Rabbit Papillomavirus (RPV), often referred to as Cottontail Rabbit Papillomavirus (CRPV) or Shope papilloma virus, is a DNA virus specific to the Leporidae family. The infection typically results in the growth of small, firm, crusty lesions, often described as warts or cutaneous horns. These growths appear most often on the face, neck, ears, and feet. RPV is species-specific, posing no known risk of transmission to humans, dogs, or other non-rabbit pets.
Evaluating the Lesions and Monitoring
The initial step upon discovering a suspicious growth is a thorough veterinary physical examination. A definitive diagnosis of Rabbit Papillomavirus usually requires a biopsy, where a small tissue sample is analyzed to confirm the presence of the virus and rule out other types of tumors. Histopathology helps determine if the lesion is a benign papilloma or if it has progressed to a malignant form, such as squamous cell carcinoma.
Many benign RPV lesions are self-limiting, supporting a management approach called “watchful waiting.” Spontaneous regression occurs when the rabbit’s immune system successfully clears the infection, which may happen within weeks to a few months. This natural resolution is seen in a variable proportion of cases, sometimes affecting up to 40% of lesions in domestic rabbits.
Active intervention is necessary if the lesions show signs of rapid, sustained growth or interfere with the rabbit’s quality of life. Warts that obstruct vision, impede eating or movement, or become ulcerated and susceptible to secondary infection generally require treatment. Given the high risk of malignant transformation—up to 75% in domestic rabbits with persistent lesions—many veterinarians recommend prompt removal or ablation if a lesion does not regress within a few months.
Active Treatment Methods
When a lesion is high-risk or causing functional problems, the most common and effective treatment is physical removal or ablation. Surgical excision is often the primary choice, especially for large, pedunculated, or suspicious masses, as it allows the entire lesion to be removed with a margin of healthy tissue. This complete removal is crucial for achieving a cure and providing a full sample for histopathological analysis to check for early signs of cancer.
Alternative physical methods include electrocautery and cryotherapy, which use heat and extreme cold, respectively, to destroy the tissue. Electrocautery uses a high-frequency electrical current for smaller, superficial lesions, burning the tissue away and cauterizing blood vessels simultaneously. Cryotherapy involves freezing the papilloma tissue with liquid nitrogen, causing the targeted cells to die off. Both methods are generally performed under anesthesia to minimize stress and ensure the procedure is thorough.
Less common methods involve topical or intralesional medications. The antiviral compound Cidofovir has shown effectiveness when injected directly into the papilloma, leading to growth elimination over several weeks. However, recurrence rates can be high, reaching approximately 50% when Cidofovir is used as a standalone treatment. Other immunomodulators, such as Imiquimod, are sometimes explored but their routine use in veterinary practice for RPV is not well-established.
Long-Term Management and Prevention
While many RPV infections can resolve completely, the potential for recurrence remains a factor in long-term management. Even after successful physical removal or ablation, the virus can persist in surrounding tissues, leading to new lesions developing at the same or nearby sites. Post-treatment veterinary follow-up is necessary to monitor the surgical site and the rabbit’s skin for any new growths or changes.
The long-term prognosis is primarily influenced by the risk of malignant transformation into squamous cell carcinoma. This progression is a significant concern in domestic rabbits, as a high percentage of persistent papillomas eventually become cancerous. If malignant change occurs, the cancer can become aggressive and potentially metastasize to distant organs, such as the lungs or lymph nodes.
Prevention focuses on minimizing exposure to the primary transmission vectors. RPV is spread through biting insects, particularly mosquitoes and ticks, and through direct contact with an infected rabbit or contaminated surfaces (fomites). Owners should reduce insect access, especially during warm seasons, and practice strict hygiene protocols in multi-rabbit environments. This includes isolating new or infected rabbits, thoroughly cleaning and disinfecting enclosures, and avoiding the sharing of food dishes or bedding.