Mutations in voltage-gated sodium channels from pyrethroid resistant salmon lice (Lepeophtheirus salmonis)

Citation

Carmona-Antoñanzas G, Helgesen KO, Humble JL, Tschesche C, Bakke MJ, Gamble L, Bekaert M, Bassett DI, Horsberg TE, Bron JE & Sturm A (2019) Mutations in voltage-gated sodium channels from pyrethroid resistant salmon lice (Lepeophtheirus salmonis). Pest Management Science, 75 (2), pp. 527-536. https://doi.org/10.1002/ps.5151

Abstract
Background Parasitic salmon lice (Lepeophtheirus salmonis) cause high economic losses in Atlantic salmon farming. Pyrethroids, which block arthropod voltage‐gated sodium channels (Nav1), are used for salmon delousing. However, pyrethroid resistance is common in L. salmonis. The present study characterised Nav1 homologues in L. salmonis in order to identify channel mutations associated to resistance, called kdr (knockdown) mutations. Results Genome scans identified three L. salmonis Nav1 homologues, LsNav1.1, LsNav1.2 and LsNav1.3. Arthropod kdr mutations map to specific Nav1 regions within domains DI‐III, namely segments S5 and S6 and the linker helix connecting S4 and S5. The above channel regions were amplified by RT‐PCR and sequenced in deltamethrin‐susceptible and deltamethrin‐resistant L. salmonis. While LsNav1.1 and LsNav1.2 lacked nucleotide polymorphisms showing association to resistance, LsNav1.3 showed a non‐synonymous mutation in S5 of DII occurring in deltamethrin‐resistant parasites. The mutation is homologous to a previously described kdr mutation (I936V, numbering according to Musca domestica Vssc1) and was present in two pyrethroid‐resistant L. salmonis strains (allele frequencies of 0.800 and 0.357), but absent in two pyrethroid‐susceptible strains. Conclusions The present study indicates that a kdr‐mutation in LsNaV 1.3 may contribute to deltamethrin resistance in L. salmonis.

Keywords
Agronomy and Crop Science; Insect Science; General Medicine;

Journal
Pest Management Science: Volume 75, Issue 2

• Accepted Manuscript