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International Society for Infectious Diseases <http://www.isid.org>

Date: Fri 20 Jul 2012
Source: Xin Hua Net [edited]

The Ministry of Health on Fri 20 Jul 2012 issued a notice to ban the sale of Nassariidae, small mud snails, that have reportedly caused people to faint and vomit after eating them.

The snail mostly inhabits the southeastern coastal areas including Zhejiang, Fujian and Guangdong provinces. After eating them, people can feel the snails' poisonous effects within 5 minutes to 4 hours, according to the notice.

"Summer and autumn are high risk periods for Nassariidae poisoning.
Food production and management companies are not allowed to purchase, process, or sell these snails, and consumers should raise self-protection awareness and refrain from buying them," said the notice.

The poison, which comes from tetrodotoxin, a toxin usually found in pufferfish, has no known antidote, said the ministry.

Communicated by:

[The 2 papers below describe the finding of tetrodotoxin & a new neurotoxin in these snails:

1. Hwang DF, Lin LC, Jeng SS: Occurrence of a new toxin and tetrodotoxin in two species of the gastropod mollusk Nassariidae.
Toxicon. 1992;30: 41-6.

The lethalities of 102 specimens of 3 species of the gastropod mollusk Nassariidae, collected from fish markets in Taiwan, were examined. The frequency of toxicity in _Zeuxis scalaris_ and _Z. castus_-like specimens was 94 and 41 percent, respectively. The range of lethal potency in toxic specimens of _Zeuxis scalaris_ and _Z. castus_-like was 2-140 and 2-13 mouse units, respectively, while all tissues of _Z.
castus_ were non-toxic. The toxins were partially purified from the toxic specimens of _Z. scalaris_ and _Z. castus_-like. Two toxin fractions were obtained from the extract of each species of Nassariidae by using Bio-Gel P-2 column chromatography. Analyses by thin layer chromatography, electrophoresis, high performance liquid chromatography and ultraviolet spectroscopy showed that toxin fraction I contained tetrodotoxin, while toxin fraction II contained a new neurotoxin.

2. Shiu Y-C, Lu Y-H, Tsai Y-H, Chen S-K, Hwang D-F: Occurrence of tetrodotoxin in the causative gastropod _Polinices didyma_ and another Gastropod _Natica lineata_ collected from western Taiwan. J Food Drug Anal. 2003;11: 159-163.

Attempts were made to elucidate the responsible toxins in the gastropod _Polinices didyma_ which recently caused food poisoning incidents in western Taiwan. The remained (cooked) and captured (live) specimens of both gastropods were assayed for toxicity (as tetrodotoxin = TTX). Average toxicity of cooked and live specimens was
118 +/- 105 and 47 +/- 28 MU/specimen, respectively. In addition, another species _Natica lineata_ collected from the same area was also found to be toxic. The toxin of each gastropod was partially purified from the methanolic extract of the gastropod by ultrafiltration and Bio-Gel P-2 column chromatography. HPLC and GC-MS analyses demonstrated that the toxin consisted of TTX. It was concluded that the causative agent of the above food poisoning was TTX.

The following was extracted from the "Bad Bug Book" regarding pufferfish tetrodotoxin, <http://www.cfsan.fda.gov/~mow/chap39.html>:

Fish poisoning by consumption of members of the order Tetraodontiformes is one of the most violent intoxications from marine species. The gonads, liver, intestines, and skin of pufferfish can contain levels of tetrodotoxin sufficient to produce rapid and violent death. The flesh of many pufferfish may not usually be dangerously toxic.

Tetrodotoxin has also been isolated from widely differing animal species, including the California newt, parrotfish, frogs of the genus _Atelopus_, the blue-ringed octopus, starfish, angelfish, and xanthid crabs. The metabolic source of tetrodotoxin is uncertain. No algal source has been identified, and until recently tetrodotoxin was assumed to be a metabolic product of the host. However, recent reports of the production of tetrodotoxin/anhydrotetrodotoxin by several bacterial species, including strains of the family _Vibrionaceae_, _Pseudomonas sp._, and _Photobacterium phosphoreum_ point toward a bacterial origin of this family of toxins. These are relatively common marine bacteria that are often associated with marine animals. If confirmed, these findings may have some significance in toxicoses that have been more directly related to these bacterial species.

The 1st symptom of intoxication is a slight numbness of the lips and tongue, appearing between 20 minutes to 3 hours after eating poisonous pufferfish. The next symptom is increasing paresthesia in the face and extremities, which may be followed by sensations of lightness or floating. Headache, epigastric pain, nausea, diarrhea, and/or vomiting may occur. Occasionally, some reeling or difficulty in walking may occur. The 2nd stage of the intoxication is increasing paralysis. Many victims are unable to move; even sitting may be difficult. There is increasing respiratory distress. Speech is affected, and the victim usually exhibits dyspnea [shortness of breath], cyanosis [turns blue], and hypotension [drop in blood pressure]. Paralysis increases, and convulsions, mental impairment, and cardiac arrhythmia [alterations in heartbeat] may occur.

A picture of a member of Nassariidae can be found at <http://aquaria-blog.com/wp-content/uploads/2009/04/nassarius.jpg>. - Mod.LL

A HealthMap/ProMED-mail map can be accessed at:

[see also:
Tetrodotoxin, sea slug, canine - NZ (02): dolphin susp. 20090906.3136 Tetrodotoxin, sea slug, canine - New Zealand 20090818.2923 Tetrodotoxin poisoning, puffer fish - Japan (Yamagata) 20090129.0399
Tetrodotoxin, monkfish - USA ex China: susp., recall 20070525.1677 Foodborne illness, fish - China (Guangdong) (02): tetrodotoxin
Food poisoning, puffer fish - Vietnam (Binh Thuan) 20060630.1809
Tetrodotoxin poisoning, fatal - Philippines (02) 20050629.1834 Tetrodotoxin poisoning, fatal - Philippines 20050531.1511
Tetrodotoxin poisoning - Philippines 20040826.2383
Saxitoxin poisoning, puffer fish - USA (02) 20020516.4228 Saxitoxin poisoning, puffer fish - USA: alert 20020418.3982] .................................................ll/msp/jw
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