http://onlinelibrary.wiley.com/doi/10.1111/jfd.12228/abstract
Potential disease interaction reinforced: double-virus-infected escaped farmed Atlantic salmon, Salmo salar L., recaptured in a nearby river.
A S Madhun, E Karlsbakk, C H Isachsen, L M Omdal, A G Eide Sørvik, O Skaala, B T Barlaup, K A Glover
Journal of Fish Diseases (Impact Factor: 1.59). 01/2014; DOI:10.1111/jfd.12228
Source: PubMed
ABSTRACT The role of escaped farmed salmon in spreading infectious agents from aquaculture to wild salmonid populations is largely unknown. This is a case study of potential disease interaction between escaped farmed and wild fish populations. In summer 2012, significant numbers of farmed Atlantic salmon were captured in the Hardangerfjord and in a local river. Genetic analyses of 59 of the escaped salmon and samples collected from six local salmon farms pointed out the most likely source farm, but two other farms had an overlapping genetic profile. The escapees were also analysed for three viruses that are prevalent in fish farming in Norway. Almost all the escaped salmon were infected with salmon alphavirus (SAV) and piscine reovirus (PRV). To use the infection profile to assist genetic methods in identifying the likely farm of origin, samples from the farms were also tested for these viruses. However, in the current case, all the three farms had an infection profile that was similar to that of the escapees. We have shown that double-virus-infected escaped salmon ascend a river close to the likely source farms, reinforcing the potential for spread of viruses to wild salmonids.
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0060924
Molecular Genetic Analysis of Stomach Contents Reveals Wild Atlantic Cod Feeding on Piscine Reovirus (PRV) Infected Atlantic Salmon Originating from a Commercial Fish Farm
Kevin Alan Glover1*, Anne Grete Eide Sørvik1, Egil Karlsbakk1, Zhiwei Zhang2, Øystein Skaala1
1 Institute of Marine Research, Bergen, Norway, 2 Jiangsu Institute of Marine Fisheries, NanTong City, P. R. China
Abstract
In March 2012, fishermen operating in a fjord in Northern Norway reported catching Atlantic cod, a native fish forming an economically important marine fishery in this region, with unusual prey in their stomachs. It was speculated that these could be Atlantic salmon, which is not typical prey for cod at this time of the year in the coastal zone. These observations were therefore reported to the Norwegian Directorate of Fisheries as a suspected interaction between a local fish farm and this commercial fishery. Statistical analyses of genetic data from 17 microsatellite markers genotyped on 36 partially degraded prey, samples of salmon from a local fish farm, and samples from the nearest wild population permitted the following conclusions: 1. The prey were Atlantic salmon, 2. These salmon did not originate from the local wild population, and 3. The local farm was the most probable source of these prey. Additional tests demonstrated that 21 of the 36 prey were infected with piscine reovirus. While the potential link between piscine reovirus and the disease heart and skeletal muscle inflammation is still under scientific debate, this disease had caused mortality of large numbers of salmon in the farm in the month prior to the fishermen’s observations. These analyses provide new insights into interactions between domesticated and wild fish.
p.6: "
Four main conclusions can be drawn from these analyses: 1. The partially digested and morphologically difficult to identify prey were revealed to be Atlantic salmon, 2. Based upon several independent genetic parameters, these salmon prey were identified as farmed and not from the local wild population, thus demonstrating this to be a human induced, as opposed to natural phenomena, 3. Despite partial digestion, the majority of the prey, including the single escapee, carried detectable levels of PRV. PRV is associated with the disease HSMI [32,33]. This disease had caused significant mortality of salmon on the local farm in the immediate time-period prior to the prey being captured in the wild cod, 4."
http://www.plosone.org/article/fetchObject.action?uri=info:doi/10.1371/journal.pone.0082202&representation=PDF
Phylogenetic Evidence of Long Distance Dispersal and Transmission of Piscine Reovirus (PRV) between Farmed and Wild Atlantic Salmon
A˚se Helen Garseth1,2*, Torbjørn Ekrem2, Eirik Biering1
1Department of Health Surveillance, Norwegian Veterinary Institute, Trondheim, Norway, 2Department of Natural History, Norwegian University of Science and Technology University Museum, Trondheim, Norway
Abstract
The extent and effect of disease interaction and pathogen exchange between wild and farmed fish populations is an ongoing debate and an area of research that is difficult to explore. The objective of this study was to investigate pathogen transmission between farmed and wild Atlantic salmon (Salmo salar L.) populations in Norway by means of molecular epidemiology. Piscine reovirus (PRV) was selected as the model organism as it is widely distributed in both farmed and wild Atlantic salmon in Norway, and because infection not necessarily will lead to mortality through development of disease. A matrix comprised of PRV protein coding sequences S1, S2 and S4 from wild, hatchery-reared and farmed Atlantic salmon in addition to one sea-trout (Salmo trutta L.) was examined. Phylogenetic analyses based on maximum likelihood and Bayesian inference indicate long distance transport of PRV and exchange of virus between populations. The results are discussed in the context of Atlantic salmon ecology and the structure of the Norwegian salmon industry. We conclude that the lack of a geographical pattern in the phylogenetic trees is caused by extensive exchange of PRV. In addition, the detailed topography of the trees indicates long distance transportation of PRV. Through its size, structure and infection status, the Atlantic salmon farming industry has the capacity to play a central role in both long distance transportation and transmission of pathogens. Despite extensive migration, wild salmon probably play a minor role as they are fewer in numbers, appear at lower densities and are less likely to be infected. An open question is the relationship between the PRV sequences found in marine fish and those originating from salmon.
