What Is Rabbit Hemorrhagic Disease?

Rabbit hemorrhagic disease is a general term for the disease caused by several related forms of highly contagious viruses, which, if contracted, are often fatal to both domesticatedAdapted over time (as by selective breeding) from a wild or natural state to life in close association with and to the benefit of humans and wild rabbitsUnless explicitly mentioned, we are referring to domesticated rabbit breeds, not wild rabbits, who may have unique needs not covered by this resource.. Caused by strains of a calicivirus, RHD causes death in rabbits extremely quickly, giving little warning. It has never been reported to affect humans or other animals. 

Up until 2010, all RHD viruses identified belonged to six previously identified genotypes. However, in 2010, an additional distinct virus emerged in Europe called RHDV2. This paper explains the epidemiology of this disease and the history of its spread worldwide. To get a sense of how RHD is currently impacting the United States, you can check out this map from the United States Department of Agriculture’s Animal And Plant Health Inspection Service. RHDV2 is the more virulent, deadly strain of the virus and has become the major form in the US infecting rabbits. For this reason, when we refer to RHD, you can assume we’re talking about RHDV2 as the causative agent. 

Generally, RHD is characterized by high morbidity, which means that most individuals who contract it will show illness. It is also characterized by a high mortality of 70-100%. This means that not only will most individuals who contract RHD show illness, they also face a high chance of death. Sudden death may also be a symptom of RHD. Rabbits who die from RHD typically pass from liver dysfunction with abnormal blood coagulation and hemorrhage.

Another reason that RHD is of concern is that this virus is exceptionally durable (especially when it is insulated by organic matter, such as the body of a deceased individual). So it is extremely hard to eradicate. For example, RHD can:

• Remain viable for 3.5 months at room temperature at 68℉ (20℃) on fabric; 
• Persist for 7.5 months at near-freezing temperatures;
• Survive temperatures of up to 122℉ (50℃) for one hour;
• Withstand most cleaners;
• And can withstand cycles of freezing and thawing. 

Because RHD can survive all of the above conditions, it can remain viable in the environment throughout the year, although more significant seasonal outbreaks may be linked to breeding season or fluctuations in the populations of insects like mosquitos and flies, which serve as vectors for the disease. (More on this below!)
There is no treatment or cure for RHD, so this disease presents a clear danger to rabbits. This resource is meant to introduce you to how it is transmitted, its signs and symptoms, and measures that you can take to protect your rabbit residents. 

Means Of Transmission

We Have A Resource To Help You Understand Infectious Disease
Having a basic understanding of infectious diseases is important when it comes to determining how best to protect your residents. We have an introductory resource on the subject that you can read here! 

When it comes to RHD, as with many infectious diseases, it can be contracted in several ways. Rabbits are infected with RHD via exposure of the mucous membranes of the eyes, nose, mouth, or digestive tract by the virus. This can happen if rabbits come into direct contact with other infected (or deceased) rabbits or their bodily fluids. This can include contact with:

• Urine
• Feces
• Blood
• Milk
• Saliva
• And mucus from the nose and mouth.  

However, direct contact with infected or deceased rabbits is not the only way your residents can contract RHD. They could also be exposed to RHD by insect vectors. Of particular concern are insects like flies, which may have come into contact with infected or deceased rabbits, or fleas or mosquitos, who may have bitten infected rabbits. Consider giving rabbits a monthly flea treatment as recommended by your veterinarian, to protect them from this vector. Keep in mind to only use vet-recommended treatments, as some treatments used in dogs and cats are toxic to rabbits! Wild birds, mice, rats, and other scavenging animals that have come in contact with infected or deceased rabbits or their bodily fluids and feces can also be infection vectors.

It’s also possible for rabbits to contract RHD from other non-rabbit residents of your organization who may have encountered and been exposed to rabbit individuals who were infected or deceased or who have touched their bodily fluids or feces. For example, even if you have a rabbit indoors only, that rabbit might be exposed to RHD should you have another resident, like an indoors/outdoors dog, and the dog came into contact with the virus and then brought it indoors. Rabbits who live indoors but have outside time where they may be infected via exposure to wild animal feces/urine, or biting insects (flies, mosquitos, fleas) may also become infected. Note that an animal who ingests either infected rabbits or their feces may excrete the virus in their own feces, which can then also infect your rabbit residents. Keeping a close eye on what other residents are “getting into” is essential to ensure they don’t track RHD into areas inhabited by your rabbit residents.

