Characterisation of parapoxviruses isolated from Norwegian semi-domesticated reindeer (Rangifer tarandus tarandus)

Abstract

Background: Two outbreaks of the disease contagious ecthyma were reported in 1999 and 2000 in Norwegian semi-domesticated reindeer (Rangifer tarandus tarandus). Contagious ecthyma is an epidermal disease of sheep and goats worldwide, which is caused by the zoonotic parapoxvirus orf virus. Characterisation of clinical samples from the two outbreaks in semi-domesticated reindeer in Norway by electron microscopy and PCR (B2L) revealed typical parapoxvirus particles and partial gene sequences corresponding to parapoxvirus, respectively. If contagious ecthyma in reindeer is caused by orf virus, the virus may be transferred from sheep and goats, via people, equipment and common use of pastures and corrals, to reindeer. Another possibility is that contagious ecthyma in reindeer is caused by a hitherto unclassified member of the parapoxvirus genus that circulates among reindeer herds and remains endemic in Norway.

Results: Genomic comparisons of one standard orf strain (orf NZ2) and the reindeer isolates, employing restriction fragment length polymorphism (RFLP) and random amplified polymorphic DNA (RAPD) analysis, demonstrated high similarity between the reindeer viruses and known orf virus strains. Partial DNA sequences of two different viral genes were determined for the different isolates and compared with corresponding parapoxvirus genebank sequences. The comparison/alignment and construction of phylogenetic trees also point to an affiliation of the reindeer viruses to the species orf virus.

Conclusion: The results of this work imply that the parapoxvirus causing contagious ecthyma in Norwegian semi-domesticated reindeer belongs to the species orf virus and that the orf virus crosses the host species barrier from sheep and goat to semi-domesticated reindeer.

Figure 1

Restriction fragment length polymorphism (RFLP) analysis of the standard orf virus strain NZ2 and the Norwegian reindeer isolate from Troms county 2000 (bands indicated by arrows) displays identical cleavage patterns for the two viruses.

Figure 2

Random amplified polymorphic DNA (RAPD) analysis of different parapoxviruses. Lane 1: reindeer Finland 1994, Lane 2: reindeer Norway 1999, Lane 3: reference strain orf 11, Lane 4: reindeer Norway 2000, Lane 5: orf virus NZ2, Lane 6: parapoxvirus from Weddell seal, Lane 7: parapoxvirus from cattle, Norway, Lane 8: mock infected cells, Lane 9 and 10: 1 kb and 100 bp ladder, respectively. Bands indicate similar patterns for orf and reindeer viruses, whereas parapoxvirus from seal and cattle are different.

Figure 3

Bayesian tree based on the partial nucleotide sequences of the B2L gene (379 nt) obtained in this study compared with corresponding DNA sequences from parapoxviruses published in Genebank. Isolates are described by Genebank accession number, parapoxvirus species, source and country of origin. Numbers at major clades indicate clade credibility values in Percent.

Figure 4

Maximum Parsimony tree based on the translated nucleotide sequences of the Norwegian and Finnish reindeer vIL-10 gene amplicons obtained in this study, compared with corresponding amino acid sequences from mammals published in Genebank. Black numbers (branch length) describe the genetic distance/number of changes along the branch. Blue numbers (bootstrap values) describe the reliability for each clade in percent.