Outbreak tracking of Aleutian mink disease virus (AMDV) using partial NS1 gene sequencing

Abstract

Background: Aleutian Mink Disease (AMD) is an infectious disease of mink (Neovison vison) and globally a major cause of economic losses in mink farming. The disease is caused by Aleutian Mink Disease Virus (AMDV) that belongs to the genus Amdoparvovirus within the Parvoviridae family. Several strains have been described with varying virulence and the severity of infection also depends on the host's genotype and immune status. Clinical signs include respiratory distress in kits and unthriftiness and low quality of the pelts. The infection can also be subclinical. Systematic control of AMDV in Danish mink farms was voluntarily initiated in 1976. Over recent decades the disease was mainly restricted to the very northern part of the country (Northern Jutland), with only sporadic outbreaks outside this region. Most of the viruses from this region have remained very closely related at the nucleotide level for decades. However, in 2015, several outbreaks of AMDV occurred at mink farms throughout Denmark, and the sources of these outbreaks were not known.

Methods: Partial NS1 gene sequencing, phylogenetic analyses data were utilized along with epidemiological to determine the origin of the outbreaks.

Results: The phylogenetic analyses of partial NS1 gene sequences revealed that the outbreaks were caused by two different clusters of viruses that were clearly different from the strains found in Northern Jutland. These clusters had restricted geographical distribution, and the variation within the clusters was remarkably low. The outbreaks on Zealand were epidemiologically linked and a close sequence match was found to two virus sequences from Sweden. The other cluster of outbreaks restricted to Jutland and Funen were linked to three feed producers (FP) but secondary transmissions between farms in the same geographical area could not be excluded.

Conclusion: This study confirmed that partial NS1 sequencing can be used in outbreak tracking to determine major viral clusters of AMDV. Using this method, two new distinct AMDV clusters with low intra-cluster sequence diversity were identified, and epidemiological data helped to reveal possible ways of viral introduction into the affected herds.

Keywords: Aleutian mink disease; Amdv; Carnivore amdoparvovirus; Denmark; NS1; Phylogenetic analysis; Plasmacytosis.

Fig. 1

Information of the location and number of sporadic cases of AMDV south of the Northern peninsula of Jutland from 2004 to 2014. NJ (Northern Jutland), MJ (Middle Jutland), SD (Southern Denmark), Zealand (SJ), HS (the regional capital and Bornholm). * from the beginning of April to the end of March

Fig. 2

a Bayesian tree of the partial NS1 from this study along with other Danish sequences from GenBank. Red cluster: the “Saeby” cluster, purple cluster: the “Holstebro” cluster, green cluster: the “Zealand” cluster, turkois cluster: the “wild mink of Bornholm” cluster and the yellow cluster: the “Sole” cluster. Danish wild mink: Brown taxon. Two Swedish sequences: Black Taxon. b Enlargement of the “Saeby” Cluster from Fig. 2a. Feed suppliers are named as follows; FP-A: purple taxon, FP-B: red taxon, FP-C: green taxon, FP-D: brown taxon, FP-E: Blue taxon. c Enlargement of the “Holstebro” cluster from Fig. 2a. Feed suppliers are named as follows; FP-A: purple taxon, FP-B: red taxon, FP-C: green taxon, FP-D: brown taxon, FP-E: Blue taxon. d Enlargement of the “Zealand” cluster from Fig. 2a: Feed suppliers are named as follows; FP-A: purple taxon, FP-B: red taxon, FP-C: green taxon, FP-D: brown taxon, FP-E: Blue taxon. Swedish sequences: black taxon