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Date: 1 February 2012
Research about to be published in the leading international journal Parasitology has confirmed 90% of salmon die when infected with ‘Sphaerothecum destruens’. Yet no tests are being carried out to determine whether salmon in England are infected despite the presence of the parasite in the UK.
The parasite, better known as the Rosette Agent, has been blamed for the rapid demise of the sunbleak ‘Leucaspius delineatus’ in parts of Europe and has caused mass mortality in US aquaculture facilities of Atlantic and Chinook salmon with more than 80% dying.
“The work demonstrates that salmon are highly susceptible to infection. This is a concern because the parasite has been reported in wild cyprinid fish stocks in the South of England,” said author Dr Demetra Andreou from Bournemouth University. “As a result, there is an urgent need to determine the pathogen’s distribution and assess the extent to which valuable UK stocks of Atlantic salmon and other species are under threat.”
Pathological tests have been carried out on a small number of salmon in Scotland and, although results have come back clear, this is not a true reflection of the rest of the country. There are currently no indications that the disease has yet made its way to Scottish waters.
Previous research at Bournemouth University has shown that the Rosette Agent can spread rapidly through the waters of the South of England, via the healthy carrier species, topmouth gudgeon ‘Pseudorasbora parva’. Topmouth gudgeon themselves have incredible invasive potential and could be moving north taking the deadly parasite with them.
Dr Andreou stressed that as a generalist parasite, the Rosette Agent has the potential to cause ‘massive unpredictable mortality outbreaks’ that could endanger species biodiversity and have a high economic cost. She believes the current pathological tests need to be supplemented with up to date molecular detection tools.
“Small populations will be particularly susceptible to extinction as the Rosette Agent can cause sudden disease and mortality outbreaks,” she said.
But research in this area would not just be beneficial in preventing mortality in salmon.
Dr Andreou said: “This research would further general understanding of this generalist parasite that belongs to a new group organisms at the animal-fungi boundary. This group of pathogens will infect pretty much anything, including dogs, horses and humans. We cannot have a single species approach. We have to get an idea of how the prevalence of the parasite varies within communities and which ones are most susceptible,” she said. “This means that a monitoring of our UK fish population for this Rosette Agent pathogen is urgently needed.”
The paper, ‘Isolation and culture of Sphaerothecum destruens from Sunbleak (Leucaspius delineatus) in the UK and pathogenicity experiments in Atlantic salmon (Salmo salar)’, by Paley, R. and Andreou, D. has been accepted in Parasitology and will be published in the next few days.
The image of the Rosette Agent parasite used in this article comes courtesy of Dr Kristen Arkush.
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