Kihara Yuko, Tsuneya Shigeki, Nakajima Makoto, Torimitsu Suguru, Chiba Fumiko, Tanaka Aki, Tanaka Hiroyuki, Osada Keigo, Saka Kanju, Noritake Kanako, Ishizuka Mayumi, Ikenaka Yoshinori, Iwase Hirotaro, Makino Yohsuke
Laboratory of Wildlife Medicine, Faculty of Veterinary Science, Nippon Veterinary and Life Science University, 1-7-1 Kyonan-cho, Musashino-shi, Tokyo, 180-8602, Japan.
Department of Forensic Medicine, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
Int J Legal Med. 2025 Nov 21. doi: 10.1007/s00414-025-03661-5.
Diatom testing is conducted in forensic medicine primarily to support the diagnosis of drowning. In our previous study, a large number of diatoms, potentially originating from methomyl, were detected in the lungs of a cat found dead under circumstances suggestive of methomyl poisoning, but not involving drowning or submersion. In the present study, we collected human and animal cases suspected of methomyl poisoning, where the bodies showed no evidence of drowning or submersion. Diatom tests were performed both quantitatively and qualitatively on the gastric contents, lungs, liver, kidney, and fur samples. Quantitative analysis using light microscopy revealed a large number of Stephanodiscus spp., the same genus of diatoms found in methomyl-containing insecticides, in the gastric contents and in some of the lung samples. Although qualitative analysis with electron microscopy did not enable species-level identification, the observed Stephanodiscus spp. were presumed to be fossil species derived from diatomaceous earth. Since diatomaceous earth is sometimes added as a carrier or diluent to concentrate the active ingredient in insecticides, it is possible that diatoms may be present in the bodies of individuals that died from methomyl poisoning. Therefore, relying solely on the quantity of diatoms may result in false-positive diagnoses of drowning. To avoid such misinterpretation, it is essential to perform qualitative analyses to assess the species composition of the diatoms in addition to quantitative assessment.
硅藻检测主要在法医学中进行，以辅助溺水诊断。在我们之前的研究中，在一只被发现死于疑似灭多威中毒（但未涉及溺水或浸没）情况的猫的肺中，检测到大量可能源自灭多威的硅藻。在本研究中，我们收集了疑似灭多威中毒的人类和动物病例，这些尸体没有溺水或浸没的迹象。对胃内容物、肺、肝、肾和毛发样本进行了硅藻的定量和定性检测。使用光学显微镜的定量分析显示，在胃内容物和一些肺样本中发现了大量的针杆藻属硅藻，这与含灭多威杀虫剂中发现的硅藻属相同。尽管用电子显微镜进行的定性分析无法进行物种水平的鉴定，但观察到的针杆藻属硅藻被推测为源自硅藻土的化石物种。由于硅藻土有时被添加为载体或稀释剂以浓缩杀虫剂中的活性成分，死于灭多威中毒的个体体内可能存在硅藻。因此，仅依靠硅藻的数量可能会导致溺水的假阳性诊断。为避免这种误解，除了进行定量评估外，进行定性分析以评估硅藻的物种组成至关重要。
