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2025 Calicivirus release: April update

Peel Harvey Biosecurity Group (PHBG) recently carried out a targeted release of calicivirus, or rabbit hemorrhagic disease (RDHV), to help manage feral rabbit populations across the Peel-Harvey region. This initiative is an annual effort and forms part of PHBG’s ongoing pest control efforts in cooperation with the community and local government.


Blood testing results

Before the release, PHBG collected 38 blood samples from rabbits across its operational area to test for calicivirus antibodies, which indicate immunity to the virus. Blood samples from 38 rabbits were analysed. The results showed that 21% tested positive for RHDV1 antibodies, while 66% carried antibodies for RHDV2 — the dominant wild strain. Rabbits can test positive for antibodies of both strains. The high presence of antibodies indicated that a region-wide calicivirus release would be ineffective at reducing rabbit numbers. 

Community participation

A total of 54 landholders registered to take part in the blood drive across five local government areas. Landholders who registered from areas of high immunity levels were not able to take part, meaning that only nine properties participated in the PHBG release of RDHV1 K5 and Czech calicivirus strains on 31 March 2025. 

Next steps

PHBG is currently gathering post-release monitoring data, with results expected by the end of April. Participating landholders are recording rabbit numbers before and after the release to help assess its effectiveness.

Ongoing blood collection, coordinated by PHBG, will further support the mapping of immunity to both RHDV1 and RHDV2 across the region. We are partnering with local pest control providers to obtain additional samples. Landholders who also wish to be involved can contact the PHBG. 

Implications of 2025 program

Blood testing conducted over the summer confirmed that calicivirus immunity levels are high across the Peel-Harvey region. This significantly reduces the effectiveness of RHDV1 K5 as a control option, limiting its viability for most landholders.
Calicivirus has never been a silver bullet to the rabbit problem — it works best when combined with other methods, such as warren destruction and baiting. Additionally, to lower immunity levels amongst a resident population, follow-up control is needed while a biocontrol like calicivirus is active in an area (either through natural spreading or a coordinated intentional release). 
PHBG strongly encourages landholders to adopt an integrated approach to rabbit management. Information on effective control strategies and how to implement them is available on the PHBG website. Landholders are also welcome to call us for a chat about how best to manage rabbit infestations.

While annual calicivirus releases will continue, ongoing blood testing and close coordination with landholders will ensure that future releases are targeted, efficient and supported by data, reducing the time and effort required to reduce rabbit numbers. 

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