Diseases and Parasites of Scallops

Knowledge of the diseases and parasites of scallops has continued to change since the second edition of this book (McGladdery et al., 2006). Advancements in the field of scallop health research have followed the broader improvements in the ability to identify disease agents in other aquatic animals. Significant progress has been made in diagnostic capability, particularly the ability to distinguish between infectious pathogens and cryptic histopathological lesions in scallops using molecular techniques. Evidence of this is the progress made in combating opportunistic infections of larvae and juveniles of several scallop species reared under hatchery conditions. There are an increasing number of investigators who pursue the unexplained mortalities in the bivalve hosts using a new generation of diagnostic tools. The diversification of scallop species being brought into stock enhancement and aquaculture programs on a global scale has led to increased contributions from our Asian colleagues. Parallel development of remote underwater photography technology for surveillance and stock assessment purposes as well as suspension culture techniques has greatly improved our capability to detect health challenges in many scallop species, challenges which previously evaded direct observation in the scallop\u27s benthic domain.The present review follows that of Getchell (1991), dividing sections by taxonomic group of pathogen. The updating of these taxonomic divisions attempted to keep up with changes made over the last decade. The listing of pathogens by scallop species also has been continued in Table 1, to facilitate scallop-specific cross-referencing. The infectious agents described in detail in the prior two editions remain to ensure as comprehensive a reference as possible. For clarity, a more encompassing definition of the term pathogen has been embraced as a microorganism capable of causing host damage (Paillard et al., 2004). The general approach is to first discuss the aetiology of the scallop disease, then cover the pathogenesis or host syndromes associated with the disease and finally, describe the mode of action of the pathogen (pathogenicity) if known (Paillard et al., 2004). The components of pathogen virulence emphasised are the genetic, biochemical and structural features that enable it to damage the host. © 2016 Elsevier B.V