Molecular characterization of a novel astrovirus associated with disease in mink.
Pre-weaning diarrhoea is a well-known problem in mink farming in Europe, causing morbidity that varies between farms, regions and season. Different causalities for the disease have been proposed, but only most recently has a novel astrovirus been identified as an important risk factor. In this report, the molecular characterization, origin and evolution of this novel astrovirus of mink are discussed. The polyadenylated, positive-stranded RNA genome was sequenced and found to contain 6610 nt, organized into three ORFs and two short UTRs. A ribosomal frameshift sequence links the 5' two ORFs, containing sequence motifs for a serine protease (ORF1a) and an RNA-dependent RNA polymerase (ORF1b). The structural proteins are encoded by ORF2 and, presumably, are expressed as a polyprotein precursor to be cleaved into the mature capsid proteins. These results indicate that mink astrovirus (MiAstV) has all of the features typical of members of the Astroviridae. Phylogenetic analyses revealed that MiAstV is distantly related to established astroviruses, showing less than 67 % similarity at the nucleotide level with its closest relative, ovine astrovirus, and even lower identities at the predicted amino acid level. Nevertheless, sequence analysis of MiAstV isolates from geographically distinct Swedish and Danish farms showed much less diversity. This suggests either the spread in the mink population of a virus that has evolved a long time ago or the recent introduction of an ancient virus into a new host species.
Department of Virology, Swedish Institute for Infectious Disease Control, S-171 82 Solna, Sweden.
Christian
C
Mittelholzer
Department of Molecular Epidemiology and Biotechnology, Swedish Institute for Infectious Disease Control, S-171 82 Solna, Sweden.
Kjell-Olof
KO
Hedlund
Department of Small Animals, National Veterinary Institute, S-751 89 Uppsala, Sweden.
Lena
L
Englund
Department of Poultry, Fish and Fur Animals, Danish Veterinary Institute, DK-8200 Århus, Denmark.
Hans-Henrik
HH
Dietz
Department of Virology, Swedish Institute for Infectious Disease Control, S-171 82 Solna, Sweden.
Lennart
L
Svensson
D000595:Amino Acid Sequence; D000818:Animals; D001257:Mamastrovirus / Q000145:classification / Q000235:genetics*; D008907:Mink / Q000821:virology*; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010802:Phylogeny; D012367:RNA, Viral / Q000032:analysis; D012324:RNA-Dependent RNA Polymerase / Q000235:genetics; D012697:Serine Endopeptidases / Q000235:genetics
D012367:RNA, Viral; D012324:RNA-Dependent RNA Polymerase; D012697:Serine Endopeptidases