Julia Gill

Infectious hematopoietic necrosis virus causes epidemic mortality in economically and culturally important salmon species, particularly in conservational fish hatcheries, across the Pacific Northwest. Viral genotypes can differentiate when transmission is clustered in parts of the landscape or within specific host species or populations, as has occurred in the IHNV system across the Pacific. In this study, we investigate how infection and mortality rates vary when juvenile rainbow trout are exposed to two viral genotypes at a range of dosages. The two different genotypes were chosen due to differences in outbreak intensity. We believe that differences in mortality are due to differences in infection among both genotypes. Here, we show that differences in mortality rates between the genotypes are due to infection and its variance. The infection rate for both genotypes reached over 80%. However, the lowest mortality rate for the high virulence strain is 35%, exceeding the highest mortality rate for the low virulence strain is 30%. The highest frequencies of mortality occurred with between 50%-60% of the fish dead for the HV genotype, and between 20%-30% of the fish dead for the LV genotype. Dosage is important in determining the infection and mortality of fish after exposure to IHNV. Finally, we use a matrix projection model to explore how these differences in infectious transmission would cause distinct patterns of population mortality in fish hatcheries.