Co‐infection patterns of infectious salmon anaemia and sea lice in farmed Atlantic salmon, Salmo salar L., in southern Chile (2007–2009)

Abstract

Infectious salmon anaemia virus (ISAV) caused a large epidemic in farmed Atlantic salmon in Chile in 2007-2009. Here, we assessed co-infection patterns of ISAV and sea lice (SL) based on surveillance data collected by the fish health authority. ISAV status and SL counts in all Atlantic salmon farms located in the 10th region of Chile were registered monthly from July 2007 through December 2009. Each farm was categorized monthly according to its ISAV and SL status. A multinomial time-space scan test using a circular window was applied to identify disease clusters, and a multivariate regression model was fitted to quantify the association between disease-clustering and farm-management factors. Most of the identified clusters (9/13) were associated with high SL burdens. There were significant associations (P < 0.05) between management factors and ISAV/SL status. Areas in which good management practices were associated with a reduced disease risk were identified. The findings of this study suggest that certain management practices can effectively reduce the risk of SL and ISAV in the face of an epidemic and will be helpful towards creating an effective disease control programme in Chile.

Disease Resistance in Atlantic Salmon (Salmo salar): Coinfection of the Intracellular Bacterial Pathogen Piscirickettsia salmonis and the Sea Louse Caligus rogercresseyi

“…Both of these studies suggested that sea lice may play an important role in the epidemiology of amoebic gill disease caused by Neoparamoeba perurans and/or in mortality of Atlantic salmon in sea farms. Similarly, Valdes-Donoso et al [25] reported that most of the ISAV outbreaks between 2007 and 2009 in the X th region of Chile were associated with high sea lice burdens. The reduced survival upon coinfection in Atlantic salmon might be explained by the direct skin damage caused by parasites that allows other pathogens to enter the fish [55].…”

“…In agreement with this hypothesis, Mustafa et al [22] reported that Atlantic salmon infected with the sea louse Lepeophtheirus salmonis showed increased susceptibility to a microsporidian parasite (Loma salmonae ). Recently, Nowak et al [23], Bustos et al [24] and Valdes-Donoso et al [25] suggested, based on field studies on Atlantic salmon, that sea lice affect disease resistance to the amoeba Neoparamoeba perurans and to ISAv.…”

Temporal variability in sea lice population connectivity and implications for regional management protocols

“…For example, in 1997, a serious epidemic of ISAV resulted in compulsory (uncompensated) slaughter at several salmon farms on the west coast of Scotland (Rodger et al 1998). In 2007, Chilean salmon farming suffered catastrophic losses of around ⇔ 1.8 billion (Aldrin et al 2011) through an ISAV epidemic (Valdes-Donoso et al 2013) which spread rapidly between farms. Annually, it is estimated that sea lice management measures cost the industry over ⇔ 33 million in the UK alone, and over ⇔ 305 million globally (Costello 2009).…”

Treatment rates for sea lice of Scottish inshore marine salmon farms depend on local (sea loch) farmed salmon biomass and oceanography

“…In Scottish salmon farms, the main problem species is Lepeo phtheirus salmonis, a salmonid specialist (Pike & Wadsworth 1999), whilst the generalist Caligus elongatus is less of a problem (although elsewhere, Caligus species cause serious problems on salmon farms, e.g. C. rogercresseyi in Chile; Valdes-Donoso et al 2013). The planktonic larval phases of sea lice (2 naupliar stages and the infectious copepodid stage) are transmitted by water movements that can lead to infection pressure at distances of several kilometres from their source (Middlemas et al 2013, Salama et al 2013.…”