TETS: Weapon of Mouse Destruction : Emergency Medicine News

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Toxicology Rounds

TETS

Weapon of Mouse Destruction

Gussow, Leon MD

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    Figure

    TETS (tetramethylenedisulfotetramine), a neurotoxic rodenticide virtually unknown in the United States, is far more toxic than potassium cyanide and a more powerful inducer of seizures than strychnine.

    In China, where it is called Dushuqiang (strong rat poison) and where manufacture or possession may be punished by death, TETS is not infrequently used as an agent of mass murder. The most notorious incident occurred in September 2002 when a foodstand owner in Nanjing added TETS to the food at a rival's establishment, poisoning about 400 people and killing 38. A Google search produces numerous other TETS incidents: 61 students and teachers poisoned in Changhu, 76 people ill at a college in Guangxi, 10 dead in Hubei Province when an estranged wife spiked the food at her ex-husband's funeral banquet.

    Recently, a case of TETS poisoning was reported in New York City. (MMWR 2003,52:199.) A previously healthy 15-month-old girl was brought to the hospital after being found playing with a white powder purchased in China by her parents to kill rodents in their kitchen. Within 15 minutes, the child developed generalized seizures that required endotracheal intubation and continued intermittently over the following four hours despite treatment with lorazepam, phenobarbital, and pyridoxine. The child survived the episode, and was extubated several days later, but was left with multiple persistent neurological defects.

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    Table:
    RATS PANIC: A Mnemonic for Rodenticides

    The package containing the rat poison did not reveal its specific ingredients. Tests on the powder were negative for some potential suspects, including sodium fluoroacetate and strychnine. After reports of the Nanjing incident appeared in New York City newspapers, further tests were performed on the powder. TETS was detected by gas chromatography-mass spectrometry at concentrations of 6.4% and 13.8% in two different packets. On follow-up five months after the poisoning, the child continued to have severe impairment of normal development.

    TETS comes as a water-soluble white crystalline powder that is odorless and tasteless. It acts by antagonizing the inhibitory neurotransmitter gamma-amino butyric acid (GABA). At the level of the neuron, TETS binds non-competitively and irreversibly to the GABA receptor, partially depolarizing the nerve cell; that is, it makes it easier to fire by blocking influx of chloride ions. Studies in mammals suggest that the LD50 of TETS is between 0.1 and 0.3 mg/kg, making the lethal human dose approximately 7 mg to 10 mg.

    Signs and Symptoms

    Symptoms of TETS poisoning typically begin within an hour of ingestion, but there are reports that onset of toxicity may be delayed as long as 13 hours. The rodenticide also may be absorbed through broken skin, and incidents of occupational inhalation exposure have occurred in China. The hallmark of severe poisoning is prolonged recurrent seizures that are difficult to control. Less severe exposure causes headache, nausea, vomiting, abdominal pain, weakness, dizziness, lethargy, and tingling around the lips and mouth. Renal insufficiency occurs as a direct result of the toxin or an indirect effect of prolonged seizure activity. Evidence of myocardial ischemia may be seen on the electrocardiogram.

    Because there is no specific antidote, treatment of TETS exposure remains supportive, focusing on control of airway, breathing, and circulation and aggressive attempts to control seizure activity. Although reports from China suggest that early treatment with pyridoxine and the chelating agent DMPS might be beneficial, there is certainly not enough evidence to recommend routine clinical use of those agents. The patient should be completely undressed and any external contamination removed with copious irrigation, taking care to avoid secondary exposure of medical personnel.

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    Figure:
    The chemical structure of tetramethylenedisulfotetramine (C4H8N4O4S2).

    When a patient presents with a history of exposure to an unidentified rodenticide, it helps to generate a list of possible agents. A convenient mnemonic that covers most (but not all) common suspects is RATS PANIC. (See table.)

    The authors of a recent review of TETS toxicity argue that the properties of water solubility, absence of taste and odor, high lethality, and lack of specific treatment make TETS a viable agent of chemical terrorism. (Ann Emerg Med 2005;45:609.) Although the likelihood of such use occurring is unknown, it remains at least theoretically possible that this weapon of mouse destruction might morph into a weapon of mass destruction.

    The best review in English of TETS toxicity is by Whitlow et al. (Ann Emerg Med 2005;45:609.) Jim Yardley's report, “Rat Poison: Murder Weapon of Choice in Rural China,” appeared in the New York Times on Nov. 17, 2003.

    © 2005 Lippincott Williams & Wilkins, Inc.