Rabbit haemorrhagic disease (RHD) is a viral disease of wild and domestic rabbits. The virus is not dangerous for humans.

Worldwide

Domestic and wild rabbits

Directly from rabbit to rabbit (via secretions and excretions), indirectly via contaminated water, bedding, food, clothing, shoes, objects, hands, blood-sucking insects

1-3 days

Sudden deaths without clinical signs or by acute onset of lassitude, loss of appetite, high fever (> 40 °C), bloody nasal discharge and occasionally respiratory and neurological signs. Diseased animals usually die after 12-72 hours.

There is no therapy

Vaccination and prevention of introduction into rabbit herds

RHD in domestic and wild rabbits is repeatedly observed in Austria. Major outbreaks in wild rabbits were detected in Vienna in 2016 and in Styria in 2022.

In 2024, 11 cases of RHD in rabbits were diagnosed at AGES and a further three cases were reported to us via the Vetmeduni Vienna.

Rabbit haemorrhagic disease (RHD) can cause high economic losses in the rabbit meat and fur industry if it occurs as an epidemic. An outbreak has a significant negative ecological impact on wild rabbit populations and indirectly also on their predators. RHD has been known since the 1980s.

The causative agent of rabbit haemorrhagic disease is the RHD virus (RHDV), an non-enveloped, single-stranded RNA virus from the Caliciviridae virus family (genus: Lagovirus). The virus is very resistant outside the host. In 2010, a new variant of the RHD virus, known as RHD virus 2 (RHDV-2), was reported in France. Rabbit haemorrhagic disease (RHD) was first described in China in 1984. A few years later, an epidemic occurrence of this disease was also detected in Europe. A similar viral infection, also caused by a calicivirus from the Lagovirus genus, had previously been detected in brown hares under the name European brown hare syndrome (EBHS).

The rabbit haemorrhagic disease virus (RHDV) is spread worldwide. One of the ways it has spread is through the import/export of rabbit meat. The starting point for the spread of the virus in Australia was an island off the Australian continent. There, the virus was used experimentally to decimate the wild rabbit population.

The host spectrum includes domestic and wild rabbits(Oryctolagus cuniculus). The classic RHD virus is very host-specific and is not infectious to humans or other mammals. In contrast to the "classic" RHDV, field hares are also susceptible to RHDV-2. Rabbits can contract RHDV-2 from the age of 10-15 days. Cases of RHDV-2 infections were first detected in Germany in 2014 and in Austria in 2016. RHDV infections in domestic and wild rabbits are repeatedly reported in Austria.

RHD is controlled and prevented by means of vaccination prophylaxis and prevention of introduction into rabbit herds. It is reported that monovalent RHDV vaccines provide additional protection against severe clinical manifestations of RHDV-2 infection after basic immunisation followed by six-monthly booster vaccinations. An RHDV-2 vaccine has been approved for fattening rabbits throughout Europe since autumn 2016. Attention should be paid to the coverage of RHDV-2 and the recommended vaccination intervals for the various vaccines available on the market.

Transmission

The pathogen is transmitted directly from rabbit to rabbit (via secretions and excretions) and indirectly via contaminated inanimate and animate vectors (e.g. contaminated water, feed, bedding, clothing, shoes, objects, hands, blood-sucking insects). The pathogen can be ingested orally, nasally, conjunctivally and parenterally via blood-sucking insects.

Symptoms

The disease is characterised by a mostly peracute course, which is accompanied by necrotising hepatitis (inflammation of the liver) and generalised coagulation disorder. Infected animals usually die after 12-72 hours. The incubation period is 1-3 days. Young animals up to the age of approx. 2 months do not fall ill with classic RHDV infection (juvenile resistance), whereas they can fall ill with RHDV-2 infection from the age of 1 month.

The peracute/acute course is characterised by sudden deaths without clinical symptoms or after acute faintness, loss of appetite, high fever (> 40 °C), bloody nasal discharge and occasionally respiratory and neurological symptoms (e.g. opisthotonos, paralysis, ataxia).

The subacute/chronic course, on the other hand, is rare and is characterised by milder clinical symptoms: jaundice, loss of appetite, lethargy. Convalescence after the disease is rather atypical.

The main findings at autopsy in deceased rabbits are a dry, brittle, tinder-coloured liver, congestive organs, minor haemorrhages, splenomegaly and pulmonary oedema. In RHDV-2 infections, the macroscopic findings may also be non-specific(https://doi.org/10.17236/sat00354)

Histologically, acute hepatitis dominates due to the virus-induced destruction of numerous liver cells and acute congestive organs with accompanying haemorrhages due to blood clotting disorders and microthrombus formation. Based on the autopsy and histological findings, the diagnosis of RHD is relatively certain, but it is not possible to differentiate between RHDV and RHDV-2. The distinction is made using molecular biological methods.

In the event of suspicion, it is recommended that the animal carcass be sent to the relevant institutes for pathological examination, e.g. the Institute for Veterinary Medical Examinations in Mödling.