VANN: Genetic and environmental factors influencing pathogenicity in the interaction between Gyrodactylus salaris and its salmonid hosts

Pop.vit.framstilling:

This project seeks to evaluate the factors contributing to pathogenicity of Gyrodactylus salaris in infections of Norwegian salmon. Pathogenicity is a result of host and parasite genotypes, and of the interaction of each of these factors with environment al factors. Previous work on G. salaris pathogenicity has focussed on the importance of host genotype, in particular researching the different outcomes of infections with the southern Norwegian Lier strain of G. salaris with a range of different salmon s tocks. In this project we will utilise a wider range of genetically characterised G. salaris strains, including a North Norwegian salmon pathogenic strain, the Palsbufiorden Charr infecting strain and a rainbow trout infecting strain. Lifetime reproduct ive output of worms on a range of salmonid stocks will be calculated under common garden laboratory conditions. The environment in which parasites are maintained will be modified to examine the effect of environment on parasite population growth and sexu ality. The environmental factors which will be modified are a). water pH/aluminium concentration (a physical factor), b). host immune response using trickle infections (a host phenotypic environmental factor) and c). host density (an ecological factor). Lifetime reproductive output will be calculated under these modified environmental conditions, and the probability of parasites reproducing sexually will be evaluated. The genetic diversity of clones derived from these experiments, under different paras ite population growth conditions )epidemic, endemic, pathogenic or non-pathogenic) will be compared, and the possibility of strain hybridisation leading to a development of parasite strains with novel host specificity or pathogenicity phenotypes will be t ested experimentally. This work will be of fundamental importance in evaluating the relative roles of host and parasite genotype and environment in determining the pathogenicity of the G. salaris-host interaction.