Infectious Fibroma in Rabbits: Viral Skin Nodules Explained

Quick Answer
  • Infectious fibroma is a poxvirus-related skin disease in rabbits, most often linked to Shope fibroma virus.
  • It usually causes soft, clearly defined nodules on the legs, feet, ears, muzzle, or around the eyes.
  • Many adult rabbits stay bright and active, and some lesions shrink over months, but young rabbits or rabbits with ulcerated masses may become much sicker.
  • Your vet may recommend an exam alone for a classic mild case, or biopsy/PCR if the lump could be an abscess, papilloma, myxomatosis, or another tumor.
  • Mosquitoes and other biting insects are thought to play an important role in spread, so vector control and limiting wild rabbit exposure matter.
Estimated cost: $90–$1,200

What Is Infectious Fibroma in Rabbits?

Infectious fibroma is a viral skin condition that causes soft nodules or lump-like swellings in rabbits. It is associated with Shope fibroma virus, a member of the poxvirus group that is closely related to myxoma virus. Under natural conditions, the disease is mainly seen in cottontail rabbits, but domestic rabbits can develop similar lesions when exposed in endemic areas, especially where biting insects are present.

These growths are usually found on the legs, feet, ears, muzzle, and around the eyes. Early on, a pet parent may notice a small thickening under the skin. Over time, that area can become a more obvious, well-defined swelling. In many adult rabbits, the masses remain limited to the skin and the rabbit otherwise acts normal.

That said, a skin lump in a rabbit should never be assumed to be harmless at home. Abscesses, papillomas, trauma, myxomatosis, and other tumors can look similar. Your vet can help sort out whether a nodule is likely to be a self-limiting viral fibroma or something that needs more active treatment.

Symptoms of Infectious Fibroma in Rabbits

  • Soft, clearly defined skin nodules
  • Lumps on the legs, feet, or ears
  • Nodules on the muzzle or around the eyes
  • Hair loss over the lump
  • Surface irritation or ulceration
  • Trouble seeing, eating, or moving because of lesion location
  • Reduced appetite, lethargy, or widespread illness in a young rabbit

Call your vet promptly for any new rabbit skin lump, even if your rabbit seems comfortable. See your vet immediately if the mass is growing quickly, bleeding, ulcerated, near the eye, or affecting eating, pooping, or movement. Rabbits hide pain well, so a lump that looks minor can still need attention.

What Causes Infectious Fibroma in Rabbits?

Infectious fibroma is caused by rabbit fibroma virus, also called Shope fibroma virus. This is a DNA virus in the leporipoxvirus group. In wildlife, it is best known in cottontail rabbits. Domestic rabbits are not the usual natural host, but they can be infected.

Transmission is believed to happen mainly through biting arthropods, especially insects such as mosquitoes and fleas. Virus exposure may also be more likely when broken skin comes into contact with infectious material. That is one reason outdoor housing, insect-heavy environments, and contact with wild rabbits can increase risk.

Not every exposed rabbit becomes seriously ill. Adult rabbits often develop localized skin tumors and stay otherwise clinically normal. Young rabbits may be more vulnerable to generalized disease. Because the virus is related to myxoma virus, your vet may also think about other poxvirus diseases when evaluating suspicious skin lesions.

How Is Infectious Fibroma in Rabbits Diagnosed?

Diagnosis starts with a hands-on exam and a close look at the lesion pattern. Your vet will consider the rabbit’s age, whether the rabbit spends time outdoors, local insect exposure, and where the nodules are located. A classic soft swelling on the legs, feet, ears, muzzle, or around the eyes may raise suspicion for infectious fibroma.

Because many rabbit skin lumps look alike, your vet may recommend tests to rule out other problems. Depending on the case, that can include fine-needle sampling, skin biopsy with histopathology, PCR testing, or virus isolation/serology. Histology may show changes such as fibroblast proliferation and intracytoplasmic inclusion bodies. PCR can support a poxvirus diagnosis, although it may not clearly separate fibroma virus from myxoma virus on its own.

