By Shraddha Parakh

New Zealand Food Safety on 10th May issued a public health warning against collecting shellfish from the western half of the Firth of Thames. Paralytic Shellfish Toxins have been detected at Waimangu Point at levels above the safe limit set by MPI. Anyone eating shellfish from this area is potentially at risk of illness. Shellfish biotoxin alert is ongoing as reported by New Zealand food safety.

As of today (18th May), the alert has been extended by New Zealand Food Safet. The entire Firth of Thames up to a line running from Raukura Point to Deadmans Point is now included in the affected region. Regular tests on samples of shellfish collected from this area have revealed levels of PSP toxins over the permissible limit of 0.8mg/kg

Paralytic Shellfish Toxin, one of the types of shellfish poisoning is detected at Waimangu Point above the safe limit. Avoid consuming shellfish from this area as this can pose a health risk. Mussels, oysters, tuatua, pipi, toheroa, cockles, scallops, catseyes, and kina shellfish are all affected. Cooking shellfish does not remove the toxin from it. Since poisons build up in the gut, pua, crab, and crayfish can still be eaten even after the gut has been fully removed. If the gut is not removed, the meat during cooking may get contaminated by its contents.

Shellfish from the Kaipara Harbour has been found to contain paralytic shellfish toxins at levels higher than the safe MPI limit of 0.8mg/kg. Any changes will be communicated in accordance with ongoing testing.

What is toxic shellfish poisoning?

Toxic shellfish poisoning is a type of food poisoning caused by swallowing shellfish tainted with dangerous toxins. Nausea, vomiting, diarrhea, abdominal pain, and in extreme cases, paralysis or even death, are all signs of toxic shellfish poisoning. To avoid this kind of poisoning, it’s crucial to stay away from shellfish from regions where there are known red tides or algal blooms.

How do these toxins build up?

Shellfish can accumulate toxins through a process known as bioaccumulation. As filter feeders, shellfish like mussels, clams, and oysters passively pump water through their bodies to draw out food particles like microscopic algae. These algae can occasionally create toxins as a defensive mechanism or as a result of environmental factors.

Shellfish can accumulate toxins through a process known as bioaccumulation. As filter feeders, shellfish like mussels, clams, and oysters passively pump water through their bodies to draw out food particles like microscopic algae. These algae can occasionally create toxins as a defensive mechanism or as a result of environmental factors.

Types of shellfish poisoning:

1. Paralytic Shellfish Poisoning: Saxitoxins and gonyautoxins, a class of compounds, are the culprits behind PSP.  PSP toxicity in New Zealand shellfish is frequently brought on by poisonous algae of the species Gymnodinium catenatum, Alexandrium minutum, and Alexandrium pacificum . Additionally, the safe limit is 0.8 mg/kg.
2. Amnesic Shellfish Poisoning: Domoic acid is a substance that leads to ASP. The majority of the symptoms are gastrointestinal, particularly at low toxin levels. However, roughly 25% of those impacted develop neurological issues, such as memory loss that could be severe and permanent. Safety limit: Less than 20 mg/kg.
3. Diarrhetic Shellfish Poisoning: Okadaic acid and similar substances are the cause of DSP. Dinophysis is the primary producer of DSP group poisons. Safety limit: Okadaic acid equivalents of less than 0.16 mg/kg
4. Neurotoxic Shellfish Poisoning: Toxins may harm the neurological system in NSP situations. The poisons are brevetoxin analogs or brevetoxins. The Karenia, Karlodinium, or Gymnodinium genus typically produces NSP., and 0.8 mg/kg brevetoxin-2 equivalents is the safe limit.