Distribution of carp edema virus in organs of infected juvenile common carp

Abstract

Introduction: The disease caused by carp edema virus (CEV) manifests with lethargy as a primary sign; this observation inkoi in Japan gained the disease the name koi sleepy disease (KSD). In the years following the discovery of the virus in Japan,KSD cases have been noted in the UK in koi and common carp. Conducting research in order to expand knowledge of theprocesses of distribution of CEV in infected fish organs will be helpful for eradication and diagnostic purposes. Material andMethods: Carp edema virus–affected fish with clinical signs of KSD were experimentally cohabited with common carp fry (30fish). Three fish were euthanised by bath in a 0.5 g L−1 tricaine solution at one week intervals (7, 14, 21 and 28 days postcohabitation). Tissue samples from the brain, gills, spleen, kidney, intestines and skin were collected, and the total DNA wasextracted and tested by real-time PCR. Results: By the seventh day post infection, CEV DNA was most often found in the skin,gills and brain and less frequently in the kidney and intestines. In many of the common carp fry, CEV DNA could typically befound in several organs of each individual fish, although it was only found in one sample of spleen tissue. Conclusion: In thisexperimental study the pathogenesis of the CEV infection process was shown, the high infectivity of CEV was confirmed and thebest organs were determined for sampling in CEV-infection experimentation. The real-time PCR method used in our cohabitationexperiments was shown to be useful at the clinical and asymptomatic stage of virus infection