Rabbit Hemorrhagic Disease Virus

What is Rabbit Hemorrhagic Disease Virus?

Rabbit Hemorrhagic Disease Virus (RHDV) is a virus similar to norovirus in humans and the feline virus that causes upper respiratory issues in cats. RHDV only infects wild and domestic rabbits and hares but is transmissible through dogs and cats. It damages the liver and causes internal bleeding.

The first strain (RHDV1) was discovered in Asia in 1984 before spreading worldwide through its primary host, the European rabbit. However, outbreaks in the United States occasionally happen in domestic rabbits. Cases have been confirmed in Utah, Illinois, Indiana, New York, Maryland, Minnesota, and Pennsylvania since 2000.

RHDV has mutated since its discovery and produced a second strain, RHDV2, a deadlier form of RHDV. This strain was first detected in the US in 2018 and has spread across multiple states. As of August 1, 2023, this disease has been confirmed in 29 states including California, Oregon, Nevada, Colorado, New Mexico, Arizona, Utah, Texas Wyoming, Montana, and Idaho.

RHDV2 is fatal to rabbits and is classified as a foreign animal disease in the United States. RHDV2 impacts wild and domestic rabbits and hares compared to RHDV1, which primarily impacted wild and domestic European hares.

RHDV1 and RHDV2 have similar clinical signs and high mortality rates in unvaccinated animals. Therefore, it should be assumed that all wild rabbits and hare species in the United States are susceptible to RHDV2. Since March 31, 2022, RHDV2 has been confirmed in the following animals:

• Domestic rabbits

• Feral rabbits

• Jackrabbits

• Cottontails

• Snowshoe hares

• Bush rabbits

• Pygmy rabbits

When this disease is found in a rabbit, it must be reported to the World Organization of Animal Health. Veterinarians should contact the USDA APHIS Area Veterinarian in charge of their state if a case is suspected. Your veterinarian can work with you on proper reporting based on your rabbit’s condition.

Symptoms of Rabbit Hemorrhagic Disease Virus

Clinical signs of RHDV1 typically appear 1-3 days after infection, while RHDV2 usually takes 3-9 days. There are four primary forms of RHDV infection.

The most severe disease is typically absent of clinical signs:

• Terminal vocalizations

• Collapse and death within 12-24 hours

Acute disease symptoms:

• Bleeding from nose and mouth, rectum, eyes

• Fever

• Difficulty breathing

• Loss of coordination, seizures

• Depression, lethargy

• Loss of appetite

• Yellow mucous membranes

• Anemia

• Death in several days

Subacute—typically similar signs to acute disease but less severe:

• Death 1-2 weeks after infection

Chronic or subclinical infection usually affects only a small amount of animals, with signs including:

• Lethargy

• Yellow mucous membranes

• Poor body condition

• Death 1-2 weeks after infection

Survivors of the subacute or chronic forms typically gain lifelong immunity.

Causes of Rabbit Hemorrhagic Disease Virus

RHDV1 primarily infects wild and domestic European hares. However, since RHDV2 has impacted so many wild and domestic rabbits in the US, all wild rabbit and hare species are likely susceptible.

The virus is spread through direct contact between rabbits or indirect contact with infected meat, fur, blood, urine, feces, or objects that came in contact with an infected rabbit. Those objects could be:

• Plants

• Bedding

• Cages

• Other household pets that go outside

• Human clothing and shoes

In addition, the virus can infect other rabbits through the mouth, nose, or eyes.

Both viruses are easily spread and highly resistant to the environment. It has been shown that RHDV2 can survive up to 15 weeks outside, and can survive freezing temperatures.

How Veterinarians Diagnose Rabbit Hemorrhagic Disease Virus

Diagnosis is usually based on clinical signs, history, and then confirmed through necropsy (post-death) and molecular tests.

Necropsy is another term for autopsy, an examination of the deceased patient’s internal organs. In necropsy, the most common lesions to appear are a pale liver, enlarged spleen, and bleeding in the lungs, liver, heart, kidney, and trachea.

Treatment of Rabbit Hemorrhagic Disease Virus

Unfortunately, there is no treatment for this virus other than supportive care such as fluid therapy, supplemental nutrition, etc. If you suspect your rabbit has RHDV2, contact your primary veterinarian immediately.

The mortality rate of RHDV2 is at 70-90%. Most infected unvaccinated rabbits will pass away. The best treatment for this disease is prevention with the RHDV2 vaccine and good hygiene practices.

Recovery and Management of Rabbit Hemorrhagic Disease Virus

If your rabbit does recover, the virus can still spread in their urine, feces, blood, and other secretions for up to a month. Keep your rabbit quarantined from other rabbits until your veterinarian says it is okay to be reintroduced.

Prevention of Rabbit Hemorrhagic Disease Virus

Since this new variant is highly resistant to the environment, can easily spread, and has a high mortality rate, it is best to do everything you can to protect your rabbit from contracting it.

The first step to preventing RHDV2 is to vaccinate your rabbit against the disease. A Medgene vaccine against RHDV2 is now licensed in the U.S. The vaccine provides up to 90% protection rates for rabbits. However, since vaccines are not 100% effective, it is vital to still practice good hygiene methods to ensure the virus cannot be spread. Consult your veterinarian about vaccinating your rabbit.

It is recommended not to let your rabbit outside in areas where wild rabbits frequent. Do not wear outdoor shoes around your rabbit, and do not feed your rabbit grass, weeds, or flowers from outdoor areas. Always wash your hands before handling rabbits.

To disinfect a pet rabbit’s habitat, remove all organic material before disinfection such as bedding, feces, fur, etc. Wash the habitat thoroughly with soap and water. Then, fully submerge or saturate items with diluted bleach for five minutes before rinsing with water. Wear appropriate protective gear such as gloves and eye protection. Visit the USDA website for a complete list of other disinfectants and protocols.