Scientists in New Zealand and Australia are looking to see whether more effective strains of rabbit calicivirus disease exist.
Otago Regional Council director of services Jeff Donaldson says rabbit numbers are booming in the Upper Clutha basin and near Cromwell, with rabbits building up a natural resistance to the calicivirus, which causes severe internal bleeding.
Almost three quarters of the rabbits in Otago are immune to the disease - and on some farms it's 100%, he says.
Scientists in New Zealand and Australia are looking at new strains of the disease to see if they could be more successful in controlling rabbit populations.
"But it has been identified in Europe that new strains are outcompeting the original strains in the field and are certainly suppressing wild rabbit populations," Mr Donaldson said.
However, it will take years of research to discover if the new strains will work or not.
In 1997, the calicivirus was illegally imported and released in New Zealand before being deliberately and illegally spread by farmers.
The Parliamentary Commissioner for the Environment described its importation and spread as an incredible breach of New Zealand's biosecurity.