Colorado Parks and Wildlife: Scary-looking rabbits were hopping around Fort Collins. These weren’t your standard cute, fluffy bunnies; they had horn-like growths protruding from their faces and bodies.

Colorado Parks and Wildlife officials have identified the cause as shope papillomavirus, a rabbit-only virus with no cure that produces wart-like tumours known as papillomas, particularly around the face and head of cottontail rabbits, 9NEWS reports.

The growths are not harmful to humans or pets, but it's recommended to keep a safe distance and avoid handling infected rabbits.