Dr Brian Cooke, a front line warrior in the nation’s never-ending rabbit wars, says the animals have developed “some sort” of resistance to the virus and in some populations had moved from 100 per cent infection rate to just 30pc.

“Ten years ago in north-west Victoria we would count one rabbit every two kilometres at night with a spotlight but now it is getting up to five or six a kilometere,” said Dr Cooke, who this month will start a three-year project that will study wild rabbits that show resistance to the present string of calicivirus.

According to the scientist, who heads up the Invasive Animals Co-operative Research Centre at the University of Canberra, up to ten strains of the calicivirus could be imported from parts of Europe, including Spain and Holland and potentialy China.

“We’ve only introduced one strain and this has limited effectiveness in cooler, wetter environments, that coincide with prime agricultural regions and many threatened ecological communities and species,” Dr Cooke said this week.

In Europe having diversity in rabbit controlling viruses has kept wild populations in check, a situation Dr Cooke said his team is hoping to emulate in Australia.

The project release comes in the wake of the 150th anniversary since Victorian grazier Thomas Austin released 12 pairs of rabbits on his property near Winchelsea for recreational hunting – and in doing so introduced the country’s biggest feral pest.

Rabbits cause more than $208 million in damage each year by grazing and burrowing.

In NSW alone, they impact 86 threatened species.

“Rabbit calicivirus has been estimated to save producers around $400 million a year, but with the rabbits coming back again it’s going to have immense economic problems,” he said.

A female rabbit has the ability to produce up to 40 offspring per annum and as a result can quickly built up resistance.