Category Archives: paralytic shellfish poisoning

Hong Kong – Food Safety Bulletin 95th Issue

Posted on January 18, 2024 by | Leave a comment

CFS

Feature Article

Shellfish Poisoning

The Centre for Food Safety (CFS) received in April 2023 a referral from the Centre for Health Protection of a suspected case of diarrhoetic shellfish poisoning in which the affected persons developed diarrhoea, nausea, vomiting and abdominal pain within an hour after consuming venus clams at a restaurant.  This article gives a brief introduction on shellfish poisoning.

What is Shellfish Poisoning?

Shellfish poisoning is caused by shellfish toxins produced by certain species of algae.  When shellfish eat toxin-producing algae, the toxins can accumulate in their tissue.  Consumption of shellfish containing shellfish toxins by humans can cause a variety of gastrointestinal and neurological illnesses, known as shellfish poisoning.  Examples of shellfish that have been involved in shellfish poisoning include mussels, clams, oysters, scallops and geoducks.

Numerous shellfish toxins have been discovered around the world; they could cause different types of shellfish poisoning.  Five major types of shellfish poisoning are discussed below:

(i) Paralytic shellfish poisoning (PSP) — caused by paralytic shellfish toxins (PSTs), which are a group of water-soluble alkaloid neurotoxins, including saxitoxins (STXs).

(ii) Diarrhoetic shellfish poisoning (DSP) — caused by diarrhoetic shellfish toxins (DSTs), which are a group of lipid-soluble polyether toxins, including okadaic acid (OA).

(iii) Neurotoxic shellfish poisoning (NSP) — caused by neurotoxic shellfish toxins (NSTs), which are a group of lipid-soluble polyether toxins, including brevetoxins (BTXs).

(iv) Amnesic shellfish poisoning (ASP) — caused by amnesic shellfish toxins (ASTs), including the water-soluble amino acid domoic acid (DA).

(v) Azaspiracid shellfish poisoning (AZP) — caused by azaspiracid shellfish toxins (AZTs), including the lipid-soluble toxin azaspiracid (AZA).

Characteristics of Shellfish Toxins

Different groups of shellfish toxins display multifarious chemical structures, which can be broadly classified into amino acids (DA), alkaloids (STXs) and polyketides (OA, BTXs and AZA).

The reasons why some algae produce shellfish toxins remain unknown.  These toxins are secondary metabolites with no explicit function for the algae.  They are probably used by the algae to compete for space, defence against predators or prevent the overgrowth of other organisms.

In general, shellfish toxins are heat stable, odourless, tasteless and not destroyed by cooking, freezing or other food preparation procedures.  It is hard to distinguish between toxic and non-toxic shellfish visually.

Bioaccumulation of Shellfish Toxins in Bivalve Molluscs

Algae are part of the natural diet of bivalve molluscs.  After shellfish has ingested shellfish toxin-producing algae, shellfish toxins will accumulate and concentrate in their internal organs, such as hepatopancreas of bivalves (Figure 1).  Generally speaking, the adductor muscle contains only a low level of shellfish toxins.

Figure 1: Internal parts of a scallop

Symptoms of Shellfish Poisoning

Shellfish toxins can cause a wide variety of symptoms in humans, depending on the type and amount of toxins ingested.  Symptoms of different types of shellfish poisoning are summarised below:

Safety Levels of Shellfish Toxins

The toxicity of various shellfish toxins was evaluated by a joint expert working group of the Food and Agriculture Organization of the United Nations (FAO), the World Health Organization (WHO) and the Intergovernmental Oceanographic Commission of UNESCO in 2004.  Acute reference doses (ARfDs) (i.e. the amount of toxins that can be ingested in a period of 24 hours or less without appreciable health risk) have been established for these shellfish toxins.  In addition, the Codex Alimentarius Commission (Codex) has established the maximum levels (MLs) for shellfish toxins in edible parts (the whole or any part intended to be eaten separately) of live bivalve molluscs.  While the ARfDs are critical in assessing the safety of food in terms of the level of shellfish toxins contained, Codex MLs are the levels recommended by Codex to be permitted in shellfish.

*An estimate of toxicity of the toxin made by mouse bioassay.

