Characterization and surveillance assessment of INFECTIOUS SALMON ANEMIA VIRUS (ISAV) Field Isolates

Description

In 2005 the ISAV surveillance program operated by the New Brunswick Department of Agriculture, Fisheries and Aquaculture has identified a preponderance of salmon infected with genetically distinct ISAV strains, both of North American and European descent, some of which seem to be more virulent than others. The apparent disparity in virulence makes management decisions on infected fish difficult in light of many unanswered questions.

Virulence assessment based on data solely from the field is difficult given the number of variables and factors that can influence observed disease at a site outside of the pathogen strain itself. For instance, at each site genetics of the fish, and hence susceptibility to disease, vary as does husbandry, stress to fish, etc. which can all affect the mortality rates and observed disease at a site. Field data, combined with controlled challenge experiments which remove many of these outlying factors, is a much better approach to uncovering the true virulence differences between isolates. Similarly, the detection of different strains, using existing diagnostics assays is important for effective disease surveillance, and it is important to study the effectiveness of existing and emerging diagnostic methods from time to time as the pathogen evolves. This is ideally done in a field setting, but is often difficult to control for and thus test completely. Analysis of different diagnostic methods in a challenge situation can provide good information regarding the ability of diagnostic methods to detect ISAV in a field setting. This information, along with information on the virulence of different ISAV strains is needed to ensure

1. appropriate diagnostic methods are used, and
2. intelligent and economical management of the disease can occur.

The goal of this project is to determine the functional virulence differences amongst the genetic variants or strains, and compare the utility of diagnostic techniques to detect the different ISAV variants

Program Name

Aquaculture Collaborative Research and Development Program (ACRDP)

Year(s)

2006 to 2007

Ecoregion(s)

Atlantic: Gulf of St. Lawrence, St. Lawrence Estuary

Principal Investigator(s)

Nellie Gagné
Email: Nellie.Gagne@dfo-mpo.gc.ca