Reassortant viruses threatening fish aquaculture

Abstract

Aquaculture provides more than half of fish destined for human consumption worldwide. In aquaculture, infectious diseases triggered by viruses are amongst the major cause of mortality of farmed fish. The cohabitation of different virus strains in the same geographical area opens the possibility to natural reassortment. Virus reassortment is a characteristic recombination process of segmented viruses in which different viruses merge their genome by the shuffling of complete segments. This is possible when two or more viral strains are cohabitating into a single host, boosting their probability to concatenate their viral cycles, getting to pack segments from distinct parental strains. Cohabitation of different viruses in a geographical area, and therefore the possibility of natural reassortment, has been aided by the increment in the transport of eggs and larvae between facilities around the world. Reassortant viruses have been described to show special tropisms for fish species opposed from those affected by parental virus strains, entailing an emerging threat for aquaculture but also for wild populations. To date, outbreaks of reassortant strains of infectious pancreatic necrosis virus, nodavirus (NNV), infectious salmon anaemia virus and tilapia lake virus have been described. Unfortunately, only the characterization of reassortant NNV has been explored. The aim of this review is compiling the information available concerning reassortant viruses affecting fish species of relevance for aquaculture highlighting their potential impact for the sector. Additionally, recent research advances in host‐NNV interaction are also included.

Antimicrobial resistance: a concern related to streptococcosis in tilapia farming

“…However, for these productive indexes to be achieved, it is necessary for producers to intensify aquaculture practices on properties, increasing the fish density in nurseries (Zimmermann et al 2023), where the application of an intensive cultivation regime must follow basic protocols of sanitary management and control of environmental variables. Nevertheless, the rapid growth and ex-pansion of aquaculture has been accompanied by the vertiginous growth of infectious diseases due to the widespread dispersal of pathogens, causing great economic losses in aquaculture farms in Asia, Central and South America (Bouwmeester et al 2021;Valero and Cuesta 2023). Despite all the advances in relation to fish diseases and how to avoid them through good management practices in aquaculture, streptococcosis is recurrent in fish farms around the world (Van Doan et al 2022).…”

Fish Iridoviridae: infection, vaccination and immune response

“…Among the many viral diseases that threaten the economic stability of the aquaculture sector, iridoviruses are emerging pathogens with a pervasive presence across diverse environmental niches and host species. Significant mortality rates characterise these diseases, affecting both wild and farmed animals and establishing viral reservoirs amongst those populations [ 1 ]. To mitigate this potentially unsafe impact, it is necessary to implement biosecurity measures that focus on four main areas: fish, pathogens, environment, and personnel management.…”