Resistance towards pyrethroids and emamectin in sea lice

Ectoparasitic copepods represents a critical economical and health related threat to the salmonid aquaculture industry, as well as to wild salmonids. The primary method of control is delousing infected fish with pyrethroids and avermectins. Resistance tow ards chemotherapeutants has been demonstrated in sealice. This project aims to elucidate the molecular and biochemical basis for resistance, investigate the extent and the time scale in which decreased sensitivity to these agents may develop and to develo p rapid diagnostic tests for the detection of important resistance mechanisms. The group at the Norwegian School of Veterinary Science has detected a novel mutation (Q945R) in the para-sodium channel gene, possibly related to pyrethroid resistance. One ma in task in the project will be to elucidate the significance of this mutation and develop a diagnostic test. Furthermore, the project will examine a larger part of the para-sodium channel gene for other possible resistance-associated mutations. Another ai m will be to isolate and clone the glutamate-gated chloride channel, the target protein of avermectins. Selection experiments will be implemented to investigate the time required for sea lice to develop resistance under controlled selection conditions, po tential cross resistance, and potential consequences on other fitness traits. Previously established bioassays will be utilised to quantify degrees of sensitivity. If resistance-associated mutations are detected, a rapid, diagnostic test will be develope d. Yet another aim will be to study the role of ATP-dependent efflux pumps (ABC-transporters) in the development of reduced sensitiv. First, the genes for ABC transporters in these species will be identified and their sequences will be determined. Then, t he qualitative and quantitative expression of ABC-transporters in various tissues will be elucidated, and the resulting transcription profiles after exposure to selected compounds will be determined by real time PCR