Creating better tomorrows for all pet rabbits
For Vet professionals
A very interesting 30-minute discussion between Dr Richard Saunders BVSc BSc CertZooMed DZooMed (Mammalian) FRCVS and Dr John Chitty BVetMed CertZooMed MRCVS covering the current situation of RVHD2 in the UK, recommended vaccination protocol, the benefits of giving two vaccines, and how it could work in practice.
Update regarding vaccines for RVHD2 HV
We are aware of differing opinions relating to the new highly virulent strain (HV) of RVHD2 and the effectiveness of rabbit vaccines against it. To put it very simply, Yurvac is tested and licenced against the new HV strains, and Nobivac Myxo RHD Plus is not.
We are not, advising that people stop vaccinating rabbits with Nobivac Myxo-RHD PLUS, and have not at any point done so. This is a vital vaccine for rabbits. We are advising that people additionally vaccinate rabbits with Yurvac.
There is a more detailed version of this here, but in summary:
- We are not and have never called for anyone to stop vaccinating with MSD’s Nobivac Myxo-RHD PLUS vaccine. We would, if anything, suggest that vaccine manufacturers, vets, NGOs and other organisations take this as an opportunity to improve rabbit health and welfare by increasing the proportion of rabbits vaccinated with this. Current figures suggest only about half of rabbits are regularly vaccinated (https://www.pdsa.org.uk/what-we-do/pdsa-animal-wellbeing-report/paw-report-2024/rabbits). We simply feel, in our opinion, that the evidence base currently suggests that this vaccine alone may not be enough, and an additional vaccine may be required, if not now, then very soon.
- There appears to be a contradiction in MSD’s statement here, in stating “To date, we have not seen any confirmed, scientific evidence of new, highly virulent variants of RVHD2 circulating within rabbit populations” and “extensive searches…are all negative for evidence of a new highly virulent RVHD2 strain” with MSD’s statement: “Nobivac Myxo-RHD PLUS has been tested against highly virulent field isolates of RVHD2…Nobivac Myxo-RHD PLUS has been shown to be very effective against field strains of RVHD2 including a highly virulent isolate from Italy in 2015” and “Previous reports and analysis of highly virulent RVHD2 strains“.
- The HV strain mentioned above is from 2015. Things have changed since then, with increasing virulence mentioned by a number of papers. The full version and references are available here
- 2 presentations at the WRC 2024 specifically identify 2 strains of highly virulent RVHD2, from France in 2020 and the Netherlands in 2022.
- Yurvac was developed in 2021, 6 years after the most recent testing mentioned by MSD for their vaccine.
- Tokarz-Deptuła et al (2024) and Cavadini et al (2024) raise, what in my opinion is the worrying proposition that both RVHD1 and RVHD2 can co-exist in other wild mammals, and this could lead to more stable and better protected versions of RVHD in the future, if not already present.
- We fully accept that there is only patchy evidence of HV strains present in the rabbit population, especially in the UK. However, this is because, at present, the existing PCR tests for RVHD can only differentiate between RVHD1 and RVHD2, and not between strains of RVHD2. For that, bespoke genetic probes need to be developed. We are working towards this, but our resources, as a small charity, are limited.
- We understand MSD’s theory that Nobivac Myxo-RHD PLUS should be effective against HV strains. However, we have to take a precautionary approach here, and cannot ignore the fact that there is currently only one vaccine available in the UK to be proven in peer reviewed studies to be effective against the HV strain.
- Finally, we should point out that Yurvac has an SPC, granted very specifically by the European Medicines Agency, for protection against “highly virulent strains” (https://www.ema.europa.eu/en/documents/smop/cvmp-post-authorisation-summary-positive-opinion-yurvac-vra-0001_en.pdf). We suggest that anyone who wishes to debate the efficacy of this vaccine vs other vaccines without that licensing wording take it up with the appropriate authority, the EMA, and not a small UK rabbit charity.
RVHD2 “High Virulence” strain
We are aware that there is, sadly, yet another strain of Rabbit Viral Haemorrhagic disease out there. It has been referred to by researchers as “virulent” or “highly virulent” RVHD2. It’s not related to the K5 strain seen in Australasia (which is closest to RVHD1), making referring to it as 2k or k2 (as some online are doing) incorrect and confusing.
It has been detected in Hungary, France, Northern Italy and the Netherlands, where it makes up approximately 50% of the cases seen (the other 50% being “classical” RVHD2. RVHD1 is barely seen at present, but see above).
As yet, we can’t be sure of its presence in the UK, as no work has been done to look for it. We are in the process of setting up surveillance for it, but we know from past experience with previous strains that it is only a matter of time before it gets here if it’s not here already, so I feel that it is best to act on the precautionary principle and make plans.
