Rabbits With Hornlike Growths Are Hopping Around Colorado. Are They OK?

Science|Rabbits With Hornlike Growths Are Hopping Around Colorado. Are They OK?

With black spikes growing on their heads, tentacles protruding from their mouths and sluglike growths blocking their eyes, several rabbits hopping around Colorado this week have invited social media comparison to nightmarish mutants.

But local residents and pet owners shouldn’t fear the unsightly creatures munching on grass in their backyards: The bunnies are simply infected with cottontail rabbit papillomavirus, a mostly benign infection that can’t spread to other species, said Kara Van Hoose, a spokeswoman for Colorado Parks and Wildlife.

Rabbits typically overcome the disease on their own, she said, and it becomes a cause for concern only if it hinders their ability to eat or see. Still, it can cause growths in infected rabbits that resemble “gross” warts or horns, she said.

A resident in Fort Collins, Colo., a city about 65 miles north of Denver, first reported an infected rabbit on Friday, Ms. Van Hoose said. Since then, her department has fielded more than a dozen calls about sightings, mostly from people in Northern Colorado.

“We’re so used to seeing rabbits, so they’re like, ‘Oh my god, what is that on its face?’” Ms. Van Hoose said. “‘I know what a rabbit is supposed to look like, and that’s not it.’”

It’s not the first time this month that bunnies have driven the internet into a frenzy. Several rabbits used in a photo shoot by the fake heiress known as Anna Delvey were recently abandoned and then rescued in Prospect Park in Brooklyn.

Cottontail rabbit papillomavirus is transmitted through biting insects such as fleas and mosquitoes, so rabbits are more likely to contract it in the summer, when interactions with bugs are more common, Ms. Van Hoose said. There’s no cure or treatment for the disease, she said, so there are few ways to help.

Officials aren’t sure how many rabbits are infected because some people may be reporting the same ones repeatedly Ms. Van Hoose said.

The virus won’t infect most household pets, but people should keep pet rabbits indoors if they see infected wild rabbits in their area, she said. The disease is more severe in domesticated rabbits and can cause cancer, according to a National Institutes of Health study. Pet rabbits should be taken to a veterinarian if they are infected, according to a tipsheet from Colorado Parks and Wildlife.

Residents should also avoid feeding or interacting with the infected rabbits, and instead should enjoy the novelty of their strange appearances from afar, Ms. Van Hoose said.

“Nature is metal,” she said, “and this can be kind of cool looking on different rabbits.”