The viral biocontrol agents Myxoma virus (MYXV) and Rabbit Haemorrhagic Disease Virus (RHDV1), released in 1950 and 1996 respectively, are the only control tools to have resulted in significant and lasting landscape-scale suppression of rabbit populations in Australia. Multiple conservation benefits and significant economic savings have resulted from the long-term and widespread reductions in rabbit numbers and impacts. In an effort to ‘boost’ rabbit biocontrol, an additional variant of RHDV1 ('K5') was recently released nationwide to counteract the decreasing effectiveness of both RHDV1 and MYXV that results from the evolutionary ‘arms race’ between viruses and their hosts. Two years prior to the K5 release, an exotic RHDV strain (RHDV2) appeared in Australia. The commercially available vaccine used to protect pet and farmed rabbits against the officially released K5 was ineffective against the exotic RHDV2, resulting in numerous deaths of domestic rabbits. This created substantial confusion about which strain was released as a biocontrol tool, as well as renewed concerns amongst pet rabbit owners and rabbit farmers about the use of viruses as lethal rabbit control tools in general. Ongoing effective control of wild rabbits in Australia is absolutely essential to protect the substantial conservation gains made by the long-term suppression of rabbit numbers over the past decades, and there is currently no alternative population control tool to achieve this at the required landscape scale. Vaccine formulations need updating to protect non-target farmed and pet rabbits from circulating field variants, including RHDV2, and to increase public acceptance for the ongoing use of viral biocontrol for feral rabbit populations.

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