Key Points to Note

  • Shellfish toxins are heat stable, odourless, tasteless and not destroyed by cooking, freezing or other food preparation procedures.
  • It is hard to distinguish between toxic and non-toxic shellfish visually.
  • In general, shellfish toxins accumulate and concentrate in the internal organs of bivalves. 

Advice to Consumers 

  • Purchase shellfish from reliable sources.
  • To reduce the health risk of shellfish poisoning, remove and discard all internal organs of shellfish where possible before consumption.
  • Seek medical attention immediately if you feel ill after eating shellfish.

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Posted in Amnesic Shellfish Poisoning, ASP, Azaspiracid Toxin, Brevetoxin, Diarrhoeic Shellfish Poisoning, DOMOIC ACID, DSP, Neurotoxic Shellfish Poisoning, NSP, okadaic acid, paralytic shellfish poisoning, PSP, Saxitoxin, Shellfish, shellfish toxin

New Zealand – Kawhia- Shellfish Toxin Alert – PSP

Posted on December 6, 2023 by | Leave a comment

MPI

Reason for alert Paralytic Shellfish Poisoning (PSP)
Date warning issued Media release: 6 December 2023
Affected area The warning extends from Papanui Point, just south of Raglan, to Tirua Point, which is just south of Marokopa. The warning also includes Kawhia and Aotea harbours.
Shellfish affected Mussels, oysters, tuatua, pipi, toheroa, cockles and scallops, as well as pūpū (cat’s eyes), Cook’s turban and kina (sea urchin).

Note, cooking shellfish does not remove the toxin.

Pāua, crab and crayfish may still be eaten if the gut has been completely removed prior to cooking, as toxins accumulate in the gut. If the gut is not removed its contents could contaminate the meat during the cooking process. Finfish are not affected by this warning.

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Posted in food contamination, food handler, Food Hazard, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Testing, Food Poisoning, Food Quality, Food Safety, Food Safety Alert, Food Safety Management, Food Safety Regulations, Food Testing, Food Toxin, MPI, paralytic shellfish poisoning, PSP, Shellfish, shellfish toxin

New Zealand – Shellfish Biotoxin Alert

Posted on November 17, 2023 by | Leave a comment

 

North Island warnings

East Cape

Reason for alert

Paralytic Shellfish Poisoning (PSP)

Date warning issued

Media release: 17 November 2023 (further extended)

Media release: 10 November 2023 (extended)

Media release: 12 October 2023

Affected area

The affected area now extends from East Cape to Blackhead Point, just north of Porangahau

Shellfish affected

Mussels, oysters, tuatua, pipi, toheroa, cockles, scallops, catseyes, kina (sea urchin) and all other bivalve shellfish.

Note, cooking shellfish does not remove the toxin.

Pāua, crab and crayfish may still be eaten if the gut has been completely removed prior to cooking, as toxins accumulate in the gut. If the gut is not removed its contents could contaminate the meat during the cooking process.

Symptoms

Symptoms typically appear between 10 minutes and 3 hours after ingestion and may include:

  • numbness and a tingling (prickly feeling) around the mouth, face, and extremities (hands and feet)
  • difficulty swallowing or breathing
  • dizziness
  • headache
  • nausea
  • vomiting
  • diarrhoea
  • paralysis and respiratory failure and in severe cases, death.

Other information

Paralytic shellfish toxins have been detected in shellfish at levels over the safe limit of 0.8mg/kg set by New Zealand Food Safety. Ongoing testing will continue and any changes will be communicated accordingly.

Map of the affected area

Map showing the area covered by the shellfish biotoxin alert extends from East Cape all the way south to Blackhead Point, just north of Pōrangahau.

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Posted in MPI, paralytic shellfish poisoning, Shellfish, shellfish toxin

New Zealand – Public health warning: shellfish biotoxin alert for Northland and East Cape

Posted on November 10, 2023 by | Leave a comment

MPI

New Zealand Food Safety is advising the public not to collect or consume shellfish gathered from the Northland east coast because of paralytic shellfish toxins.

In addition, it has extended an existing shellfish biotoxin warning from Cape Kidnappers right up to East Cape.

“Routine tests on mussels from Houhora have shown levels of paralytic shellfish toxins over the safe limit,” says New Zealand Food Safety deputy director-general Vincent Arbuckle.

