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Hybrids of koi, Cyprinus carpio x crucian carp, Carassius carassius and koi x goldfish, Carassius auratus, proved to be susceptible to koi herpesvirus (KHV, syn. CyHV-3) and developed KHV disease (KHVD). While hybrids of koi x goldfish were partly resistant to mortality following infection by immersion, most koi x crucian carp hybrids died after bath infection. KHV DNA was detected in dead fish but also in all surviving animals by different polymerase chain reactions (PCRs). According to these results, hybrid crossbreeding does not seem to prevent severe losses associated with KHV in terms of inducing KHVD. The present study showed severe losses after a waterborne KHV infection of between 35% and 100% in koi x goldfish and koi x crucian carp hybrids as well as in SPF carp.

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A novel picornavirus was isolated from specimens of a diseased European eel (Anguilla anguilla). This virus induced a cytopathic effect in eel embryonic kidney cells and high mortality in a controlled transmission study using elvers. Eel picornavirus has a genome of 7,496 nucleotides that encodes a polyprotein of 2,259 amino acids. It has a typical picornavirus genome layout, but its low similarity to known viral proteins suggests a novel species in the family Picornaviridae.A ll members of the family Picornaviridae are small, nonenveloped, icosahedral viruses with positive-strand RNA genomes. Genome sizes range from 7,000 to 9,100 nucleotides. The 5= end of the RNA is covalently linked to a small virus-encoded peptide (3B); the 3= end is polyadenylated. The genome encodes one or two polyproteins that are processed co-and posttranslationally into 10 to 14 mature polypeptides. Cap-independent translation initiation is stimulated by one or two internal ribosome entry site (IRES) elements. Common to all picornaviruses are homologous capsid proteins and the nonstructural proteins 2C, 3Cpro , and 3Dpol . The sequences of other nonstructural proteins (leader protein, 2A, 2B, 3A, and 3B) are not conserved and may be unique to some picornavirus genera (1, 2).The family Picornaviridae is currently comprised of 37 species grouped into 17 genera (Aphthovirus, Aquamavirus, Avihepatovirus, Cardiovirus, Cosavirus, Dicipivirus, Enterovirus, Erbovirus, Hepatovirus, Kobuvirus, Megrivirus, Parechovirus, Salivirus, Sapelovirus, Senecavirus, Teschovirus, and Tremovirus; http: //ictvonline.org/). However, picornavirus taxonomy is still in flux, as next-generation sequencing technologies facilitate metagenomics studies using viral nucleic acid-containing specimens. Analysis of viral genomes without prior virus isolation led to the identification of more than 30 approved or tentative picornavirus species from humans (cosavirus [3] Although all published picornaviruses were identified in mammals and birds, there are reports of picornavirus-like viruses of reptiles (24, 25), fish (26-31), and marine invertebrates (32-35), indicating circulation of such viruses in aquatic ecosystems. Here, we describe a fish picornavirus which proves that picornavirus ecology indeed includes lower vertebrates of freshwater and probably marine ecosystems. Eel picornavirus 1 (EPV-1) was isolated from a European eel (Anguilla anguilla) from Lake Constance on the Rhine River. The viral genome contains an open reading frame (ORF) of 6,777 nucleotides (2,259 amino acids [aa]), and the predicted polyprotein displays the typical organization of a picornavirus. According to the Picornavirus Study Group criteria (www .picornastudygroup.com/definitions/genus_definition.htm), low similarity to the conserved P1 and 3CD precursor proteins of EPV-1 suggests a novel genus in the family Picornaviridae.Starting in May 2005, an increased number of diseased or dead eels were observed in fish traps and aquacultures in the Lake Constance area. Diseased fish presented with...