Rabbits are conservatively estimated to be costing New Zealand $50 million in lost production each year and another $25 million in pest control.

A rabbit virus to be released across the country, including 100 sites in Otago, is hoped to kill more than 40 per cent of the population.

Environment Canterbury (ECan) applied in November to the Ministry for Primary Industries for approval to introduce and use the Rabbit Haemorrhagic Virus Disease RHDV1-K5 for pest rabbit management.

The K5 virus is a Korean variant of a strain that is already in New Zealand, which was illegally released here in 1997 by a collective of vigilante Otago farmers.

SUPPLIED Over 40 per cent of the rabbit population is hoped to be eradicated after the K5 virus is released nationwide.

ECan regional leader biosecurity Graham Sullivan said the virus would be released in March and April, but would not eradicate the population.

"While not the silver bullet for rabbit control, we anticipate that the new strain will greatly assist the control of wild rabbit populations by supplementing more traditional control methods.

"The controlled release will use a high-quality commercially prepared product at selected sites identified by participating local councils."

JO MCKENZIE-MCLEAN/STUFF A popular recreation spot on the shore of Lake Dunstan, in Central Otago, is being overtaken by dangerous rabbit holes.

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Otago Regional Council (ORC) director environmental monitoring and operations Scott MacLean said the approval of K5 was good news.

"Rabbits are the number one pest in Otago. Ten rabbits can eat as much grass as one sheep. They are a threat to our biodiversity, not to mention the soil degradation and loss of soil caused by rabbit holes and warrens.

"The K5 virus, which only affects the European rabbit, may give us the opportunity to reduce rabbit numbers to the level where they are manageable. It will be especially beneficial in areas where traditional rabbit management methods are either not possible or not acceptable."

ORC would release the virus in Otago in late March or April and was monitoring rabbit numbers so it could give updates on its effectiveness.

The virus would be spread nationally in a coordinated programme. There would be more than 100 release sites in Otago and the council would coordinate the release to make sure it had maximum impact, MacLean said.

"These sites were selected based on science to ensure we have the best chance of creating an epidemic and a high knock-down (kill) rate."

The virus would be released in the form of a commercially-prepared product, he said.

Rabbit Council of New Zealand member Gary Stephenson, who submitted against ECan's application, feared rabbit owners had not been given enough time to get their animals vaccinated against the "abhorrent" virus.

"There are thousands of rabbit owners up in arms and really, really worried about this … The pet rabbit population deserves the same care and protections from government and the animal welfare rights [groups] as pet cats and dogs … There are many other means of controlling wild rabbits that do not threaten pet rabbits or treat pet rabbits as collateral damage.

"I have been fighting this since June 2015 … It's absolutely abhorrent."

He said it took 21 days for a vaccination to be effective, which, if released next month, did not give pet rabbit owners much time.

High country MacKenzie Basin farmer Andrew Simpson – who represented Federated Farmers on the cross-sector group co-ordinating the K5 initiative, the Rabbit Co-ordination Group (RCG) – said there were "some desperate farmers out there".

"The timing of this is critical in some areas. If another year goes by without release of this virus, the ecological damage to some properties would be mind-numbing."

K5 was introduced into Australia last year and had reportedly been "very effective, better than anticipated. Knock-down rates are averaging above 40 per cent at the moment and in some areas they're achieving up to 80 per cent".

The operation would be run by regional councils with input from land owners and other RCG stakeholders, he said.

"No-one is under the illusion this is the silver bullet to deal to wild rabbit populations once and for all. Farmers and councils will have to continue with the other forms of rabbit control that they've employed for years.

"But with the carefully planned strategy we have in place, there is confidence this will put a major hit on what is a very expensive and environmentally damaging pest, particularly in Otago, North Canterbury, the Mackenzie, the high country, Marlborough and Hawke's Bay."

MacLean said ongoing support from the community would be important to keep rabbit numbers down after the virus started to take effect.

"The virus is just one tool to help land owners manage rabbit populations, but it doesn't replace primary methods. In areas like Moeraki and Naseby, where traditional management methods are more challenging, the virus will definitely help."

He said pet rabbit owners should discuss any virus concerns with their vet. No vaccinated pets in Australia, where the virus was released last year, had caught it.

The vaccine, which rabbit owners were already encouraged to get for their pets to protect against the existing virus, costs around $50.

Otago Regional councillor Michael Laws said agriculturalists and landowners would be relieved some assistance would soon be on hand.

"It's been a dreadfully laboured process to get approval, but we should thank the Australian scientists for all their groundbreaking work on this version.

"The 40 per cent estimated kill rate may be overly optimistic so the ORC still needs to do far more work around rabbit control in the region. Their current hands-off policy has failed. The rabbits are likely to breed an immunity to this Korean virus, so in five years time we will back to square one."

Rabbits infected with K5 developed symptoms between 24 hours and 72 hours after infection and usually died within six hours to 36 hours after the first symptoms appeared.

For more information visit the Ministry for Primary Industries' website.