The warning extends from Cape Karikari north to Kokota (the Sandspit), just south of Parengarenga Harbour.

The current warning in Hawkes Bay has now been extended to extend from Cape Kidnappers right up to East Cape. Levels of paralytic shellfish toxins are increasing and the latest results from Tolaga Bay mussels have risen dramatically and are now 11 times over the safe limit.

As algal blooms increase in size, the levels of toxins in shellfish can reach higher levels.

“Please do not gather and eat shellfish from these affected areas because anyone doing so could get seriously sick.”

“Cooking the shellfish does not remove the toxin, so shellfish from these areas should not be eaten.”

See a map of the warning for Northland region

See a map of the warning for East Cape

Symptoms of paralytic shellfish poisoning usually appear within 10 minutes to 3 hours of eating and may include:

  • numbness and a tingling (prickly feeling) around the mouth, face, hands, and feet
  • difficulty swallowing or breathing
  • dizziness and headache
  • nausea and vomiting
  • diarrhoea
  • paralysis and respiratory failure and, in severe cases, death.

Pāua, crab and crayfish may still be eaten if the gut has been completely removed prior to cooking, as toxins accumulate in the gut. If the gut is not removed, its contents could contaminate the meat during the cooking process.

New Zealand Food Safety has had no notifications of associated illness.

If anyone becomes ill after eating shellfish from an area where a public health warning has been issued, phone Healthline for advice on 0800 61 11 16, or seek medical attention immediately. You are also advised to contact your nearest public health unit and keep any leftover shellfish in case it can be tested.

“New Zealand Food Safety is monitoring shellfish in the region and will notify the public of any changes to the situation,” says Mr Arbuckle.

Commercially harvested shellfish – sold in shops and supermarkets or exported – is subject to strict water and flesh monitoring programmes by New Zealand Food Safety to ensure they are safe to eat.

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Posted in food recall, MPI, paralytic shellfish poisoning, product recall, Recall, Shellfish, shellfish toxin

New Zealand – Do not collect or eat shellfish from areas where shellfish biotoxin warnings have been issued – Hawke Bay – PSP

Posted on November 2, 2023 by | Leave a comment

MPI

Hawke Bay

Reason for alert Paralytic Shellfish Poisoning (PSP)
Date warning issued Media release: 1 November 2023
Affected area Hawke Bay: Cape Kidnappers to Mohaka River.
Shellfish affected Mussels, oysters, tuatua, pipi, toheroa, cockles, scallops, catseyes, kina (sea urchin) and all other bivalve shellfish.

Note, cooking shellfish does not remove the toxin.

Pāua, crab and crayfish may still be eaten if the gut has been completely removed prior to cooking, as toxins accumulate in the gut. If the gut is not removed its contents could contaminate the meat during the cooking process.
Symptoms Symptoms typically appear between 10 minutes and 3 hours after ingestion and may include:

  • numbness and a tingling (prickly feeling) around the mouth, face, and extremities (hands and feet)
  • difficulty swallowing or breathing
  • dizziness
  • headache
  • nausea
  • vomiting
  • diarrhoea
  • paralysis and respiratory failure and in severe cases, death.
Other information Paralytic shellfish toxins have been detected in shellfish at levels over the safe limit of 0.8mg/kg set by New Zealand Food Safety. Ongoing testing will continue and any changes will be communicated accordingly.

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Posted in Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Testing, microbial contamination, Microbial growth, Microbiology, Microbiology Investigations, Microbiology Risk, MPI, paralytic shellfish poisoning, PSP, Shellfish, shellfish toxin

New Zealand – Public health warning: shellfish biotoxin alert for East Cape region

Posted on October 13, 2023 by | Leave a comment

MPI

New Zealand Food Safety is advising the public not to collect or consume shellfish gathered from near Tolaga Bay due to the presence of toxins.

“Routine tests on mussels from Tolaga Bay have shown levels of paralytic shellfish toxins over the safe limit,” says New Zealand Food Safety deputy director-general Vincent Arbuckle. “The warning extends from Tatapouri Point just north of Gisborne, up to Koutunui Point in Tokamaru Bay.

“Please do not gather and eat shellfish from this area because anyone doing so could get sick.

