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

Cyprinid herpesvirus-3 (CyHV-3) is an etiological agent of a notifiable disease that causes high mortality rates affecting both the common and koi carp Cyprinus carpio L. There is no current treatment strategy to save CyHV-3 infected fish. RNA mediated interference (RNAi) is an emerging strategy used for understanding gene function and is a promising method in developing novel therapeutics and antiviral medications. For this study, the possibility of activating the RNAi pathway by the use of small interfering (si)RNAs was tested to inhibit in vitro viral replication of CyHV-3 in common carp brain (CCB) cells. The siRNAs were designed to target either thymidine kinase (TK) or DNA polymerase (DP) genes, which both code for transcripts involved in DNA replication. The inhibition of viral replication caused by the siRNAs was measured by a reporter gene, termed ORF81. Treatment with siRNA targeting either TK or DP genes reduced the release of viral particles from infected CCB cells. However, siRNA targeting DP was most effective at reducing viral release as measured by qPCR.

Bovine herpes virus-1 (BoHV-1) is a serious viral pathogen of domestic and wild cattle. Herein, we report development of a new molecular diagnostic assay for rapid and sensitive detection of BoHV-1 utilizing the loop-mediated isothermal amplification (LAMP) technique. BoHV-1-LAMP assay was optimized to amplify the target DNA by incubation the Bst-DNA polymerase enzyme with a set of specially constructed six primers, based on the gE-gene of BoHV-1 virus, at 65 ◦C for 60 min. BoHV-1-LAMP products were detected by visual inspection using SYBR Green-I stain and had a ladder-like appearance by gel electrophoresis analysis. Negative results obtained with DNA from other tested fish viruses confirmed the specificity of the assay. The analytical sensitivity of the BoHV-1-LAMP assay was 1 fg of BoHV-1 DNA (dilution of 106). The developed assay could successfully detect BoVH-1 DNA from clinical samples. Results of this study indicate that the developed BoHV-1-LAMP is rapid and highly sensitive assay not only for detection of BoHV-1 in clinical samples, but also for differentiation between wild-type (gE-positive) and gE-negative BoHV-1 viruses, which will improve the control programs of BoHV-1 in Egypt. © 2014 Elsevier B.V. All rights reserved.