Large-scale lagovirus disease outbreaks in European brown hares (Lepus europaeus) in France caused by RHDV2 strains spatially shared with rabbits (Oryctolagus cuniculus)

Abstract

Rabbit haemorrhagic disease virus (RHDV) is a lagovirus that causes rabbit haemorrhagic disease (RHD) in European rabbits (Oryctolagus cuniculus). In 2010, a new genotype called RHDV2 emerged in France. It exhibits a larger host range than classical RHDV strains by sporadically infecting different hare species, including the European hare (Lepus europaeus). Phylogenetic analyses revealed that closely related RHDV2 strains circulate locally in both hares and rabbits, and therefore that RHDV2 strains infecting hares do not belong to a lineage that has evolved only in this species. We showed that RHDV2 is widely distributed in France and that it was responsible for more than a third of cases of lagovirus disease in European hare populations in 2015. The oldest RHDV2 positive hare was sampled in November 2013 and we reported two hares co-infected by EBHSV and RHDV2. All together, our results raise important epidemiological and evolutionary issues. In particular, along with the potential emergence of recombinant EBHSV/RHDV2 strains in hares, the enlargement of the host range changes the host population structure of RHDV2 and may alter the impact of the virus on rabbit and hare populations.

Figure 1

Spatial distribution of analyzed RHD2 outbreaks in French hare and rabbit populations (January 2013–February 2015). Data are pooled by department (administrative area) and the color indicates the species involved in the analyzed outbreaks. Black: Lepus europaeus; light grey: Oryctolagus cuniculus; dark grey: the two leporid species. White: no data. The numbers refer to RHDV2 strains characterized in hares and the letters to RHDV2 strains characterized in rabbits. The order of the numbers and the letters corresponds to the order in which the VP60 sequences are positioned in the phylogenetic tree from top to bottom (Figure 2). *Recombinant RHDV-G1/RHDV2 strains, ^†unsuccessful 1U/1L PCR amplification.

Figure 2

Phylogenetic tree derived for VP60 nucleotide sequences of 381 rabbit lagoviruses including 15 French RHDV2. The tree was obtained using the Neighbor-Joining method and was drawn to a scale of nucleotide substitutions per site. The percentages greater than 70% of replicate trees in which the associated taxa clustered together in the bootstrap test (1000 replicates) are given in italics before each major branch node. The European brown hare syndrome virus (EBHSV) strain GD (Z69620) was used as an outgroup to root the tree. The RHDV2 strains characterized in hares are underlined. The 15 French RHDV2 strains characterized in this study (in rabbits and hares) are in bold and their names are followed by the number (for hares) or the letter (for rabbits) mentioned in the Figure 1 for each strain. The RHDV, the non-pathogenic and weakly pathogenic lagoviruses, most of the Iberian and Azorean RHDV2 and the Australian non-pathogenic viruses were collapsed to lighten the figure. *Recombinant RHDV-G1/RHDV2 strains, ^†unsuccessful 1U/1L PCR amplification.

Figure 3

Spatial distributions of EBHSV and RHDV2 outbreaks in hare populations in France in 2015. Data are pooled by department (administrative area) and the color indicates the lagoviruses involved in the outbreaks. Department in white: negative samples for lagovirus or absence of sampling.