“Cooking the shellfish does not remove the toxin, so shellfish from this area should not be eaten.”

See a map of the warning

Symptoms of paralytic shellfish poisoning usually appear within 10 minutes to 3 hours of eating and may include:

  • numbness and a tingling (prickly feeling) around the mouth, face, hands, and feet
  • difficulty swallowing or breathing
  • dizziness and headache
  • nausea and vomiting
  • diarrhoea
  • paralysis and respiratory failure and, in severe cases, death.

Pāua, crab, and crayfish may still be eaten if the gut has been completely removed prior to cooking, as toxins accumulate in the gut. If the gut is not removed, its contents could contaminate the meat during the cooking process.

New Zealand Food Safety has had no notifications of associated illness.

If anyone becomes ill after eating shellfish from an area where a public health warning has been issued, phone Healthline for advice on 0800 61 11 16, or seek medical attention immediately. You are also advised to contact your nearest public health unit and keep any leftover shellfish in case it can be tested.

“New Zealand Food Safety is monitoring shellfish in the region and will notify the public of any changes to the situation,” says Mr Arbuckle.

Commercially harvested shellfish – sold in shops and supermarkets or exported – is subject to strict water and flesh monitoring programmes by New Zealand Food Safety to ensure they are safe to eat.

A public health warning remains in place in the Queen Charlotte Sound due to high levels of Diarrhetic Shellfish Toxins.

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Posted in Biotoxin, food recall, Lipophilic Marine Biotoxin, Marine Biotoxin, paralytic shellfish poisoning, product recall, Recall, Shellfish, shellfish toxin

New Zealand – Public health warning: shellfish biotoxin alert for Marlborough Sounds

Posted on September 29, 2023 by | Leave a comment

MPI

New Zealand Food Safety is advising the public not to collect or consume shellfish gathered from part of Queen Charlotte Sound due to the possible presence of toxins.

“Routine tests on mussel samples taken from Okiwa Bay (The Grove) have shown levels of diarrhetic shellfish toxins more than 3.5 times the safe limit,” says New Zealand Food Safety specialist adviser Piers Harrison.

“The warning extends from The Grove up to a line from Dieffenbach Point across to West Head in the Marlborough Sounds.

“Please do not gather and eat shellfish from this area because anyone doing so is potentially at risk of getting sick.

“Cooking the shellfish does not remove the toxin, so mussels, oysters, tuatua, pipi, toheroa, cockles, scallops, catseyes, kina (sea urchin) and all other bivalve shellfish from this area should not be eaten.”

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Posted in Amnesic Shellfish Poisoning, Diarrhoeic Shellfish Poisoning, Food Temperature Abuse, Food Testing, Food Toxin, MPI, paralytic shellfish poisoning, Shellfish, shellfish toxin

New Zealand -Public health warning: shellfish biotoxin alert for Raglan coastline

Posted on September 14, 2023 by | Leave a comment

MPI

New Zealand Food Safety today issued a public health warning advising the public not to collect or consume shellfish harvested from the Raglan coastline.

The warning extends from Port Waikato, southward to Tauratahi Point at the entrance of Kawhia Harbour. The warning includes the entire Raglan and Aotea Harbours but not Kawhia Harbour. Paralytic Shellfish Toxins have been detected in shellfish from Raglan at levels above the safe limit set by MPI.

Mussels, oysters, tuatua, pipi, toheroa, cockles, scallops, catseyes, kina (sea urchin) and all other bivalve shellfish should not be eaten.

Note that cooking shellfish does not remove the toxin.

Pāua, crab and crayfish may still be eaten if the gut has been completely removed prior to cooking, as toxins accumulate in the gut. If the gut is not removed, its contents could contaminate the meat during the cooking process.

Symptoms typically appear between 10 minutes and 3 hours after ingestion and may include:

  • numbness and a tingling (prickly feeling) around the mouth, face, and extremities (hands and feet)
  • difficulty swallowing or breathing
  • dizziness
  • headache
  • nausea
  • vomiting
  • diarrhoea
  • paralysis and respiratory failure and in severe cases, death.

If anyone becomes ill after eating shellfish from an area where a public health warning has been issued, phone Healthline for advice on 0800 61 11 16, or seek medical attention immediately. You are also advised to contact your nearest public health unit and keep any leftover shellfish in case it can be tested.

