Anti-Sea Lice Agents in Norwegian Aquaculture

Anti-sea lice agents in Norwegian aquaculture surveillance, treatment trends and possible implications for food safety Hannisdal, Rita; Nøstbakken, Ole Jakob; Hove, Helge; Madsen, Lise; Horsberg, Tor Einar; Lunestad, Bjørn Tore Published in: Aquaculture DOI: 10.1016/j.aquaculture.2020.735044 Publication date: 2020 Document version Publisher's PDF, also known as Version of record Document license: CC BY Citation for published version (APA): Hannisdal, R., Nøstbakken, O. J., Hove, H., Madsen, L., Horsberg, T. E., & Lunestad, B. T. (2020). Anti-sea lice agents in Norwegian aquaculture: surveillance, treatment trends and possible implications for food safety. Aquaculture, 521, [735044]. https://doi.org/10.1016/j.aquaculture.2020.735044 Download date: 09. apr.. 2020 Aquaculture 521 (2020) 735044 Contents lists available at ScienceDirect Aquaculture journal homepage: www.elsevier.com/locate/aquaculture Anti-sea lice agents in Norwegian aquaculture; surveillance, treatment T trends and possible implications for food safety ⁎ Rita Hannisdala, , Ole Jakob Nøstbakkena, Helge Hovea, Lise Madsena,c, Tor Einar Horsbergb, Bjørn Tore Lunestada a Institute of Marine Research (IMR), Bergen, Norway. b Norwegian University of Life Sciences (NMBU), Norway. c Department of Biology, University of Copenhagen, Copenhagen, Denmark ARTICLE INFO ABSTRACT Keywords: Sea lice are a major challenge for the Norwegian aquaculture, and to cope with sea lice infections, several Aquaculture physical, biological and chemical treatments are applied. This study presents data on the use of anti-sea lice Salmon agents for Norwegian farmed fish from 1992 to 2017, and results from the surveillance of residues of suchagents Surveillance in samples collected from 2002 to 2017. In the period 2002–2007 the use of anti-sea lice agents included Veterinary drug emamectin, cypermethrin and deltamethrin. Azamethiphos and flubenzurons were introduced in 2008 and Anti-sea lice agent 2009, respectively. In the ongoing surveillance of Norwegian farmed fish, more than 3000 pooled samples have been examined for residues of anti-sea lice agents in the period from 2002 to 2017. Residues were detected in 3% of the samples. Emamectin was detected in 5.0% of the samples analyzed for emamectin, while cypermethrin was detected in 2.1% of the samples analyzed for cypermethrin. Furthermore, residues of diflubenzuron and teflubenzuron were detected in 1.2 and 0.1% of the samples analyzed for these compounds, respectively. Noneof the other anti-sea lice agents were detected. No measurements were above the respective maximum residue limit (MRL) set by the EU. 1. Introduction In recent years, several strategies involving physical, biological and chemical approaches have been developed to cope with sea lice in Sea lice (Lepeophtheirus salmonis) are ectoparasitic copepods natu- salmon farms. Although the use of cleaner fish, that prey on sea lice rally occurring in the sea. Their lifecycle involves eight stages (Hamre (Imsland et al., 2014), and numerous physical treatments (Powell et al., et al., 2013). Each stage is separated by a moult (Johnson and Albright, 2015; Stien et al., 2016) has increased, chemical treatment is still an 1991). During the two first naupliar stages and the following infectious important tool to control the level of infestation. Anti-sea lice agents copepodid stage, the sea lice are planktonic: they cannot swim direc- can be administered by bath treatment or as additives in the feed tionally against the current but are able to adjust their vertical depth. (Urbina et al., 2019). Since 1992, the chemicals used as bath treatment For the two next stages, the chalimus stages, the lice are attached to the in Norwegian aquaculture comprise the organophosphates; me- fish. Thereafter follows two pre-adult stages and one adult stage, where trifonate, azamethiphos and dichlorvos, the pyrethroids; pyrethrins, the lice are able to move around on the surface of the fish (Hamre et al., cypermethrin and deltamethrin, and hydrogen peroxide. The aver- 2013). During the last decade, sea lice have become one of the main mectin; emamectin, and the flubenzurons; teflubenzuron and di- challenges in the Norwegian fish farming industry. Sea lice feed on the flubenzuron have been used as additives in the feed. mucus, skin and blood of the hosts, and their impact varies from mild The anti-sea lice agents differ in their mode of action and efficacy. skin damage to stress-induced mortality of individual fish. Lice-infested The organophosphates are acetylcholinesterase inhibitors, they are ef- fish can exhibit reduced appetite, growth rate and food-conversion effective against adult and pre-adult stages of sea lice (Roth et al., 1996). ficiency (Pike and Wadsworth, 2000). Sea lice also affect wild salmo- The pyrethroids disrupt the sodium channel function, and are effective nids, the extent of the impact of aquaculture on sea lice infestation on in both chalimus, preadult and