title: Sea lice population and sex differences in P-glycoprotein expression and emamectin benzoate resistance on salmon farms in the Bay of Fundy, New Brunswick, Canada.
abstract: BACKGROUND
  Parasitic sea lice are a major challenge for salmon aquaculture. This is especially due to the recent development of resistance to emamectin benzoate (EMB) in the parasite. We investigated: (1) whether EMB treatment success in Grand Manan, Bay of Fundy, NB, Canada can be explained through EMB bioassay and P-glycoprotein (P-gp) mRNA expression studies; (2) if other populations of sea lice not under EMB selective pressure possess similar EMB sensitivity as Grand Manan sea lice populations; and (3) the heritability of EMB resistance in Lepeophtheirus salmonis.
  
  
  RESULTS
  EMB bioassay results indicated population, species, sex and temporal differences in EMB EC50 values. RT-qPCR analyses revealed population and sex differences in P-gp mRNA levels, correlating with the bioassay results. Laboratory-reared sea lice maintained their EMB sensitivity status up to the F3 generation. Caligus elongatus, collected from Grand Manan showed more than twofold lower EMB EC50 values compared with L. salmonis collected from the same site. Concurrent exposure to EMB and verapamil yielded no increase in C. elongatus sensitivity to the parasiticide.
  
  
  CONCLUSIONS
  Sea lice bioassay and P-gp mRNA studies can be used to track EMB resistance and sex differences in EMB sensitivity and P-gp mRNA levels exist in the parasite.
authors.affiliation: Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada; Hoplite Research Group, Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada.
authors.forename: Okechukwu O
authors.initials: OO
authors.lastname: Igboeli
authors.forename: John F
authors.initials: JF
authors.lastname: Burka
authors.forename: Mark D
authors.initials: MD
authors.lastname: Fast
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D000222:Adaptation, Physiological; D000818:Animals; D000977:Antiparasitic Agents / Q000633:toxicity*; D017756:Aquaculture; D033342:Copepoda / Q000187:drug effects* / Q000235:genetics*; D005260:Female; D005393:Fish Diseases / Q000469:parasitology; D007559:Ivermectin / Q000031:analogs & derivatives* / Q000633:toxicity; D008297:Male; D009509:New Brunswick; D012333:RNA, Messenger; D018570:Risk Assessment; D012474:Salmon / Q000469:parasitology; D012737:Sex Factors; D014874:Water Pollutants, Chemical / Q000633:toxicity
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D000977:Antiparasitic Agents; D012333:RNA, Messenger; D014874:Water Pollutants, Chemical; D007559:Ivermectin; C108024:emamectin benzoate
keywords: Caligus elongatus); P-glycoprotein; drug resistance, Atlantic salmon (Salmo salar); emamectin benzoate; sea lice (Lepeophtheirus salmonis