Rabbit hemorrhagic disease is a fatal disease in rabbits and is considered a foreign animal disease in the United States. This disease is caused by several virus strains. Animal health officials detected one of these strains, Rabbit Hemorrhagic Disease Virus Serotype 2 (RHDV2), in North America in the past few years. RHDV2 does not impact human health.
RHDV2 can be spread through direct contact or exposure to an infected rabbit's excretions or blood. The virus can also survive and spread from carcasses, food, water, and any contaminated materials. People can spread the virus indirectly by carrying it on their clothing and shoes.
A vaccine for RHDV2 is not currently available in the U.S. Instead, it is up to owners to protect rabbits by practicing good biosecurity. Biosecurity means taking simple steps every day to keep germs and viruses away from your animals. These actions will significantly reduce the chance of RHDV2 or other contagious diseases affecting your rabbits.
Frequently Asked Questions
These FAQs were developed by the National Assembly of State Animal Health Officials' (NASAHO) RHDV2 Subcommittee in June 2020.
What are the differences between the different RHD virus types?
Rabbit hemorrhagic disease is caused by rabbit hemorrhagic disease virus (RHDV), a member of the genus Lagovirus and family Caliciviridae. There are many strains of RHDV, and three major viral subtypes: RHDV (“classical RHDV"), the antigenic variant RHDVa, and the recently emerged virus RHDV2 (also called RHDVb). Related lagoviruses, called rabbit caliciviruses, circulate in healthy rabbits. These viruses can confer varying degrees of cross-protection to RHDV.
While most rabbit caliciviruses do not appear to cause any illness, two potentially pathogenic strains have been reported. One virus identified in the U.S. (proposed name “Michigan rabbit calicivirus") was isolated from an outbreak that resembled rabbit hemorrhagic disease, although an attempt to reproduce the disease in experimentally infected rabbits resulted in little or no illness. A related strain, the Ashington strain of rabbit calicivirus, was recovered from dead wild rabbits during an outbreak in Europe.
What are the differences between the different RHDV1 and RHDV2 virus types?
There are many strains of the RHD virus, but three are of most concern. RHD Type 1 has two forms, RHDV and RHDVa. RHD Type 2 has just one form, RHDV2. The two forms of Type 1 are quite similar and their vaccines are cross-protective. They tend to not affect young bunnies but have a very high mortality rate for adult rabbits. RHDV2, on the other hand, seems less deadly than the Type 1 strains, but affects all ages of rabbits. The RHDV2 vaccine only protects against that type.
How can I tell if my rabbit has RHD?
Only laboratory tests can confirm a diagnosis of RHD. However, RHD should be suspected if a rabbitry experiences illness in most/all rabbits, high fevers, poor appetites, depression, inactivity, bloody discharges, seizures, and/or sudden death. Call your veterinarian right away if you have any concerns about your rabbit's health. Usually RHDV2 is associated with mass morbidity (illness) and mortality (death) in a colony or herd.
How is RHD transmitted?
It spreads between rabbits mostly by ingestion and inhalation of the virus. The virus is present in urine and feces from infected rabbits, so contaminated bedding, food or forage can be a source of infection. The virus can be moved from place to place mechanical vectors and fomites (flies, predators, scavengers, feral domestic and wild rabbits, vehicle tires, clothing, footwear, cages, equipment, and wind and water movement).
Can humans, dogs or other animals contract RHD?
RHD is not a zoonotic disease and there is no public health significance. RHD is specific to rabbits. Dogs, cats, and other pets cannot contract the disease, but can transport the virus just like vehicles, shoes, and equipment can.
Can rabbits that have been exposed and recover or never become ill carry the virus?
Exposure to the virus does not necessarily mean a rabbit is infected with the virus. Some rabbits will just be exposed; others will be exposed and become infected and either die or recover. Recovering rabbits will develop antibodies to the virus and become resistant to related calicivirus strains for an unknown period. Infected rabbits can “carry" or shed the virus for over a month, perhaps up to four months (when experimentally infected); they are not believed to be infected and shed for life.
Is it true wild rabbits are susceptible to the RHDV2 strain of virus?
RHDV2 has a wide host range and can infect wild rabbit species. The Southwest U.S. outbreak of RHDV2 in 2020 affected native North American rabbits and hares including black-tailed jackrabbits, desert cottontail rabbits, mountain cottontail rabbits, and antelope jackrabbits. Eastern cottontail rabbits have been shown to be susceptible in experimental studies.
How long can RHD persist in the environment?
The virus can survive for long periods outside the host. Environmental temperature, humidity, and protection by organic material are important factors in virus survival. Viable virus has been detected for as long as 105 days on a fomite at room temperature and in decaying tissue of infected carcasses for up to 90 days; it persists in chilled or frozen rabbit meat. The virus can remain viable for 22-35 days at 72°F. It survives freeze-thaw cycles. Pelts from dead wild or domestic rabbits in premises or geographic areas during an RHDV outbreak should not be processed, transported or sold.