Perspectives on RHDV Vaccines from Alicia McLaughlin, DVM, at The Center for Bird and Exotic Animal Medicine

Oct 17, 2021 by Christie Taylor

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We wanted to update our clients about a new development in the battle against Rabbit Hemorrhagic Disease Virus Variant 2 (RHDV2).

TL;DR – there is now a domestically produced RHDV2 vaccine available from Medgene on an emergency-use basis (it is not yet USDA approved). We are going to finish using our current stock of Filavac vaccines before ordering Medgene’s vaccines for a variety of reasons listed below.

BACKGROUND:
Rabbit Hemorrhagic Disease Virus Variant 2 (RHDV2) is a highly contagious viral disease of domestic and wild rabbits caused by a Calicivirus. Morbidity and mortality rates are very high (up to 100%), and symptoms range from lethargy and bloody discharge from multiple orifices to sudden death. Historically, this virus was categorized as a foreign animal disease, meaning that it was not present in the US. However, in 2019-early 2020, RHDV2 was confirmed to be the cause of multiple rabbit deaths in several locations in Washington State (San Juan Islands, Whidbey Island, and Clallam County). A more virulent strain of RHDV2 spread across the southwestern United States in summer 2020 and was able to infect native lagomorph populations such as cottontail rabbits and hares, even though the disease had previously only been reported only in European rabbits (the species kept domestically in the United States). As it will be extremely difficult to eliminate this disease from the wild population due to issues regarding cost, vaccine technology, and other logistics, this disease is likely going to become endemic to the US from now on. RHDV2 was found recently in both Portland, OR, and Boise, ID, so it is very likely that it will show up in WA state again in 2021.

CBEAM’s own Dr. McLaughlin was the first veterinarian in the United States to successfully obtain a permit from the federal government to import vaccines against this virus from Europe. The brand of vaccine that the Washington state vet permitted to be imported was Filavac, which is made in France and protects against both RHDV1 and RHDV2. (Follow this link to see the data sheet for the vaccine: https://mri.cts-mrp.eu/…/dow…/FR_V_0315_001_FinalSPC.pdf).

This vaccine is very safe and has been shown to be 90% effective at preventing both strains of RHDV. A single dose of Filavac is protective against RHDV infection 7 days after administration. Filavac is a killed vaccine, meaning that vaccinated rabbits will NOT infect non-vaccinated animals and they do not become carriers of the disease. Rabbits must be at least 10 weeks old in order to receive the vaccine. Here is a link to a paper looking at protective nature of Filavac vaccine against a wild-type strain of RHD2 in France (the same genotype as the virus identified in WA): https://polipapers.upv.es/…/wrs/article/view/11082/11767.
In this study, all but 1 of the unvaccinated rabbits died following exposure to the disease, while all of the vaccinated rabbits remained healthy. The vaccine is licensed overseas to be effective for at least 1 year for 90% of vaccinated animals (some rabbits had immunity for 18 months according to Morin et al, 2015 in Journées de la Recherche Cunicole).

NEW VACCINE AVAILABLE!
A brand new, domestically produced, recombinant-technology vaccine made by Medgene Labs is currently undergoing the USDA approval process, and this week it was made available for veterinarians in some states (including WA) to use on an emergency basis.

https://medgenelabs.com/rhdv2-vaccine/ This is great news since it eliminates the need for the complicated international vaccine importation process, which will make it easier to get more rabbits vaccinated for RHDV2.

The Medgene vaccine shares several similarities with Filavac, including:
– Administered subcutaneously
– High levels of efficacy (trials showed that none of the vaccinated rabbits died after being exposed to RHDV2)
– Neither vaccine can infect rabbits with the virus or make them carriers of the virus
There are quite a few differences as well:
– Medgene vaccine only protects against RHDV2, not RHDV1.
– Medgene utilizes cutting edge recombinant technology to make their vaccine, while Filavac uses a killed/inactivated virus
– Medgene’s vaccine can be administered as early as 4 weeks of age (sooner than Filavac).
– Medgene’s vaccine requires administration of 2 doses three weeks apart, and protective antibodies are not produced until 35 days after the 1st dose (compared to Filavac’s single dose that is protective 7 days later).
– Medgene vaccine is currently only available in multi-dose vials that must be used up completely within hours of opening them, which makes stock management and appointment scheduling more complicated for veterinarians.
– We don’t yet know how frequently this vaccine will need to be boostered to remain effective since it is brand new, but the company is currently expecting an annual (single dose) booster will be necessary.

We still have several hundred doses of Filavac. After we use up our Filavac stock, we will be switching over to using this new vaccine, as the government will not renew licenses to import vaccines now that there is a domestically produced version available. We will charge less for each dose of the Medgene vaccine compared to the Filavac vaccine ($17.50 instead of $35.00 per vaccine) because we do not have to cover the exorbitant costs of international shipping, but since the new vaccine needs 2 doses to be effective, the cost will end up being equivalent for the first year’s set. Subsequent vaccination years will be less expensive.

The CBEAM Team will continue to update this page and our medical recommendations based on the latest information available. Stay tuned!



About the Author – Alicia McLaughlin, DVM, CertAqVet, FFCP (Veterinary – Avian, Elite)

Dr. Alicia McLaughlin received her veterinary degree from Oklahoma State University, and has practiced exotic animal medicine exclusively ever since. She is a managing veterinarian at The Center for Bird and Exotic Animal Medicine in Bothell, WA. Dr. McLaughlin was the first veterinarian in the United States to successfully import a vaccine for Rabbit Hemorrhagic Disease from France to help control the 2019-2020 outbreak in Washington state.

https://www.theexoticvet.com/

This article was used with permission of the author and republished from CBEAM’s Facebook page, posted October 9, 2021.