There are other indirect means of transmission which should be of concern. For example, consider fomitesObjects or materials that may become contaminated with an infectious agent and contribute to disease spread, which include things like food or hay, bedding, clothes, shoes, buckets, cleaning tools like shovels, or even car tires that have been contaminated with the virus.  

Note also that while most rabbits who contract RHD develop illness and die quickly, it is possible for a small proportion of individuals to recover and for others to be asymptomatic carriers, which means that they display little or no sign of illness. However, these individuals are also of concern because their bodies are still producing live virus, which can “shed” in their bodily fluids and waste and infect other rabbits. Most sources indicate that such individuals can remain infectious for at least two months after contracting RHD.

Symptoms

After exposure, the incubation period for RHD can range between 1 to 3 days. It is important to note that the most common way that RHD manifests in infected individuals is sudden death. Any sudden death in a rabbit resident is a cause of concern and should be discussed with your veterinarian as soon as possible. For rabbits who show symptoms of RHD, death usually occurs within 12 to 36 hours of developing a fever. Daily observation of your rabbit residents is crucial in light of RHD. You should also be on the alert for the following symptoms in your rabbit resident, and speak to your veterinarian immediately should you observe them. 

• Gastrointestinal symptoms (loss of appetite, weight loss, and/or diarrhea)
• Lack of energy or lethargy
• Fever
• Neurological signs such as seizures, weakness, wobbliness
• Jaundice, which is yellowing of the skin (most notably around the ears) and of the mucosal membranes
• Vocalizations such as cries or moans
• Bleeding from the nose, mouth, genital openings and rectum
• Nasal discharge
• And difficulty breathing.

Typically, RHD manifests in infected individuals in one of three ways.

1. Peracute. As noted above, the most common manifestation of RHD is sudden death. Rabbits may be found dead within a few hours of eating and behaving normally. Many rabbits with the North American RHDV2 strain will not exhibit any external bleeding.
   
2. Acute. In this manifestation, affected rabbits will show lethargy and a heightened fever (>104℉/ 40°C) with an increased respiratory rate. They often die within 3 to 5 days of showing symptoms, though this may occur even within twelve hours.
   
3. Subacute. Infected rabbits may be entirely asymptomatic or may show mild or subclinical signs from which they recover. However they may be contagious for up to 3 months as their bodies continue to produce live virus. Note that the asymptomatic carriers or individuals who recover from the virus are the minority of domestic rabbits. 

As noted above, there is no cure for RHD. The only treatment options available are to offer supportive and/or palliative care while keeping the affected individuals in isolationIn medical and health-related circumstances, isolation represents the act or policy of separating an individual with a contagious health condition from other residents in order to prevent the spread of disease.  In non-medical circumstances, isolation represents the act of preventing an individual from being near their companions due to forced separation. Forcibly isolating an individual to live alone and apart from their companions can result in boredom, loneliness, anxiety, and distress. to prevent further disease spread. As a result, the most important thing you can do to protect your residents is to focus on prevention! 

What You Can Do

Staying informed on whether RHD is present in your locality is critical. If you care for rabbit residents, contact your local veterinarian or state and federal animal health officials to determine if RHD has been detected in your area. If it is present, it is imperative to take protective measures. Due to the severity of this disease, even if it is not present in your area, it is still wise to consider taking precautions to protect your rabbit residents! Below, we’ll discuss some of the measures you can take!

Vaccination

If you care for rabbit residents, we recommend discussing vaccinating them for RHDV with your veterinarian. A few different types of vaccines are commercially available and in use in many countries. These may include RHDV or RHDVa vaccines and vaccines specific for the RHDV2 variant of the virus. They include:

1. Filavac (France). Rabbits 10 weeks of age can be vaccinated with this drug. It is administered in a single dose, and your rabbit will require seven days for onset of immunity, 
2. Eravac (Spain). Rabbits aged 30 days can be vaccinated with this drug. It is administered in a single dose, and your rabbit will require seven days for onset of immunity.
3. Medgene (US). Rabbits 7 weeks of age can be vaccinated with this drug. It is administered in two doses which are spaced three weeks apart. Your rabbit will require two weeks after the second dose for the onset of immunity. Please note that this is the only RHD vaccine approved for use by the USDA in the United States, and conditional approval may vary by state.

