The parasitic salmon louse, and its documented resistance to chemotherapeutants, represents the most persistent environmental challenge to global salmonid aquaculture. We used a genetic marker associated with pyrethroid resistance to analyse ∼15 000 lice collected from the North Atlantic in the period 2000–2017. The genotype associated with resistance was not detected in lice collected from throughout the North Atlantic in the year 2000 or 2002. However, by the year 2009 onwards, it was found in lice from fish farms throughout much of the North Atlantic. It was also found in modest frequencies in lice collected from wild Atlantic salmon captured off Greenland. The most recent samples displayed very high frequencies of the genotype associated with resistance, particularly in intensive aquaculture regions of Norway (>90%) and Scotland (>70%). These results closely align with observations from the field. We suggest that pyrethroid resistance first emerged in Europe just before or around the year 2000 and was thereafter dispersed throughout much of the North Atlantic where its increased frequency was driven by extensive pyrethroid use. Although the resistant genotype was not detected in lice from Canada, it is likely to occur in very low frequencies that would quickly increase if pyrethroids were to be used in that region.

中文翻译：

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水产养殖驱动的演变：2000-2017年整个北大西洋鲑鱼虱中拟除虫菊酯抗药性的分布

寄生鲑鱼虱及其对化学治疗剂的抗药性是全球鲑鱼养殖的最持久的环境挑战。我们使用了与拟除虫菊酯抗药性相关的遗传标记来分析2000-2017年间从北大西洋收集的约15,000虱子。在2000或2002年在整个北大西洋收集的虱子中未检测到与抗性相关的基因型。但是，到2009年以后，在北大西洋大部分地区的养鱼场的虱子中发现了这种基因型。在从格陵兰岛附近捕获的野生大西洋鲑鱼中收集到的虱子中也发现了这种细菌。最近的样本显示出与抗性相关的基因型频率很高，特别是在挪威（> 90％）和苏格兰（> 70％）的集约化水产养殖地区。这些结果与实地观察非常吻合。我们建议拟除虫菊酯抗药性首先出现在欧洲，大约在2000年之前或前后，然后分散在整个北大西洋的大部分地区，在北大西洋的大部分地区，拟除虫菊酯的使用受到广泛使用的推动。尽管在加拿大的虱子中未检测到抗药性基因型，但很可能以非常低的频率发生，如果在该地区使用拟除虫菊酯，这种频率会迅速增加。