What is syphilis?
Syphilis is a complex sexually transmitted infection (STI) caused by the bacteria Treponema pallidum. Episodes of active disease occur, followed by latent periods, when the person remains infected but there are no signs or symptoms.
Initially syphilis appears as a painless sore (ulcer) where the infection entered (usually around the genitals) and may go unnoticed. The sore is known as a chancre and this phase is known as primary syphilis.
Widespread rash and 'flu-like symptoms appear next (secondary syphilis).
If left untreated, tertiary syphilis may develop years later and cause a variety of problems affecting the heart, eyes, brain & bones.
Who is at risk of syphilis and how is it spread?
Reported cases of syphilis have increased in New Zealand over the last few years, particularly among men who have sex with men (MSM).
Sexually active people may be at risk of syphilis. It is passed from person to person through direct contact with syphilis ulcers. These are most commonly on the genitals and anal area but may also be found on the lips or mouth. Hence, vaginal, anal or oral sex is the main way of passing the infection from one individual to another.
Syphilis can also be passed on through:
- Infected products e.g. blood transfusions, if donors are not screened
- The placenta to an unborn baby.
- If a pregnant woman has syphilis, the outcome for her baby is dependent on the stage of pregnancy and of the disease, and whether appropriate treatment was received.
Men and women are equally at risk of syphilis. The peak incidence arises between the age of 15 and 34 years.
What are the signs and symptoms of syphilis?
Once infected there is an incubation period of anywhere from 10-90 days (on average 21 days) before any signs become apparent.
Laboratory tests for syphilis
Syphilis can be detected during the early infectious stages by a dark-field examination of tissue or tissue fluid taken from a primary ulcer (chancre) or condylomata lata.
In the later stages of syphilis, blood or cerebrospinal fluid for serological tests are necessary for diagnosis.
- Non-specific non-Treponemal tests e.g. RPR, VDRL
- May cross-react resulting in low-level false-positive tests during pregnancy, other infections, drug abuse, connective tissue disease and aging.
- Levels usually relate to disease activity and are used for monitoring treatment.
- After effective treatment of syphilis, these tests usually become negative but in some people, may remain positive at low levels
- Specific anti-treponemal antibody tests e.g. TPHA, EIA
- These detect antibody due to past or present infection with T. pallidum or another Treponema species (e.g. yaws or pinta).
- They cannot distinguish between different types of Treponemal infection e.g. yaws or syphilis or the duration of infection
- Most people with reactive treponemal tests will continue to have reactive tests for the remainder of their lives, regardless of treatment or disease activity.
- An EIA treponemal test (enzyme immunoassay antibody) is sometimes used as a screening test, as it avoids the false positives found when RPR or VDRL are used.
- Skin biopsy may or may not show characteristic histopathological features.
Other tests such as PCR are not yet routinely available. Other tests that may be required include X-ray and heart examinations.
Genital ulcer disease e.g. syphilis and chancroid, increases the risk of HIV infection so HIV testing should be undertaken as well.
What is the treatment for syphilis?
Penicillin by injection is still the mainstay of treatment for all stages of syphilis. Other antibiotics are less reliable but tetracyclines, erythromycin or cephalosporins may be used in those allergic to penicillin. Pregnant woman who are allergic to penicillin should be desensitised and treated with penicillin. People who also have HIV infection may respond less well to treatment so careful follow-up is needed.
Treatment failures can occur at any stage of the infection so follow-up for one to two years is important. Asymptomatic (latent) syphilis should be treated to prevent occurrence of late complications (tertiary syphilis). The response to treatment for those with tertiary syphilis is variable, particularly if the person has had the infection for a long time.
All sexual activity should be refrained from until all syphilis sores or lesions are completely healed.
Can syphilis be prevented?
If you think you are infected, stop all sexual contact and see your doctor or STD clinic. Notify all sexual contacts immediately so they can be checked for infection and treated appropriately.
Other measures to prevent the spread of syphilis include:
- Limiting the number of sex partners
- Use condoms
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On DermNet NZ:
- Syphilis CDC: Sexually Transmitted Diseases (STDs)
- Syphilis – Medscape Reference
- Pediatric Syphilis – Medscape Reference
- Endemic Syphilis – Medscape Reference
- Treponematosis (Endemic Syphilis) – Medscape Reference
- Neurosyphilis – Medscape Reference
- Charcot Arthropathy – Medscape Reference
- Syphilis – EmedicineHealth
- Syphilis – MedlinePlus
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