危険なヒラムシを宿主とするカタツムリが広く分布していることが判明 Snail that hosts potentially dangerous flatworms found to be widespread
2022-11-07 カリフォルニア大学サンディエゴ校(UCSD)
Trematodes Centrocestus formosanus (left) and Haplorchis pumilio
また、南カリフォルニアの湖や貯水池に生息するカタツムリから3種のヒト感染性ヒラムシが発見された。この扁形虫は、発育のある時期になるとカタツムリの体内から遊泳する段階を迎える。その一部が魚の体内に入り込む。魚が捕獲され、生や加熱不十分な状態で食べられた場合、腹痛から脳出血に至るまで、様々な症状を引き起こす危険性がある。
研究チームは、カタツムリに加えて、8種のトレマトードを保有していることを発見した。このうち3種は人に感染することが知られており、2種は世界の他の地域で、人の健康を脅かす重要な存在でありながら無視されていることが認識されている。残りの5種は、人へのリスクはないと思われるが、おそらくアジアから持ち込まれたものであろう。これらのことから、地元の水域にはさらに多くの種類のトレマトーデスが生息している可能性がある。カタツムリは世界全体で35種類もの振戦虫を持ち、そのうち11種類は人に感染することが知られている。
<関連情報>
- https://today.ucsd.edu/story/parasites-associated-with-eating-fish-showing-up-in-southern-california-fishing-locales
- https://academic.oup.com/jid/advance-article-abstract/doi/10.1093/infdis/jiac413/6754904?redirectedFrom=fulltext&login=false
カリフォルニア州および米国各地における外来カタツムリ(Melanoides tuberculata)を媒介とする食品由来トレマトジアーゼの出現の可能性 Potential for Emergence of Foodborne Trematodiases Transmitted by an Introduced Snail (Melanoides tuberculata) in California and Elsewhere in the United States
Daniel C G Metz, Andrew V Turner, Alexandria P Nelson, Ryan F Hechinger
Journal of Infectious Diseases Published:10 October 2022
DOI:https://doi.org/10.1093/infdis/jiac413
Abstract
We document that 3 human-infectious trematodes and their introduced first intermediate host snail (Melanoides tuberculata) are widespread throughout southern California. We surveyed 41 fishing localities, 19 of which harbored snails infected with zoonotic trematodes. Two of the parasites, Haplorchis pumilio and Centrocestus formosanus, are fishborne intestinal trematodes recognized as being important human pathogens in other areas of the world; the third, Philophthalmus gralli, can infect the human eye. An additional 5 species detected infecting M. tuberculata are likely of little direct threat to people; however, they may be recently introduced to the Americas, highlighting the risk that additional pathogenic trematodes transmitted by the snail in its native range could be introduced to the United States. The current, possible human-infection risk in California clarifies the need to consider the introduced snail and its parasites from a public health perspective anywhere in the United States the snail has been introduced.
Lay Summary
We report that 3 human-infecting trematodes and their introduced intermediate host snail are widespread in southern California freshwater fishing localities. Eating undercooked or underfrozen fish is the way people get infected by 2 of the parasite species, which are recognized as important human pathogens in other areas of the world. We also found 5 non–human-infectious trematodes carried by the snail that may be cointroduced, highlighting the possibility that other dangerous pathogens transmitted by the snail where it is native could arrive later or already be present in the United States. The common presence of the human-infecting fishborne trematodes at fishing localities, the widespread popularity of eating uncooked fish (eg, as sashimi, sushi, poke, or ceviche), and the potential for additional human-infecting trematodes to also be introduced, all justify consideration of the introduced snail and its parasites from a public health perspective in California and other areas in the United States where the parasites or the host snail have already been reported.
