Epidemiology of marine gill diseases in Atlantic salmon (Salmo salar) aquaculture: a review

Abstract

Gill disease of farmed Atlantic salmon (Salmo salar) in the marine environment has emerged as a significant problem for the salmon aquaculture industry. Different types of marine salmon gill disease reported include amoebic gill disease (AGD), parasitic gill disease, viral gill disease, bacterial gill disease, zooplankton (cnidarian nematocyst)‐associated gill disease, harmful algal gill disease and chemical/toxin‐associated gill disease. The term ‘multifactorial gill disease’ is used when multiple distinguishable types of disease (as opposed to an obvious single primary type) are present. When gill disease is non‐specific, it is referred to as ‘complex gill disease’ (CGD) or ‘complex gill disorder’. These two terms are often used interchangeably and are overlapping. The significance of many infectious and non‐infectious agents that may be associated with CGD is often unclear. In this review, we summarise aspects of the different types of gill disease that are relevant to the epidemiology of gill disease and of CGD in particular. We also tabulate simultaneously occurring putative pathogens to explore the multifactorial nature of gill disease.

Diseases Caused by Amoebae in Fish: An Overview

“…AGD is nowadays one of the most relevant diseases in Atlantic salmon ( Salmo salar ) farming in different geographical locations (Norway, Scotland, Ireland, Australia, Chile), with a substantial disease burden including high mortality (sometimes up to 85% in a total production cycle) and a substantial reduction in growth. It is also one of the most relevant gill diseases in this species [ 57 ]. The disease and particularly the fish response, as it plays a major role in the pathogenesis and effects of the disease, has recently been extensively reviewed [ 58 ].…”

Vibrio species are predominantly intracellular within cultures of Neoparamoeba perurans, causative agent of Amoebic Gill Disease (AGD)

“…and contribute directly, or indirectly to AGD pathogenesis. This potential interaction and contribution is supported by the emergence of complex gill disease (CGD), a multi-pathogen disease associated with N. perurans infection, and various other pathogens, including a paramyxovirus, pox virus, phytoplankton, and Candidatus Branchiomonas cisticola (Boerlage et al, 2020). AGD and CGD occurrences have coincided, which demonstrates there may multifactorial contributors to AGD and gill health (Herrero et al, 2018).…”

Immersion challenge of naïve Atlantic salmon with cultured Nolandella sp. and Pseudoparamoeba sp. did not increase the severity of Neoparamoeba perurans‐induced amoebic gill disease (AGD)

“…Gill disease in the marine phase of Atlantic salmon aquaculture has become more significant in recent years (Boerlage et al., 2020), increasing the need to understand the complexity of disease expression. This trial provides evidence that cultured Nolandella sp.…”