Rabbit Hemorrhagic Disease is a highly contagious and fatal viral disease of rabbits caused by a Calicivirus. There are three major Rabbit Hemorrhagic Disease Virus serotypes; RHDV1, RHDVa, and RHDV2, with RHDV2 causing problems in the Unites States. The three serotypes are prevalent in most of Europe, parts of Asia, and Africa, Middle East, Australia, New Zealand, and Cuba. RHDV is considered a foreign animal disease in the United States. RHDV2 affects Oryctolagus, which includes most domestic rabbits, and wild European rabbits, wild jackrabbits and hares (Lepus), wild American cottontails (Sylvilagus) and Pikas. In the United States this virus has been reported in New Mexico, Arizona, Texas, Ohio, California, Nevada, Colorado, San Juan Islands in Washington, New York, and southwestern British Columbia. Veterinarians and research scientists feel that RHDV2 will likely persist in British Columbia, Washington and New Mexico and eventually be considered endemic in these states. It is too early to predict the final outcome in states recently affected the presence of RHDV2.

Clinical disease will not vary between the different serotypes. However, RHDV1 and RHDVa have slightly shorter incubation periods and higher mortality rates than RHDV2. The incubation period for RHDV2 is 3-9 days.  Rabbits suffer from liver inflammation (necrotizing hepatitis) and blood clotting disorders. Rabbits can die acutely without showing clinical signs, or may present with fever, inappetence, lethargy, breathing difficulties, blue colored lips or mucus membranes, and bleeding from body cavities.  Mortality ranges from 80-100% and all ages may be affected. Death can be acute or within 36 hours of developing clinical signs. Rabbits who survive are carriers of this virus and have the ability to shed the virus for up to 2 months. Wild rabbit populations, feral rabbits (domesticated rabbits abandoned or escaped outdoors), pet rabbits, and rabbit production facilities are all at risk. 

RHDV does not pose a threat to humans, other animals or the food supply (wild food chain or domestic) however, there is great concern that as this virus spreads, the wild rabbit population will be severely affected. This will reduce the number of rabbits available as a food source for many wildlife species, including birds of prey. A shortage of this prey item may lead to increased predation of more sensitive species and affect not only their stability, but also affect the predator’s ability to survive and reproduce. 

 RHDV is highly stable in organic materials and can remain viable for months. RHDV is very resistant to extreme temperatures; freezing will not kill the virus and it may survive 122⁰ F heat for one hour. This virus only affects rabbits. The concern is how easily this virus can spread. Direct contact of a rabbit with an infected rabbit or with the urine and feces of an infected rabbit will spread this disease.  Contaminated carcasses, contaminated food, water and fomites (inanimate objects) will enhance the spread of this virus. People can spread this virus indirectly by carrying it on their shoes, clothing and equipment.  It has been documented that biting insects (flies, fleas and mosquitoes) may act as mechanical vectors transmitting this virus over long distances. Flies are also able to deposit this virus through their feces onto vegetation, which can then be eaten by a rabbit. Mammals and birds (including raptors) can excrete infectious RHDV in their feces after eating an infected rabbit. RHDV is inactivated by 0.5% sodium hypochlorite (bleach) or  potassium peroxymonosulfate (Virkon-s 1%). Quaternary ammonium compounds are not effective against RHDV.

There is no specific treatment for RHDV except supportive care. Owners with pet rabbits or rabbit breeders should have strict biosecurity measures to protect their rabbits.  Information on establishing a complete biosecurity program can be found at the House Rabbit Society web site (rabbit.org), United States Department of Agriculture-Rabbit Hemorrhagic Disease fact sheet (www.aphis.usda.gov) and your state department of food and agriculture.  Vaccines for RHDV are available in countries where the disease is considered endemic (Europe). This vaccine must be given yearly to provide continued protection against RHDV and is used for pet rabbits and production facilities.  Although not 100% effective in preventing disease, vaccinated rabbits have a greater ability to survive if exposed to RHDV. At the present time, a RHDV vaccine is not widely available to veterinarians in the United States or Canada. However it is possible for veterinarians to work with their state regulatory agencies to receive special permission to import the European vaccine. 

This virus is known to only affect rabbits, both wild and domestic.  The goal is to prevent the spread of this deadly virus, both in wild rabbit and domestic rabbit populations.  Here are some recommendations:

• Contact your local state and federal animal health agencies to learn if RHDV is in your area.

• If in the field for falconry and you see multiple dead wild rabbits, report it immediately to the state wildlife officials. Be cautious of hunting in areas affected by this virus and do not handle the dead rabbits. Although you and your bird are not at risk to become infected with this virus, you both have the ability to spread this virus by contact with an infected rabbit. If you are suspicious of having contact with a rabbit infected with RHDV, disinfecting your equipment, shoes etc with a bleach solution (1part bleach to 9 parts water) is recommended. Clothing should be washed with the addition of bleach. As for your hawk, wash the feet with soap and water. Giving your dog a full bath with a dog shampoo is recommended.  

• If you volunteer at a wildlife rescue or animal shelter, practice biosecurity measures when handling rabbits.

• Anyone working with rabbits or having exposure to wild rabbits should practice good biosecurity measures.

• RHDV is a reportable disease. When detected in the United States, this disease should be reported immediately to the U.S. Department of Agriculture, Animal and Plant Health Inspection Service or to the state wildlife officials. The United States has an obligation to report all detections to the World Organization for Animal Health (www.oie.int). With knowledge and understanding of this virus, we can all take an active role in helping to reduce the spread of this devastating virus.