Emergence of Viral Diseases Challenging Sustainability of Aquaculture: Novirhabdovirus Adaptation to Climate Change – ThermoFish

The control and management of infectious diseases that affect aquaculture fish are major challenges for improving animal and human health. Climate change raises the critical question of the adaptation of pathogens to rising temperatures. While the importation of tropical pathogens into our latitudes has now become a reality, much less is known about how pathogens already present in aquaculture farms in temperate climates adapt to higher temperatures. Thus, this project proposes to study the determinants of adaptation to global warming of Novirhabdoviruses, a group of major viral pathogens for several fish species in Europe, Asia and North America and against which no vaccines are available. The originality of this project is based on an extensive collection of Novirhabdoviruses available at ANSES as well as several variants empirically adapted to replicate efficiently at high temperature. We propose to define the molecular basis of this temperature adaptation and to determine the susceptibility of different species of fish: a model fish species, zebrafish and the natural host, trout. We will also assess the efficacy of prototype vaccines against high temperature-adapted strains. Thus this project will answer the following essential questions: 1) What are the effects of increased temperature on Novirhabdovirus evolution and fish responses to infection? 2) What are the molecular determinants of thermo-adapted Novirhabdovirus strains? 3) At a cellular level, is host species spectrum modified for thermo-adapted variants? 4) Is it possible to induce vaccine protection against high temperature-adapted strains?