Cottontail rabbit papillomavirus (CRPV) Bites from CRPV-carrying mosquitoes and ticks cause some cottontail (genus Sylvilagus) and European rabbits (Oryctolagus cuniculus) to develop hornlike protuberances around their head and face. (more) What Is Causing the “Horns” on Rabbits in Colorado? Ask the Chatbot a Question More Actions Share Share Share to social media Facebook X URL https://www.britannica.com/topic/What-Is-Causing-the-Horns-on-Rabbits-in-Colorado Feedback Corrections? Updates? Omissions? Let us know if you have suggestions to improve this article (requires login). Feedback Type Select a type (Required) Factual Correction Spelling/Grammar Correction Link Correction Additional Information Other Your Feedback Submit Feedback Thank you for your feedback Our editors will review what you’ve submitted and determine whether to revise the article.

　　External Websites Ask the Chatbot a Question Written by John P. Rafferty John P. Rafferty writes about Earth processes and the environment. He serves currently as the editor of Earth and life sciences, covering climatology, geology, zoology, and other topics that relate to... John P. Rafferty Fact-checked by The Editors of Encyclopaedia Britannica Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree. They write new content and verify and edit content received from contributors. The Editors of Encyclopaedia Britannica Last Updated: Aug 14, 2025 • Article History Table of Contents Table of Contents Ask the Chatbot Unsettling photographs of wild cottontail rabbits near Fort Collins, Colorado, sporting hornlike or tentacle-like tumors on the face and head surfaced in news reports in August 2025. Although these images caused some shock and confusion, the tumors are the product of a relatively common viral disease in rabbits spread by mosquitoes and ticks, according to researchers and wildlife officials. The virus—called cottontail rabbit papillomavirus (CRPV), Shope papillomavirus, or Shope virus—was first identified by American physician Richard Edwin Shope in 1933. CRPV affects cottontail rabbits (genus Sylvilagus) and European rabbits (Oryctolagus cuniculus and its domesticated form, O. cuniculus domesticus), presenting as ...(100 of 212 words)

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