Treponematosis in Lagomorphs 

Disease Summary

• Treponema cuniculi is a sexually transmitted bacterial infection which characteristically causes swelling and erythema at the mucocutaneous junction, initially surrounding the external genitalia, then progressing to the anus and spreading to the mouth, nose and periocular region with grooming. The lesions often progress to papules and crusts. (B609.2.w2)
• Clinical signs are not common in pet rabbits but they can occur, particularly in newly acquired young rabbits within a few months of their purchase. (B600.9.w9, B609.2.w2, B609.2.w2)
• This disease is common in some breeding colonies. (B603.4.w4)
• Subclinical infection is thought to be common. (B609.2.w2)
• The disease is also found in wild lagomorphs including hares. (B600.9.w9)
  • This disease is surprisingly common in the wild hare and may contribute to poor body condition, increased likelihood of predation, amyloidosis leading to death. (B284.10.w10)

Alternative Names (Synonyms)

• Rabbit syphilis
• Venereal spirochaetosis
• Vent disease
• Treponema infection
• Spirochetosis
• Cuniculosis
• Treponemiasis
• Treponema paraluis-cuniculi or Treponema paraluiscuniculi are synonyms of Treponema cuniculi.

Disease Type

Infectious/Non-Infectious Agent associated with the Disease

• Treponema cuniculi is a spiral shaped, microaerophilic, gram-negative bacterium that is between 10 and 30 µm in length. (B336.42.w42, B604.5.w5, J213.4.w4)
• Treponema cuniculi is a spirochaete that is antigenically similar to Treponema pallidum which causes human syphilis. (B600.9.w9, B609.2.w2, B611.9.w9 )
• Treponematosis was first reported in rabbits in 1912. (B600.9.w9, B611.9.w9, B614.8.w8)

Treponema paraluisleporis occurs in Lepus europaeus - Brown hare. (J1.41.w6, J69.18S3.w1)

Pathophysiology

• Treponema cuniculi organisms localise and proliferate in the mucosa and skin near mucocutaneous junctions. An initial acute stage is followed by a chronic inflammatory reaction with focal skin ulcerations. 
• The inital site of involvement is usually the external genitalia but there may also be lesions on the lips, chin, nostrils, eyelids, face, and ears. Spread of the infection from one body surface to another to another occurs by autoinfection. 
• The organism can spread to local lymph nodes via the lymphatics. In experimental infections, rabbits inoculated with Treponema cuniculi may have subsequent lymph node infection where the organisms can survive for long periods of time. 
• It is not known whether a bacteraemia occurs in this condition. 

(B611.9.w9)

Infective "Taxa"

• Treponema cuniculi

Non-infective agents

Physical agents

References

Disease Author

Referees

Major References / Reviews

Code and Title List

Other References

Code and Title List

Detailed Clinical and Pathological Characteristics

Clinical Characteristics

Clinical history

• Impaired breeding activity. (B602.18.w18)
  • The lesions can become painful and inhibit mating. (B603.4.w4)
• Colony epidemics can result in a decreased conception rate and an increased incidence of:
  • placenta retention; (B602.18.w18, B603.4.w4, B604.5.w5)
  • metritis; (B602.18.w18, B603.4.w4, B604.5.w5)
  • still births; (B603.1.w1)
  • abortions; (B604.5.w5, B609.2.w2)
    • these occur at 12 to 22 days of gestation. (B604.5.w5)
  • and neonatal deaths. (B602.18.w18, B603.4.w4, B609.2.w2)
    • high incidence of death of young rabbits under the age of nine days. (B609.2.w2)
• Waxing and waning clinical signs as the disease can spontaneously resolve but then reappear following stress. (B602.19.w19, B609.2.w2)
  • Overt disease can occur sometimes months or even years after the initial exposure. (B610.23.w23)

Clinical findings

• Treponematosis causes proliferative scaly lesions that may become painful and are found at mucocutaneous junctions. (B601.13.w13, B609.2.w2
• Affected rabbits are often alert and healthy otherwise. (B604.5.w5, B606.4.w4, B611.9.w9)

Skin lesions

• Initial signs of disease:
  • Erythema
  • Oedema
• Skin lesions may then progress to:
  • Vesicles (1-2 mm in diameter) that often ulcerate and form brownish crusts. 
  • Papules  
  • Macules
  • Large papillary nodules that may erode on the surface and exude serum and then become crusty.
  • Ulceration  
  • Hyperkeratosis 
  • Scabs 
  • Focal haemorrhage: sporadic bleeding can occur in chronic lesions due to epidermal ulceration beneath the crusty surface.
• Chronic lesions are often dry, scaly, slightly raised areas. 
• Lesions are not pruritic. 
• Lesions may persist for a long period of time in untreated cases (over twenty weeks in many rabbits).

