Novel Pestivirus Species in Pigs, Austria, 2015

Abstract

A novel pestivirus species was discovered in a piglet-producing farm in Austria during virologic examinations of congenital tremor cases. The emergence of this novel pestivirus species, provisionally termed Linda virus, in domestic pigs may have implications for classical swine fever virus surveillance and porcine health management.

Keywords: Austria; Bungowannah virus; Flaviviridae; Linda virus; atypical porcine pestivirus; classical swine fever virus; congenital tremor; livestock; pestivirus; pigs; viruses.

Video

Congenital tremor visible in piglets that were affected by a novel pestivirus provisionally termed Linda virus, Austria, 2015.

Figure 1

Histologic and phylogenetic examination in investigation of piglets with congenital tremor (CT) on a farm in southeastern Austria, 2015. A) Cerebellar white matter of CT-affected piglet showing multiple sharply bordered vacuoles but normal myelination (stained in blue; luxol fast blue/hematoxylin-eosin staining; original magnification ×10). B) Control piglet with normal cerebellar white matter (original magnification ×10). C) Spinal cord white matter in CT-affected piglet shows a severely reduced amount of myelin (original magnification ×10). D) Control piglet with normal myelination of the spinal cord white matter (original magnification ×10). E, F) Phylogenetic neighbor-joining analysis using the nucleotide (E) and polyprotein (F) sequences of the novel virus isolated from piglets, provisionally termed Linda virus (GenBank accession no. KY436034); approved pestivirus species BVDV-1 NADL (accession no. M31182.1), BVDV-2 890 (accession no. U18059.1), CSFV Alfort_187 (accession no. X87939.1), and BDV X818 (accession no. AF037405.1); and tentative species Bungowannah virus (accession no. EF100713.2), sheep pestivirus Aydin (accession no. NC_018713.1), pronghorn pestivirus (accession no. NC_024018.2), reindeer pestivirus (accession no. AF144618.2), giraffe pestivirus (accession no. NC_003678.1), BVDV-3 D32_00_HoBi (accession no. AB871953.1), APPV NL1 (accession no. KX929062.1), Rhinolophus affinis pestivirus (accession no. JQ814854.1), and Norway rat pestivirus (accession no. KJ950914.1). Assumed relationships between the species are shown in a radial branching diagram with numbers indicating the bootstrap values of 1,000 replicates in percentages. Scale bars indicate number of substitutions per site. BDV, border disease virus; BVDV, bovine viral diarrhea virus; CSFV, classical swine fever virus.

Figure 2

Detection of pestivirus E2 protein with monoclonal antibody 6A5 in investigation of piglets with congenital tremor (CT) on a farm in southeastern Austria, 2015. A) Western blot analysis of cells infected with novel virus provisionally termed Linda virus. Total protein of SK-6 cells infected with Linda virus and MDBK cells infected with BVDV-1 (strain NADL) was probed with the pestivirus E2-specific antibody 6A5. The apparent molecular mass of monomeric E2 (LV 50 kDa and BVDV-1 55 kDa) shows that Linda virus E2 has a lower molecular weight than BVDV-1 E2 as a result of fewer N-linked glycosylation sites. In contrast, the mass of E1-E2 heterodimers is comparable (≈70 kDa in Linda virus and BVDV-1), because Linda virus E1 has an additional N-linked glycosylation site. B, C) Focus size of Linda virus 48 hours after infection of SK-6 cells (B) and MDBK cells (C) (original magnification ×20). D, E) Detection of pestiviral E2 within neuronal tissue of Linda virus–positive, congenital tremor–affected piglets showing positive signals in neurons of the nucleus of the trigeminal nerve (D) (original magnification ×10) and within glial cells in the cerebellar white matter (E) (original magnification ×20). BVDV, bovine viral diarrhea virus.