Recombinant Myxoma Virus in European Brown Hares, 2023-2024

Abstract

Recombinant myxoma virus has emerged in European brown hares (Lepus europaeus), causing increased deaths associated with swollen eyelids, head edema, and dermatitis at face, legs, and perineum. Introduction may date back as far as September 2020. As of August 2024, the disease is spreading radially from the Germany-Netherlands border area.

Keywords: Germany; Lagomorpha; hare; myxoma virus; myxomatosis; poxviridae infections; the Netherlands; viruses; wild animals.

Figure 1

Location of an outbreak of ha-MYXV during 2024 in European brown hares (Lepus europaeus) in the border area of the Netherlands and Germany compared with ranges of the hares and the Iberian hare (Lepus granatensis). A) Municipalities and provinces in the Netherlands and the Germany federal state of North-Rhine Westphalia, showing the presumed epicenter of the outbreak (municipalities in which ha-MYXV occurred in 2023), as well as the spatiotemporal development of the outbreak in European brown hares during August 1–October 20, 2024. Confirmed ha-MYXV cases occurred in the Netherlands provinces Limburg, Gelderland, Overijssel, and Groningen and in North-Rhine Westphalia. Municipalities without laboratory-confirmed ha-MYXV cases during the study period, but where ha-MYXV-infection in hares was suspected on the basis of pathology, electron microscopy, or photographs of affected hares provide an indication of the probable area of virus presence, are indicated. Map created in R version 4.4.1 (The R Project for Statistical Computing, https://www.r-project.org). B) Extant ranges of both hare species. The outbreak area in northwest Europe is in the western part of the extant range of the European brown hare and far from the extant range of the Iberian hare, in which ha-MYXV was discovered in 2018, causing disease in both Spain and Portugal. Source of extant range shapes: International Union for Conservation of Nature. ha-MYXV, hare-adapted natural recombinant myxoma virus.

Figure 2

European brown hare (Lepus europaeus) with myxomatosis caused by a hare-adapted natural recombinant myxoma virus during a 2024 outbreak in the border area of the Netherlands and Germany. A) Conjunctivitis (black arrow) and nodular skin proliferations at the lips and nose (white arrows). B) Inflammatory swelling of male genital mucous membranes with ulcerations (white arrows).

Figure 3

Time-based phylogeny of MYXV from a 2024 outbreak in European brown hares (Lepus europaeus) in the border area of the Netherlands and Germany and reference sequences. Ten full-length MYXV sequences from the outbreak were aligned to 114 available full-length MYXV reference genome sequences from GenBank and used for time-based phylogenetic analyses with BEAST version 1.10.4 (https://github.com/beast-dev/beast-mcmc/releases/tag/v1.10.4). Red indicates isolates belonging to ha-MYXV; bold text indicates sequences from this study. Branch labels represent statistical support values; values closer to 1 indicate stronger support. GenBank accession numbers are shown. ha-MYXV, hare-adapted natural recombinant MYXV; HPD, highest posterior density; MYXV, myxoma virus.