A lethal rabbit virus is spreading across the southwestern United States, killing wild rabbits on this continent for the first time and causing concern for some fragile species and the animals that prey on them.

The most recent deaths were reported last week in southern California, where employees at a wind farm happened upon the carcasses of 10 to 20 black-tailed jack rabbits scattered across the desert near Palm Springs. That followed thousands of deaths since March in wild and domestic rabbits in New Mexico, Texas, Arizona, Colorado and Nevada.

While rabbit hemorrhagic disease virus type 2 can produce symptoms such as seizures or fever, it often causes sudden death, marked by “terminal squeals” and collapse. In wild die-offs, some rabbits have been found with blood near their noses and mouths, “but a lot of the time, the reports are just, ‘dead,’” said Deana Clifford, senior wildlife veterinarian for the California Department of Fish and Wildlife. “That’s a little bit startling to see a bunch of dead rabbits.”

As the nation struggles to slow the spread of the coronavirus, agriculture and wildlife officials across the southwest are emphasizing the rabbit virus is not linked to the coronavirus or known to be dangerous to humans. But like the coronavirus, the rabbit virus is highly contagious and hard to contain. It can remain viable for months and spreads easily — through contact with infected rabbits or via scavengers, insects, feces, a handler’s clothing or bedding that might line a rabbit hutch.

The Washington Post's Karin Brulliard explains how pet owners can protect their pets and stay safe as the novel coronavirus continues to spread. (The Washington Post)

Vaccines are available in Europe, where the virus has caused significant mortality in wild and domestic rabbits since emerging in France in 2010, but they are not approved for sale in the United States. Some U.S. states, including Nevada — where the virus has killed domestic rabbits at an animal rescue near Las Vegas — are scrambling to help veterinarians obtain approval from the U.S. Department of Agriculture to import limited numbers of doses.

Those would be administered to domestic animals that are part of what the USDA says is a $2.2 billion rabbit industry that is mostly pet-focused. But they would be of no help to native rabbits and hares, which until March were not known to be susceptible to the virus, known as RHDV2.

“There’s not really much we can do with the wilds,” said Ralph Zimmerman, state veterinarian for New Mexico, where the nation’s first wild rabbit deaths occurred in March. “It’s moving from area to area. We’ve had bigger die-offs in some areas, and we’re still getting reports of dead rabbits — like, hundreds,” at each site, he said.

As of Thursday, the virus had also killed 470 domestic rabbits in New Mexico, Zimmerman said. Nearly 600 others have been euthanized at affected sites that keep rabbits — as pets, or for breeding, meat or pelt — a step the state is requiring to prevent the virus’s spread. About 30 sites are under quarantine, he said. New Mexico received 500 doses of vaccine from France on Wednesday, he said.

Rabbit hemorrhagic disease first emerged in China in 1984, where it may have been introduced by imported angora rabbits, according to a report by Iowa State University. Outside Europe, the newer variant, type 2, has occurred in Australia and Canada, and there have been a few domestic cases in the United States since 2018.

But wildlife officials hoped North America’s native wild rabbits, which are different from European species, might be immune.

So far, the virus has killed four native species, according to the World Organization for Animal Health, to which the USDA reports various animal diseases: desert and mountain cottontails and black-tailed and antelope jack rabbits. Those are all abundant, but wildlife officials say they are worried about more fragile members of the rabbit family, as well as broader ecosystem effects. In Europe, researchers have linked lynx declines in some areas to rabbit die-offs.

In Texas, there is concern for the rare Davis Mountain cottontail but also the possibility lower rabbit numbers could force animals that eat them — among them, coyotes, bobcats and mountain lions — to target other prey, such as the dwindling population of pronghorn antelope. “It could have an effect on those predator numbers as well,” said Bob Dittmar, a wildlife veterinarian at the Texas Parks and Wildlife Department.

In California, a handful of native rabbit species, including the federally endangered riparian brush rabbit, are at risk. It is possible the virus also could infect the pika, a mountain-dwelling mammal that belongs to rabbits’ lagomorph family and is threatened by climate change, Clifford said.

“This has the potential to depress those populations, and if we have depressed prey, then potentially we have predators who often heavily rely on rabbits that may have trouble finding some food,” said Clifford, referring to species including golden eagles and foxes.

Scientists and conservationists already are discussing moving riparian brush rabbits into captivity to prevent their exposure to the virus, Clifford said.

Wildlife officials said the focus is on mitigating the spread in domestic populations, via quarantines and sanitation, and instructing the public to stay away from dead rabbits and report them to authorities. The specter of the virus has already halted some adoptions of domestic rabbits — often the most common animal at shelters after dogs and cats — and rescues by wildlife rehabilitation groups.

“Eventually it might taper off and some of the remaining animals will develop immunity to it,” Zimmerman said. “And then it’s a slow climb back for the population numbers.”

That is little consolation to the American Rabbit Breeders Association, whose members show their animals at more than 4,000 events a year.

“This is probably the most significant issue that has faced the hobby since its inception,” said Jay Hreiz, a North Carolina veterinarian who chairs the group’s health committee and who said he expects the virus to race across the nation. “We are almost irrelevant now that it’s in the wild population. … I just fear the damage is already done.”

The association has asked the USDA to ease restrictions on vaccine imports and pleaded with U.S. companies to release a vaccine, Hreiz said. But “rabbits sit in this weird interstitial space between companion animal and livestock in the United States,” he said. “It boils down to money.”

One good thing, he said, is that the covid-19 pandemic had already forced the association to cancel its spring shows, which would have fueled the virus.

“If there was ever a good time for a deadly rabbit virus to spread through the United States, that time is now,” he said.

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