First detection and analysis of a fish circovirus

Abstract

Circoviruses are present worldwide in birds and pigs but their occurrence in fish has not yet been reported. Recently, increased mortality was observed in barbel fry (Barbus barbus) in Hungary. This paper reports the detection of previously unknown circular viral DNA genomes in barbels by the use of a circovirus-specific wide-range nested PCR. The analysis of two complete genomes (Barbel circovirus, BaCV1 and BaCV2) indicated that they belonged into a new genetic group within the family Circoviridae, distinct from known circoviruses and circovirus-like genomes. Their genome size was 1957 bases and contained two major ORFs similar to the capsid and replication-associated protein genes of circoviruses. A connection between the presence of the virus and clinical manifestations of the infection could not be proved.Circoviruses are small non-enveloped viruses with a short single-stranded circular DNA genome of 1.7-2.3 kilobases. Since the first discovery of the virus in a porcine cell culture (Tischer et al., 1974(Tischer et al., , 1982 a number of novel viruses have been described with similar characteristics, providing a basis for the establishment of the family Circoviridae. The family is currently divided into two recognized genera (Fauquet et al., 2005). Chicken anaemia virus (CAV) is the only member of the genus Gyrovirus, the rest of the circoviruses belong to the genus Circovirus. Strangely enough, besides the first porcine circovirus (PCV1) identified, the only other circovirus of mammalian origin is a pathogenic variant of PCV, designated PCV2 genotype (Allan et al., 1998). The rest of the so far detected circoviruses are of avian origin. PCV is known to infect animals other than domestic pigs, like wild boars (Ellis et al., 2003; Cságola et al., 2006) or rodents (Lőrincz et al., 2010) and it was also detected in cattle (Nayar et al., 1999;Kappe et al., 2010), but circoviruses characteristic to mammalian species other than swine are not known at present.As molecular biology tools evolve the chances of discovering novel viral species or even virus families increase. Using viral metagenomics, novel circovirus-like genomes were detected recently in reclaimed water and marine samples (Rosario et al., 2009a, b). Ng et al. (2009) reported the presence of a single-stranded circular DNA virus in sea turtle fibropapilloma cases, a potential novel representative of circoviruses. Based on similar methods Li et al. (2010) identified distantly related circovirus-like genomes in human and chimpanzee stools, and suggested the establishment of a tentative new genus (Cyclovirus) within the family Circoviridae. Using random PCR amplification and sequencing Blinkova et al. (2010) described circular viral genomes resembling circoviruses, plant geminiviruses and nanoviruses in size and genome organization, suggesting an evolutionary link among them. These findings show that circoviruses were perhaps more widespread than previously thought, and samples from water sources suggest that fish might also be carriers of circovir...

Metagenomic identification of a nodavirus and a circular ssDNA virus in semi-purified viral nucleic acids from the hepatopancreas of healthy Farfantepenaeus duorarum shrimp

“…Although many genomes have been identified in seawater and one was found associated with fish (Rosario et al 2009, Lorincz et al 2011, with regard to marine invertebrates, circular ssDNA viruses have only recently been found associated with 2 copepod species (Acartia tonsa and Labidocera aestiva; Dunlap et al 2013). Due to their prevalence in the environment, it is not unexpected that circular ssDNA viruses should be found associated with marine organisms.…”

Revisiting the taxonomy of the family Circoviridae: establishment of the genus Cyclovirus and removal of the genus Gyrovirus

“…In fact, until 2010, pigs were the only mammals known to be affected by circoviruses and most of the diversity for this group of viruses was reported from avian species (Table 1). However, studies employing viral metagenomic-based strategies and degenerate PCR for circoviruses in unconventional hosts have since identified the presence of circovirus genomes in freshwater fish [45,46] and various mammals, including bats [34-36, 42, 91], chimpanzees [34], dogs [37], humans [34] and minks [41]. Although a definitive host has not been confirmed for some of these newly-detected circoviruses (e.g., bat-associated circoviruses), phylogenetic analyses indicate that circovirus genomes detected in mammals, in general, are more closely-related to each other than to avian circoviruses (Fig.…”

Viral vaccines for farmed finfish

“…Examples of recently identified diseases include cadiomyopathy syndrome (CMS) [43], and hemorrhagic kidney syndrome (HKS) involving Toga-like virus in Atlantic salmon [11]. Another example of a recently identified virus that has been implicated in increased mortality in barbel fry (Barbus barbus) in Hungary includes a circovirus (single-stranded DNA containing virus) although a relation between the presence of the virus and clinical manifestations has yet to be established [65]. As more improved diagnostic methods are developed to meet the needs of the burgeoning aquaculture industry, new diseases are likely to be discovered that may otherwise be enzootic in wild fish populations [75].…”