Rabbit Haemorrhagic Disease Virus (RHDV)

General information

Rabbit haemorrhagic disease (RHD), also known as rabbit calicivirus disease or viral haemorrhagic disease, is a highly contagious disease of European rabbits (Oryctolagus cuniculus). It occurs in both wild and domestic rabbits and causes peracute, acute or subacute diseases.

RHD is caused by caliciviruses, small, non-enveloped, single-stranded RNA viruses. Rabbit haemorrhagic disease virus (RHDV) is closely related to the european brown hare syndrome virus, which causes a similar disease in hares (Lepus spp.). There are several genetically and serologically different variants of RHDV. Until 2010, six different genotypes were known which cross-react serologically. These are called “classic” RHDV or RHDVa. A new serotype, called RHDV2 or RHDVb, was first detected in France in 2010 and has since spread throughout Europe and other parts of the world. The disease caused by RHDV2 is similar to that of classic RHDV strains but is associated with a slightly lower (but extremely variable) mortality rate. RHDV2 can also infect some hare species and, unlike RHDVa, also infects very young rabbits.

From January 2015 to June 2017, only 0.6% of Laboklin samples were RHDV/RHDVa positive, but 37.4% were RHDV2 positive. RHDV/RHDVa was only detected in samples from Germany and the Netherlands, while RHDV2 was detected in animals from Germany, Great Britain, Luxembourg, the Netherlands, Spain, Switzerland, Poland, Belgium, Austria, Sweden and Finland.

RHDV/RHDVa and RHDV2 are mainly transmitted orally. Contaminated herbage can play a role here. Insects also act as mechanical vectors.

Infected animals often show general clinical symptoms such as anorexia and lethargy, but also neurological symptoms such as opisthotonus, excitement, ataxia or paralysis. Conjunctivitis and respiratory symptoms such as dyspnoea and nasal discharge (possibly bloody) are also frequently observed. In some cases, an increased tendency to bleed can be observed. The chronic form of RHD only occurs in a small number of animals which then develop jaundice.

Hepatomegaly and splenomegaly are the most common pathologies. Histologically, acute necrotising hepatitis can be detected in affected animals. Bleeding and blood stasis in various organs are frequently observed. Affected rabbits often die within a few days.

In addition to the clinical examination and histopathology, RHD is mainly diagnosed by virus detection using real-time PCR. Due to the genetic differences between the RHDV strains, both RHDV/RHDVa and RHDV2-specific methods must be used.

Treatment is not possible. A prophylactic vaccination is recommended. Several vaccines are available. It must be noted that vaccination should take place against both RHDV/RHDVa and RHDV2. Currently, RHDV2 cases are being observed in Germany, but classic RHDV strains still occur.