RHDV is one of the most deadly and horrific viruses a rabbit can contract. Until a few years ago, I myself had never heard of it. Depending on where you live, or if you are a new bun parent, you too may not know what it is. Let me be frank, this is one illness you must not only be educated about, but know there is no room for complacency regarding it.
RHDV stands for Rabbit Hemorrhagic Disease Virus. It’s a highly contagious and often fatal viral disease that affects rabbits. And only rabbits. It belongs to the genus Lagovirus and the Caliciviridae family and is classified into two genogroups: RHDV (classic RHDV) and RHDVa (RHDV2). It affects the liver and blood vessels… not allowing the body to clot
The History of RHDV
The exact origin of this virus is not definitively known. It seems to have evolved from a previous virus known as RCV. This form, not capable of causing disease, was found in Europe, Australia and New Zealand. The morphed virus is believed to have originated from a wild rabbit reservoir first identified in China in 1984, where it caused a significant outbreak in domestic rabbit populations. It was initially known as the “China Rabbit Calicivirus Disease.” The virus subsequently spread to other parts of Asia and Europe.
According to the Australian Government, “the classical RHDV1 strain was first released in Australia in 1996 to control wild rabbits. Over time the effectiveness of the virus as a biocontrol agent has been decreasing. To boost the RHDV1 strain’s effectiveness, state and territory governments around Australia released RHDV1a, a new naturally occurring variant of RHDV1, in March 2017.” It is not known how RHDV2 entered Australia.
Over time, RHV has evolved into RHDV1 and RHDV2. It was first indicated in France in 2010, the UK in 2013, in Canada and the United States in 2018. This strain has shown increased resistance to existing vaccines and has spread worldwide.
The virus likely jumped from wild rabbits to domestic rabbits, possibly through pathogens like insects or contaminated materials. Once introduced into domestic rabbit populations, it spread rapidly due to its highly contagious nature and the lack of natural immunity in domestic breeds.
Key Points
Symptoms: The disease progresses rapidly, and affected rabbits often show symptoms such as:
• Fever
• Shortness of breath
• Loss of appetite
• Listlessness
• Neurological signs such paddling, seizures, and paralysis
• Jaundice
• Blood spots in eyes
• Sudden death
• Bleeding from nose at time of death
RHDV1 is the more virulent. Death occurs typically within a day with massive hemorrhaging. Bloody discharge from the nose, mouth, or vulva is common, as is blood in the feces or urine. In many cases, sudden death occurs without any apparent symptoms. Rabbits generally die within 12 to 36 hours from the onset of fever.
Rabbits contracting RHDV2, although most often fatal, do have the possibility of survival with vet care. Unfortunately, the rabbit has a longer infectious period and this is how the virus can spread. Symptoms can take 1-9 days to present. If the rabbit does survive, it can take up to 42 days to shed from it’s system.
Impact: The virus poses a significant threat to rabbit populations (both domestic and wild), especially in areas where rabbits are kept in close proximity, such as breeding facilities, farms, or shelters.
Expansion: RHDV has been reported in various parts of the world, including Europe, Asia, Africa, Australia, and the Americas.
Transmission
Rabbit Hemorrhagic Disease Virus strains, including both 1 and 2, are primarily transmitted through direct and indirect contact with infected rabbits or their bodily fluids.
Direct Contact: Direct contact with infected rabbits is a common mode of transmission. This can occur through close contact between infected and susceptible rabbits, such as in shared living spaces, breeding facilities, or during transportation. Direct contact includes interactions such as grooming, fighting, mating, or simply being in close proximity to an infected rabbit.
Indirect Contact: It can also be transmitted indirectly through contaminated materials or environments including contact with surfaces, equipment, or objects that have been contaminated with the virus such as bedding, food and water bowls, cages, clothing, shoes, and vehicles. The virus can survive for extended periods in the environment (3-4 months), particularly under favorable conditions. It can last more than 1 hour at 122 degrees and freezing does not destroy it.
