Mutant Rabbits Spark Attention in Wisconsin

In northern Wisconsin and beyond, peculiar rabbits sporting horn-like growths on their heads and faces have caught the eye of many, creating quite a stir online. Although such sightings happen annually, recent photographs of these bunnies in Colorado have gone viral, leading social media users to label them as “Frankenstein” bunnies or draw comparisons to zombies from the HBO series “The Last of Us.”

While their appearance might seem alarming, experts like Nancy Businga, a wildlife disease specialist with the Wisconsin Department of Natural Resources, clarify that the wart-like growths are due to the Shope papillomavirus, which is not indicative of an apocalypse. “That can certainly be very striking and unusual for those who haven’t encountered it before. Each year, we get a handful of reports about these rabbits with lesions,” Businga explained.

Businga noted that there’s been a slight increase in reported cases this year in northwestern Wisconsin, with the agency logging eight reports concerning 23 rabbits in counties like St. Croix and Dunn. In comparison, only one report was recorded last year.

Paul Lambert, an oncology professor and director of the McArdle Lab for Cancer Research at the University of Wisconsin School of Medicine and Public Health, pointed out that the Shope virus is historically significant as it was the first virus identified to cause tumors. Discovered by Richard E. Shope in the 1930s, it is predominantly harmless. “This isn’t a bloodborne pathogen,” Lambert stated, adding that papillomaviruses spread through skin contact.

Typically, the infections are benign, and most rabbits shed the warts as their immune systems tackle the virus. However, Lambert mentioned that some strains of human papillomaviruses in humans can lead to serious health issues, including cancer. There are over 300 known papillomaviruses, with more than 200 relating to humans.

“This isn’t a new phenomenon,” Lambert elaborated. “Pictures of these rabbits tend to attract attention because of their strange appearance.” He also referred to the legendary jackalope, which has existed in folklore for ages and ties into this bizarre aspect of nature.

Kristen Bernard, a virology professor at the University of Wisconsin School of Veterinary Medicine, emphasized that the Shope virus doesn’t pose a risk to humans, though it can be transmitted between wildlife through insects and ticks. “When an insect bites an infected animal to feed, it can pick up the virus and then transfer it to another animal,” Bernard explained.

Businga indicated the rise in rabbit sightings might correlate with warmer weather, which supports insect activity like mosquitoes and ticks. Although some suggest climate change may be a factor, Lambert expressed skepticism about direct evidence linking climate change to a rise in papillomavirus infections. “I do believe in climate change, but I don’t know of any studies that show it’s increasing papillomavirus infections,” he said.

While Bernard acknowledges some diseases spread by ticks and mosquitoes could be related to climate change, she noted it’s uncertain whether this affects the Shope virus. “I wouldn’t claim there’s strong evidence for that, but I wouldn’t be surprised if climate change enhances its spread through insects during the summer,” she remarked.

It’s not just rabbits in Wisconsin facing similar issues; there have been reports of papillomavirus-related growths in deer and even a few instances among squirrels this year. Bernard urged caution when encountering wildlife exhibiting these growths. Although the virus isn’t transmittable to humans or pets, other diseases like tularemia, which can affect humans, might still be present.

Individuals who come across sick wildlife should report their findings to the DNR, either by submitting a form through the agency’s website or by calling 608-267-0866.