Update on hare myxomatosis

In August 2024, the Dutch Wildlife Health Centre (DWHC) received the first reports of European hares (Lepus europaeus) with myxomatosis-like symptoms. This was surprising because, unlike rabbits, myxomatosis in hares was very rare. Cases had also been reported across the border in Germany.

This resulted in a joint investigation with colleagues from Germany. We found that the infection in these hares was caused by the hare myxomatosis virus (ha-MYXV). This is a new variant of the myxomatosis virus (a recombinant myxomatosis virus).

Ha-MYXV was discovered in 2018 in the Iberian hare (Lepus granatensis) in Spain and Portugal, where it caused large outbreaks with mortality in the Iberian hare. The European rabbit (Oryctolagus cuniculus) is also susceptible to ha-MYXV. Research indicated that the virus likely originated in the Iberian Peninsula and spread, possibly as early as September 2020, to the Netherlands and Germany. For more details, see the article by Fischer et al., 2025 (doi: 10.3201/eid3108.241969).

Ha-MYXV is therefore an emerging virus. The DWHC is trying to track its spread in the Netherlands and understand its modes of transmission. Below is a map of the municipalities with confirmed cases of hare myxomatosis. Green indicates the municipalities where the disease was first diagnosed in 2024, and purple indicates the municipalities where the disease was first diagnosed in 2025.

Reference

Fischer, L., de Bruin, E., Jongepier, E., Koffeman, E., König, P., Pfaff, F., Peters, M., van den Brand, J. M. A., Bussi, M., Fischer, D., Caliendo, V., Weerts, E., IJzer, J., Müller, J., Kühling, A. K., Kummerfeld, M., Müller, J., Petersen, H., Merbach, S., Beer, M., Uiterwijk, M., de Boer, K., & Rijks, J. M. (2025). Recombinant Myxoma Virus in European Brown Hares, 2023-2024. Emerging infectious diseases, 31(8), 1608–1612. https://doi.org/10.3201/eid3108.241969