Addressing viral and bacterial threats to salmon farming in Chile: historical contexts and perspectives for management and control

The rapid growth of the salmon farming industry in Chile has led to the appearance of various viral, bacterial, parasitic, and fungal pathogens affecting farmed fish. The Chilean salmon industry has suffered several health crises associated with high fish mortalities, such as caused by the infectious salmon anaemia virus (2007) and harmful algal blooms (2016). In addition to these events, marine farms are continuously affected by outbreaks of harmful pathogens, including the bacteria Piscirickettsia salmonis and, most recently, a reappearance of Renibacterium salmoninarum, and the infectious pancreatic necrosis virus. These outbreaks have led to stricter regulations, but the salmon farming industry continues to struggle despite reforms. In addition to the aforementioned pathogens, which are a continuous threat, other apparently under control pathogens have also reappeared in recent years. In this review, we analyse the current state of knowledge on four of the main pathogens affecting salmon farming in Chile. The infectious pancreatic necrosis virus is relevant as it affects freshwater-stage fish, with survivors then acting as carriers. The infectious salmon anaemia virus currently appears to be under control; however, P. salmonis and R. salmoninarum continue to be the cause for high mortalities in the Chilean aquaculture industry.