Rabbit haemorrhagic disease (RHD) frequently asked questions

Rabbit haemorrhagic disease is an acute, highly contagious disease of rabbits and hares (lagomorphs).

What causes rabbit haemorrhagic disease?
RHD is caused by rabbit haemorrhagic disease virus (RHDV) from the calicivirus family. Three distinct groups of RHDV have been identified that cause severe disease, of which the emerging RHDV2 has been reported from most European countries, Asia, North Africa, Australia, nearly half the USA and Canada, and now from South Africa in 2022.

RHD and South Africa
South Africa was previously free from RHD and it is therefore a controlled animal disease in terms of the Animal Diseases Act (Act No 35 of 1984). Stringent import requirements have been in place for several decades (import of hares and rabbits is not allowed) to prevent the introduction of this disease into South Africa.

Which animals in South Africa may be susceptible?
Apart from domesticated rabbits related to the European rabbit, South Africa has the indigenous Cape hare (vlakhaas), scrub hare (kolhaas; Fig. 1), red rock hare (rooiklipkonyne; Fig. 2) and the critically endangered riverine rabbit (oewerkonyn), of which only hundreds are left. We do not know yet which of our indigenous species are susceptible, but RHDV2 affects both hares and rabbits in other parts of the world.

What are the signs of RHD in rabbits and hares?
Sudden death is the most striking sign. However, other possible clinical signs include fever, neurological and respiratory signs, depression, inactivity and poor appetite. Death usually occurs 12–36 hours after the onset of fever but animals infected with RHDV2 may survive longer. RHDV2 causes disease and mortality in young animals from 15–20 days old and is believed to have an incubation period of 3-5 days.

What signs are visible on necropsy?
There is primary liver necrosis (pale, often with a lobular pattern), splenic congestion and a disseminated intravascular coagulopathy in all organs and tissues, causing hyperaemia of the trachea and oedematous and congested lungs.

How can one test for RHDV?
Testing for RHDV can only be done in a laboratory approved by the national Director: Animal Health. Currently the only approved laboratory is at ARC-Onderstepoort Veterinary Research. Liver is the sample of choice but spleen, blood, urine or faeces (the latter three also from live rabbits) can also be submitted fresh, on ice for PCR testing. Swabs can be submitted but must be transported in PBS. Testing of domestic rabbits will be at the cost of the owner, but the national Director: Animal Health will consider applications to test wild lagomorphs, submitted via the responsible state veterinarian.

What will happen if domestic rabbits are infected or suspected to be infected with RHDV?
The state vet must be notified of any suspected or confirmed cases. He or she can assist with advice on limiting spread of the disease and in disposing of carcasses and will place the property under quarantine to ensure that the virus does not spread to other properties.

How many animals will die?
The morbidity and mortality rates vary among populations. RHDV2 has been reported as causing 5-70% mortality. In Europe, RHD has caused dramatic declines in wild rabbit populations in France, Portugal and Spain, but wild rabbits in the United Kingdom and some other Northern European countries have been less severely affected possibly due to the presence in wild rabbits of non-virulent RHDV-like strains, which may induce variable levels of cross protection within each population. Rabbits that recover from infection will develop good immunity to RHDV2.

How do animals get RHD?
RHDV is present in faeces and urine of infected rabbits and transmitted through either inhalation or ingestion. Contact with contaminated feed, bedding or equipment is also a possible source of RHDV, as it is highly resistance to physical and chemical inactivation, particularly when protected by organic material. It can survive for months in carcasses and possibly in feed. Other animals, including insects, are not infected by the virus but may act as mechanical vectors and play a role in spreading virus.

Can humans and other animals get RHD?
No, the disease is specific to rabbits and hares.

What disinfectants work against RHDV?
Remember to clean off all biological material and then use one of the following:

• Bleach (3.5% sodium hypochlorite) mixed at 200ml per litre of water with 10 minutes contact time
• 1 % potassium peroxymonosulfate (e.g. Virkon S) with 10 minutes contact time
• F10 SC mixed STRONG (same as for parvoviruses): 8ml/L water with 30 minutes contact time
• 1% Sodium hydroxide (e.g. Milton sterilising fluid)
  

How can RHD be prevented?
Like many contagious diseases, RHD can be prevented from entering a property by practicing good biosecurity:

• Avoid buying in/ introducing any new rabbits until there is a better idea of the disease’s distribution in South Africa. If it is absolutely necessary, keep new rabbits completely separate from the others, use separate equipment, wear gloves and wash hands and clothes thoroughly after working with the new rabbits.
• Do not allow other rabbit owners onto your property.
• Do not allow any possible contact between pet rabbits and wild hares or rabbits.
• Do not touch any rabbits or hares belonging to anyone else.
• Disinfect any potentially contaminated equipment or other objects, after removing all dirt, with a disinfectant listed above. Ensure the correct concentration and contact time
  

Is there a RHD vaccine available?
There are several vaccines available overseas but not registered in SA. As RHD is a controlled disease, no vaccine can be imported or used without a permit. The DALRRD has stated that they are “actively working… to make provision for the legal use of RHD vaccines in South Africa. Only legally imported, registered vaccines approved by SAHPRA/Act 36 may be used. For more information on the relevant import permits… contact SAHPRA and Agricultural Inputs Control (Act 36)”

What should be done with dead wild hares and rabbits?
Notify your local state veterinarian of the species, number and location, take photographs so that accurate species identification can be done.
If not required for testing, bury carcasses at least 1,5m deep but ensure that it is not too close to the groundwater level and is at least 100m from marshes, dams and waterways. A maximum of 60kg of carcasses can be buried but larger numbers of carcasses need to be dealt with via an application to Western Cape Waste Management. Complete burning is an alternative. Remember that anything that touches a carcass may be able to spread virus to healthy animals, so wear gloves that can be disinfected afterwards and disinfect any equipment used.

Sources and more information:
WOAH RHD card
Spickler, Anna Rovid. 2020. Rabbit Hemorrhagic Disease
Department of Agriculture, Land Reform and Rural Development, South Africa. Guidelines for Rabbit Haemorrhagic Disease control. Version 1: Nov 2022.

Epidemiology Report edited by State Veterinarians Epidemiology:
Dr Lesley van Helden (Lesley.vanHelden@westerncape.gov.za)
Dr Laura Roberts (Laura.Roberts@westerncape.gov.za)