Migratory host vectors can maintain the high-dose refuge effect in a structured host-parasite system: the case of sea lice and salmon Evolutionary Applications

• Author(s) / Creator(s)

  • Andrew W. Bateman
  • Stephanie J. Peacock
  • Martin Krkošek
  • Mark A. Lewis

• Migration can reduce parasite burdens in migratory hosts, but it connects populations and can drive disease dynamics in domestic species. Farmed salmon are infested by sea louse parasites, often carried by migratory wild salmonids, resulting in
  a costly problem for industry and risk to wild populations when farms amplify louse
  numbers. Chemical treatment can control lice, but resistance has evolved in many
  salmon-farming regions. Resistance has, however, been slow to evolve in the northeast Pacific Ocean, where large wild-salmon populations harbour large sea louse
  populations. Using a mathematical model of host–macroparasite dynamics, we explored the roles of domestic, wild oceanic and connective migratory host populations
  in maintaining treatment susceptibility in associated sea lice. Our results show that a
  large wild salmon population, unexposed to direct infestation by lice from farms; high
  levels of on-farm treatment; and a healthy migratory host population are all critical to
  slowing or stopping the evolution of treatment resistance. Our results reproduce the
  “high-dose/refuge effect,” from the agricultural literature, with the added requirement of a migratory host population to maintain treatment susceptibility. This work
  highlights the role that migratory hosts may play in shared wildlife/livestock disease,
  where evolution can occur in ecological time.

• Date created

  2020-04-15

• Subjects / Keywords

  • host–parasite model
  • salmon farming
  • salmon
  • sea lice
  • emamectin benzoate
  • high dose/refuge effect
  • treatment resistance

• Type of Item

  Article (Published)

• DOI

  https://doi.org/10.7939/r3-49n7-tn20

• License

  Attribution-NonCommercial 4.0 International