Insects: While not the primary mode of transmission, certain insects, particularly biting insects like flies and mosquitoes, can act as mechanical vehicles for for the virus. These insects can pick it up from infected rabbits or contaminated surfaces and transmit it to susceptible rabbits through bites or by carrying the virus on their bodies.
Fecal-Oral Route: RHDV can be shed in the feces of infected rabbits, and ingestion of contaminated fecal material is another potential route of transmission. This can occur if rabbits come into contact with contaminated food, water, or bedding, or if they eat another rabbits feces.
Aerosol Transmission: While less common, RHDV can also be transmitted through aerosolized respiratory secretions from infected rabbits. This mode of transmission is more relevant in situations where rabbits are housed in close quarters, such as in overcrowded breeding facilities or shelters.
Vaccination
Vaccination is the primary method for preventing this virus and is a crucial tool in controlling it. For more information on other vaccinations, read my article on rabbit medications.
Classic RHDV Vaccine: The classic RHDV vaccine is based on inactivated (killed) virus particles. These vaccines stimulate the rabbit’s immune system to produce antibodies against the classic RHDV strain. They are typically administered via injection, either subcutaneously or intramuscularly. Some vaccines require booster shots to maintain immunity.
RHDV2 Vaccine: The emergence of the RHDV2 strain prompted the development of specific vaccines targeting this variant. Like the classic RHDV vaccine, RHDV2 vaccines are based on inactivated virus particles. However, they are formulated to provide protection against the RHDV2 strain specifically. These vaccines are administered in a manner similar to classic RHDV vaccines.
Combination Vaccines: Some vaccines are formulated to provide protection against both the classic strains. These combination vaccines offer convenience and comprehensive protection against both variants of the virus.
Nasal Vaccines: In addition to injectable vaccines, there are also nasal vaccines available. These vaccines are administered intranasally and offer an alternative method of immunization. Nasal vaccines may provide rapid onset of immunity and are suitable for mass vaccination campaigns.
Vaccination Schedule: Your rabbit will receive two portions of the RHDV2 vaccine three weeks (21 days) apart from each other. But after those doses, a yearly vaccine booster is required in order to ensure that your rabbit maintains immunity. In areas where the virus is endemic or outbreaks occur, rabbits may be vaccinated annually or semi-annually.
Efficacy and Monitoring: Vaccination effectiveness can vary depending on factors such as vaccine formulation, administration technique, and the presence of other pathogens. Regular monitoring of vaccine efficacy and disease prevalence is important for adjusting vaccination strategies as needed.
If you are unable, for any reason, to get your rabbit vaccinated, there are measures you can take to cut down the chances of contraction.
- Keep them indoors: however, the virus can be brought inside via shoes and clothing. If you have an outbreak near you, remove shoes and clothing before entering your house and thoroughly wash yourself before touching your rabbit.
- If you cannot have your rabbit indoors, double fence or block the bottom portion of the pen so as to not allow wild rabbits near yours.
- Add mosquito netting around their enclosure.
- Make sure to purchase produce from states that do not have outbreaks.
- Disinfect everything with a solution of 1:10 bleach to water.
- If you show your rabbit, do not use others equipment.
- Make sure to educated your bunsitters, groomers etc…
- If you live in a state with outbreaks of the virus, purchase your hay from a reputable dealer that is invested in protecting rabbits from this disease.
Side Effects: swelling at the site of injection, slight fever, lethargy for a day or two. You can find out more information on the vaccine at Megdene Labs.
Final Thoughts
Efforts to monitor, prevent, and control RHDV continue to be important in safeguarding rabbit populations worldwide. Overall, the highly contagious nature of the virus, coupled with its ability to persist in the environment and spread through various routes, contributes to its rapid transmission within rabbit populations. Implementing strict biosecurity measures and vaccination programs are essential for preventing and controlling the spread of it.