adult stages of sea lice (Burka et al., wild fish is fiercely debated in countries where wild salmonids and 1997). Hydrogen peroxide is a strong oxidizing agent and cause sea lice farmed salmonids coexist (Krkosek, 2008). to separate from its host (Thomassen, 1993), and is most effective ⁎ Corresponding author at: Postboks 1870 Nordnes, 5817 Bergen, Norway. E-mail address: [email protected] (R. Hannisdal). https://doi.org/10.1016/j.aquaculture.2020.735044 Received 19 September 2019; Received in revised form 28 January 2020; Accepted 29 January 2020 Available online 30 January 2020 0044-8486/ © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). R. Hannisdal, et al. Aquaculture 521 (2020) 735044 against lice in their mobile life stages (Treasurer and Grant, 1997). 2.2. Sampling and sample preparation Emamectin blocks nerve transmission, causing paralysis and death of the sea lice (Arena et al., 1995; Vassilatis et al., 1997). Emamectin has a Data was obtained from the ongoing surveillance of Norwegian high efficacy against all parasitic stages of sea lice on farmed salmon, farmed fish according to council directive 96/23/EC, on measures to and treatment also prevents recruitment of new lice for approximately monitor certain substances and residues thereof in live animals and 10 weeks (Stone et al., 2000). Flubenzurons inhibit chitin synthesis, and animal products (European Commision, 1996). The total number of their efficiency are therefore restricted to the moulting stages ofsea samples collected in the surveillance is dependent on the production lice, and no effect is thus perceived on adult lice that has already volume (European Commision, 1996). From 2002 to 2017 the pro- formed their final exoskeleton (Branson et al., 2000; Burka et al., 1997). duction of Norwegian farmed salmonids increased from 546,000 t to Norway is one of the main producers and exporters of marine 1,285,000 t, leading to an increase in the total number of samples to be farmed fish (FAO, 2016). In 2017, approximately 1.3 mill tons of monitored. The number of samples examined for each veterinary drug farmed fish, mainly Atlantic salmon (Salmo salar) were produced. The is set by the Norwegian Food Safety Authority (NFSA). The priorities scope of the present study is to delineate the use of anti-sea lice agents, are mainly based on the prescription of pharmaceuticals used in the and assess their possible impact on food safety. Prior to market au- industry. The samples were collected annually from 2002 to 2017, thorization in Norway any veterinary drug requires approval by the throughout the season in all fish-producing regions in Norway. The European Commission (EU 37/2010) and The Norwegian Medicines samples were collected at processing plants by inspectors from the Di- Agency (NoMA). Drugs intended for therapeutic use in farmed fish re- rectorate of Fisheries until 2004, and by inspectors from the NFSA from quire prescriptions from veterinarians or fish health biologists. From 2005. The samples include salmonid species in Norwegian aquaculture, 1989, it has been mandatory for both prescribing veterinarians and feed primarily Atlantic salmon (Salmo salar) (n = 2993), and to a lesser mills to send a copy of each prescription, first to the Norwegian Gov- extent rainbow trout (Oncorhynchus mykiss) (n = 219) and Arctic char ernment Fish Inspection and Quality Control Service (NFCS) and (Salvelinus alpinus) (n = 2). Standardised muscle samples, the Norwe- thereafter from 2004 to the Norwegian Food Safety Authority (NFSA). gian Quality Cut (NQC) (Johnsen et al., 2011), were collected from five Further, to ensure food safety, a systematic surveillance system is ob- fish from the same net pen, and frozen (−20 °C) in sealed plasticbags liged under the current EU regulations (European Commision, 1996). before sent in a frozen state to The Institute of Marine Research (IMR). The aim of this study is to describe the amount of anti-sea lice Upon arrival at IMR, composite samples were prepared by pooling agents used in Norwegian aquaculture and using data on residues from equal amounts of muscle from five individual fish. The samples were the Norwegian monitoring program on farmed fish, to describe the stored at −20 °C prior to analysis. For all samples, a back-up sample possible implications in regards to food safety. was stored. From 2014, the skin was included in the back-up sample. The MRL for fish is set for muscle and skin in natural proportions (European Commision, 2010), where the proportions between muscle 2. Materials and methods and skin is 9:1. Therefore, any detection of anti-sea lice agents in the muscle sample led to reanalysis of the back-up sample where skin was 2.1. The use of veterinary drugs in Norway included. For these samples the reported results are from muscle and skin. Statistics on drugs sold for use in Norwegian farmed fish were obtained from the Norwegian Institute of Public Health (NIPH). To cal- 2.3.

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