The effects of sea lice in modulating salmonid susceptibility to viruses



The sea louse, Lepeophtheirus salmonis, is a naturally occurring parasite and a serious pest of farmed Atlantic salmon in both eastern and western Canada. As sea lice are found on a number of wild host species in the marine environment and co-occur with endemic viruses, mixed infections of sea lice and viruses are likely. Despite the widespread occurrence of sea lice in both wild fisheries and aquaculture, there have been no controlled studies that have explicitly examined the effect of L. salmonis on disease caused by viral pathogens. Sea lice infected salmon may be more likely to develop severe infections with second pathogens, either because the louse serves as a vector, transmitting the secondary pathogens, or because the louse infection compromises the host immune response. The latter possibility is supported by the observation of reduced expression of genes associated with anti-viral responses and adaptive immunity in several salmon species during laboratory infections with L. salmonis. This research project will focus on two viral pathogens, the Infectious Hematopoietic Necrosis Virus (IHNV) and the Infectious Salmon Anemia Virus (ISAV). IHNV infects wild and cultured salmonids throughout the Pacific Northwest of North America. ISAV infects and causes disease in farmed Atlantic salmon in eastern Canada. For both viral pathogens, there is a need to better understand if sea lice parasitism influences virus transmission and susceptibility of salmon to infection. This research project addresses this issue by integrating parallel investigations into IHNV and ISAV interactions with sea lice in western and eastern Canada, respectively. The goal of the study is to determine level of sea lice infestation at which intervention or pest management strategies may be needed to prevent further damage from viral infection. This research will provide scientific information for management decisions regarding sea lice infestation thresholds for use in salmon aquaculture.





Program Name

Program for Aquaculture Regulatory Research (PARR)


2014 - 2017


Pacific: Vancouver Island West Coast

Principal Investigator(s)

Simon Jones
Research Scientist, Pacific Biological Station
3190 Hammond Bay Rd., Nanaimo, British Columbia

Team Member(s)

Kyle Garver

Collaborative Partner(s)

Mark Fast, AVC