New Vaccine Could Save Rabbits From Deadly Hemorrhagic Disease

Scientists have a new tool in the fight against a spreading virus that threatens the small mammals

An image of two riparian bush rabbits standing in the grass. Both rabbits are small and tan in color.
Researchers are most concerned with the disease affecting endangered species like these riparian bush rabbits. Pacific Southwest Region USFWS via Wikimedia Commons under Public Domain

Veterinarians are racing to save domestic and wild rabbits from a devastating virus. The virus, called RHDV2, is a form of hepatitis that causes rabbit hemorrhagic disease. Across North America, RHDV2 is progressing rapidly through rabbit populations. The virus moves from animal to animal as a result of close contact and the exchange of bodily fluids. Some symptoms include fever, lethargy, bleeding from the nose or mouth, and breathing difficulties—though in many cases the disease does not have symptoms before death. The virus is 90 percent fatal among infected rabbits, reports Tatum McConnell in Scientific American

Now, a new vaccine developed by Medgene Labs in collaboration with the United States Department of Agriculture (USDA) may help protect bunnies. In 2021, the USDA's Center for Veterinary Biologics used an emergency authorization to use the vaccine against the disease. More than 40 states and Washington, D.C. should have access to the vaccine this spring, according to the manufacturer Medgene Labs.

"We are excited to extend the use of our platform technology and achieve emergency use authorization for our RHDV2 vaccine from the USDA. We have worked closely with their team since the major outbreak to reach this milestone. We are dedicated to helping rabbit owners and veterinarians combat this devastating foreign animal disease," says Medgene Lab's chief executive officer, Mark Luecke, in a statement.

Rabbit hemorrhagic disease was first detected in the 1980s among European rabbit populations. In 2010, the RHDV2 variant was detected in wild and farmed rabbits in France. Since then, officials have seen the virus in the United States three times since 2018. The virus has caused outbreaks in five continents altogether, according to a study published in 2021 in Transboundary and Emerging Diseases. The virus does not impact humans. However, vets are urging that domestic rabbits get vaccinated against RHDV2. It is estimated that 1.7 million households in the U.S. have a bunny as a pet, per Scientific American.

"This is a disease that is 100 percent deadly to the rabbits, and it's a really scary death," Susan Keller, a veterinarian at the Broward Avian and Exotic Animal Hospital in South Florida, tells WPTV's Tania Rogers. "They die very suddenly, with a high fever, with blood coming out of their nose and mouth. It's important that we vaccinate our domestic rabbits." Keller also explains to WPTV that the virus is hardy, and can enter homes through shoes, food items and be carried around in the environment.

For now, RHDV2 is endemic to 11 states in the South and West, in areas including California, Arizona, Texas and New Mexico. Nineteen other cases in wild and domestic rabbits have popped up in 19 states over the past year, according to a USDA Map tracking rabbit hemorrhagic disease.

Researchers are most concerned with the disease affecting endangered species like the riparian bush rabbit, a species of cottontail rabbit, and other rare species of lagomorphs.

The long-term impacts of the virus and the vaccine are unknown. Carlos Rouco Zufiaurre, an ecologist at the University of Córdoba, tells Scientific American that viral spread between bunnies could start up again as a vaccine's protection fades.

The California Department of Fish and Wildlife (CDFW) is acting by vaccinating riparian bush rabbits located at the San Joaquin River National Wildlife Refuge against RHDV2. About 700 rabbits at the sanctuary have been immunized to keep between 15 to 20 percent of the population vaccinated in the event of an outbreak, Deana Clifford, a wildlife veterinarian with CDFW, tells Scientific American.

Vaccines are also being used for the endangered Columbia Basin pygmy rabbit, the smallest rabbit in North America. Experts say that while not all rabbits can be vaccinated, in cases where endangered species are involved, vaccination can have a significant impact. For now, experts are counting on veterinarians to recommend vaccinations to pet owners to stop the spread of the virus in the U.S., Scientific American reports. 

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