Rabbit virus working as expected: Science behind RHDV1-K5

Rabbit Virus Update

Rabbit virus working as expected – Science behind the RHDV1-K5.

Friday 1st June 2018

It’s been several weeks since regional councils began the nationwide release of the RHDV1-K5 rabbit virus in New Zealand.

Following extensive overseas research, the Rabbit Haemorrhagic Virus Disease (RHDV) RHDV1-K5 was released by councils at more than 150 sites across New Zealand as a longer term biocontrol for pest rabbit management.

Manaaki Whenua Landcare Research is leading the science behind the virus. Since the release, research teams have been intensely monitoring sites, to study the impact of the virus and how well it is establishing.

‘So first thing we wanted to know was whether the virus was killing rabbits within 5 km’s of our release sites and that seems to be the case - so far we’ve detected the RHDV1-K5 from carcasses at all of the research sites,’ says Manaaki Whenua Lead Researcher Dr Janine Duckworth.

The Ministry for Primary Industries (MPI) approved applications for the importation and release of the RHDV1 K5, to help reduce the significant environmental and agricultural impacts caused by wild rabbits.

The virus is a Korean variant of a virus that is already in New Zealand, which was illegally released in 1997. But questions have been asked as to why every farmer is not seeing dramatic numbers of dead rabbits on their property.

The answer is simple - it was never expected to act that way. RHDV1-K5 is expected to improve rabbit knockdown by up to 40% above the current strain and results will vary with the location and the number of susceptible animals within the population. “One of the major differences with this virus release is the rabbits have already seen RHDV type viruses and have built up some antibodies against them, so it’s not going to see the huge 80-90% die off that we saw back in 1997, but it will be more effective over time,” she said.

“When you use a biocide it only affects the rabbits that eat the virus and then they die within one to two weeks. With a natural spread, the infection builds much more gradually but we see a longer period of infection. It will be six to eight weeks that the virus will still be slowly spreading through a rabbit population and we want to see this virus establish and be here long term as a new biocontrol agent,’ said Dr Duckworth.

Now the research focus is on finding out how quickly the virus is moving away from the release sites through natural spread to infect nearby rabbit populations.

“RHDV spreads either from rabbit to rabbit contact, contact of rabbits with feces from an infected rabbit, or from bedding material. But it also spreads across the land much faster than it could by rabbit to rabbit contact, and what we believe is that it’s the flies that are carrying the virus from one area to another,” she said.

Ongoing monitoring and research is continuing with the project. Spotlight night counts of rabbit populations are underway and are expected to be completed in a few weeks’ time.

To find out more about the RHDV1-K5 virus go to: https://www.landcareresearch.co.nz/science/plants-animalsfungi/animals/vertebrate-pests/biological-control-of-rabbits

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