If the lesion is ulcerated, painful, or in a tricky location, your vet may also check for secondary bacterial infection and assess whether sedation, pain control, or surgery is needed. The goal is not only naming the lump, but also deciding how much treatment your individual rabbit actually needs.

Treatment Options for Infectious Fibroma in Rabbits

Spectrum of Care means you have options. Here are treatment tiers at different price points.

Budget-Conscious Care

$90–$250
Best for: Small, classic-appearing nodules in an otherwise bright adult rabbit with no ulceration, pain, or interference with eating or movement.
  • Rabbit-savvy exam
  • Lesion measurement and photo monitoring
  • Discussion of likely viral vs nonviral causes
  • Home monitoring plan for appetite, droppings, and lesion changes
  • Environmental cleanup and insect-control guidance
Expected outcome: Often fair to good when lesions stay localized. Many fibromas regress over several months.
Consider: Lower upfront cost range, but less diagnostic certainty. A mass that is actually an abscess, papilloma, or another tumor could be missed without sampling.
Most Common

Recommended Standard Treatment

$250–$650
Best for: Most pet rabbits with a new skin nodule, uncertain diagnosis, facial lesions, ulceration, or masses that are enlarging.
  • Rabbit-savvy exam and recheck
  • Cytology or biopsy planning
  • Sedation if needed for safe sampling
  • Histopathology submission
  • Pain control and wound-care plan if the lesion is irritated
  • Targeted treatment for secondary infection if your vet finds one
Expected outcome: Good in many localized cases once the diagnosis is clarified and complications are managed.
Consider: Higher cost range and more handling. Sedation or anesthesia may be needed, which adds risk in rabbits, though it is often worthwhile for a clear diagnosis.

Advanced / Critical Care

$650–$1,200
Best for: Young rabbits, rabbits with generalized illness, lesions affecting the eyes or mouth, or cases where the mass is causing major discomfort or function problems.
  • Advanced imaging or broader workup if disease is atypical
  • Surgical removal or debulking of problematic masses
  • Full anesthesia and perioperative monitoring
  • PCR and/or additional pathology testing
  • Hospitalization, assisted feeding, and intensive supportive care if the rabbit is systemically ill
  • Management of severe ulceration, eye involvement, or mobility-limiting lesions
Expected outcome: Variable. Localized lesions can still do well, but widespread disease or severe complications carry a more guarded outlook.
Consider: Most intensive cost range and more procedures. It offers the most information and support, but not every rabbit with infectious fibroma needs this level of care.

Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.

Questions to Ask Your Vet About Infectious Fibroma in Rabbits

Bring these questions to your vet appointment to get the most out of your visit.

  1. Does this lump look most consistent with infectious fibroma, or are abscesses and other tumors still on the list?
  2. Based on the location and appearance, is monitoring reasonable or do you recommend biopsy now?
  3. Could this be related to insect exposure or contact with wild rabbits in my area?
  4. What signs would mean the lesion is becoming painful, infected, or urgent?
  5. If we do testing, which option gives the best balance of answers, stress, and cost range for my rabbit?
  6. Does my rabbit need pain relief, wound care, or protection from self-trauma while we monitor this?
  7. If the mass is near the eye or mouth, how often should we recheck it?
  8. What insect-control and housing changes do you recommend to lower future risk?

How to Prevent Infectious Fibroma in Rabbits

Prevention focuses on reducing exposure to the virus and the insects that may spread it. Keep your rabbit in clean, secure housing, and use screens or other rabbit-safe barriers to reduce mosquito and fly exposure. Avoid standing water near outdoor enclosures, and ask your vet which environmental insect-control steps are safest around rabbits.

Limiting contact with wild rabbits also matters. Domestic rabbits housed outdoors or in areas where cottontails are common may have more opportunity for exposure. If your rabbit spends time outside, check the skin regularly for new lumps, scabs, or irritated areas, especially on the ears, feet, and face.

There is no routine, widely used prevention program specifically for infectious fibroma in pet rabbits in the United States. Because of that, early detection is important. If you notice any new skin nodule, schedule a visit with your vet before it becomes ulcerated or starts interfering with normal rabbit behavior.

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