Neds Corner Station is so vast that contract rabbit controller Trent Wilkin has to use an extensive grid map — like that used to search for missing flight MH370 — to pinpoint the location of warrens.

"The quad bikes don't like it much," he said, as he prepared for another search-and-destroy mission across the 30,000-hectares of harsh scrub land of the former sheep station just west of Mildura.

"We look for their scratching. It gives away where the warrens might be. We throw a tablet down each hole, fill them in by hand."

As well as toxic tablets, Victoria's largest nature reserve is littered with carrots laced with RHDV-K5, a new virus rolled out in March over some 600 sites across the country.

Most have reported good results in the control of their rabbit pests.

Contractor Trent Wilkins' GPS maps rabbit warrens at Neds Corner Station in north-west Victoria. ( Supplied: Peter Barnes )

But for Peter Barnes, the manager of Neds Corner, there has been both good news and bad news.

The good news is there are fewer rabbits. The bad news is they can not find the dead ones.

"To date we haven't had a positively identified rabbit death," he said.

"We like to think that it has worked through the property but we can't confirm that, which is a bit disappointing."

Mr Barnes said evidence of depleted rabbit number was obvious as land that was once eroded by rabbit grazing is now regenerating and sightings of live rabbits are fewer.

But dead rabbits were needed for forensic analysis to prove that RHDV-K5 is the culprit.

"Some of the rabbits will get back in to the warren before they die, so possibly some have done that," he said.

Neds Corner Station manager Peter Barnes is always on the look out for rabbits on the nature reserve. ( ABC Rural: Cherie von Hörchner )

"Others die on the trails where you will pick them up, and we just haven't found that at the moment.

"It could be the other viruses. Or whatever."

Since Neds Corner was purchased by the Trust for Nature organisation in 2002, a variety of methods had been deployed to reduce the rabbit numbers that had seriously degraded the ecosystem on the 168-year-old station.

Four known rabbit caliciviruses in Australia: RHDV1: escaped from quarantine on Wardang Island, SA, in 1995 and officially released following year. Killed up to 90 per cent of rabbit population

RHDV1: escaped from quarantine on Wardang Island, SA, in 1995 and officially released following year. Killed up to 90 per cent of rabbit population Benign calicivirus: not known how long it has been in Australia. Does not kill rabbits but enables immunity against other caliciviruses. More common in cool, wet districts

Benign calicivirus: not known how long it has been in Australia. Does not kill rabbits but enables immunity against other caliciviruses. More common in cool, wet districts RHDV2: first identified in ACT in 2016. Not known how it came to Australia. Current vaccine doesn't protect against it

RHDV2: first identified in ACT in 2016. Not known how it came to Australia. Current vaccine doesn't protect against it RHDV-K5: Korean strain, was released nationally in March 2017

"Rabbits are a major influence on biodiversity and they're just such a massive job across the whole community," Mr Barnes said.

"We've done so many works on Neds Corner and now we're starting to see the results.

"When the numbers are low it allows for re-vegetation projects to happen. We've had wonderful regeneration in the local species."

But until a dead rabbit can be found and tested, proof of the effectiveness of RHDV-K5 will remain elusive.

"You get the reptiles and cats and foxes taking rabbits, so that could possibly happen," he said.

"It's such a vast area, and most of our immediate surveys were only within a couple of hundred metres of our bait release sites.

"So it's highly likely that we can miss the rabbits, just because of the vastness of the area."