Overview

• Colorado Parks and Wildlife has received about a dozen reports since August 8 but cannot determine how many distinct rabbits are affected due to possible repeat sightings.
• The keratinized protrusions are caused by Shope (cottontail) papillomavirus, a species-specific virus first identified in the 1930s by Dr. Richard E. Shope.
• Infections rise in summer months when mosquitoes, ticks and fleas transmit the virus between wild cottontails.
• Wildlife officials emphasize that the virus does not infect humans or most household pets but can cause more severe disease and cancer risk in domestic rabbits.
• Social media claims of similar sightings in Minnesota and Nebraska remain unverified by wildlife agencies outside northern Colorado.