Ciguatera incidence and fish toxicity in Okinawa, Japan Naomasa Oshiro a, b, * , Kentaro Yogi a, c , Shuko Asato a, c , Toshiki Sasaki d, 1 , Koji Tamanaha a , Masahiro Hirama c, e , Takeshi Yasumoto f , Yasuo Inafuku a a Okinawa Prefectural Institute of Health and Environment, 2085 Aza-Ozato, Ozato, Nanjo, Okinawa 901-1202, Japan b Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo 108-8477, Japan c SORST, Japan Science and Technology Agency, Japan d Minamata Environmental Research and Develop Center Co., Ltd., 5-98 Hamamatsu, Minamata, Kumamoto 867-0068, Japan e Department of Chemistry, Graduate School of Science, Tohoku University, 6-3 Aramaki, Aoba-ku, Sendai, Miyagi 980-8578, Japan f Okinawa Science and Technology Promotion Center, 12-75 Suzaki, Uruma, Okinawa 904-2234, Japan article info Article history: Received 15 January 2009 Received in revised form 19 May 2009 Accepted 19 May 2009 Available online 9 June 2009 Keywords: Ciguatera Incidence Fish Toxicity Ciguatoxin Okinawa Mouse bioassay abstract Okinawa being located in the subtropical region has the highest incidence of ciguatera in Japan. Officially, 33 outbreaks involving 103 patients have been reported between 1997 and 2006. The implicated species were Variola louti, Lutjanus bohar, Lutjanus monostigma, Epinephelus fuscoguttatus, unidentified Lutjanus sp., Plectropomus areolatus, Oplegnathus punctatus, Epinephelus polyphekadion, Caranx ignobilis and moray eel. Toxicities of the leftover meals, as determined by mouse bioassays, ranged from 0.025 to 0.8 MU/g or above (equivalent to 0.175–5.6 ngCTX1B/g). We collected 612 specimens of fish belonging to L. monostigma, L. bohar, Lutjanus argentimaculatus, Lutjanus russellii, V. louti, Variola albi- marginata, and E. fuscoguttatus from the coasts around Okinawa and examined the toxicity of the flesh by the mouse bioassay. The rate of toxic fish was as follows: L. monostigma: 32.3%, L. bohar: 11.9%, V. louti: 14.3%, E. fuscoguttatus: 20.8%. Only one out of 36 samples of V. albimarginata and two of 74 samples of L. russellii were found toxic. None of the 35 samples of L. argentimaculatus was toxic. Nor the L. bohar samples weighing less than 4 kg were toxic. In all toxic samples, CTX1B was detected by LC/MS analysis but CTX3C and 51- hydroxyCTX3C were not. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Ciguatera fish poisoning (CFP) associated with gastro- intestinal, cardiovascular and neurological symptoms and signs is one of the largest scale food poisonings of nonmi- crobial origins annually affecting 20,000–60,000 people worldwide (Lehane and Lewis, 2000; Yasumoto, 2005). While ciguatera endemic areas are tropical and subtropical Indo-Pacific Ocean and Caribbean Sea where coral reef developed, increasing world trade of seafood and interna- tional tourisms cause outbreaks in other climate (Lehane and Lewis, 2000; Yasumoto, 2005; Wong et al., 2005). Original forms of principal toxins, ciguatoxins (CTXs), are produced by an epiphytic dinoflagellate Gambierdiscus toxicus and transferred to herbivorous and carnivorous fish via food chain (Yasumoto et al., 1977; Yasumoto, 2005). The chemical structures of ciguatoxins in G. toxicus and in fish have been elucidated (Yasumoto, 2001, 2005). Ciguatoxin- 4A (CTX4A) and ciguatoxin-3C (CTX3C) produced by the dinoflagellate were presumed to undergo structural changes in fish to produce the most representative toxin, ciguatoxin-1B (CTX1B), 51-hydroxyCTX3C and other metabolite toxins (Yasumoto, 2001, 2005). Occurrence of * Corresponding author at: Okinawa Prefectural Institute of Health and Environment, 2085 Aza-Ozato, Ozato, Nanjo, Okinawa 901-1202, Japan. Tel.: þ81 98 945 0329; fax: þ81 98 945 9366. E-mail address: ooshronm@pref.okinawa.lg.jp (N. Oshiro). 1 Present address: Minamata Research Center, Chisso Corporation. 1-1 Noguchi-cho, Minamata, Kumamoto 867-8501, Japan. Contents lists available at ScienceDirect Toxicon journal homepage: www.elsevier.com/locate/toxicon 0041-0101/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.toxicon.2009.05.036 Toxicon 56 (2010) 656–661