China CDC collaborated with the local poison control center to conduct an investigation to clarify how this poisoning occurred. This outbreak was exactly attributed to the ingestion of Millettia pachycarpa seeds, and the etiological association was confirmed based on the evidence in epidemiological correlation, clinical manifestations, plant species identification and rotenone toxin analysis. This work demonstrated that Millettia pachycarpa has potential for poisoning and that the public should be warned about the severe toxic effects and potential fatal effects.
Although ingestion of Millettia pachycarpa seeds is relatively rare, it may be fatal without appropriate and timely treatment. This incident involved 3 persons, 2 of whom experienced slightly transient dizziness and recovered fast, while the other suffered severe central nervous and respiratory depression, due to the difference in intake amount. The neurological symptoms of the 32-year-old male patient progressed rapidly from dizziness to coma with respiratory depression in about 10 minutes after the ingestion. The scarlet foam ejected from the trachea and the chest CT indicated aspiration pneumonia developed, which was accounted for the central nervous depression and vomiting caused by gastrointestinal irritation. The patient was intubated and ventilated immediately after admission to the emergency department, then, the gastric lavage was carried out to break off more toxin absorption. In addition, the patient underwent hemoperfusion therapy and administered sodium bicarbonate to maintain acid-base balance.
The toxicity of Millettia pachycarpa seeds is attributed to its rotenone and rotenoids. Rotenone mainly exerts toxicity to the nervous, respiratory, and gastrointestinal systems when ingested orally. There is no specific antidote available for rotenone poisoning, and treatment mainly relies on symptomatic and supportive measures (1), including intubation, mechanically-assisted ventilation, maintenance of acid-base balance, and stabilizing the vital signs. Gastrointestinal decontamination, such as emetic and gastric lavage, should be used to prevent more toxin absorption even when the patient is unconsciousness. There is insufficient evidence that hemoperfusion therapy is effective for eliminating rotenone, but it is one of the choices for the treatment of rotenone poisoning. The recognition and treatment of the inhalation of pneumonia should be a priority when such patients are encountered.
Millettia pachycarpa is a rotenone-containing plant and is widely distributed in the south of China. Reports of Millettia pachycarpa poisoning were uncommon in China, but 2 incidents occurred in Guizhou and Hunan provinces in 2020. Another rotenone-containing plant, Pachyrhizus erosus, has an edible root and is cultivated extensively in southeastern China, but its rotenone-containing seeds can cause occasional poisonings by accidental ingestion. Additionally, there were several reports of poisonings caused by rotenone-containing plants in other countries and regions. In China (Taiwan) (2–3) and Thailand (4), Pachyrhizus erosus seeds, also called “yam beans,” were reported to result in life-threating poisonings and deaths. In French Guiana (5), a woman ingesting another rotenone-containing plant belonging to Lonchocarpus genus committed suicide, and the exact species was unable to be determined.
In the region where Millettia pachycarpa and other rotenone-containing plants were distributed, ingestion and misuse of the plants should be prevented. Therefore, the public should be educated to distinguish the plants and recognize its toxic effects. Clinicians should be aware and trained to recognize clinical toxicological characteristics and treatment of rotenone-containing plants intoxication. In addition, the pathophysiological, toxicokinetic, and treatment strategy of rotenone-containing plants poisoning should be further reviewed and studied.