New vaccine can save rabbits from deadly diseases News and research

Driving his car through an ice storm in Tennessee in early February was a risk that veterinarian Logan Kopp knew he had to take. The reward: rescue four vials containing 40 doses of a new vaccine against a highly contagious and deadly virus that affects rabbits. A storm-related power outage had knocked out cooling at Priest Lake Veterinary Hospital in Nashville-Antioch, Tenn., threatens to break down vaccine doses in cold storage there.

Kopp managed to preserve the vials of vaccine by transferring them from his workplace to his home refrigerator. “It was pretty awful,” he recalls of the treacherous drive, which took almost six hours to complete in the storm. But he felt he had no other choice.

The virus, known as RHDV2, causes rabbit hemorrhagic disease, a form of hepatitis. It is currently spreading through wild and domestic rabbit populations in the United States, Mexico and beyond. The disease progresses rapidly and is fatal to up to 90 percent of infected rabbits. The virus is largely spread through contact between the animals and their body fluids. Surfaces, such as human clothing, can also transmit it.

RHDV2 is not known to infect humans. But human movement of rabbits is likely to be a significant factor in the spread of the disease, with geographically random cases occurring in domestic rabbits, says Bryan Richards, emerging disease coordinator at the National Wildlife Health Center in Madison, Wis.

Fortunately, as Easter approaches, it looks better for at least some rabbits. In September 2021, the U.S. Department of Agriculture approved the Center for Veterinary Biologics emergency for a vaccine against the disease. The following month, a vaccine clinic appeared in California, where southern counties had experienced a wild outbreak of the virus. Rabbit owner groups shared resources and information online about the revived virus and the recently available vaccine. This spring, more than 40 states and Washington, DC, have access vaccine, according to manufacturer Medgene Labs. A website that serves rabbit owners lists more than 400 clinics and other websites that offer RHDV2 vaccination. Many veterinary clinics with vaccines in stock reach out to customers who own rabbits and encourage vaccination.

When Tennessee’s first case of rabbit haemorrhagic disease was confirmed in late January, Kopp knew the clock was ticking to protect the area’s rabbits. The vaccine doses he saved during the storm were among the first Priest Lake Veterinary Hospital to receive.

That clinic has since vaccinated about 170 rabbits, 110 of them at a drive-through vaccination event organized by the clinic in March. But there are many more rabbits out there: about 1.7 million households in the United States keep at least one pet, according to the American Pet Products Association. In some parts of the country it is difficult to find vaccination times. One of Kopp’s customers drove nine hours back and forth to get his rabbit vaccinated.

The virus is now endemic in 11 states in the United States, and cases have appeared in wild or domestic rabbits in 19 states over the past year, according to a frequently updated USDA map.

Estimates of population sizes for the country’s dominant rabbit species – such as domestic rabbits, which are usually kept as pets, eastern cotton tails and species of jack rabbits – are difficult to obtain. As many as 3,500 striped brush rabbits, an endangered species, live at the San Joaquin River National Wildlife Refuge, said Deana Clifford, a senior wildlife veterinarian at the California Department of Fish and Wildlife (CDFW).

Researchers are concerned that RHDV2 could threaten the population of rabbits with beach edges, along with other rare or endangered species of lagomorphs. A total of 24 rabbit species, or closely related species, worldwide have been identified as endangered or vulnerable to extinction by the International Union for Conservation of Nature’s Red List of Threatened Species. Since 2010, RHDV2 has caused outbreaks of rabbit haemorrhagic disease on five continents, according to a study from 2021 published in Cross-border and new diseases.

The long-term effects of the virus and its vaccine are unclear. Vaccination can save the lives of pet rabbits. But catching and vaccinating enough of most wild rabbit species – at least 60 percent of a region’s population – to control an outbreak can be challenging and costly, says Carlos Rouco Zufiaurre, an ecologist at the University of Córdoba in Spain. He explains that the vaccine’s protection will eventually diminish, which may allow virus spread to resume in groups of wild rabbits.

Nevertheless, CDFW and other partners have undertaken an attempt to vaccinate the shores of the San Joaquin River refuge. The team obtained vaccines made in France, which were available under special conditions before the US-made vaccine. About 700 rabbits in the sanctuary have so far been vaccinated, says Clifford. “What we are trying to do is keep about 15 to 20 percent of the population vaccinated at any given time [so] that if and when the disease ever comes to the sanctuary … we will not lose everyone, ”she adds.

Vaccines have also reached the endangered Columbia Basin pygmy rabbit, the smallest species in North America, during a recovery effort led by the Washington Department of Fish and Wildlife and the U.S. Fish and Wildlife Service. Clifford explains that although not all rabbits can be vaccinated, “in these particular circumstances, we believe that vaccination can have an effect.”

The outbreak in California, which also affected rabbits in southwestern Mexico, occurred from 2020 to 2021. The episode in these regions together represents one of the largest recorded North American outbreaks of RHDV2, according to the 2021 era. Cross-border and new diseases study. The rapid spread of the virus was a surprise, said Andrea Mikolon, a veterinarian at the California Department of Food and Agriculture and a co-author of the study.

The outbreak first caught the attention of the CDFW in May, when state biologists found over a dozen dead black-tailed rabbits in the desert north of Palm Springs, said Clifford, who is also co-author of the outbreak study. In 2021, the CDFW typically received citizen reports of one to five dead rabbits at a time, with occasional reports of a large number of deaths.

No wild cases have been confirmed in California this year, but Clifford says the disease can be spread undetected.

At the moment, the hope is that the campaign among veterinarians to vaccinate pet rabbits could slow down the spread of RHDV2 in the United States. Kopp takes time to talk to many clients, and explains that reliable clinical trials have shown that the vaccine is safe and effective. “There is definitely a certain tension, but I think a lot of people are just nervous just because it’s unknown,” says Kopp. Until further notice, he will continue to work to protect rabbits, one phone call and one vaccine at a time.

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