Salmon louse - prevention and treatment

The Prevent project was designed to implement and improve monitoring of salmon lice and to contribute towards development of new salmon louse treatments in the form of vaccines. The project participants were Institute of Marine Research (IMR), University of Bergen (UoB), The Norwegian Veterinary Institute (NVI), Norwegian School of Veterinary Science (NSVS), Norsk Regnesentral, CIGENE and NINA. To improve monitoring of salmon louse infection pressure an infection model that covers the entire cost and integrates available information on temperature, reproduction, lice densities and stocking densities from the aquaculture industry was developed. Since the model is using continuously reported data infection pressure and stage presence predictions can be made in close to real time and the model has been used to simulate scenarios of different management regimes on both wild and farmed fish. The project has furthermore contributed to the development of an oceanographic model validated against data comprising salmon lice on wild salmonids and salmon in sentinel cages which will be implemented as a management tool. To understand the interconnectivity of possible populations a state of the art genome marker based tool was developed and used to generate a genome map and to investigate salmon lice across its distribution in the North Atlantic showing that sea lice effectively consist of a single population. Using the same tool resistance of emamectin benzoate resistance was studied showing that it originated in one location and spread throughout the population in the North Atlantic in less than 11 years. This is a very important finding as it shows that resistance management is an international task. Furthermore the tool was used to unsurprisingly demonstrate that lice in a region with partial resistance consist of a mixture of sensitive and susceptible lice. This clearly points to the importance of effective resistance monitoring tools. Such tools in the form of simplified bioassays that may be implemented by regional fish health service providers were therefore developed and validated in the project. Furthermore mechanisms behind some of these cases of resistance were clarified and in vitro tests developed. As resistance emerges the need of alternative treatments becomes evident and the project accordingly aimed to contribute towards development of one or more vaccines. Studies towards vaccines against ectoparasites such as the salmon louse is not trivial but involves state of the art molecular studies involving advanced methodologies. Not all tools needed were in place when the project commenced and the project henceforth involved development of improved challenge models and improved methods for gene silencing. The molecular work included functional studies of genes involved in blood digestion, transmembrane proteins and proteins interacting with the host immune system. A total of 28 genes were studied in considerable detail and 3 were chosen for vaccine trials. Two of the candidates did not yield encouraging results and despite promising indications from the third candidate methodological challenges precludes firm conclusions to be reached. The project produced one completed PhD and one PhD still in progress, a total of 4 popular science reports, 3 scientific reports, 6 posters at international conferences, 24 peer reviewed papers, 1 paper accepted with minor changes and 10 papers in prep. The project thus delivered results as pr. the revised contract with RCN as of Jan. 15th 2015 with minor deviations reported separately.

A robust and sustainable solution to control lice infection of farmed salmonids is required. Three tasks are necessary to meet this requirement: Task 1: To monitor the situation in order to enable governmental management to act according to the actual sit uation. Task 2: To develop tools that will facilitate more detailed and thorough monitoring. Task 3: To develop new treatments and farming regimes that will bring the situation under control. The PrevenT platform is structured to address the above tasks. The platform will address the three tasks through 4 work packages (WPs). Task 1 will be mainly addressed by WP1-Epidemiology. In WP 1 reported data on salmon lice abundances, salmon abundances and delousing will be used to generate models that will estim ate abundances of different functional stages of salmon lice in close to real time. These models will enable management decision makers to identify areas with problems, avoid locating farms to areas with increased infection risks and manage resistance out breaks rationally. Task 2 will mostly be completed through WP 2 - Genetic markers and WP 3 - Mechanisms of drug resistance development. In WP 3 a single-dose resistance bioassays for field use will be developed and evaluated. Furthermore laboratory-based diagnostic tools will be established if possible, a process that may greatly benefit from the results from WP2. The data that can be obtained by the tools generated in WP3 can be used to detect resistance at an early stage and model dispersal of resistanc e and will provide important data for management decision makers. Task 3 will be addressed by WP 4 - Vaccine development. In WP 4 the functional biology of the salmon louse intestine will be studied since the gut is the part of the salmon louse that is in most intimate contact with salmon immune factors. The objective will be to identify intestinal ?Achilles heels? targetable by vaccines or other treatment strategies.