Treponematosis - rabbit syphilis

 

Esther van Praag, Ph.D.

 

 

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Warning: this file contains pictures that may be distressing to some persons

Rabbit syphilis is a bacterial disease caused by the spirochete Treponema cuniculi. The bacterium is universal and found all over the world. It infests wild and domestic or pet rabbits. The transmission of the bacterium is not well understood. It may be

·      Direct, between adult rabbits during mating;

·      Indirect, passed through the milk from an infected doe to her offspring.

Other modes of transmission cannot be excluded since active syphilis infections have found in pet rabbits that were living individually, without contact with other rabbits.

Incubation time for the disease is long, 3 to 16 weeks. Treponema cuniculi can be dormant for a long period of time. A rabbit can thus remain asymptomatic during several years. A stressful event or suppression of the immune system can trigger the onset of the bacterial disease.

The incidence of syphilis in house rabbits is not known, but it is likely more common than previously thought. The disease is not zoonotic, and cannot be passed from rabbits to other animals and humans.

Clinical signs

The classical form of syphilis affects the junction between the mucosa and the epithelium of genital organs, the anus and/or the face, mainly the eyelids and nostrils.

Rémy Favre

Classical signs of treponematosis (syphilis) in a rabbit: crusted external genital parts, thinning of fur around the nose and eye, and possible appearance of crusts.

Lesions develop slowly. Large thick crusts will cover the damaged ulcerated skin. Secretion of a white creamy exudate bleeding is possible.

Whitney Abrams

Breeding doe with a swollen perianal region, covered with scales and crusts, a typical sign of treponematosis

Whitney Abrams

Detail view of the perianal region, here after treatment with bag balm to soothe the irritated skin 

The immune response to the infecting agent is slow. For this reason, the infection can spread to the surrounding areas and other susceptible regions on the body (e.g., from the anus/genitalia to the face) when left untreated.

Lately, an atypical form of treponematosis has been observed in rabbits. The infection develops on the face or chin only while the genital and perineal areas remain unaffected. The infected area will present with crusty lesions. If left untreated, the infection will increase in size slowly. The skin is raw, inflamed, with deep ulcerations, and may bleed or exude a white fluid.

Ariane Heller

Further classical signs of treponematosis (syphilis) in a rabbit: development of crusts at the muco-cutaneous junction on the lips, and on the front of the lower lip and appearance of a swelling on the top of the nose. Crusts growing under the chin can sometimes have the shape of little horns.

.

Ariane Heller

Under the crusts, the skin is ulcerated, with appearance of deep "crevices".

Treatment

Administration of the narrow spectrum antibiotic penicillin G (benzathine/procaine: 42.000 - 84.000 UI/kg, SC, IM), 4-6 repeats at intervals of 5 to 7 days, is the treatment of choice against rabbit syphilis. (Rabbits should NEVER be given penicillin orally; it often leads to severe diarrhea).

Other antibiotics will not cure the infection. Mostly, healing of the skin lesions is observed during the treatment, but relapse will occur as soon as the treatment is stopped as the Treponema cuniculi bacterium is not killed. This is particularly the case of fluoroquinolone antibiotics. Clinical signs and skin lesions develop rapidly after the treatment is stopped, often in a more severe form than before.

If the rabbit is in pain, analgesics can be administrated (e.g. meloxicam).

It is imperative to monitor the rabbit's eating during the treatment. Indeed, dying bacteria release toxins inside the rabbit's body and blood circulation and appetite may be affected. Inappetence can last 2-3 days, but the rabbit usually begins eating again on its own. It is essential that the antibiotic is not stopped to avoid onset of bacterial resistance. The rabbit should be encouraged to eat by its own and drink. If this is not the case, force feeding food with a syringe and subcutaneous fluid administration is necessary.

 

Vivian Barna

Rescued rabbit that has been diagnozed with untreated rabbit syphilis.  

Acknowledgements

Many thanks to Ariane Heller (Switzerland), Rémy Favre, the photographer of the rabbit rescue "La Colline aux Lapins” (Switzerland), Vivian Barna (USA) and Whitney Abrams (USA) for their pictures and their permission to use on this page.

References

Baker-Zander SA, Lukehart SA. Antigenic cross-reactivity between Treponema pallidum and other pathogenic members of the family Spirochaetaceae. Infect Immun 1984;46:116-121

Bayon H. A new species of Treponema found in the genital sores of rabbits. Br Med J 1913;ii:1159

Bellangeon M. Tréponématose chez le Lapin de Compagnie PASE 2, deuxième trimestre 2001.

Graves S, Downes J. Experimental infection of man with rabbit-virulent Treponema paraluis-cuniculi. Br J Vener Dis 1981;57:7-10.

Hougen KH, Birch-Andersen A, Jensen HJ. Electron microscopy of Treponema cuniculi. Acta Pathol Microbiol Scand B Microbiol Immunol 1973;81:15-28

Noguchi, H., A note on the venereal spirochetosis of rabbits. A new technique for staining Treponema pallidum, J. Am. Med. Assn 1921, lxxvii, 2052.

Quesenberry KE, Carpenter JW. Ferrets, rabbits and rodents. Clinical Medicine and Surgery. St Louis, USA: Saunders; 2004

Saito K., Tagawa M., and Hasegawa A. Rabbit Syphilis Diagnosed Clinically in Household Rabbits J. Vet. Med. Sci. 65(5): 637-639, 2003

Saito K., Tagawa M., and Hasegawa A. RPR Test for Serological Survey of Rabbit Syphilis in Companion Rabbits J. Vet. Med. Sci. 65(7): 797-799, 2003

Saunders RA, Davies RR. Notes of rabbit internal medicine. Oxford, UK: Blackwell Publishing; 2005

Small JD, Newman B. Venereal spirochetosis of rabbits (rabbit syphilis) due to Treponema cuniculi: a clinical, serological, and histopathological study. Lab Anim Sci 1972;22:77-89

 

 

 

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