Anthelmintic activity of benzimidazoles against Gyiodactylus sp. infecting rainbow trout Oncorhynchus mykiss

Abstract

Various anthelmintics belonging to the pharmacological group of benzimidazoles (oxibendazole, thiabendazole, albendazole, oxfendazole, flubendazole, mebendazole, parbendazole, fenbendazole and triclabendazole) were tested and compared for their in vitro and in vivo activity against an infection of rainbow trout Oncorhynchus mykiss by Gyrodactylus . The trout were also observed for signs of toxic reaction to the drugs. Oxibendazole, albendazole, mebendazole, parbendazole, fenbendazole and triclabendazole, despite their insolubility, showed anti-Gyrodactylus activity in vivo that increased with time of exposure to the drug. Complete efficacy (100% reduction) with no toxic effects was achieved only by fenbendazole (1.5 mg /l) and triclabendazole (25 mg/l) over 12 h. In our tests, thiabendazole, oxfendazole, and flubendazole were totally ineffective; oxibendazole and albendazole were less than 100% effective and were toxic; mebendazole and parbendazole were non-toxic but less than totally effective