Vaccination is generally safe, but your veterinarian should determine the most appropriate choice for your rabbit residents. While many rabbits may not show any side effects after vaccination, some may exhibit lethargy, lowered appetite, and muscle or joint discomfort. These side effects should abate within 48 hours; if not, consult your veterinarian! Once vaccinated, rabbits will produce strong systemic immunity. However, no vaccine is 100% effective and some rabbits may still be infected via ingestion of infected material, so limiting exposure is still recommended. 

Vaccination And Microchipping
Microchipping your rabbit residents in conjunction with RHD vaccination is required in some states. You should check with your veterinarian for your local requirements, or for any relevant requirements if you need to do any interstate travel with your rabbit. Even if you live in a state where a microchip is not required to have rabbits vaccinated, we recommend that you do so to aid in demonstrating your rabbits’ vaccination status. Because RHD is a reportable disease, this can be a crucial part of protecting your rabbit residents should RHD become a problem in your area.

To remain effective, vaccines should be boosted annually, especially in areas where RHD is present. Keep track of your rabbit residents’ vaccination schedules in your resident recordkeeping! To find a veterinarian who administers vaccinations for RHD, you can check out this resource from Rabbitors or this resource from The House Rabbit Society, which will link you to sources that can help you locate vaccines in the United States, Canada, and South Africa. 

 Biosecurity

Practicing careful biosecurityMerck Veterinary Manual defines biosecurity as ”the implementation of measures that reduce the risk of the introduction and spread of disease agents [pathogens].” is critical to keeping your rabbit residents safe. Because RHD viruses are so durable, you will need to take special precautions. Consulting with your veterinarian to develop a biosecurity plan is an important step in ensuring that your rabbits are as safe as possible.

We Have Resources To Help You Understand Biosecurity
To learn more about biosecurity, you can check out our two part series on the subject! The first part introduces biosecurity and provides some background on how infectious diseases can spread in a sanctuary context. The second part gives you a step-by-step guide on creating your own biosecurity plan! 

As a general overview, your biosecurity plan when it comes to RHD prevention should address at least the following:

1. Secure Rabbit Living Spaces From All Disease Vectors.  If rabbits are housed outdoors and you live in an area where RHD is present, you should strongly consider moving them indoors to protect them from disease vectors such as wild rabbits, insects, scavenging animals and wild birds. Outdoor rabbits’ living spaces should be impenetrable to all such vectors, including screening areas where insects might enter. Indoor rabbit living spaces should also be carefully assessed and removed from areas trafficked by indoor/outdoor residents, such as dogs, and should be kept apart from areas of heavy indoor and outdoor traffic from humans. Consider limiting all outdoor playtime for rabbits to fully secured areas and/or eliminating outdoor playtime altogether, as well as giving all your rabbit residents monthly flea treatments. Consult with your veterinarian on appropriate treatments!
   
2. Caregivers Must Practice Careful Hygiene. Caregivers should NOT go near or touch any dead wild rabbits they may see. They should also wash their hands before handling or caring for rabbit residents. Using boot covers (and potentially other PPE) in outdoor rabbit living spaces and boot washing stations with RHD-effective disinfectants is a good idea in areas of high risk. For caregivers of indoor rabbits, you may wish to consider a blanket “no shoes” policy in your home, changing clothing after any outdoor activity near wild rabbit habitats, and cleaning any potentially exposed clothing with RHD-effective disinfectant. For a list of disinfectants recommended for use in eliminating RHD, you can check out this list from the USDA.
   
3. Use Dedicated Equipment For Rabbit Living Spaces, Store It In Areas Secure From Disease Vectors, And Sanitize It Regularly! Any tools used in rabbit living spaces should be dedicated to use in only these spaces. Tools such as rakes or shovels must be stored carefully where they will not come into contact with any disease vectors, and should be sterilized regularly. Also, be mindful of rabbit crate storage! Do NOT share crates or equipment with other organizations.
   
