Wildlife officials in Colorado are monitoring an unusual increase in cases of Shope papillomavirus, a disease affecting wild and domestic rabbits, following a higher number of sightings this summer.
Shope papillomavirus, also known as cottontail rabbit papillomavirus (CRPV), is a DNA virus first identified in the 1930s by Dr Richard E. Shope. The virus primarily infects wild cottontail rabbits but can also spread to domestic species. It causes firm, horn-like growths, benign papillomas, that usually appear on the head, neck, and genital regions. While these lesions are not inherently fatal, they can grow large enough to interfere with eating, vision, or movement, leaving the rabbit vulnerable to starvation, injury, or predation.
There are two known types of CRPV: CRPV-1, the progressor type, in which lesions continue to grow and may lead to further health complications, and CRPV-2, the regressor type, in which lesions can eventually shrink and disappear without intervention. The type present in an individual rabbit influences the course of the disease and its impact on survival.
Colorado Parks and Wildlife (CPW) has reported a marked rise in sightings of infected rabbits in both rural and suburban areas. Wildlife health officers say most cases are identified visually in the field due to the distinctive wart-like growths. According to veterinary sources, the virus is transmitted mainly through direct contact between rabbits or via insect vectors such as mosquitoes, fleas, and ticks. The risk of transmission is higher during warmer months when insect activity peaks. CRPV is not known to infect humans, but it can spread rapidly through rabbit populations.
State veterinary laboratories are analysing tissue samples from affected animals to confirm diagnoses and assess the prevalence of the disease. These findings will help wildlife managers monitor the spread and compare it with historical data.
Owners of pet rabbits are being advised to minimise contact between their animals and wild rabbits. CPW recommends keeping domestic rabbits indoors or in secure outdoor hutches protected from insects, and avoiding free-roaming in areas frequented by wildlife. Handling wild rabbits is discouraged to prevent stress to the animal and the possible transfer of the virus to pets. The public is encouraged to report sightings of rabbits with obvious growths via CPW’s wildlife observation channels. These reports help biologists track the disease geographically and identify any localised clusters. While there is no specific treatment for Shope papillomavirus in wild rabbits, lesions in domestic rabbits may sometimes regress on their own. In severe cases, surgical removal is possible under veterinary care. For wild populations, management focuses on monitoring and reducing environmental stressors that could worsen the spread.
