Overview

• Colorado Parks and Wildlife confirmed the growths are papilloma tumors caused by the Shope papillomavirus, which exclusively infects cottontail rabbits.
• The virus spreads through insect vectors such as fleas, ticks and mosquitoes and is not known to infect humans or other species.
• Although most lesions are benign, they can enlarge to impede feeding, vision or breathing and in rare cases can evolve into cancerous tumors.
• No treatment exists for wild populations and euthanasia is only recommended when growths prevent rabbits from eating or drinking, while domestic cases can receive surgical removal.
• Widely shared social media images have prompted public reports and ongoing seasonal monitoring by Colorado Parks and Wildlife.