title: A Novel Virus Causes Scale Drop Disease in Lates calcarifer.
abstract: From 1992 onwards, outbreaks of a previously unknown illness have been reported in Asian seabass (Lates calcarifer) kept in maricultures in Southeast Asia. The most striking symptom of this emerging disease is the loss of scales. It was referred to as scale drop syndrome, but the etiology remained enigmatic. By using a next-generation virus discovery technique, VIDISCA-454, sequences of an unknown virus were detected in serum of diseased fish. The near complete genome sequence of the virus was determined, which shows a unique genome organization, and low levels of identity to known members of the Iridoviridae. Based on homology of a series of putatively encoded proteins, the virus is a novel member of the Megalocytivirus genus of the Iridoviridae family. The virus was isolated and propagated in cell culture, where it caused a cytopathogenic effect in infected Asian seabass kidney and brain cells. Electron microscopy revealed icosahedral virions of about 140 nm, characteristic for the Iridoviridae. In vitro cultured virus induced scale drop syndrome in Asian seabass in vivo and the virus could be reisolated from these infected fish. These findings show that the virus is the causative agent for the scale drop syndrome, as each of Koch's postulates is fulfilled. We have named the virus Scale Drop Disease Virus. Vaccines prepared from BEI- and formalin inactivated virus, as well as from E. coli produced major capsid protein provide efficacious protection against scale drop disease.
authors.affiliation: MSD Animal Health / Intervet International bv., Department Discovery & Technology, Boxmeer, The Netherlands.
authors.forename: Ad
authors.initials: A
authors.lastname: de Groof
authors.affiliation: MSD Animal Health / Intervet International bv., Department Discovery & Technology, Boxmeer, The Netherlands.
authors.forename: Lars
authors.initials: L
authors.lastname: Guelen
authors.affiliation: Laboratory of Experimental Virology, Department of Medical Microbiology, Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Martin
authors.initials: M
authors.lastname: Deijs
authors.affiliation: MSD Animal Health / Intervet International bv., Department Discovery & Technology, Boxmeer, The Netherlands.
authors.forename: Yorick
authors.initials: Y
authors.lastname: van der Wal
authors.affiliation: MSD Animal Health Innovation Pte Ltd, Singapore.
authors.forename: Masato
authors.initials: M
authors.lastname: Miyata
authors.affiliation: MSD Animal Health Innovation Pte Ltd, Singapore.
authors.forename: Kah Sing
authors.initials: KS
authors.lastname: Ng
authors.affiliation: MSD Animal Health / Intervet International bv., Department Discovery & Technology, Boxmeer, The Netherlands.
authors.forename: Lotte
authors.initials: L
authors.lastname: van Grinsven
authors.affiliation: MSD Animal Health / Intervet International bv., Department Discovery & Technology, Boxmeer, The Netherlands.
authors.forename: Bartjan
authors.initials: B
authors.lastname: Simmelink
authors.affiliation: MSD Animal Health / Intervet International bv., Department Discovery & Technology, Boxmeer, The Netherlands.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Biermann
authors.affiliation: MSD Animal Health / Intervet International bv., Department Discovery & Technology, Boxmeer, The Netherlands.
authors.forename: Luc
authors.initials: L
authors.lastname: Grisez
authors.affiliation: Laboratory of Virology and Wageningen Electron Microscopy Centre, Wageningen University, Wageningen, The Netherlands.
authors.forename: Jan
authors.initials: J
authors.lastname: van Lent
authors.affiliation: Laboratory of Experimental Virology, Department of Medical Microbiology, Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Anthony
authors.initials: A
authors.lastname: de Ronde
authors.affiliation: MSD Animal Health Innovation Pte Ltd, Singapore.
authors.forename: Siow Foong
authors.initials: SF
authors.lastname: Chang
authors.affiliation: MSD Animal Health / Intervet International bv., Department Discovery & Technology, Boxmeer, The Netherlands.
authors.forename: Carla
authors.initials: C
authors.lastname: Schrier
authors.affiliation: Laboratory of Experimental Virology, Department of Medical Microbiology, Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Lia
authors.initials: L
authors.lastname: van der Hoek
mesh_terms: D000818:Animals; D001492:Bass; D005393:Fish Diseases / Q000473:pathology / Q000821:virology*; D007497:Iridoviridae; D010802:Phylogeny; D016133:Polymerase Chain Reaction