Syphilis

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, anus or mouth) 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 brain, eyes, heart and 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 or infected blood through microtraumas during unprotected sexual intercourse. Syphilis ulcers 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 eg 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.

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Differential diagnosis of clinical symptoms of syphilis

Ulcers

• Genital ulcers: genital herpes, trauma, cancer; and less commonly, tuberculosis, chancroid
• Anal ulcers: genital herpes, anal fissure, bacterial infections, trauma, inflammatory bowel disease
• Mouth ulcers: herpes simplex (cold sore), aphthous ulcers, trauma

Rash

• Drug eruption
• Pityriasis rosea
• Psoriasis
• Eczema/dermatitis

Laboratory tests for syphilis

Syphilis can be detected during the early infectious stages by a dark-field microscopy examination of tissue or tissue fluid taken from a primary ulcer (chancre) or condylomata lata.

Blood for serological tests is necessary for diagnosis. Serological tests turn positive about 5 to 6 weeks after acquiring the infection. In some cases, cerebrospinal fluid can be tested to confirm neurosyphilis.

• Non-specific non-Treponemal tests eg Rapid plasma reagin (RPR), Venereal disease research laboratory (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 eg Treponenam pallidum particle agglutination assay (TPPA), enzyme immunoassays (EIA or AIA), fluorescent treponemal antibody absorption (FTA-ABS), microhaemagglutination assay (MHA-TP) and Western Blot (WB).
  • These detect antibody due to past or present infection with T. pallidum or another Treponema species (eg yaws or pinta).
  • They cannot distinguish between different types of Treponemal infection eg 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 test 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. Molecular testing using polymerase chain reaction (PCR) can confirm the presence of genetic material from the bacteria in ulcers, on the skin surface, in blood, lymph nodes and other tissue.

Other tests that may be required include X-ray, heart examination (ECHO), neurological and eye examinations.

Genital ulcer disease eg syphilis and chancroid, increases the risk of HIV infection so HIV testing should be undertaken as well.

What is the treatment for syphilis?

For detailed and up to date guidelines for treatment of syphilis, refer to the WHO guidelines for the treatment of Treponema pallidum (syphilis)(2016)

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 close follow-up with repeated serology tests for one to two years is important. In some countries patients with syphilis are followed up lifelong. 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 and treatment is completed.

Can syphilis be prevented?

There is no vaccine available for syphilis.

Syphilis can be acquired repeatedly; antibodies and treatment do not protect against a new infection.

Early treatment of syphilis has very good outcomes and prevent later complications. However, treatment in advanced stages can leave irreversible consequences, for example neurological or visual problems.

If you think you are infected, stop all sexual contact and see your doctor or sexual health 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
• Using condoms
• Regular blood tests if sexual behaviour is high risk