Results of identification of species and toxic nature in samples of sea crabs causing food poisoning in Thanh Hoa on March 27, 2021

01/07/2021
On March 29, 2021, the Institute of Oceanography under the Vietnam Academy of Science and Technology received 02 crab specimens collected in the poisoning case provided by the Poison Control Center, Bach Mai Hospital, Hanoi, to determine the scientific name of the crab species and analyze the toxic composition. Identification results show that both specimens are species of Demania reynaudii belonging to family Xanthidae.

As reported by the media, there was a case of food poisoning in Tinh Gia, Thanh Hoa, on March 27, 2021, after the patients ate about 1 to 4 crabs caught at sea. Symptoms of poisoning appeared about 2 hours after eating, including tiredness, nausea, vomiting and numbness of the mouth, tongue and limbs. The victim was taken to the emergency room at Hop Luc General Hospital, Tinh Gia District, with difficulty in speaking and weak limbs. Symptoms of poisoning continued to get worse. The patient was unable to speak, could not move his limbs, had breathing difficulty, respiratory failure and stopped circulation, was transferred to a higher level hospital in a state of coma, complete paralysis, given vasopressors, and placed endotracheal. According to information from the Poison Control Center, Bach Mai Hospital, the patient's poisoning condition was very serious, requiring close monitoring and intensive care.

On March 29, 2021, the Institute of Oceanography under the Vietnam Academy of Science and Technology received 02 crab specimens collected in the poisoning case provided by the Poison Control Center, Bach Mai Hospital, Hanoi to determine the scientific name of the crab species and analyze the toxic composition.

The results show that both specimens are Demania reynaudii (Figure 1) belonging to the family Xanthidae. According to documents, Demania reynaudii is a bottom-dwelling marine crustacean, commonly found in coral reefs in the tropical Indo-Pacific waters. Nearly 300 species of marine Demania reynaudii have been identified, some of which contain saxitoxin (STX) or tetrodotoxin (TTX), two toxins that cause fatal poisoning if ingested. In our country, there have been previously recorded cases of fatal poisoning due to eating Devil's face crab Zosimus aeneus or some other coral reef Demania reynaudii species.

Figure 1. Specimens of Demania renaudii crab collected from the food poisoning case in Thanh Hoa March 27, 2021 (Photo: Truong Si Hai Trinh)

After identifying the species name, 02 crab specimens were transferred to the key laboratory of the Vietnam Academy of Science and Technology on Food Safety and Environment (Central region), also under the Institute of Oceanography, for analysis of toxic chemical composition. Using liquid chromatography system coupled with LCMS 8040 Shimadzu mass spectrometer detector, experts have determined the presence of tetrodotoxin (TTX) and Anhydro-TTX derivatives in both of the above 2 Demania reynaudii specimens ( figure 2). With the content of tetrodotoxin (TTX) and Anhydro-TTX derivatives in crab samples, eating just 2 animals (about 50-60 g/individual) is enough to kill an adult.

Figure 2. LCMS chromatograms of TTX and Anh-TTX toxins in Demania renaudii specimens collected from the food poisoning case in Thanh Hoa March 27, 2021

TTX toxin is heat and acid stable, so it does not decompose at high temperatures when cooked and can exist in processed products (without removing the toxin), even in frozen, canned products. According to studies, TTX toxin affects the central nervous system of humans and high ranking animals by inhibiting sodium ion exchange on the membrane of neuromuscular cells, stopping the transmission of nerve signals. Symptoms of poisoning usually appear about 30 minutes after eating, including numbness of the tongue, numbness of the lips, dizziness, headache, abdominal pain, nausea, vomiting, speaking and swallowing difficulty, movement imbalance. In severe cases, the victim suffers convulsions, foaming at the mouth, coma and possibly death. When suffering from food poisoning, it is necessary to follow the instructions of the health authorities and quickly bring the person with food poisoning to the nearest medical agency.

As noted, this crab species has caused many poisoning deaths in some countries in the region such as the Philippines, Taiwan (China) and Indonesia.

Translated by Phuong Huyen
Link to Vietnamese version



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