Rosette Agent parasite risk to UK coarse fish

Lab tests carried out by researchers at Bournemouth University (BU) have shown UK carp, bream and roach are all susceptible to infection by the deadly parasite Sphaerothecum destruens, better known as the Rosette Agent.

The research published in PLoS ONE journal showed death rates in bream exceeding 50% with 75% of bream being infected. Carp and roach showed a lower level of susceptibility, although the parasite prevalence was still as high as 20 percent.

Given that BU researchers have already found the Rosette Agent in one wild UK fish population, the risk of spread to these vulnerable coarse fish is high.

“To minimise the risk of spread and infection of native fish, they should be checked for this parasite,” said Dr Demetra Andreou, researcher at BU and author of this latest paper. “At present fish undergo a series of health checks when they are moved between water bodies, but those checks do not currently specifically test for the presence of the Rosette Agent.”

In light of these new statistics, the lack of specific Rosette Agent testing will undoubtedly prove alarming for lake managers, fishing enthusiasts and other stakeholders in the UK’s coarse fishing industry, which is currently estimated to be worth £1.2 billion.

Previous research at Bournemouth University has indicated the Rosette Agent’s potential to spread rapidly through the waters of the South of England via the healthy carrier species, Pseudorasbora Parva, or topmouth gudgeon. Topmouth gudgeon themselves have incredible invasive potential and could be moving across the country taking the deadly parasite with them.

Dr Andreou stressed that as a generalist parasite, the Rosette Agent has the potential to cause ‘unpredictable mortality outbreaks’. But what steps can be taken to minimise the risk posed to carp, bream, roach and other UK fish species?

“The next step,” said Dr Andreou, “is to establish the influence of multiple hosts on the susceptibility to the Rosette Agent. The presence of multiple hosts can have unpredictable consequences on susceptibility. As we are interested in the effect that the pathogen can have on species communities, we need to understand the impact that different species composition can have on the virulence to the pathogen.”

The full paper, ‘Introduced pathogens and native freshwater biodiversity: A case study of Sphaerothecum destruens’, by Andreou, D., Arkush, K.D., Guegan, J-F. and Gozlan, R.E is published in PLoS ONE now.

To find out more about the Rosette Agent risk and to register your concern visit TheRosetteAgent.com

This blog is written by staff at International Aquafeed Magazine which is published and supported by Perendale Publishers Limited. To get your copy of PPL's web application, 'PPLAPP' click here.