Aphanomyces invadans is the main causative agent of epizootic ulcerative syndrome (EUS), a seasonal epizootic condition, which is associated with morbidity and mortality in farmed and wild fish worldwide (Roberts and others 1993, Blazer and others 1999, Baldock and others 2005, Andrew and others 2008, Boys and others 2012, Oidtmann 2012). EUS is now considered to be indistinguishable from mycotic granulomatosis (MG), red spot disease (RSD), ulcerative disease syndrome (UDS) or ulcerative mycosis (UM) (Lilley and others 1998). Approximately 76 species of fish have been confirmed by histological diagnosis to be naturally affected by EUS (OIE 2009). Experimental infection revealed that European catfish (Silurus glanis) were highly susceptible to A invadans zoospores and rainbow trout (Oncorhynchus mykiss) had moderate to low susceptibility, whereas European eels (Anguilla anguilla) appeared largely unaffected (Oidtmann and others 2008). Some fish such as common carp (Cyprinus carpio), Nile tilapia (Oreochromis niloticus) and milk fish (Chanos chanos) seem to be resistant to EUS (Lilley and others 1998). A invadans is transmitted horizontally from fish to fish through water, where the zoospores attach to the damaged fish skin and germinate into fungal filaments or hyphae (OIE 2009). Infected fish demonstrate petechiae, associated with distinct dermal lesions appearing as red spots, blackish burn-like marks or deeper ulcers with red centres and white rims (Pathiratne and others 1994, Lilley and Roberts 1997). The disease has been reported in Australia, countries in Asia, the USA and Africa (FAO 2009). Recently, EUS was confirmed in wild brown bullhead (Ameiurus nebulosus) in Lake Ontario, Canada (OIE 2011). No reports have yet been published showing the presence of EUS in South America (European Food Safety Authority (EFSA) 2011). In recent years, iridoviruses have attracted much attention due to their ecological and economic impact in various parts of the world (Caipang and others 2004). In aquaculture, iridoviruses have been implicated as the cause of severe disease, mortality and economic