A screening of multiple classes of pharmaceutical compounds for effect on preadult salmon lice Lepeophtheirus salmonis

Abstract

The salmon louse, Lepeophtheirus salmonis Krøyer, is the major obstacle facing a sustainable future for farmers of salmonids in the North Atlantic Ocean. Medicinal compounds have been the most utilized tool to prevent salmon lice infestation; however, the active compounds have become less effective or considered environmentally unfriendly in the past years. Novel medicinal compounds are thus highly desired. In two experiment series, 26 medicinal compounds were screened for their efficacy against salmon lice, in a 30-min exposure and 24-h exposure, respectively. Pyriprole, imidacloprid, cartap and spinetoram were effective at 50 mg L(-1) in the short-time exposure. In the 24-h exposure, pyriprole, propoxur, cartap, imidacloprid, fenoxycarb, pyriproxyfen, nitenpyram, spinetoram, spiromesifen and diflubenzuron induced a high level of immobilization at 5 mg L(-1) . The EC50 values of the effective compounds were calculated in further titration studies for both exposure periods. Several physiological and biochemical pathways were discovered as possible targets for medicinal intervention against the salmon louse.

Nicotinic acetylcholine receptors: Ex-vivo expression of functional, non-hybrid, heteropentameric receptors from a marine arthropod, Lepeophtheirus salmonis

“…The exposure of preadult 2 parasites were conducted as described in [48]. The parasites originated from a salmon louse strain sensitive to all tested compounds [49].…”

Behaviour in the toolbox to outsmart parasites and improve fish welfare in aquaculture

“…Pesticide resistance is linked to the frequency and dosage of treatments in farms, and the population structure of lice (Denholm et al 2002;McEwan et al 2015), with the rate of evolved resistance likely to exceed the development of new drugs. In fact, no new chemotherapeutants have been approved for use in the industry since 1999 (Aaen & Horsberg 2016). Still, the evolution of resistance to chemotherapy remains a major obstacle for the sustainable growth of salmon aquaculture, which has driven the research community and industry to look elsewhere for solutions.…”

A screening of medicinal compounds for their effect on egg strings and nauplii of the salmon louse Lepeophtheirus salmonis (Krøyer)

“…Therefore, this instar possesses other properties than the parasitic instars chalimus, preadults and adults. A thorough comparison with L. salmonis and other parasitic species with respect to the medicinal compounds mentioned in this manuscript is available in another text (Aaen & Horsberg ).…”

“…Egg strings were exposed to 50 mg L À1 of the test substance, a concentration selected after pilot studies and considered high enough to identify interesting compounds. The compounds were formulated by weighing 5 mg of each substance into glass test tubes and dissolving them in 50 lL room-tempered dimethyl sulphoxide (DMSO, Sigma-Aldrich) and 50 lL heated (40°C) blank emulsion (4.5 g polysorbatum 80, 2 g sorbitan monostearate, 100 mL propylene glycol and 150 mL purified fresh water, mixed and heated to 50°C [Muan et al 1985;Aaen & Horsberg 2016]). Every test tube was vortexed until the test substance was sufficiently dispersed.…”