Rabbit Hemorrhagic Disease Fact Sheet
History of Arizona state outbreak
On March 25, the Arizona State Veterinarian's Office received Information from the State Veterinarian in New Mexico that they had a confirmed case of RHDV2 in a domestic rabbit and were seeing a die off of wild rabbits as well. On April 2, New Mexico reported that since the March 24, 2020 diagnosis of RHDV2 in pet rabbits was confirmed at Foreign Animal Disease Diagnostic Laboratory (FADDL), 5 additional detections on premises in 5 counties have been confirmed, and this investigation is ongoing. On April 2, they confirmed RHDV2 in a wild black-tailed jackrabbit and wild cottontails, representing the first detection of this virus in wild rabbits in the United States.
On April 1st, Arizona Game and Fish received 2 separate reports from wildlife managers in the Douglas area of dying cottontails and jackrabbits. A cottontail and black-tailed jackrabbit were collected and delivered on April 4th to Dr. Justice-Allen, wildlife veterinarian for AZGFD. Lesions were found consistent with RHDV2. Samples from these rabbits were sent to the FADDL at Plum Island. On April 8th, the laboratory confirmed that these animals had died from RHDV2.
On April 6th the AZDA received a report of a sudden die off in a domestic rabbit population in North Eastern Arizona. Samples were collected and sent to FADDL and were reported out as positive on April 9, 2020.
RHDV2 is a viral disease that only affects rabbits (not people, pets, or livestock). Until very recently, it was not known whether or not North American native rabbits would be susceptible to it. They are not susceptible to another strain of the virus, RHDV1. This virus is not related to coronavirus; it is a calicivirus. Infection with this virus is associated with a high mortality rate and it is quite contagious. The virus can survive in the environment for an extended period of time.
Origin of the disease
The RHD virus was first diagnosed in 1984 in China. It spread widely throughout the world and is well established in some countries. It was introduced and used as a natural population control measure in both New Zealand and Australia, where rabbit numbers were raging unsustainably.
RHD probably developed from non-pathogenic caliciviruses present in wild European rabbits. There are three forms of the RHD virus. The form identified in the Arizona and New Mexico was RHDV2, believed to infect all ages of domestic rabbits but less deadly than types RHDV and RHDVa.
Signs of infection
The first sign of infection with RHD is often sudden and unexpected death in previously healthy rabbits. Those that do not die immediately may demonstrate poor appetite, depression, inactivity, and listlessness; they will have a fever and bloody nasal discharge may be noted. Later signs relate to organ failure and include jaundice, respiratory distress, diarrhea, weight loss, bloating, and death.
Caretakers of rabbits affected by but recovering from the virus in the current outbreak on the San Juan Islands observed rabbits did not come to the front of their cages with interest when fed; even those that survived appeared “limp” and inactive at the back of their cage for a day or two before recovering completely.
How the virus spreads
The RHD virus is very contagious and easily spread through numerous means:
- Ingestion of contaminated food or water
- Direct contact with infected live or dead rabbits
- Contact with contaminated equipment, tools, hutches, bedding, etc.
- Viral movement by flies, birds, biting insects, predators, scavengers, and humans
- Contact with urine, manure, and respiratory discharges of infected rabbits
- Ocular (conjunctival) infection via flies, dust, or secretions of infected rabbits
- Contact with feces of predators or scavengers that have eaten infected rabbits
Control and prevention
Because the RHD virus is highly contagious, can be spread by many means, and can be maintained in wild rabbit populations, controlling outbreaks is challenging once the virus is present in an area. The virus can live in flies for as much as nine days, in carcasses for up the three months, and for a few weeks in dried excretions/secretions.
Rabbits surviving infection are believed to shed the virus for at least 30 days, but in experimental cases, they shed the virus as many as 105 days. Long term/permanent shedding is unlikely. Exposed and surviving rabbits have immunity to that viral strain for an unknown amount of time.
Vaccines exist for RHDV/RHDVa and RHDV2; there is no cross protection between strains, and annual revaccination is recommended. Because RHD is considered a foreign animal disease, vaccines are only available in the U.S. through private veterinarians who have applied for and been granted permission by the USDA to purchase and distribute the vaccine.
Strict biosecurity practices are the backbone of prevention. Essential steps include:
- Keep a closed rabbitry
- Exclude wild and feral rabbits and predators from rabbitry
- Wash hands between handling rabbits in different pens or cages
- Clean and disinfect* equipment, tools, footwear, feed and water containers, cages, etc.
- Control flies and biting insects
- Remove brush, grass, weeds, trash, and debris from rabbitry
- Protect feed from contamination by flies, birds, rodents, etc.
- Do not feed grass or other forage that could be contaminated with the virus
- Do not use forage, branches, etc. for bedding
- House rabbits indoors if possible
- Do not share equipment with others who raise rabbits
- Remove and bury or dispose of dead rabbits promptly
- Submit carcasses for examination and sampling promptly
- Contact a veterinarian promptly if sick or dead rabbits are observed
- Do not transport rabbits into or out of RHD quarantine areas
- Quarantine new rabbits or those returning from shows for one month
*Recommended disinfectants include those in the phenol class or 10 percent bleach. Clean thoroughly with soap and water first and apply disinfectant for recommended contact time. Rinse well and let dry before allowing animal contact.