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Rabbit Hemmorrhagic Disease Virus (RHDV) is a virus that affects rabbits and possibly other small rodents. It is also known as Viral Hemmorrhagic Diseas (VHD). It is a highly infectious and lethal form of viral hepatitis that affects European rabbits. Some viral strains also affect hares and cottontail rabbits.
There are currently two known strains, RHDV1 and RHDV2. RHDV1 has been around since the 1980s and was identified in the US in 2000. RHDV2 first emerged in France in 2010 and was first confirmed in North America in the Vancouver area In 2018. The most important difference between the two viruses is that, unlike RHDV1, RHDV2 has been confirmed to affect both domesticated rabbits AND our wild populations of North American rabbits, such as cottontails and jackrabbits.
Mortality for RHDV1 are 40-100% and mortality rates from RHDV2 are more variable at 5-70%. Even though it does not appear to be as fatal, RHDV1 affects rabbits as young as 15 days old (RHDV1 does not seem to cause fatalities in rabbits younger than 6-8 weeks of age).
Until 2020, it had not been known to affect North American native rabbits or hares, such as cottontails, snowshoe hares, and jackrabbits. In 2020, outbreaks of the disease in domestic rabbits, as well as cottontail rabbits and hares, have been reported in Arizona, New Mexico, Colorado, Texas, Nevada, California and Utah. Mountain cottontail, desert cottontail, antelope jackrabbits, and black-tailed rabbits have all been affected throughout these states. RHDV2 has also had a presence in New York, Washington, Ohio, and British Columbia. The sources of these outbreaks is unknown, but the spread has been wider than previous outbreaks in North America, and the strain spreading in the Southwestern United States is distinct from that in the Northwest. As we entered 2021, further outbreaks have occured in Idaho, Montana, Oregon, Wyoming, Mexico and Florida.
How RHDV is Spread
Both viruses causing RHD are extremely contagious. can be spread through direct contact or exposure to an infected rabbit’s excretions, blood and hair. The virus can also survive and spread from contact with carcasses and any contaminated materials. People can spread the virus indirectly by carrying it on items such as clothing, shoes, food, cages, bedding, feeders, and in water. Rabbits that survive and rabbits who are infected but never show symptoms are contagious for an extended period, at least 42 days and possibly as long as 2 months. Flies, fleas, and mosquitoes can also carry the virus between rabbits and predators and scavengers can shed the virus in their feces, further contaminating the enviroment, leading to more spreading of the virus.
RHD is highly resistant in the environment and can survive 3.5 months at room temperature. It can also survive freeze and thaw cycles as well as extended periods just above freezing (225 days). The virus can persist in infected meat for months, and for prolonged periods in decomposing carcasses. Current estimates from the USDA indicate that RHDV2 could theoretically remain viable on a carrier for up to 3 months under ideal environmental conditions.
Now that I have your attention regarding how contagious and deadly this disease is, let's look at what you need to know as a rabbit owner or breeder.
Symptoms
Loss of appetite
Lethargy
High fever
Seizures
Jaundice
Bleeding from nose, mouth, or rectum
Difficulty breathing
Sudden death
RHDV is often a very swift and sudden killer, giving little warning. Rabbits may die without showing any symptoms at all. Any sudden rabbit death is suspicious and should be reported to your veterinarian as a possible case of RHDV. The incubation period is 3-5 days and death rate in the 2020 Southwest US and Mexico RHDV2 outbreak, has been reported to be about 90%.
Treatment
Animals vaccinated for RHDV1 do not appear to be protected from RHDV2. There are vaccines for RHDV2 currently being used in Europe where the disease has been present for a longer period of time. The two vaccines currently available for import to the US in 2020, Eravac (RHDV2) and Filavac (RHDV1 and RHDV2), are produced by infecting rabbits with RHDV in a laboratory and killing them to make liver-derived vaccines. There are other vaccines being made that are not produced using live animals, but they are not available for import into the U.S. yet. With that being said, it is important to note that the risk in most areas of the United States remains extremely low. If you want to find out about vaccines available in your area, contact your veterinarian.
Once an animal falls ill, most treatment is focused on suportive care, but many rabbits that fall ill are humanely euthanized to prevent spread to healthy rabbits.
Prevention
It’s important to note that risk to domestic populations of rabbits in most parts of the United States remains extremely low. With that said, there are measures all rabbit owners can and should take to keep their animals healthy from RHDV2.
If you bring new rabbits into your home or have rabbits returning from a show, keep them separated from your existing rabbits by quarrantining them for 14 days
Wash your hands with soap and water before and after interacting with your rabbits.
Do not introduce new rabbits from unknown or untrusted sources.
Practice good cleaning and sanitation measures in an around your rabbit’s habitat.
Eliminate possible contact with wild rabbits such as cottontails or jackrabbits through monitoring and the use of protective fencing.
Avoid gatherings that involve your animals coming into contact with other rabbits. Also, be aware of traveling through affected areas.
Operate a "closed rabbitry" to avoid visitors bringing in RHDV (or other illnesses).
Do not feed plants, grasses, vegetables, or tree branches foraged from outside in areas where there is an outbreak.
To reduce spread by fleas, you can use a monthly flea treatment such as Revolution or Advantage II (DO NOT use Frontline, it is not safe for rabbits).
Pay close attention to you rabbit and contact your veterinarian right away if you notice any potential symptoms.
Do not touch any dead wild rabbits you may encounter in your local area. If you see multiple dead wild rabbits, report it to your state wildlife officials.
Spread the word to other rabbit owners in your area. Stress the importance of biosecurity measures and awareness of potential contamination.
Disinfecting
This virus resists many disinfectants on the market, so be sure to use one that is known to work against RHDV. The simplest effective option is to wipe down surfaces with a 10% bleach solution, allowing 10 minutes of contact time before rinsing. Be sure to remove any surface debris before disinfecting.
Other disinfectants shown to work include 10% sodium hydroxide, Virkon® S, Clorox® Healthcare Bleach Germicidal Wipes, and hydrogen peroxide cleaners.
The veterinary and public health communities are working diligently to expand our understanding about RHDV2, but as rabbit owners and breeders, it is our responsibility to use the best and most complete information available to ensure we do not contribute to the spread of this virus.
For more information, visit The House Rabbit Society's information page.