10 - Host—Pathogen Interactions in Salmonids

Abstract

This chapter reviews the current knowledge of the host-pathogen relationship between the bacterium Aeromonas salmonicida and its host, salmonids. Compared to classical models of host-pathogen relationships in mammals, the study of the interaction of A. salmonicida with the fish immune system is still in its infancy yet probably represents the most comprehensive model of one pathogen and its relationship with a fish host. Information from other host-pathogen interactions in fish are utilized only as needed since it is quite clear that each pathogen has evolved a series of virulence mechanisms that are quite distinct. To understand host-pathogen relationships, both the host and the pathogen must be studied. Knowledge of how a pathogen evades host defense mechanisms is in large part dependent upon the level of understanding of the host immune system. Studies in the past have greatly improved the understanding of the fish immune system. It is also important to understand that the interaction of any given pathogen with its host is generally related to its surface characteristics.