LAUSR

Although aquaculture activity has experienced a great development during the last decades, infectious diseases are a limiting factor for further growth and sustainability, which can severely impact socio-economic development in many countries. Given that aquaculture usually requires large-scale production facilities, animals are constantly exposed to stressful conditions, providing an ideal environment for the emergence (or re-emergence) and spread of diseases of diverse aetiology. Moreover, this situation can be exacerbated by several interconnected factors such as the increased globalization of trade in live aquatic animals and their products; the intensification of aquaculture through the translocation of broodstock, postlarvae, fry and fingerlings; and the development and expansion of the ornamental fish trade, just to name a few. Therefore, investigation of the mechanisms and factors underlying infectious diseases in farmed fish and shellfish species is greatly needed to implement the effective control strategies. This Special Issue of Journal of Applied Microbiology is dedicated to the understanding of several fish and shellfish diseases, including review and research articles on the latest advances in the aetiology and pathogenesis of such diseases, as well as suitable strategies to prevent their occurrence. The Special Issue is divided into two sections. The first one focuses on viral and bacterial diseases, which includes both a review of two important viral diseases caused by the Infectious Salmon Anaemia virus and the koi herpesvirus, and six articles on bacterial diseases. These latter include a review of iron uptake mechanisms as key virulence factors in bacterial pathogens, whereas the remaining five provide insights into pathogenic aspects of Streptococcus agalactiae, Photobacterium sp. and Vibrio sp. Because the use of antimicrobial agents has led to the emergence and spread of antimicrobial resistance, the search for alternative approaches is urgently required. The second section, therefore, focuses on environmentally friendly approaches for preventing and controlling diseases. In this section, six articles highlight the use of probiotics and prebiotic substances, three of them being about the advantages and shortcomings of probiotics used in aquaculture and three articles about the effect of several natural substances on the health, growth rate and application to fish and shellfish farming. We believe that the collection of articles included in this Special Issue will provide new perspectives on the study of fish and shellfish diseases in aquaculture. We would like to sincerely thank all the authors in this issue for sharing their work and insights, as well as the reviewers for their suggestions.