Rabbit Hemorrhagic Disease

by Amy Young
November 24, 2020

What is rabbit hemorrhagic disease?

Takeaways

Rabbit hemorrhagic disease (RHD) is caused by two groups of highly contagious viruses.
Rabbit hemorrhagic disease virus (RHDV, sometimes called RHDV1) primarily affects domestic rabbits and wild European rabbits.
Rabbit hemorrhagic disease virus 2 (RHDV2) affects domestic and wild rabbits and their relatives, including jackrabbits, hares, cottontails, and pikas.
Both viruses have high mortality rates in infected rabbits.
It is a reportable animal disease in the United States, meaning cases must be reported to state and federal authorities.
Protect domestic rabbits from infection by employing biosecurity protocols, including washing hands before and after working in the rabbitry, changing clothes between rabbit groups, and not sharing equipment with other facilities or owners.

Rabbit hemorrhagic disease (RHD) is caused by two different highly contagious groups of viruses, rabbit hemorrhagic disease virus (RHDV, sometimes called RHDV1) and rabbit hemorrhagic disease virus 2 (RHDV2). For both groups of viruses, the disease is usually fatal. Rabbits that survive RHDV can carry the virus for up to 2 months; the same is likely true for RHDV2. Both RHDV and RHDV2 are reportable animal diseases in the United States, meaning cases must be reported to state and federal agencies.

Rabbit hemorrhagic disease virus primarily affects rabbits of the genus Oryctolagus, which includes many domestic rabbits and wild European rabbits. It was associated with outbreaks in the 1970s - 1990s in Europe and China and negatively influenced some ecosystems in Europe where rabbits were a food source for endangered predator species.

Rabbit hemorrhagic disease virus 2 affects domestic and wild rabbits and their relatives, including jackrabbits, hares, cottontails, and pikas. As of November 2020, RHDV2 has spread across multiple states, including Arizona, California, Colorado, Nevada, New Mexico, Texas, Utah, and Washington, infecting wild, domestic, and feral rabbits. It is transmitted through direct contact with infected animals, their tissues or fluids, contaminated food and water, and on clothing, shoes and equipment. Insect vectors such as flies and mosquitoes can transmit the virus between rabbits, and predators and scavengers can shed the virus in their feces.

The virus cannot be transmitted from rabbits to humans or other domestic animals. The virus has been found in wild mice living near RHD outbreaks, but these mice did not show signs of disease from the virus.

What are the clinical signs and gross changes of rabbit hemorrhagic disease?

For RHDV, animals between 4-8 weeks may be resistant to disease if they received maternal antibodies. In nonvaccinated adults, death often occurs within 1 day of infection. The incubation period can be up to 6 days, with clinical signs lasting up to 4 days. Clinical signs include bleeding from the mouth or nose, fever, lethargy, lack of appetite, difficulty breathing, muscle spasms, liver failure, disseminated intravascular coagulation (DIC), and sudden death.

Unlike RHDV, RHDV2 can affect animals under 4 weeks of age. The incubation time is slightly longer with RHDV2 (3-9 days) and clinical signs, which are similar to those with RHDV, can last up to 5 days. Wild species such as hares appear to die more rapidly. More animals develop chronic infections with RHDV2 than with RHDV.

How is rabbit hemorrhagic disease diagnosed?

A presumptive diagnosis of rabbit hemorrhagic disease is based on clinical presentation, bloodwork, and analysis of urine samples. Molecular tests, including reverse transcription polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA), are used to identify the virus.

How is rabbit hemorrhagic disease treated?

Treatment for RHD is currently limited to supportive care.

What is the prognosis for rabbit hemorrhagic disease?

Mortality depends on age of the rabbit and virus strain, but can be up to 90-100% for both RHDV and RHDV2. Young rabbits have higher mortality rates than adults, especially with RHDV2.

How can rabbit hemorrhagic disease be prevented?

There is currently no licensed vaccine for RHDV2 available in the U.S., but veterinarians can apply for a special license to import a vaccine with state veterinarian approval on an emergency basis in affected states. For California, veterinarians should contact the California Department of Food and Agriculture (CDFA).

Protect domestic rabbits from infection by employing biosecurity protocols, including washing hands before and after working in the rabbitry, changing clothes between rabbit groups, and not sharing equipment with other facilities or owners.

The United States Department of Agriculture (USDA) lists the following biosecurity recommendations:

Do not allow pet or wild rabbits to have contact with your rabbits or gain entry to the facility or home. Do not release pet rabbits into the wild.
Do not allow visitors in rabbitries or let them handle pet rabbits without protective clothing (including coveralls, shoe covers, hair covering, and gloves).
Always wash hands with warm soapy water before entering your rabbit area, after removing protective clothing and before leaving the rabbit area.
Do not introduce new rabbits from unknown or untrusted sources. Do not add rabbits to your rabbitry from animal shelters or other types of rescue operations.
If you bring outside rabbits into your facility or home, keep them separated from your existing rabbits for at least 30 days (quarantine). Use separate equipment for newly acquired or sick rabbits to avoid spreading disease. Examination by a veterinarian is recommended prior to ending quarantine.
Sanitize all equipment and cages on or off premises before they are returned to the rabbitry. Disinfect with 10% bleach or 10% sodium hydroxide mixed with water.
Avoid feeding hay grown or stored outdoors in areas where wild rabbits are affected.
Establish a working relationship with a veterinarian to review biosecurity practices for identification and closure of possible gaps.
Do not touch dead wild rabbits. Report multiple dead wild rabbits to state wildlife officials.

Prevention of RHD in wild rabbits is much more challenging. Outbreaks could have significant impacts on wild rabbit populations, which in turn could impact predators that rely on them as food sources.

Report dead domestic rabbits in California to CDFA at 909-747-4462 and/or submit to your local California Animal Health and Food Safety (CAHFS) laboratory for a diagnostic work-up. Consult your private veterinarian if your domestic rabbit is sick. Dead wild rabbits in California may be reported to the California Department of Fish and Wildlife (CDFW) online or by calling 916-358-2790.

Danielle Tarbert, DVM
Companion Exotic Animal Medicine & Surgery Service