Rabbit syphilis, caused by the bacterium Treponema paraluiscuniculi, is a common but often overlooked contagious skin disease in domestic rabbits. It typically causes crusty scabs around the nose, lips, eyelids, and genitals — and responds well to penicillin once correctly diagnosed.
Last reviewed: June 2026
What Is Rabbit Treponematosis (Rabbit Syphilis)?
Rabbit treponematosis is an infectious disease caused by Treponema paraluiscuniculi, a spiral-shaped bacterium that is species-specific to rabbits and cannot infect humans. Transmission occurs through direct contact, primarily during mating or from an infected mother to her kits during birth and nursing. Despite the name, it has no relationship to human syphilis other than being caused by a related genus of organism. As described in Quesenberry & Carpenter's Ferrets, Rabbits & Rodents: Clinical Medicine and Surgery, this condition is widespread in rabbit colonies and may remain subclinical for months before producing visible lesions. Stress, immunosuppression, or concurrent illness can trigger flare-ups in carriers.
Signs and Lesions to Recognize
The hallmark of rabbit treponematosis is crusty, scabby skin lesions concentrated in specific anatomical areas. Because these lesions can look like many other rabbit skin problems — ringworm, mite infestation, or bite wounds — the location pattern is the most important diagnostic clue.
Classic lesion sites (in order of frequency):
- Nostrils and muzzle — crusty, brownish scabs around the nose are among the first signs owners notice
- Lips and face — thickened, reddened, or scabby skin around the mouth
- Eyelids — crusting or ulceration at the lid margins, sometimes causing mild eye discharge
- Genitals and perineum — reddened, swollen, ulcerated, or scabby skin around the prepuce, vulva, and anus; may be the only site in sexually active rabbits
Less common findings:
- Lesions on the paws or skin folds if spread by self-grooming
- Mild lymph node enlargement near affected areas
- Secondary bacterial infection causing more severe ulceration
Importantly, rabbits with treponematosis almost never show systemic illness — they eat, drink, and behave normally. A sick rabbit with these lesions likely has an additional problem. Lesions may wax and wane, appearing to partially heal before recurring, which can falsely reassure owners (AEMV Pet Care Guides, 2024).
Diagnosis and Treatment
Diagnosis is usually clinical — the combination of characteristic lesion locations in a rabbit with appropriate exposure history is highly suggestive. Definitive confirmation can be achieved by darkfield microscopy of lesion scrapings (visualizing the spirochetes) or serology, though these are not always necessary when the clinical picture is clear.
Treatment is highly effective. Penicillin G benzathine/procaine, given by subcutaneous injection once weekly for three consecutive weeks, is the standard protocol. As described in Quesenberry & Carpenter's Ferrets, Rabbits & Rodents, oral penicillin must never be used in rabbits — it disrupts the cecal flora and can cause fatal enterotoxemia. Azithromycin is an alternative for rabbits in which injectable penicillin is impractical. All rabbits in contact with an infected animal should be treated simultaneously to prevent reinfection. Lesions typically begin to heal within two to three weeks of starting treatment.
When to See a Vet
Call your vet today if:
- Your rabbit has crusty scabs around the nose, lips, or eyes that do not resolve in a few days
- You notice redness, swelling, or sores around your rabbit's genitals or rear end
- You have recently introduced a new rabbit and the existing rabbit is developing skin lesions
- A nursing doe has facial or genital lesions that her kits could be exposed to
- Skin lesions have appeared and then seemed to partially heal, only to return
Go to the ER immediately if:
- Your rabbit stops eating, becomes lethargic, or has rapid breathing alongside skin lesions (suggests a different or concurrent serious illness)
- Lesions around the genitals have become severely ulcerated or are producing discharge and your rabbit is in obvious pain
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Frequently Asked Questions
What does rabbit syphilis look like? Rabbit treponematosis most commonly appears as brownish crusty scabs around the nostrils and muzzle, along the lip margins, at the eyelid edges, and around the genitals or anus. The lesions may look raw, reddened, or thickened between the crusty phases. A key clue is that affected rabbits typically feel and behave normally — eating well and staying active — despite the visible skin changes.
Can rabbit syphilis spread to humans or other pets? No. Treponema paraluiscuniculi is species-specific to rabbits and does not infect humans, dogs, cats, or other animals. You can safely handle an infected rabbit with normal hygiene. The disease does spread between rabbits through direct contact, so infected rabbits should be kept separate from unaffected housemates until treatment is complete.
How is rabbit treponematosis treated, and does it work? Treatment with injectable penicillin G (given once weekly for three weeks) is very effective — most rabbits show clear improvement within two to three weeks. All in-contact rabbits must be treated at the same time to prevent reinfection. Oral penicillin must never be used in rabbits, as it can cause life-threatening gut dysbiosis. With correct treatment, the prognosis is excellent.
How much does treating rabbit syphilis cost? An exotic vet consultation typically runs $75–180, and the three weekly penicillin injections cost approximately $40–100 total. If skin scrapings or bloodwork are needed to rule out other conditions, add $80–200. Total costs for a straightforward case are generally $150–400. Because exotic vets charge roughly 1.5–2× standard fees, costs at a general practice experienced with rabbits may be slightly lower.
Can I prevent rabbit treponematosis? Quarantine any new rabbit for at least 30 days before introducing it to existing rabbits, and have a vet examine it during that period — an infected rabbit may show no lesions early on. Avoid breeding rabbits with visible facial or genital lesions. Because the organism does not survive long outside a host, contaminated bedding and surfaces pose minimal risk if basic hygiene is maintained.
Still Not Sure if Your Rabbit Needs a Vet?
When you're not sure if this is wait-and-see or call-tonight, Voyage AI Vet triages in under 2 minutes. Describe what you're seeing in chat, share photos of your rabbit's nose, lips, eyelids, or any genital area lesions, or hop on a live video call if you want a second pair of eyes. Every answer comes with citations to the actual veterinary literature it's pulling from — so you see exactly where the guidance comes from, not just a chatbot's word.