(B600.9.w9, B601.13.w13, B603.4.w4, B604.5.w5, B606.4.w4, B608.21.w21, B609.2.w2, B610.23.w23l, B611.9.w9, B614.8.w8, J213.4.w4)

Distribution of lesions

• Prepuce or vulva - lesions often begin here. 
• Anus or perianal region - lesions may progress to this area. 
• Spread via grooming to:
  • Lips 
  • Nose: nostrils and philtrum.  
  • Eyelids .  
  • Occasionally the chin and paws may be affected.
• Lesions may occur on the face and legs alone if there has been contact by sniffing affected rabbits. 

(B600.9.w9, B601.12.w12, B602.19.w19, B604.5.w5, B606.4.w4, B608.21.w21, B609.2.w2, J213.4.w4)

Other reported clinical findings

• Blepharitis and blepharoconjunctivitis
• Enlarged inguinal lymph nodes 
• Enlarged popliteal lymph nodes 
• Preputial or scrotal star shaped scars are indicative of healed lesions and may be found in asymptomatic bucks.
• There may be symptoms of reproductive disorders: stillbirths, infertility, neonatal mortality and metritis. 

(B600.9.w9, B600.11.w11, B602.18.w18, B603.4.w4, B604.5.w5, B606.4.w4, B611.9.w9, J213.7.w1)

Wild hares

• Treponematosis may contribute to poor body condition, increased likelihood of predation, and amyloidosis leading to death. (B284.10.w10) See: Amyloidosis in Waterfowl with notes on Lagomorphs

Incubation

• The incubation period can be prolonged:
  • Three to 12 weeks. (B609.2.w2)
  • Ten to 16 weeks. (B600.9.w9, B603.4.w4)
  • Three to six weeks.. (B601.13.w13, B602.19.w19, B610.23.w23, B614.8.w8, J213.4.w4)
  • From eight weeks after infection. (B606.4.w4)
• A positive serological titre develops eight to twelve weeks after exposure. (B601.13.w13, B610.23.w23, B614.8.w8, J213.4.w4)
• In experimental infections, rabbits inoculated with Treponema cuniculi may have subsequent lymph node infection where the organisms can survive for long periods of time. Rabbits may be clinically healthy with lymph node infection and then stress can cause clinical disease. (B611.9.w9)

Mortality / Morbidity

• --

• Treponematosis is occasionally seen in the pet rabbit but is reportedly endemic in some breeding colonies. (B600.16.w16, B603.4.w4)
• The prevalence of this infection in rabbitries increases with parity:
  • frequently, breeding does that have had six litters are seropositive; (B602.18.w18, B603.4.w4)
  • bucks that have been used for breeding for six to twelve months are also often seropositive. (B602.18.w18, B603.4.w4)
• Subclinical infection is thought to be common, with serological findings suggest that about 25% of asymptomatic rabbits may have been infected. (B609.2.w2, J213.4.w4)
• This disease is surprisingly common in the wild hare. (B284.10.w10) 
• Australia: treponematosis is virtually nonexistent in some wild rabbit populations in this country. (B614.8.w8)

Pathology

• The skin of the perineum and genitals, and also the mucous membranes of the external genitalia, are the tissues most often affected. (B604.5.w5) 

Gross pathology

In Lepus europaeus - Brown hares

• In two Lepus europaeus - Brown hares in The Netherlands, dermatitis, with ulcerations and crusts around the mouth (on the lower lip) and on the prepuce. (J93.32.w1)
• In Lepus europaeus - Brown hares experimentally inoculated with Treponema pallidum, males inoculated by intratesticular injection developed orchitis or testicular atrophy. Females inoculated into the skin developed a local papule. (J267.27.w1)

In domestic rabbits

• Skin - epidermis and superficial dermis 
  • Affected epidermis has acanthosis and hyperkeratosis with rete pegs that extend deep into the dermis. (B611.9.w9)
  • Shallow ulcers or erosions covered by necrotic cellular debris. (B600.9.w9, B609.2.w2, J213.4.w4)
  • Macrophages, lymphocytes, and plasma cells in the underlying dermis. (B600.9.w9, B604.5.w5, B611.9.w9, J213.4.w4)
  • Numerous spirochaetes can be demonstrated with the use of silver stain. (B611.9.w9)
• Inguinal and popliteal lymph nodes
  • Hyperplastic with large germinal centres that contain many immature lymphoreticular cells. (B611.9.w9)
  • There may also be focal accumulations of epithelioid cells. (B611.9.w9)

In Lepus europaeus - Brown hares

• In two Lepus europaeus - Brown hares in The Netherlands, in the prepuce, an inflammatory reaction with infiltration of plasma cells, lymphocytes and neutrophils. Spirochetes were found, particularly in the superficial epithelial layer but also deep to inflammatory reaction, with some organisms invading blood vessel walls. The spirochetes were morphologically similar to Treponema paraluiscuniculi and Treponema pallidum. (J93.32.w1) (J93.32.w1)

