Abundant rain over most of Australia in the past two years has delivered record harvests - and record numbers of rabbits, news reports say.

Farmers thought the intentional release of the rabbit-borne calicivirus in the 1990s would knock out a feral population of the non-native, invasive species that was beginning to recover after the devastating effect of the release of the disease myxomatosis in 1950.

Young rabbits not killed by the calicivirus are immune to it and have thrived in the post-drought period in a country that sees millions of dollars in damage to its crops, erosion and species loss because of the animals.

"Numbers are now back around those numbers that we saw pre-calicivirus," John Matthews, a pest control officer in the Victorian state government, told the national broadcaster ABC.

Before myxomatosis carried off an estimated one-sixth of the rabbit population, an estimated 600 million rabbits roamed the Australian continent.

Scientists are working on new strains of the calicivirus.