Increasing immunity among rabbits means the existing RHDV1, or Czech strain, has become less effective and advocates say the RHDV1 K5, also known as the Korean strain, would overcome protective antibodies and improve kill rates by up to 40%.
Federated Farmers South Canterbury high country section representative Andrew Simpson said the original RHD strain was still working to a point but growing immunity had allowed populations in some areas to recover, meaning a new, virulent strain was needed.
Rabbits less than three months of age exposed to the Czech strain became immune, which resulted in the population returning to plague proportions in some parts of the South Island.
“That is not necessarily throughout the whole island,” he said.
An application has been made to the Environment Protection Authority and Ministry for Primary Industries for approval to import the strain with a target release window of April-June this year.
Simpson said RHD was already established in NZ and the Korean strain was a derivative of that.
The applicants were determined not to have a repeat of the disorganised release in 1997 when the virus was illegally released after officials rejected the import application.
“We really want to make sure this release is done methodically and to the best possible advantage to maximise its impact.”
When it became clear in 1997 that Ministry of Agriculture and Forestry officials would decline an import application lodged by regional councils and farming interests because of what they claimed was a lack of information, farmers smuggled in a sample of the virus, which had broken out of containment trials in Australia.
A clandestine network of South Island farmers used a variety of backyard methods and recipes to spread the virus as widely and as quickly as possible so it could not be contained once officials realised.
Simpson said this time the release process would be done at the right time and strategically to ensure the maximum impact.
The approval process has been run as a Sustainable Farming Fund project and as part of that, Landcare Research would prepare a release and monitor strategy.
The Korean variant of the virus has been approved for registration by the Australian Pesticides and Veterinary Medicines Authority and Simpson said an Australian release was planned for March-April this year.
While the Czech strain infected only the European rabbit and there were no human health risks, Simpson said the virus in itself would not result in the eradication of the pest.
