Erratum to: Genetic characterization of betanodavirus isolates from ...

Genetic characterization of new isolates of betanodavirus 1545Fig. 1 Phylogenetic tree ofbetanodaviruses sequenced inthis study based on nucleotidesequence similarity of fulllength-RNA2. Note that theisolates from India in this studyare grouped along with theRGNNV clusterinfection used in this study seem to exhibit high genetichomology and belong to a single genotype, as is evidentfrom the phylogenetic tree (Fig. 1). They were grouped into a single cluster together with isolates from the RGNNVspecies. It is currently believed that RGNNV is the onlyspecies whose members prefer the tropical temperatureprevailing in India. From these observations, it was concludedthat the isolates from this study belong to theRGNNV species of betanodavirus.The environmental and physical conditions to which thefish are subjected are known to affect the severity of betanodavirusinfection. Generally, disease is observed moreoften in marine fish at earlier stages of life. However, suchinferences cannot be drawn from the present data. Acuteinfection was observed in all age groups from larvae toyearlings at 4-32 ppt salinity. A salinity preference of thevirus was not apparent in the present study, as both latentand acute isolates were seen in low- as well as high-salineenvironments. The nucleotide sequence data also show thatisolates from the two environments did not significantlydiffer at the molecular level. Acute infection was observedat higher water temperature (28 °C), but an association inthis regard can be drawn only after conducting experimentsunder controlled conditions.The observation that the betanodaviruses in India belongto the RGNNV species raises concerns to the boomingaquaculture industry in this country. Members of this speciesare known to have the widest host range of all the fishnodaviruses, and latently infected fish pose more of a threatto aquaculture as asymptomatic carriers, which can spreadthe virus to a naïve environment. Acute infection wasobserved in farms, whereas latent infection was observed inwild environments as well. However, more study is neededto determine the local transmission route of the virusresulting in acute infection, as the seabass culture in India issustained by both hatchery production and wild collectionof seeds. The occurrence of betanodaviruses in the wildenvironment where no commercial fish culture activitieshave been launched suggests a wider distribution of thevirus in nature. Horizontal transmission from carrier fish inthe wild or vertical transmission from parents, or both, mayhave contributed to the spread of betanodavirus in farms.Acknowledgment Assistance provided by Dr. K.P. Jithendran,Central Institute of Brackishwater Aquaculture, Chennai, towardsgeneration of nucleotide sequence data is acknowledged.References1. Azad IS, Shekhar MS, Thirunavukkarasu AR, Poornima M,Kailasam M, Rajan JJS, Ali SA, Abraham M, Ravichandran P(2005) Nodavirus infection causes mortalities in hatchery producedlarvae of Lates calcarifer: first report from India. DisAquatic Org 63:113–1182. Breuil G, Pepin JFP, Boscher S, Thiery R (2002) Experimentalvertical transmission of nodavirus from broodfish to eggs and123