4. QuarantineThe policy or space in which an individual is separately housed away from others as a preventative measure to protect other residents from potentially contagious health conditions, such as in the case of new residents or residents who may have been exposed to certain diseases. Your Rabbits From Anyone Who May Have Been Exposed To RHD. If a human (or other animal) could have been exposed to RHD, do not allow them to handle or come into contact with your rabbit residents. Avoid bringing rabbits off-site to events, particularly those where other rabbits might be present, unless it is necessary to get veterinary care. Remember that if you live in an area where RHD is present, there may be a quarantine order on rabbits. Check in with your vet for any restrictions that may be in place.
   
5. Quarantine Any New Rabbit Intakes From Existing Residents Diligently! While establishing and maintaining quarantine protocols is always important, it is particularly critical to avoid the risk of transmitting RHD from any new intakes to your existing residents. Given that some rabbits can be asymptomatic carriers of RHD and can shed the virus for at least two months, we recommend that you discuss an appropriate quarantine period for new rabbit intakes with your veterinarian and make sure to observe careful biosecurity when moving between quarantine living spaces and existing resident living spaces!
   
6. Take Special Care With Rabbit Food! Because RHD is so robust and can be transmitted if rabbits consume contaminated foods, it’s important to revisit where your rabbits’ food is coming from. While many rabbits may enjoy homegrown vegetables or wild foods and branches foraged by their humans, if you live in an area with RHD, you will want to avoid those practices. You may also want to investigate your sources of pelleted feed and hay and consider purchasing from sources in states or areas that do NOT have RHD detections yet. If you cannot determine where your hay and food come from, talk to your veterinarian about effective practices for “quarantining” these foods for three months before feeding, if you suspect they may come from areas where RHD is endemic.

7. Once You Have Your Biosecurity Plan, Review It With Your Veterinarian! Having your veterinarian assess your biosecurity plan for any gaps or oversights is a great way to ensure that you have covered as many bases as possible when it comes to protecting your rabbit residents from RHD.
   
8. If A Resident Becomes Ill Or Suddenly Dies, Contact Your Veterinarian! Asking your veterinarian for a necropsy can help to confirm whether or not a deceased resident has succumbed to RHD. Further, because the RHD virus is so robust, you will need to consult with your veterinarian on the safest way to treat a deceased rabbit’s body, as well as for any other guidance they can give you on the care of any other residents you may have.

Conclusion

While the risk of RHD is significant, staying informed and in close contact with your veterinarian can go a long way to assuring that you are aware of all relevant information and circumstances. Considering vaccination (with all necessary boosters) for rabbit residents is a great way to protect them from this disease, as is developing a thoughtful biosecurity plan in conjunction with your veterinarian.

SOURCES:

Understanding Infectious Disease | The Open Sanctuary Project

Daily Observation For Rabbit Health And Well-Being | The Open Sanctuary Project

Biosecurity Part 1: Introduction | The Open Sanctuary Project

Biosecurity Part 2: Creating And Implementing A Biosecurity Plan | The Open Sanctuary Project

Establishing Safe And Effective Quarantine And Isolation Protocols For Your Animal Sanctuary | The Open Sanctuary Project

RHDV2 Resources | The House Rabbit Society 

US RHDV2 Vaccination Sources | Rabbitors

RHDV2 Conditional License – State Permissions | Medgene

Rabbit Hemorrhagic Disease | American Veterinary Medical Association (Non-Compassionate Source)

Recommendations for Disinfectants for Rabbit Hemorrhagic Disease Calicivirus | U.S. Department Of Agriculture (Non-Compassionate Source)

Factsheet: Rabbit Hemorrhagic Disease | U.S. Department Of Agriculture (Non-Compassionate Source)

Rabbit Haemorrhagic Disease: Aetiology, Epidemiology, Diagnosis, Prevention And Control, References | World Organization For Animal Health (Non-Compassionate Source)

2020-23 Rabbit Hemorrhagic Disease Disease Map Application: USDA APHIS – Affected Counties As of March 31, 2024 | U.S. Department Of Agriculture (Non-Compassionate Source)

Rabbit Hemorragic Disease | World Organization For Animal Health (Non-Compassionate Source)