Migratory hosts can maintain the high‐dose/refuge effect in a structured host‐parasite system: The case of sea lice and salmon

Bateman, Andrew; Peacock, Stephanie J.; Krkošek, Martin; Lewis, Mark A.

doi:10.1111/eva.12984

Cited by 8 publications

(10 citation statements)

References 90 publications

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“…In the Pacific, the wild hosts of L. salmonis (North America) and C. rogercresseyi (Chile) far outnumber the farmed salmonid population. The selection pressure from aquaculture on lice is thus less compared to Europe, where the farmed salmonids constitute the majority of salmon lice hosts [ 42 ]. However, in the intensely farmed regions of Chile, loss of sensitivity to both organophosphates and pyrethroids have been documented in C. rogercresseyi [ 43 , 44 ].…”

Section: Discussionmentioning

confidence: 99%

Losing the ‘arms race’: multiresistant salmon lice are dispersed throughout the North Atlantic Ocean

et al. 2021

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Nothing lasts forever, including the effect of chemicals aimed to control pests in food production. As old pesticides have been compromised by emerging resistance, new ones have been introduced and turned the odds back in our favour. With time, however, some pests have developed multi-pesticide resistance, challenging our ability to control them. In salmonid aquaculture, the ectoparasitic salmon louse has developed resistance to most of the available delousing compounds. The discovery of genetic markers associated with resistance to organophosphates and pyrethroids made it possible for us to investigate simultaneous resistance to both compounds in approximately 2000 samples of salmon lice from throughout the North Atlantic in the years 2000–2016. We observed widespread and increasing multiresistance on the European side of the Atlantic, particularly in areas with intensive aquaculture. Multiresistant lice were also found on wild Atlantic salmon and sea trout, and also on farmed salmonid hosts in areas where delousing chemicals have not been used. In areas with intensive aquaculture, there are almost no lice left that are sensitive to both compounds. These results demonstrate the speed to which this parasite can develop widespread multiresistance, illustrating why the aquaculture industry has repeatedly lost the arms race with this highly problematic parasite.

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Section: Discussionmentioning

confidence: 99%

Losing the ‘arms race’: multiresistant salmon lice are dispersed throughout the North Atlantic Ocean

et al. 2021

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“…Refugia are particularly effective at preventing parasite adaptation if counter‐adaptions incur fitness costs on susceptible host strains 666,667 . Wild populations can act as refugia, provided they are large enough 665,668 . In the Atlantic, however, farmed salmon are significantly more abundant than wild hosts 34 .…”

Section: Optimising Implementation and Dissemination To Achieve Popul...mentioning

confidence: 99%

Applying genetic technologies to combat infectious diseases in aquaculture

Robinson

Robledo

Sveen

et al. 2022

Reviews in Aquaculture

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Disease and parasitism cause major welfare, environmental and economic concerns for global aquaculture. In this review, we examine the status and potential of technologies that exploit genetic variation in host resistance to tackle this problem. We argue that there is an urgent need to improve understanding of the genetic mechanisms involved, leading to the development of tools that can be applied to boost host

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“…Despite the local and global forewarnings of EMB resistance, industry was exclusively permitted to use EMB for delousing treatments in the BA until late 2019, a strategy which imposes strong selection and likely resulted in accelerated evolution of resistance 15 (but see 7 , 9 ). Three additional treatment options (i.e., freshwater baths, hydrogen peroxide baths, and jets of pressurized water) have since been introduced and are now used frequently; these other treatments accounted for 62% of treatments in 2021.…”

Section: Discussionmentioning

confidence: 99%

“…Until recently, the Pacific Ocean was considered the last stronghold of treatment-susceptible salmon lice 7 , but our results suggest that resistance has now emerged. EMB resistance in BC could have arisen from depleted wild salmon populations 7 , 22 , ill-advised reliance on a single treatment 15 , or insufficiently aggressive treatment on the part of farms 9 , 23 , any of which would suggest a failure of management at some level. Whatever the cause, the emergence of resistant salmon lice in the Pacific poses serious challenges for controlling outbreaks to protect wild salmon in the coming years, further exacerbating the negative consequences of lice on salmon predicted in a warming climate 24 .…”

Section: Discussionmentioning

confidence: 99%

“…In stark contrast to the situation in the Atlantic, salmon lice in the Pacific Ocean appeared to have avoided widespread evolution of EMB resistance 7 despite EMB being virtually the only treatment option used in the region until roughly 2017. Canada is the main salmon-farming country in the north Pacific, and genetic evidence has revealed only localized ephemeral resistance here 8 , potentially due to the large wild Pacific salmon populations that act as untreated refuges for susceptible lice 7 , 9 . Pacific Canada is unique globally for having substantial populations of both farmed and wild salmon 1 .…”

Section: Introductionmentioning

confidence: 99%

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Salmon lice in the Pacific Ocean show evidence of evolved resistance to parasiticide treatment

Godwin

Bateman²,

Kuparinen

et al. 2022

Sci Rep

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Parasitic salmon lice (Lepeophtheirus salmonis) threaten the economic and ecological sustainability of salmon farming, and their evolved resistance to treatment with emamectin benzoate (EMB) has been a major problem for salmon farming in the Atlantic Ocean. In contrast, the Pacific Ocean, where wild salmon are far more abundant, has not seen widespread evolution of EMB-resistant lice. Here, we use EMB bioassays and counts of lice on farms from the Broughton Archipelago, Canada—a core region of salmon farming in the Pacific—to show that EMB sensitivity has dramatically decreased since 2010, concurrent with marked decrease in the field efficacy of EMB treatments. Notably, these bioassay data were not made available through public reporting by industry or by the federal regulator, but rather through Indigenous-led agreements that created a legal obligation for salmon-farming companies to provide data to First Nations. Our results suggest that salmon lice in the Pacific Ocean have recently evolved substantial resistance to EMB, and that salmon-louse outbreaks on Pacific farms will therefore be more difficult to control in the coming years.

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Migratory hosts can maintain the high‐dose/refuge effect in a structured host‐parasite system: The case of sea lice and salmon

Abstract: Long-distance migration is a striking feature of many animals' life histories, and one that is closely tied to disease. Migration can offer refuge from sources of infection, and reduced parasite loads in some migrants suggest the role parasites may have in the evolution of mi

Cited by 8 publications

References 90 publications

Losing the ‘arms race’: multiresistant salmon lice are dispersed throughout the North Atlantic Ocean

Losing the ‘arms race’: multiresistant salmon lice are dispersed throughout the North Atlantic Ocean

Applying genetic technologies to combat infectious diseases in aquaculture

Salmon lice in the Pacific Ocean show evidence of evolved resistance to parasiticide treatment

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