RHDV2 overcoming RHDV immunity in wild rabbits (Oryctolagus cuniculus ) in Australia

THE emergence of rabbit haemorrhagic disease (RHDV) virus 2 (RHDV2) in Europe (Le Gall-Recule and others 2011) has been associated with declines in wild rabbit ( Oryctolagus cuniculus ) populations (Delibes-Mateos and others 2014, Guerrero-Casado and others 2016, Monterroso and others 2016) previously exposed to RHDV. All RHDV genotypes of the G1–G6 genogroups, hereafter referred to as RHDV, belong to the same antigenic serotype (Le Gall-Recule and others 2013). The unique antigenic nature of RHDV2 (Le Gall-Recule and others 2013, Barcena and others 2015) is reflected in its capacity to kill rabbits vaccinated against RHDV (Le Gall-Recule and others 2011, Dalton and others 2014, McGowan and Choudhury 2016) and its rapid spread in Europe (Dalton and others 2012, Le Gall-Recule and others 2013, Abrantes and others 2014, Baily and others 2014, Westcott and others 2014) and Australia (Hall and others 2015) with associated peaks in RHD epizootics. The capacity of RHDV2 to overcome RHDV immunity, reported so far only in vaccinated rabbits, may partly explain the observed decline in wild rabbit populations where RHDV had already been circulating. Here the authors report the infection by RHDV2 of three Australian wild rabbits with a known RHDV antibody-positive serological history, with clinical signs of RHD visible in one fresh carcase, the first documented cases of RHDV-immune wild rabbits being infected with and/or succumbing to RHDV2 infection. This demonstrated capacity of RHDV2 to overcome immunity derived from natural infections with RHDV supports an immunogenic difference between RHDV and RHDV2 at the level of serotype. With the emergence and spread of RHDV2 …