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Scan for outdated or missing drivers - takes under a minuteDriver Scan →Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Cottontail rabbits in the United States can carry a papillomavirus that causes wart-like growths on the skin and sometimes inside the mouth. The virus is usually called cottontail rabbit papillomavirus (CRPV), and older literature refers to it as Shope papillomavirus or Shope papilloma virus. It has been documented most thoroughly in Midwestern cottontails, with a Colorado report extending it to a desert cottontail. What the evidence does not show is how common it is in wild populations today, or exactly how it moves from one rabbit to another.
What the virus is and what it is called
CRPV is a papillomavirus, a group of viruses that cause benign growths in many animal species. In the scientific literature it also appears as Sylvilagus floridanus papillomavirus (SfPV), after the eastern cottontail, Sylvilagus floridanus. Because the name has changed across decades of papers, a reader searching for “Shope papilloma virus” and a reader searching for “cottontail rabbit papillomavirus” are often looking at the same subject.
The virus is associated with papillomas, the medical term for these growths, in cottontails. Associated is the right word here. A growth that looks like a papilloma is not proof of infection on its own, and the reviewed sources describe the link between virus and lesion without claiming that appearance alone settles a diagnosis.
What the growths look like
Reported lesions vary in form. The main descriptions in the reviewed material include:
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- Dark skin lesions that stand out from the surrounding fur and skin.
- Warts, the familiar rounded or raised growths typical of papillomaviruses.
- Elongated, horn-like growths, which give the condition its historical nickname in some older accounts.
- Cylindrical masses on the mouth, recorded in a Colorado case report.
Oral growths matter more than their size suggests, because they sit where feeding happens. That point is covered below.
Where it has been documented
Most of the historical work on CRPV was done in the U.S. Midwest, and that is where the virus was first described in detail. A later Colorado report documented infection in a desert cottontail, which shows the virus is not limited to the eastern cottontail. That is a single report of a single animal, so it demonstrates that the virus has been found outside the Midwest, not how widespread it is in the West.
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How common it is: what the museum numbers show
The most detailed recent count comes from a University of Kansas study of museum specimens, published in 2015. Its figures describe a historical collection, not the rabbits living in the field today.
- Of 1,395 rabbits in the museum collection, 20 showed symptoms of papillomas.
- Of those 20 symptomatic individuals, 13 tested positive for the virus.
- Three of the 17 lagomorph species (rabbits, hares and pikas) in the collection were symptomatic.
These counts are useful for showing which species and regions the virus has appeared in. They cannot be turned into a percentage of wild cottontails with the virus, because museum specimens were collected for other purposes and were not sampled to represent populations. No reviewed source gives a current, nationwide prevalence estimate for CRPV in U.S. cottontails, so any single rate you see quoted for the whole country is going beyond the evidence.
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The earliest transmission work is also the most often quoted. In his 1935 paper, Richard E. Shope wrote in the abstract:
“It was reported that the virus of infectious papillomatosis produced warts which were readily transmissible in its natural host, the wild cottontail rabbit.”
That confirms the virus was understood as transmissible between cottontails more than eight decades ago. It does not identify the complete route. The reviewed sources do not establish a full natural transmission pathway for wild cottontails, and they do not name an insect, environmental source or contact route as settled fact. Readers should treat any specific vector claim they encounter as unverified.
Why the growths matter for the animal
A Colorado wildlife-agency fact sheet notes that some lesion locations can interfere with feeding or vision. Oral growths are the clearest example of the first concern, since a rabbit that cannot eat normally is under stress regardless of how the lesion originated. Growths near the eyes raise the second concern. The fact sheet is a general agency summary, so it describes possible effects rather than measured mortality rates from CRPV.
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CRPV compared with RHDV2
Rabbit diseases are often confused in news reports and social media posts. Rabbit hemorrhagic disease virus 2 (RHDV2) is a different disease. The USDA describes it as fatal to wild and domestic lagomorphs, and it is subject to federal surveillance. The table below separates the two on the points that matter to a reader.
| Feature | Cottontail rabbit papillomavirus (CRPV) | Rabbit hemorrhagic disease virus 2 (RHDV2) |
|---|---|---|
| Disease agent | Papillomavirus, also called SfPV or Shope papillomavirus | Rabbit hemorrhagic disease virus 2, a distinct virus |
| Affected hosts | Cottontails, with a desert cottontail case reported in Colorado | Wild and domestic lagomorphs |
| Characteristic signs | Dark skin lesions, warts, horn-like growths, oral masses | Not stated in the reviewed USDA material |
| Severity | Growths can interfere with feeding or vision; no reviewed source gives a fatality rate | Described by USDA as fatal |
| Surveillance or reporting | No federal surveillance program identified in the reviewed sources | Federal surveillance by USDA |
A visible growth on a cottontail is therefore not evidence of RHDV2, and an RHDV2 concern should not be dismissed because the animal has growths.
If you find a rabbit with growths
- Do not handle the animal bare-handed, and avoid touching the growths.
- Keep dogs and cats away from the rabbit as a precaution, since the transmission route is not established.
- Report sightings of a sick wild rabbit to your state wildlife agency, which can tell you whether it wants records of such observations.
- If the animal is a pet or a domestic rabbit, consult a veterinarian rather than relying on an online photograph.
A photograph can suggest a papilloma but cannot confirm the virus. Confirmation requires laboratory testing, which is how the museum study distinguished symptomatic animals from virus-positive ones.
The evidence supports a clear picture: CRPV is a papillomavirus that causes visible growths in cottontails, it has been documented in the Midwest and in Colorado, and its transmission has been studied but not fully mapped. The current extent of infection across U.S. cottontail populations is not known from the sources available.
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