Wildlife officials in Colorado have confirmed a troubling rise in cases of shope papillomavirus, a rare disease causing wild rabbits to grow tentacle-like growths from their heads and mouths. While the condition is not new to science, the unsettling images—widely shared online—have reignited public concern and prompted health officials to clarify the implications for humans, pets, and local ecosystems.
A Virus With a History—and a New Spotlight
First identified in the 1930s by virologist Richard Shope, shope papillomavirus has long been known to infect wild rabbits, especially cottontail species common throughout the Midwest. The virus leads to the formation of papillomas, or wart-like tumors, often growing along the head, face, and mouth. While these growths are technically benign, they can resemble black spikes or quills and, in advanced cases, resemble alien-like appendages.
This summer, reports from Fort Collins, Colorado, and surrounding areas have brought the disease back into public focus. According to NBC affiliate KUSA, local residents began noticing rabbits with what looked like “black toothpicks” sticking out of their faces. One Fort Collins resident, Susan Mansfield, said, “I thought he would die off during the winter, but he didn’t. He came back a second year, and it grew.”
Images of these so-called “Frankenstein rabbits” have circulated widely on platforms like Reddit, sparking both fascination and alarm.
Why It’s Happening Now—and How It Spreads
The rise in sightings is largely tied to seasonal insect activity. Shope papilloma virus is spread primarily through biting insects like mosquitoes, ticks, and fleas, which are far more active in the warmer months. This explains the seasonal pattern of outbreaks and the current concentration of cases in Colorado, as well as additional reports in South Dakota, Minnesota, and Texas.
Rabbits like this one with tentacle-like growths have caused a stir in Colorado. Credit: Amanda Gilbert / 9News
The virus is transmissible between rabbits via close contact or shared exposure to these insect vectors. However, it’s not known to infect other animals or humans. Kara Van Hoose, public information officer for Colorado Parks and Wildlife (CPW), emphasized that the condition is “mostly benign in rabbits,” adding that, “The animal can clear the virus from its system on its own. We would be concerned only if the growths are on the eyes or impede the rabbit’s ability to eat.”
Despite its bizarre visual effects, the virus does not pose a threat to humans, nor is it contagious to pets. Infections in domestic rabbits are extremely rare, though they remain possible if pets are exposed to infected wild rabbits or insect bites.
What To Do If You Spot an Infected Rabbit
Colorado wildlife officials are urging residents not to approach or attempt to handle rabbits with visible growths. While the appearance can be alarming, these animals do not require euthanasia unless the growths impair their ability to see or eat.
According to CPW guidance, most rabbits will recover on their own as their immune systems fight off the infection. Intervening could cause unnecessary stress to the animal and expose humans to other zoonotic diseases unrelated to papillomavirus.
If you’re a rabbit owner, the best preventative measure is to keep domestic rabbits indoors, especially during peak mosquito hours around dawn and dusk. Outdoor hutches should be screened and regularly cleaned to reduce insect exposure.
Could the Virus Spread Beyond the U.S.?
The current outbreaks remain localized, and experts agree the likelihood of a global spread is low. According to Vetlexicon, a widely used veterinary knowledge base, shope papilloma virus “does not occur in the UK or Europe.” That’s reassuring news for rabbit owners and wildlife managers abroad.
Still, the virus has a wide host range among rabbit species, including jackrabbits, brush rabbits, snowshoe hares, and even European rabbits, raising concerns about long-term ecological implications if the virus becomes more widespread.
Monitoring and research will remain important as climate patterns shift and insect populations expand, potentially increasing the risk of more frequent or intense outbreaks.