Science

Does the rabbit virus ‘RHDV2’ have an advantage over ‘RHDV1’ strains?

RHDV2

Rabbit haemorrhagic disease virus 2 (known as RHDV2) is a novel virus that has rapidly spread and become the dominant calicivirus in wild rabbits worldwide, including in Australia, where it is suggested to have arrived in 2014.

Our Centre’s national rabbit biocontrol research team, consisting of staff from our member organisations, CSIRO, NSW Department of Primary Industries (DPI) and Primary Industries and Regions SA (PIRSA), have analysed more than 3,900 wild rabbit blood samples, which were collected over a seven-year period (2011-2018) from 12 Australian sites (VIC, NSW, QLD, WA, SA, ACT) to further understand the epidemiology of RHDV2.

RHDV2 has been hypothesised to have several competitive advantages over RHDV1, including an ability to lethally infect very young rabbits, which RHDV1 cannot. However, if or how RHDV2’s differences provide it a competitive advantage in the field, in wild rabbits, has never been shown.

This was the topic of the team’s most recent paper, published in the journal Transboundary and Emerging Diseases.

After analysing all samples for RHDV1 and RHDV2 antibodies they found that since the arrival of RHDV2 in Australia, seasonal virus transmission has changed and in fact shifted forward by several months.

What does this mean?

The study found that the ability of RHDV2 to infect younger rabbits allows it to enter and disseminate/transmit within wild rabbit populations several months prior to RHDV1. This means that RHDV2 removes the rabbits from the population that would have later become susceptible to RHDV1, and facilitated its dissemination/transmission in several months’ time. This simultaneously allows RHDV2 to rapidly spread and dominate, while limiting the transmission of RHDV1 within rabbit populations.

Does this new research have management implications?

Yes, it does!

The authors suggest that when rabbit impacts are being managed on small scales in local populations, it is important to consider factors such as rabbit age, abundance, the timing of virus release and the time elapsed since RCV‐A1 (a benign strain) last moved through the population, prior to undertaking a release program using RHDV1 strains.

However, the authors suggest that on large scales, and at the overall population level, many of these factors have only weak effects on the ability of RHDV1 and RHDV2 to transmit naturally and effectively reduce rabbit numbers.

The authors recommend that agencies who may be releasing virus at a landscape scale should most strongly consider the timing of releases if their aim is to maximise virus transmission and subsequent reductions in rabbit populations.

You can view the full research paper here – https://onlinelibrary-wiley-com.ezproxy.canberra.edu.au/doi/full/10.1111/tbed.14071

The Centre for Invasive Species Solutions rabbit biocontrol research program receives direct funding from Australian Wool Innovation, Meat and Livestock Australia and the Australian Government Department of Agriculture, Water and Environment. Project partners leading the research include the CSIRO, NSW DPI and PIRSA.

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