Monitoring of toxin levels will continue and any changes will be communicated accordingly. Commercially harvested shellfish – sold in shops and supermarkets, or exported – is subject to strict water and flesh monitoring programmes by MPI to ensure they are safe to eat.

Leave a comment

Posted in food contamination, food handler, Food Hazard, Food Hygiene, Food Inspections, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Testing, Food Poisoning, Food Quality, food recall, Food Safety, Food Safety Alert, Food Safety Management, Food Safety Regulations, Food Temperature Abuse, Food Testing, Food Toxin, paralytic shellfish poisoning, PSP, Shellfish, shellfish toxin

Research – A Comprehensive Review for the Surveillance of Human Pathogenic Microorganisms in Shellfish

Posted on September 2, 2023 by | Leave a comment

MDPI

Abstract

Bivalve molluscan shellfish have been consumed for centuries. Being filter feeders, they may bioaccumulate some microorganisms present in coastal water, either naturally or through the discharge of human or animal sewage. Despite regulations set up to avoid microbiological contamination in shellfish, human outbreaks still occur. After providing an overview showing their implication in disease, this review aims to highlight the diversity of the bacteria or enteric viruses detected in shellfish species, including emerging pathogens. After a critical discussion of the available methods and their limitations, we address the interest of technological developments using genomics to anticipate the emergence of pathogens. In the coming years, further research needs to be performed and methods need to be developed in order to design the future of surveillance and to help risk assessment studies, with the ultimate objective of protecting consumers and enhancing the microbial safety of bivalve molluscan shellfish as a healthy food.

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Posted in Amnesic Shellfish Poisoning, Decontamination Microbial, Diarrhoeic Shellfish Poisoning, Enteropathogenic E. coli, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Food Pathogen, microbial contamination, Microbial growth, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Microbiology Risk, paralytic shellfish poisoning, Pathogen, pathogenic, Shellfish, shellfish toxin

New Zealand – Public health warning: shellfish biotoxin alert for Nydia Bay/Pelorus Sound area in the Marlborough Sounds

Posted on July 6, 2023 by | Leave a comment

MPI

New Zealand Food Safety today issued a public health warning against collecting shellfish from the Pelorus Sound area in the Marlborough Sounds. The area includes Pelorus Sound from Hikapu Reach at Koutuwai Point up to Spencer and Capsize Points.

Paralytic Shellfish Toxins have been detected in shellfish at Nydia Bay at levels several times above the safe limit set by MPI. There is extreme risk from consuming shellfish in this area.

Mussels, oysters, tuatua, pipi, toheroa, cockles, scallops, catseyes, kina (sea urchin) and all other bivalve shellfish should not be eaten.

Note that cooking shellfish does not remove the toxin.

Pāua, crab and crayfish may still be eaten if the gut has been completely removed prior to cooking, as toxins accumulate in the gut. If the gut is not removed, its contents could contaminate the meat during the cooking process.

Symptoms typically appear between 10 minutes and 3 hours after ingestion and may include:

  • numbness and a tingling (prickly feeling) around the mouth, face, and extremities (hands and feet)
  • difficulty swallowing or breathing
  • dizziness
  • headache
  • nausea
  • vomiting
  • diarrhoea
  • paralysis and respiratory failure and in severe cases, death.

If anyone becomes ill after eating shellfish from an area where a public health warning has been issued, phone Healthline for advice on 0800 61 11 16, or seek medical attention immediately. You are also advised to contact your nearest public health unit and keep any leftover shellfish in case it can be tested.

Monitoring of toxin levels will continue and any changes will be communicated accordingly. Commercially harvested shellfish – sold in shops and supermarkets, or exported – is subject to strict water and flesh monitoring programmes by MPI to ensure they are safe to eat.

Leave a comment

Posted in food contamination, food handler, Food Hazard, Food Hygiene, Food Inspections, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Testing, Food Poisoning, Food Quality, food recall, Food Safety, Food Safety Alert, Food Safety Management, Food Safety Regulations, Food Testing, Food Toxin, Lipophilic Marine Biotoxin, Marine Biotoxin, paralytic shellfish poisoning, PSP