Epidemiological surveillance of myxoma virus in European hares (Lepus europaeus) in the Iberian Peninsula: First evidence of infection by the emerging ha-MYXV.

We investigated the circulation of myxoma viruses (MYXV) in European hare (Lepus europaeus) populations from Spain. A total of 140 individuals were sampled through passive and active surveillance from 2018 to 2024. Myxoma virus DNA was confirmed in two out of 114 (1.8 %, CI 95 %=0.2-6.2) hares analysed by PCR. One was infected with the classic MYXV strain, and the other with the recombinant ha-MYXV strain. This is the first report of ha-MYXV infection in a European hare. A commercial indirect ELISA detected antibodies against MYXV in 3.2 % (4/126; CI 95 %=0.9-7.9) of animals tested. Both molecular and serological results suggest occasional transmissions of MYXV from sympatric European rabbits (Oryctolagus cuniculus) and/or Iberian hares (Lepus granatensis) to European hares. These sporadic infections appear to be scattered across time and space, predominantly in areas where lagomorph species overlap. Because European hares appear to be immunologically naïve to MYXV, another recombination event could have a significant impact on populations, similar to what occurred with Iberian hares. This study highlights the importance of enhancing our understanding of MYXV epidemiology in wild lagomorph species through large-scale monitoring efforts.