RVHD2 update, August 2017

For the latest advice please see this post.

Cases of new variant rabbit haemorrhagic disease (RHD2) continue to be reported on a regular basis. Several laboratories will undertake PCR testing for RHD2 and it is now possible to test samples from live animals, making it quicker and easier to diagnose and more likely to get owner agreement for testing. However, these are PCR tests which depend on the virus being present in the blood or shed into urine and faeces, and so a negative is not conclusive, although a positive is. Liver remains the best sample for testing in the post mortem rabbit.

During 2016, in the absence of an effective UK-licenced vaccine to protect against RHD2, we arranged for the import of a number of RHD2 vaccines from around Europe. Filavac VHD K C+V, manufactured by Filavie, has been the main vaccine imported, primarily due to its proven efficacy, safety and availability in single dose vials. In the ten months Filavac was being imported through the Special Import scheme, 3420 special import certificates (SIC) were granted, making it the second most granted SIC over that period. Based on an earlier Freedom of Information Act request, we estimate that this accounts for nearly 100,000 doses of the vaccine, almost certainly making it the most imported medicine of 2016 by some significant margin.

In October 2016, Eravac RHD2 became the first RHD2 vaccine to receive an EU-wide licence, making it available in the UK without the need for an import licence. This has now been followed by Filavac, which received its UK licence in April 2017. The fact that two separate companies have gone to the trouble and expense of getting their products licenced indicates that they believe there to be sufficient clinical need and ongoing product demand to make this investment worthwhile.

We anticipate that Filavac will become the main product used in UK veterinary practices due to its availability in single dose vials and information on efficacy and vaccination protocol for pet rabbits, requiring only a single booster every 12m in normal circumstances. Eravac is only available in multi-dose vials, and the vaccine is oil adjuvanted, presenting a risk to the user in the event of accidental self-injection. Its vaccination protocol and efficacy data is also less clear from its EU authorisation, with a booster currently recommended by the manufacturer every 6 months.

While in most circumstances we believe that Filavac is the more appropriate choice, it is still not perfect for use in the UK alongside Nobivac myxo-rhd, the only licenced recombinant vaccine against myxomatosis and classic RHD. The Filavac is not only effective against RHD2; it is a dual vaccine which also includes protection against classic RHD. This means that rabbits will receive duplicate vaccines against classic RHD when they are vaccinated according to the protocols for each product. While the benefits are thought to outweigh the risks, it is nevertheless not ideal. Multiple vet visits is also more likely to reduce owner compliance. The ideal situation would be the development of a single vaccine incorporating protection against myxomatosis, classic RHD and RHD2, allowing full protection without multiple visits or duplication of agents. Alternatively, a vaccine combining myxomatosis with RHD2 rather than classic RHD would provide cover for the increasingly prevalent and dominant strain reported in the UK.All recent reports of strain specific testing for RHD received by the RWAF have been for type 2, and so it is concluded that this has become the most prevalent virus strain now.

Now there are two RHD2 vaccines authorised for use in the UK, our priority is to continue raising awareness of RHD2 and the availability/selection of vaccines among veterinary professionals and pharmaceutical companies. We believe that RHD2 is a real and continuing threat to pet rabbits and this view is validated by two companies now producing an RHD2 vaccine for the UK market. We therefore aim to ensure that the UK’s pet rabbits are protected against RHD2 as well as myxomatosis and classic RHD in the most effective and straightforward manner, ideally in a single vaccine to maximise owner compliance and minimise rabbit stress.

In the past few years, anecdotally we have also observed an increasing number of reports of rabbits vaccinated with Nobivac myxo-rhd contracting serious cases of myxomatosis, with more than may be expected dying as a result. Whether this is a result of mutating strains which are not covered as effectively by the existing vaccine, or whether there are other reasons (such as latent RHD2 infection) for insufficient immune response is not yet understood. If further work is to be undertaken to create a new recombinant vaccine incorporating RHD2, would urge that the efficacy of the myxomatosis element of the vaccine be considered as part of this review.

Please also read our post from January on RVHD2 & Filavac with FAQs