Syphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema, subspecies pallidum (Treponema Pallidum). The primary route of transmission is through sexual contact (vaginal or anal); however, it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis. Syphilis is particularly common in developing countries, agmong commercial sex works and among MSMs.
Its symptoms and signs of syphilis vary widely depending on which of the 4 stages of the disease (primary, secondary, latent or tertiary). In primary syphilis, it typically presents with a chancre (a firm, painless, non-itchy ulcer) which can be on the penis, outside the anus, on labia and even inside the vagina or rectum. Because it is painless and non-itchy, therefore it is quite easy to miss. Without treatment, the chancre will disappear by itself in about 1-2 weeks.
Then syphilis goes into an asymptomatic period which can last for months. In secondary phase, a rash may appear on the body, hand or feet. But the rash is again non-itchy and non-painful, therefore again can be easily missed. Quite often the patients or even doctors may think it is just an allergy and dismiss it. The rash typically last for about 2 weeks and will disappear again.
The infection then enter a very long latent phase without symptom. However, syphilis is usually only infectious in the first 6 months. The infection stay within the infected person without symptom for many years and later develops into tertiary syphilis which can affect major organs such as the brain and heart and causing permanent damage. The most common form of tertiary syphilis is call gummatous syphilis which the person will develop inflammatory nodules on skin, bone, brain or other parts of the body. In about 6-10% of patients may develop neuro-syphilis (affecting central nervous system) or cardiovascular syphilis (commonly causing aortic aneurysm).
During its asymptomatic stages it can only be detected through regular blood tests. If syphilis is treated early, not only it can be eradicated much easier, it also help to reduce the chance of spreading the infection.
There are 4 different tests for syphilis.
In general, they should be done in combination to determine the presence of infection and whether the infection is new or old.The earliest time to have test for syphilis is at least 2 weeks after at-risk exposure.
1. Treponema Pallidum (TP) antibody
This tests for the presence of antibody IgM and IgG in blood.
IgM is usually developed from 2 weeks after infection by Treponema Pallidum.Therefore this test can detect early infection by Treponema Pallidum.
IgG is usually produced by the body about 4 weeks after contact with the infection and remains positive for life even after treatment. Therefore, it is used to determine infection over 4 weeks or previous infection of syphilis.This test us usually used as a screening test for syphilis.
VDRL is a secondary test for syphilis which provides a semi-quantitative level of antibody in blood.It is used as a confirmation if TP antibody is positive, determine the likely stage of infection and response to treatment.If positive, conventionally it is reported as "reactive" instead of positive and a negative result is reported as "non-reactive".In a positive result, a level is also given as 1:2, 1:4, 1:8...1:32 etc.The higher the second number indicts the level of dilution that the test remains positive, ie higher number indicates high concentration of antibody and more advanced infection.After treatment, the level will reduce and it can take up to 6-12 months for the test to become "non-reactive" again.In some cases, the report may show "NEAT" which indicates the test is only positive in an undiluted sample which may still indicate treated syphilis.
3. FTA antibody and TPHA
FTA and TPHA are confirmation tests to verify a positive TP antibody test.These 2 tests will always remain positive after infection of Treponema Pallidum.However, these two tests are subjected to higher technician variability, therefore they are usually not used as first line tests
Treatment of syphilis is usually with intramuscular injection of Penicillin-G as a single dose or three doses once a week for 3 weeks depending on which stage of infection the person is at. Ceftriaxone may be used in people who are allergic to Penicillin. Follow-up VDRL test is usually done 1, 3, 6 and 9 months after treatment.
A drop in VDRL titre should be observed. Reactivation of infection is not common but re-infection is quite common if partner(s) are not being treated. Therefore it is important to inform partners within the last 6 months.
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