There is currently no data available on Nobivac Myxo-RHD Plus with regard to this strain. There is currently no published work to demonstrate the efficacy of any vaccine against this new strain, apart from the new Hipra one (YURVAC RHD) (see downloads below), but we will update our information and advice according to any new research as it comes through. We will continue to follow the scientific evidence base, advise the use of licensed products where possible, and follow the Veterinary Cascade.
The new vaccine is being produced by Hipra and is called YURVAC RHD. For any queries relating to this vaccine, please contact Hipra directly. It will replace ERAVAC, their current RVHD2 vaccine, when it comes out. It arrived in early December 2024 wholesalers in 40 vial doses, with the 10 x 1 vial doses being available in January 2025. The initial 40 vial doses are now out of stock with new stocks expected in March 2025. Once breached, the vaccines must be used in 10 hours.
Whilst vaccination sessions could be offered so that any owners who want to vaccinate in December can be invited in and make use of the 40-dose vial, this is fraught with difficulty from a practical biosecurity perspective. It requires changing PPE and adequate cleaning of all areas one household/ rabbit has been in before another comes in. This often requires prolonged contact times, slowing the rate at which rabbits can be safely vaccinated. We would advise caution if carrying out multi-household vaccination clinics unless such strict biosecurity can be enforced.
We suggest contacting any local rabbit rescues and inviting them to vaccinate their rabbits, as they are likely to have sufficient numbers, and to be at relatively much higher risk due to constant new arrivals. Individual rabbits and small groups are both at higher risk if vaccinated en-masse and at a lower risk of infection, as biosecurity is easier for those households. The more rapid onset of protection of YURVAC RHD also makes this more suitable for vaccination in the face of infection.
This situation may change as the smaller vials become available.
This vaccine covers the “classical” RVHD2 strain and RVHD1, but not myxomatosis. Because of the restriction placed on us by the Veterinary Medicine Directorate we are not able to provide the names of any vaccinations to rabbit guardians and caregivers, only to clinicians such as vets. We are giving general info on RVHD2 to owners and advising them to speak to their veterinary practice for more information.
We are attaching some papers which you might find interesting; any questions on these papers can be directed to Hipra directly.
Testing for RVHD1/2 can be done by PCR, and we would recommend that where the cause of disease or death is unclear or RVHD is suspected. But, at present, there isn’t a test which can differentiate between the old and new strains of RVHD2, so it’s impossible to tell whether it’s the standard or high virulence strain without using testing methods which aren’t commercially available. We are looking into the possibility of genetic sequencing testing currently.
In light of many reports online, it is clear that some of you have lost client’s rabbits to RVHD2, some of which may be from the new, highly virulent strain. Reporting any such cases will provide more data to help guide the most effective vaccine use. If you have had a patient of yours acquire, or die from, suspected RVHD after vaccination, please could you report it via the scheme below, as well as to the vaccine manufacturers MSD and/or Hipra directly, or email adverse.events@vmd.gov.uk
At present our vaccination advice is firstly to ensure that all rabbits are fully up to date with the Nobivac vaccine. We would advise offering both Nobivac Myxo-RHD Plus and YURVAC RHD to large groups of rabbits at higher risk of catching RVHD2 HV, such as rescues and shelters, but the risk: benefit decision is far more challenging in smaller groups, and that should be at the discretion of the individual practice, after discussion with owners. This is likely to change when smaller vials become available, and also as more information becomes available.
We would suggest that once rolling it out to all rabbits, the aim would be to eventually give the two vaccines 6 months apart to ensure that the rabbits get regular vet checkups. However, as we are advising all owners to get their rabbits protected by YURVAC RHD as soon as it is safe and beneficial to do so, we would suggest initially giving Nobivac and YURVAC RHD at least 2 weeks apart and then spacing them out further over subsequent boosters.
It’s also worth pointing out, just to confuse things even more, that the use, by breeders in the UK, of stand-alone Myxomatosis vaccines imported under an SPC could interfere with the efficacy of later Nobivac protection against RVHD2. (From MSD’s website: ‘Rabbits that have been vaccinated previously with another myxomatosis vaccine, or that have experienced natural myxomatosis infection in the field, may not develop an adequate immune response against rabbit haemorrhagic disease following vaccination.’). As breeders often have large groups of rabbits, they may approach veterinary practices regarding the new vaccine.
We expect there to be a lot of discussion as this situation emerges. Unfortunately, we cannot answer lots of individual questions about this, so can we please encourage everyone to join our Facebook group for veterinary professionals, where we can all share questions and knowledge? This advice is likely to be updated as events develop. This edition was produced on Dec 17th 2024.
Richard Saunders (he/him) BSc (Hons) BVSc FRSB CBiol DZooMed (Mammalian) DipECZM(ZHM) FHEA FRCVS
Rabbit Welfare Association and Fund Veterinary Advisor