (CFP) is caused by the dinoflagellate Gambierdiscus toxicus, which grows on filamentous macroalgae associated with coral reefs. The threshold level for toxicity in humans is estimated to be 0.5 ng/g .
The symptoms of CFP generally include gastrointestinal disturbances (nausea, vomiting and diarrhea) within 2–6 hours, followed by neurologic symptoms such as numbness of the perioral area and extremities, a reversal of hot/cold temperature sensation, muscle and joint aches, headache, itching, tachycardia, hypertension, blurred vision and paralysis. In rare cases, CFP is fatal.
2.Toxins not involving algae
Gempylotoxin
There are naturally occurring toxins in some species that do not involve marine algae. Escolar (Lepidocybium flavobrunneum, Figure 8), and Oilfish or Cocco (Ruvettus pretiosus), a marine fish of the snake mackerel family, are sometimes sold under the category of ―butterfish‖, and contain a strong purgative oil, that when consumed can cause diarrhea known as Gempylid Fish Poisoning, Gempylotoxism or Keriorrhea.
Ingestion of fish containing wax esters in large amounts, coupled with their indigestibility and low melting point, results in diarrhea.
Tetramine in whelks
Tetramine is a toxin found in the salivary glands of Buccinum, Busycon or Neptunia spp., a type of whelk or sea snail that is distributed in temperate and tropic waters and has long been a food source for humans.
Whelk are associated with a heat-stable neurotoxin, tetramine, which upon ingestion produces, among other symptoms, eyeball pain, headache, dizziness, abdominal pain, ataxia, tingling in the fingers, nausea and diarrhea.
