Publication Abstract

Epizootic Ulcerative Syndrome (EUS), caused by the oomycete Aphanomyces invadans, is a disease affecting both wild and farmed fish in freshwater and estuarine environments. The disease has spread widely across Asia, and to some regions of Australia, North America and Africa. No reports are yet published showing the presence of the disease in Europe, or South America. A wide range of species appear to be susceptible to the disease. However, very limited data are currently available on the susceptibility of European fish species to the pathogen. The epizootic nature and broad susceptible fish species range, suggest that the disease has the potential for further spread.

In order to provide evidence in order to assess the likelihood of establishment and potential consequences of an introduction of the pathogen into England and Wales, brown trout (Salmo trutta), mullet (Chelon labrosus), tench (Tinca tinca) and common carp (Cyprinus carpio) were challenged with A. invadans zoospores by intra muscular injection; three spot gouramis (Trichogaster trichopterus) a known susceptible species were challenged as a positive control. Mullet, tench, and common carp developed clinical signs and A. invadans was re-isolated from these species. In contrast, brown trout did not develop any gross signs of infection.

Our study confirms previous reports of the susceptibility of common carp to infection with A. invadans and identified 2 new susceptible species. Clinical signs varied substantially between species.

An overview of the currently known susceptible species range will be given. Potential pathways of introduction of EUS into European countries will be highlighted and factors influencing the likelihood of establishment will be summarised. The implications of identifying further European fish species as susceptible with regards to the likelihood of establishment of EUS  in populations of aquaculture reared or wild fish in Europe will be discussed.