Syphilis: symptoms and treatments

How is syphilis diagnosed?
Syphilis is usually diagnosed and treated when the painless, primary ulcer (chancre) appears. The ulcer fluid is examined and the bacteria are easily seen.

Blood tests: Syphilis is also diagnosed by detecting specific antibodies in the circulation. These blood tests give positive results in secondary, latent and tertiary syphilis. False-negative results can occur during primary syphilis, however, as it can take up to three months for the antibodies to be produced after infection. False-positive tests can also occur, so repeat tests are usually made to confirm diagnosis.

Blood tests cannot distinguish between syphilis and other treponemal diseases such as yaws (which can occur in the tropics), or between treated and untreated syphilis infections. Someone with suspected advanced syphilis might be investigated with a lumbar puncture test to examine cerebro-spinal fluid and look for evidence of neurological involvement.

Testing for syphilis during pregnancy: This is routinely performed, as syphilis can be passed from mother to baby through the placenta after the tenth week of gestation. One in four affected pregnancies will, sadly, end in stillbirth or neonatal death. Those born with congenital syphilis may have various deformities such as a flattened face, saddleback nose, notched peg-shaped teeth plus infectious skin sores, rashes, fever, swollen organs, jaundice and anaemia. If left untreated, late-stage syphilis may develop in late childhood or early adulthood.

How is syphilis treated?
Usually with a penicillin antibiotic given as an intramuscular injection daily for 10 to 14 days in early stages (less than two years since infection), and for 21 to 28 days for treating late syphilis (more than two years since infection).

There is no evidence of resistance to treatment but if someone is allergic to penicillin, other antibiotics (for example, doxycycline, erythromycin) may be given by mouth. Unfortunately, any tissue destruction that has already occurred cannot be reversed by treatment.

As many as one in two people treated with penicillin suffer a reaction within six to twelve hours of the first penicillin injection. This is due to the large number of Treponema bacteria killed and is known as the Jarisch-Herxheimer reaction. Symptoms include fever, headache, and worsening of any current syphilis symptoms. This is usually treated with paracetamol and resolves within 24 to 48 hours.

Those with advanced syphilis affecting the nervous system are usually given penicillin plus steroids (started three days beforehand) to help reduce the severity of this reaction.

Anyone with syphilis should refrain from sex until they and any infected partners are treated.

Follow-up blood tests are recommended at three months, six monthly for two years, and then annually to detect any reactivation or re-infection.

If you're worried you have an STI or want to find out more, check out the symptoms, diagnosis and treatments for:

• Chlamydia
• Genital herpes (HSV)
• Genital warts
• Gonorrhoea
• HIV and AIDS
• Pubic lice
• Scabies
• Trichomonas