Human Health Considerations

• Treponematosis in rabbits is not transmissible to humans. (B601.13.w13, B603.4.w4, B604.5.w5, B609.2.w2, B610.23.w23)
• After the discovery of rabbit syphilis, two researchers reportedly inoculated themselves with Treponema cuniculi hoping that an asymptomatic infection would occur and that it would convey protection against Treponema pallidum leading to vaccine development against human syphilis. The result of the research demonstrated that humans could not be infected with Treponema cuniculi. However, rabbits could be experimentally infected with Treponema pallidum. (B600.9.w9)

Disease has been reported in either the wild or in captivity in:

• Oryctolagus cuniculus - European rabbit
  • Seen in wild rabbits in England (B611.9.w9)
• Oryctolagus cuniculus domesticus - Domestic European rabbit 
• Wild hares (Lepus - (Genus)) in Britain. (B284.10.w10)
• In a study of 202 trapped wild Lepus europaeus - Brown hares [probably in Hungary], some had testicular atrophy and/or lesions on their external genitalia. A total of 27% (some, but not all, individuals with lesions) were seropositive for Treponema infection with several serological tests. (J267.27.w1)
• In two Lepus europaeus - Brown hares in The Netherlands, with oral and anogenital lesions. (J93.32.w1)
• Lepus europaeus - Brown hares in The Netherlands, Hungary and elsewhere in Europe. (J69.18S3.w1)
  • In The Netherlands, about 60% of a sample of 100 hares were seropositive  by the Treponema pallidum hemagglutination assay (TPHA). (J69.18S3.w1)

Further information on Host species has only been incorporated for species groups for which a full Wildpro "Health and Management" module has been completed (i.e. for which a comprehensive literature review has been undertaken). Host species with further information available are listed below:

Host Species List

• Oryctolagus cuniculus - European rabbit
• Oryctolagus cuniculus domesticus - Domestic European rabbit 
• Wild hares (Lepus - (Genus))
  • Lepus europaeus - Brown hare

(List does not contain all other species groups affected by this disease)

Disease has been specifically reported in Free-ranging populations of:

• Oryctolagus cuniculus - European rabbit
  • Seen in wild rabbits in England. (B611.9.w9)
    • However, in Australia, treponematosis is virtually nonexistent in some wild rabbit populations. (B614.8.w8)
• Wild hares in Britain. (B284.10.w10)
• In a study of 202 trapped wild Lepus europaeus - Brown hares [probably in Hungary], some had testicular atrophy and/or lesions on their external genitalia. A total of 27% (some, but not all, individuals with lesions) were seropositive for Treponema infection with several serological tests. (J267.27.w1)
• In two Lepus europaeus - Brown hares in The Netherlands, with oral and anogenital lesions. (J93.32.w1)
• Lepus europaeus - Brown hares in The Netherlands, Hungary and elsewhere in Europe. (J69.18S3.w1)
  • In The Netherlands, about 60% of a sample of 100 hares were seropositive  by the Treponema pallidum hemagglutination assay (TPHA). (J69.18S3.w1)

Further information on Host species has only been incorporated for species groups for which a full Wildpro "Health and Management" module has been completed (i.e. for which a comprehensive literature review has been undertaken). Host species with further information available are listed below:

Host Species List

• Oryctolagus cuniculus - European rabbit
• Wild hares (Lepus - (Genus))
  • Lepus europaeus - Brown hare

(List does not contain all other species groups affected by this disease)

General Information on Environmental Factors/Events and Seasonality

• Cold environments are thought to predispose to the disease. (B604.5.w5, B608.21.w21)
  • One study reported that rabbits that were housed outside or in a cold barn in winter developed more extensive lesions than rabbits living in warm quarters. (B611.9.w9)

Regions / Countries where the Infectious Agent or Disease has been recorded

• England (B611.9.w9, B614.8.w8)
• Russia (B611.9.w9, B614.8.w8)
• United States (B614.8.w8)
• In Lepus europaeus - Brown hares, in The Netherlands, Hungary and elsewhere in Europe. (J69.18S3.w1)

Regions / Countries where the Infectious Agent or Disease has been recorded in Free-ranging populations

• England (B611.9.w9, B614.8.w8)
• Russia (B611.9.w9, B614.8.w8)
• United States (B614.8.w8)
• In Lepus europaeus - Brown hares, in The Netherlands, Hungary and elsewhere in Europe. (J69.18S3.w1)

Note: In Australia, treponematosis is virtually nonexistent in some wild rabbit populations. (B614.8.w8)