Detection of a novel astrovirus in brain tissue of mink suffering from shaking mink syndrome by use of viral metagenomics

Abstract

In 2000, farmed mink kits in Denmark were affected by a neurological disorder. The characteristic clinical signs included shaking, staggering gait, and ataxia. The disease, given the name shaking mink syndrome, was reproduced by the inoculation of brain homogenate from affected mink kits into healthy ones. However, the etiology remained unknown despite intensive efforts. In this study, random amplification and large-scale sequencing were used, and an astrovirus was detected in the brain tissue of three experimentally infected mink kits. This virus also was found in the brain of three mink kits naturally displaying the disease but not in the six healthy animals investigated. The complete coding region of the detected astrovirus was sequenced and compared to those of both a mink astrovirus associated with preweaning diarrhea and to a recently discovered human astrovirus associated with a case of encephalitis in a boy with x-linked agammaglobulinemia. The identities were 80.4 and 52.3%, respectively, showing that the virus described in this study was more similar to the preweaning diarrhea mink astrovirus. For the nonstructural coding regions the sequence identity was around 90% compared to that of the astrovirus, which is associated with preweaning diarrhea in mink. The region coding for the structural protein was more diverse, showing only 67% sequence identity. This finding is of interest not only because the detected virus may be the etiological agent of the shaking mink syndrome but also because this is one of the first descriptions of an astrovirus found in the central nervous system of animals.

FIG. 1.

Genetic organization of astrovirus and the relative position of the different astrovirus sequences obtained by large-scale sequencing.

FIG. 2.

mVISTA plot showing the sequence identity of ORF2 between SMS-AstV and MiAstV.

FIG. 3.

(a) Phylogenetic study of the complete coding region of astroviruses obtained from different species. SMS-AstV is marked with a square. (b) Phylogenetic comparison of a partial sequence of the ORF1b region with different mink astrovirus sequences available in GenBank. SMS-AstV is marked with a square.