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By  Ian Dewar 22 February 2024 6 min read

Key points

  • Citizen science has increased surveillance of viruses in rabbits and hares.
  • Improved surveillance enabled early detection of the arrival of Rabbit Haemorrhagic Disease Virus type 2 (RHDV2).
  • We’re tracking evolution of these viruses across Australia to inform rabbit management and future biocontrol.

Citizen science is the special sauce in our ongoing rabbit biocontrol program.

Samples collected by Australian citizen scientists show the distribution and genetic diversity of viruses affecting rabbits and hares across the country.

Rascally rabbits on the rampage

Feral rabbits are one of the most destructive invasive pest species in Australia. They’re estimated to cost around $239 million per year to the agricultural industry alone.

Rabbits eat pasture and crops, compete with native animals, cause soil erosion, and prevent regeneration of native vegetation. This leads to loss of plant biodiversity and reduced crop yields.

Rabbit haemorrhagic disease virus (RHDV) is also known as Rabbit Calicivirus or Lagovirus. It is used as a biocontrol agent to manage rabbit populations across Australia. RHDV is a form of hepatitis that attacks the liver, so it is most easily detected by testing liver samples. It only infects rabbits and hares and is highly contagious with high mortality rates for infected animals.

The biocontrol backstory

Our research is focused on understanding rabbit viruses in Australia and how we can use biocontrol to manage wild rabbits. Such efforts are designed to support the health of our vulnerable ecosystems.

Extensive economic analysis has told us that classical viral biocontrol of rabbits is unparalleled when it comes to effectiveness, safety and cost benefit.

However, it’s crucial to have a thorough understanding of naturally-circulating viruses in wild rabbit populations before implementing any new biocontrol tools.

So, we need to be able to detect new recombinant versions of RHDV as they emerge. We also need to monitor declines in older variants, because they can impact the effectiveness of future forms of biocontrol.

 European rabbit (Oryctolagus cuniculus) in Eastern Australia two brown rabbits on brown background
Feral rabbits are one of our most destructive invasive pest species in Australia ©  CSIRO

Citizen science to the rescue

Dr Nias Peng is a virologist with us. He said that rabbit disease testing from tissue samples supplied by members of the public was added to an existing citizen science program called RabbitScan in 2015.

“It’s the longest running citizen science survey of rabbit diseases in the world. We now have nine years of data,” Nias said.

Samples are submitted either directly to our rabbit team or through RabbitScan itself.

Citizen science sampling with lab-based molecular analysis makes for a powerful combination. Scientist Dr Maria Jenckel said it has been key to tracking rabbit viruses across Australia.

“It goes beyond ‘who saw what where’ survey data to scientific testing. This testing shows exactly which viruses are present and how the virus populations across Australia are evolving,” Maria said.

“It takes a little time for our citizen scientists to take the sample. However, it’s a free service and we publish the results online on our research site.”

Ina Smith is our Rabbit Research Team Lead. She said the free test kits explain how to collect and store samples for delivery to our testing laboratory.

“Citizen scientists take a sample of liver tissue. They then store it in an RNA stabilisation solution and send it to us for analysis,” Ina said.

If samples are ample then data is smarter

The citizen science project helped to expand the sampling area for rabbit viruses right across Australia. This meant our researchers could conduct in-depth analysis on lagovirus distribution, genetic diversity and interactions.

From January 2015 to December 2022, a total of 2771 samples were tested. Most were lagovirus-positive (60 per cent). On average 345 samples were submitted each year.

Nias said citizen science is a great way to increase sampling, build big datasets and involve the public in impactful research.

“The big boost from a citizen science project like this is the huge increase in samples for scientists to work on. It just gives much wider coverage across Australia and a bigger number of samples than we’d be able to collect ourselves,” Nias said.

Between 2007 and 2014, before the project, fewer than 30 samples were tested annually for lagoviruses. Ina added that there was no systematic national molecular testing of lagoviruses.

“Now, we get samples in every week, so we’re able to track the viruses in the field in real time. We can see the peaks and troughs, seasonal effects and what viruses are where,” Ina said.

Rabbits are one of Australia's most widespread and destructive pest animals threatening the viability of native plant and animal species. They contribute to soil erosion by removing vegetation and disturbing soil and they compete with native wildlife for food and shelter, increasing their exposure to the danger of predators. ©  Liz Poon CSIRO

Down the hutch – the role of domestic rabbits

For the first few years, most samples came from wild rabbits. But from 2018, following the wrap up of the national release of RHDV-K5, the number of wild rabbit sample submissions decreased.

“This could be due to fewer reminders to submit samples after the end of the release project and a decrease in wild rabbit population and sightings,” Ina said.

“This RHDV virus is pretty hardy. So, even if the dead rabbit lies in the sun for two weeks we can still test if it is positive,” Ina said.

Now most samples come from domestic rabbits. These can be submitted by owners or vets.

“Domestic rabbits are great sentinels for what is happening in wild rabbit populations locally. They give a good indication of the lagovirus variants circulating in wild rabbit populations,” Nias said.

And domestic rabbit owners are grateful for advice on how to decontaminate and protect their pet rabbits from these viruses.

“It can also be hard to get people who see a wild rabbit to pick it up, take a sample and send it to us,” Maria added.

“Domestic rabbit owners are more aware of the program and motivated to get their deceased rabbits diagnosed so they know how to protect their pets.”

Hare-raising lagovirus variants emerge

Rabbit caliciviruses recombine to generate new variants. This is happening much more frequently than our researchers first anticipated. This means the viruses take on genetic information from other circulating rabbit calicviruses as they constantly evolve in the wild. Lagoviruses had at least six recombination events between 2014 and 2020 in Australia.

Four different lagovirus recombinants have been detected in Australia to date. Two are exotic arrivals and two emerged locally as new types of RHDV2 evolved. From 2020 the dominant variant has been RHDV2-4c.

“Without the depth of sampling provided by our citizen scientists, we wouldn’t be able to do this level of analysis to understand the evolution of these viruses,” Nias said.

“These contributions ultimately inform biosecurity and conservation decisions to benefit the environment and our native biodiversity in the longer term. As a result, they will have a big impact."

European rabbit (Oryctolagus cuniculus) specimen on green background

Teamwork makes the dream work

Our citizen science-based program is key to monitoring rabbit viruses in Australia. It engages members of the public directly in vital sample collection which contributes to our rabbit team's research for long-term impact.

Maria encourages community members from across Australia, particularly in rural and regional areas, to continue contributing samples.

“This is really practical applied science – it’s not just some theoretical study in a laboratory. It’s about seeing what’s happening out in the Australian environment and finding solutions for rabbit management for the future,” Maria said.

We want to thank all our citizen scientists for submitting samples!

Funding for this program was originally provided by the Australian Government through the Invasive Animals CRC, the Centre for Invasive Species Solutions and CSIRO. Funding to continue the program is being provided by the Australian Department of Agriculture, Fisheries and Forestry.

Our research is focused on understanding rabbit viruses in Australia and how we can use biocontrol to manage wild rabbits. ©  CSIRO

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