Nodavirus infection causes mortalities in hatchery produced larvae ...

116 Dis Aquat Org 63 113-118, 2005heavy and complete necrotlc vacuolation of the brainand splnal cord (Fig le,f) by 20 dphElectron microscopy of the braln and splnal cordindicated typical membrane bound cytoplasmic incluslons(Fig 2a,b) wlth densely packed pockets of vmonsVlrions released Into the surroundings of the cellmeasured 28 to 30 nm m dlameter (Flg 2c) Several ofthe nerve cells m the splnal cord showed marginatednucleus and emptled cytoplasm after the vlral mclusionswere shed into the extracellular spaces (Flg 2d)RT-PCRArnphficatlon wlth speclfic pnmers for RNA2 encodmgthe T4 regon of coat proteln gene of nodavlrusresulted In the expected PCR product slze of 430 bp asshown in Flg 3DISCUSSIONObservations made in the present lnvestlgatlon onabnormalltles In body colouratlon, feeding and swmmingbehavlour were similar to those reported bymany workers lnvestlgatlng nodavirus-associated infectionsin Asian sea bass and other fish species(Glazebrook et a1 1990, Yoshlkoshl & Inoue 1990,Munday & Nakai 1997, Breull et a1 2001, Barker et a12002) In the present lnvestigatlon more than 60 S/o ofthe larvae dled wlthln 48 h of onset of observed clinicalsymptoms, indlcatlng the severity of the nodavirusFig 2 Electron micrographs of the central nervous system (a) Membrane bound viral particles m the cell organelle (arrows) and(b) viral inclusions (double-ended arrows) depict~ng lntracytoplasm~c localisatlon of the virus (c) Vlral particles measurmg 28 to30 nm in the lntracellular spaces, (mset) very high magnlficatlon of the viral partlcles (dl Nerve cell of the splnal cord ~ t hemptied cytoplasm and cornered nucleus Arrows indicate probable exit points of viral particles VP vlral partlcles M muscle,N nucleus Magnrfication (a,b) 70 OOOx

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ICAS PublicationNo. 2, p 111-114van Regenmortel MHV, Fauquet CM, Bishop DHL, CarstenseEB and 7 others (eds) (2000) Virus taxonomy, classificationand nomenclature of viruses, 7th edn. Academic Press,San Diego, CAWong SY, Leong TS (1989) A comparative study of Vibrioinfections in healthy and diseases marine finfishes culturedin floating cages near Penang, Malaysia. SpecialIssue, Asian Fish Sci 3:353-359Yoshikoshi K, Inoue K (1990) Viral nerve necrosis in hatcheryrearedlarvae and juveniles of Japanese parrotfish, Oplegnathusfascjatus (Temmink & Schlegel) J Fish Dis 13:69-77Zafran, Harada T, Koesharyani I, Yuasa K, Hatai K (1998)Indonesian hatchery reared seabass larvae (Lates calcarifer),associated with viral nervous necrosls (VNN).Indonesian Fish Res J 4:19-22Submitted: April 2, 2004; Accepted: June 3, 2004Proofs received from author(sj: December 17,2004