This is why:
"In the 1980s, the European rabbit populations were devastated by a virus that caused an extremely lethal and highly contagious disease, rabbit haemorrhagic disease (RHD). The 1st outbreak of this new disease was reported in 1984 in the Jiangsu Province of China within a group of commercially-bred Angora rabbits imported from Germany. As the virus spread worldwide, naturally occurring RHD outbreaks were reported in geographically distant regions, such as Cuba, Uruguay and Reunion Island.
RHD is a highly virulent lagovirus endemic in Europe and Australasian populations of the European rabbit. It has also caused several unexplained disease outbreaks in domestic European rabbits in North America.
RHD is characterised by high morbidity and high mortality (70-90%), and spreads very rapidly by direct and indirect transmission. Infection can occur by nasal, conjunctival or oral routes. Transmission of RHD is facilitated by the high stability of the virus in the environment. Lesions are primary liver necrosis and a massive disseminated intravascular coagulopathy in all organs and tissues. The most severe lesions are in the liver, trachea and lungs.
RHD-2 is a variant form of the original RHD-1 virus and differs in the following ways.
- Rabbits infected with the RHD-2 virus typically DO NOT show the symptoms that are common with RHD-1 infection so it is far more difficult to diagnose from simple observations.
- Death from RHD-2 occur later and over a longer period of time than RHD-1: typically this is 3-9 days following infection and can last up to 5 days, instead of 2-6 days infection and lasting 3-4 days as generally observed with classical RHD-1. Although this is marginal it is important to note from a quarantine perspective.
- Only following post-mortem examination will initial diagnosis be possible, however further tests are required to definitively confirm RHD-2 which is now recommended for unexplained deaths.
- In mainland Europe, RHD-2 is now very common particularly in France where it was 1st identified in 2010 and spread country-wide where it was mainly transmitted through the wild rabbit population with cross-over with domestic rabbits. In Italy it has not spread very wide given the differences in wild rabbit population density. A research study has been published that describes the proliferation in RHD-2 in France since 2010 and of relevance to the current situation in the Great Britain and Ireland.
RHD-2 is a genetically and antigenically different from RHD-1, and the immunogenic differences occur at the serotype level, for which vaccination against both variants is needed.
These viruses, which have been circulating in pet rabbits, have now reached wild populations in Ireland. The impact of this pathogen in these populations is a concern for the conservation of wild rabbits. Continued surveillance should be implemented to assess this impact".
Portions of this comment were extracted from
https://www.oie.int/fileadmin/Home/eng/Animal_Health_in_the_World/docs/pdf/Disease_cards/RHD.pdf.