{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,10]],"date-time":"2026-09-10T11:10:45Z","timestamp":1789038645083,"version":"build-2803163510"},"reference-count":29,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2025,10,21]],"date-time":"2025-10-21T00:00:00Z","timestamp":1761004800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"\u201cLeading Goose\u201d R&D Program of Zhejiang","award":["2024C02005"],"award-info":[{"award-number":["2024C02005"]}]},{"name":"Hubei Provincial Key Laboratory of Fish Resources Protection in the Three Gorges Project","award":["2021045-ZHX"],"award-info":[{"award-number":["2021045-ZHX"]}]},{"name":"Huzhou Municipal Public Welfare Agricultural Applied Research Project","award":["2023GZ28"],"award-info":[{"award-number":["2023GZ28"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Pathogens"],"abstract":"<jats:p>White spot disease, caused by the parasitic Ichthyophthirius multifiliis, induces mortality exceeding 80% in intensive aquaculture systems, resulting in global annual losses of &gt;$1 billion. Current chemical controls (e.g., formaldehyde) face environmental persistence and drug resistance challenges. This study developed a synthetic isoquinoline derivative, BHTCA (s)-2-tert-butoxycarbonyl-7-hydroxy-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid), as a biodegradable alternative against I. multifiliis in grass carp (Ctenopharyngodon idella). In vitro assays revealed stage-selective efficacy: theronts exhibited higher susceptibility (EC50 = 0.10 mg\/L at 4 h) than tomonts (EC50 = 0.40 mg\/L at 24 h), with BHTCA disrupting ciliary structures and compromising cyst integrity. In vivo trials (0.6 mg\/L) reduced parasite loads by 78.1% and host mortality by 66.7% versus untreated controls. Acute toxicity tests confirmed a high therapeutic index (LC50 = 16.75 mg\/L; &gt;167\u00d7 effective concentration). With demonstrated efficacy, low production cost, and minimal eco-toxicity, BHTCA presents a sustainable strategy for Ichthyophthiriasis management in aquaculture.<\/jats:p>","DOI":"10.3390\/pathogens14101069","type":"journal-article","created":{"date-parts":[[2025,10,21]],"date-time":"2025-10-21T14:53:19Z","timestamp":1761058399000},"page":"1069","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Effects of a Synthetic Isoquinoline Derivative Against Ichthyophthirius multifiliis In Vivo and In Vitro in Grass Carp (Ctenopharyngodon idella)"],"prefix":"10.3390","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-7143-8307","authenticated-orcid":false,"given":"Xianqi","family":"Peng","sequence":"first","affiliation":[{"name":"Hubei Key Laboratory of Three Gorges Project for Conservation of Fishes, Chinese Sturgeon Research Institute, China Three Gorges Corporation, Yichang 443100, China"},{"name":"Key Laboratory of Healthy Freshwater Aquaculture, Ministry of Agriculture and Rural Affairs, Key Laboratory of Fish Health and Nutrition of Zhejiang Province, Key Laboratory of Fishery Environment and Aquatic Product Quality and Safety of Huzhou City, Zhejiang Institute of Freshwater Fisheries, Huzhou 313001, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xialian","family":"Bu","sequence":"additional","affiliation":[{"name":"Hubei Key Laboratory of Three Gorges Project for Conservation of Fishes, Chinese Sturgeon Research Institute, China Three Gorges Corporation, Yichang 443100, China"},{"name":"Key Laboratory of Healthy Freshwater Aquaculture, Ministry of Agriculture and Rural Affairs, Key Laboratory of Fish Health and Nutrition of Zhejiang Province, Key Laboratory of Fishery Environment and Aquatic Product Quality and Safety of Huzhou City, Zhejiang Institute of Freshwater Fisheries, Huzhou 313001, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Weisong","family":"Ma","sequence":"additional","affiliation":[{"name":"Hubei Key Laboratory of Three Gorges Project for Conservation of Fishes, Chinese Sturgeon Research Institute, China Three Gorges Corporation, Yichang 443100, China"},{"name":"Key Laboratory of Healthy Freshwater Aquaculture, Ministry of Agriculture and Rural Affairs, Key Laboratory of Fish Health and Nutrition of Zhejiang Province, Key Laboratory of Fishery Environment and Aquatic Product Quality and Safety of Huzhou City, Zhejiang Institute of Freshwater Fisheries, Huzhou 313001, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9236-794X","authenticated-orcid":false,"given":"Jinbiao","family":"Jiao","sequence":"additional","affiliation":[{"name":"Key Laboratory of Healthy Freshwater Aquaculture, Ministry of Agriculture and Rural Affairs, Key Laboratory of Fish Health and Nutrition of Zhejiang 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