Syphilis is a Sexually Transmitted Disease (STD) that is usually associated with high-risk behaviors such as drug addiction, HIV-infected people and men who have sex with other men. Syphilis is transferred from one person to another by direct contact of externally occurring syphilis sores or from pregnant women to their unborn children (CDC Fact Sheet, 2012).
The stages of the disease syphilis are early, late and latent stages. The early stage consists of primary and secondary symptoms which are characterized by the occurrence of sores, rashes, swollen lymph glands, fever and fatigue (CDC Fact Sheet, 2012). The sore typically last for 3-6 weeks after the initial infection has entered the body and occurs at the site of infection. The sores are small, round and painless and usually disappear on their own even in the absence of any treatment. Rashes may occur on various parts of the body such as the hands or mouth and these are part of the secondary symptoms of syphilis (CDC Fact Sheet, 2012).
The infection then usually becomes latent (after the disappearance of primary and secondary symptoms) and the late stage can persist for years in the absence of any treatment. However untreated Syphilis can be a serious health risk. In the late stages of the disease the internal organs get damaged and can result in the death of the infected person (CDC Fact Sheet, 2012).
If left untreated during pregnancy, syphilis can be very dangerous to the neonate and can even result in still births or other complications (CDC Report, Mortality and Morbidity Weekly Report, 2010). Thus the US Preventive Services Task Force (USPSTF) mandates syphilis screening in all pregnant women at the first pre-natal appointment along with other STDs such as gonorrhea, herpes, hepatitis B and HIV (Calogne N, et. al, Annals of Internal Medicine, 2009).
The Center for Disease Control (CDC) estimates approximately 50,000 new infections per year in the US alone with most cases occurring in the South, in metropolitan areas and among Hispanic and African-American populations (Calogne N, et. al, Annals of Internal Medicine, 2009). Among pregnant women, those who are low-income, uninsured, drug users, commercial sex workers, living in poverty are disproportionately affected (Calogne N, et. al, Annals of Internal Medicine, 2009).
The causative agent of the disease Syphilis is Treponema pallidum which is a bacterial spirochete. Spirochetes move by twisting motion and have typical flagella which run along the length of the bacteria. Treponema pallidum is an anaerobic and fastidious type of bacteria which means that is has a complex nutritional requirement (Sena A. et.al, Clinical Infectious Diseases, 2010).
The other sub-species along with Treponema pallidum are sub-species endemicum, pertenue and carateum. These 4 sub-species cannot be distinguished from each other by serological tests since there is considerable DNA homology (more than 95%) between these 4 sub-species. However, of these 4 sub-species only T. pallidum causes venereal syphilis and occurs in the US population while the other sub-species have other different pathogenic effects (Sena A.C. et.al, Clinical Infectious Diseases 2010).
The diagnosis of syphilis is based on serological tests since the causative agent Treponema pallidum cannot be cultured in vitro. (Sena A. et.al, Clinical Infectious Diseases, 2010). There are various kinds of diagnostic tests for syphilis but only some of these tests are approved by the Food and Drug Administration (FDA) in the US. Various syphilis tests include non-treponemal tests such as Venereal Disease Research Laboratories (VDRL) test, treponemal tests and Enzyme-linked Immunoassays (EIAs).
The newer serologic treponemal tests use specific T. pallidum antigens to detect the presence of antitreponemal IgG and IgM antibodies (Sena A.C. et.al, Clinical Infectious Diseases, 2010). IgA antibody detection is usually used in the case of congenital syphilis since IgA does not cross the placental barrier.
These rapid tests for syphilis have many advantages such as low costs and quick results but they cannot distinguish between active untreated infection and treated infections. These tests also need to be validated against reference standards (Sena A.C. et.al, Clinical Infectious Diseases, 2010). False positives are another problem with these rapid treponemal syphilis tests and need to be positively confirmed by performing other more reliable non-treponemal tests.
Syphilis infection can be treated by correct antibiotics prescribed by a physician. Penicillin G is the preferred drug for treating all stages of syphilis. Penicillin used for the treatment of syphilis is usually administered by a parenteral mode of administration such as intramuscularly or intravenously. The duration of treatment depends largely on the stage of the infection and other factors (CDC Treatment Guidelines for STDs Vol. 59, 2010).
The type of preparation of the penicillin is very important since the causative agent T. pallidum can be found in inaccessible sites such as the central nervous system (CNS) which cannot easily be reached by certain forms of penicillin (CDC Treatment Guidelines for STDs Vol. 59, 2010). Pregnant women infected with syphilis are usually treated in the same was as other syphilis infected adults.
Special considerations for syphilis treatment are to be made in the cases of individuals with an allergy to penicillin, neurosyphilis and congenital syphilis in newborns. For non-pregnant individuals with an allergy to penicillin the alternatives to penicillin are tetracycline and doxycycline. Usually doxycycline is preferred to tetracycline as an alternative since patients are more likely to be compliant in its usage (CDC Treatment Guidelines for STDs Vol. 59, 2010). Another alternative to penicillin for syphilis treatment is the antibiotic azithromycin however it needs to be used with caution since there is evidence of azithromycin resistance and consequent treatment failure (CDC Treatment Guidelines for STDs Vol. 59, 2010).
Desensitization of the allergic individual to penicillin is another alternative. Skin testing to test if the allergic individual can tolerate certain dosages and preparations of penicillin are useful. For pregnant syphilis patients with allergy to penicillin desensitization is performed followed by penicillin treatment since the alternatives tetracycline and doxycycline cannot be given to pregnant patients safely (CDC Treatment Guidelines for STDs Vol. 59, 2010).
Syphilis can be prevented by practicing safe sexual habits and avoiding contact with infected, untreated individuals (CDC Fact Sheet, 2012). The CDC aims for complete elimination of the disease in the US but certain groups with high-risk behaviors make this total elimination very difficult. In addition STDs transferred to the victim due to sexual assault or from an infected mother to her unborn child cannot easily be prevented. These cases must be treated correctly, quickly and aggressively as soon as possible after the Treponema pallidum infection has occurred and been confirmed.
The USPSTF strives to protect newborns from syphilis being transferred from an infected mother by screening all pregnant women in the US at some point during their pregnancy. State laws mandate these STD screenings for pregnant women in order to prevent new cases.
Figure 1: Syphilis Sores
1A. Primary Sore (Ref: CDC.gov)
1B. Secondary Sore (Ref: Web MD)
Figure 2: Anatomical illustration of T. pallidum in lateral section
Centers for Disease Control (CDC) Fact Sheet “Syphilis CDC Fact Sheet” (October, 2012) Website Syphilis - http://www.cdc.gov/std/syphilis/
Calogne, Ned, and Diana Petiti, and Allen Dietrich, et.al and Kimberly Gregory "Screening for Syphilis Infection during Pregnancy: US Preventive Services Task Force Reaffirmation Recommendation Statement" Annals of Internal Medicine 150 (May, 2009): 705-709.
Centers for Disease Control (CDC) Report "Congenital Syphilis-United States 2003-2008" Morbidity and Mortality Weekly Report 59 (April, 2010): 413-446.
Sena, Arlene C, and Becky White, and P. Frederick Sparling "Novel Treponema pallidum Serologic Tests: A Paradigm Shift in Syphilis Screening for the 21st Century" Clinical Infectious Diseases 51 (September, 2010): 700-708.
Centers for Disease Control (CDC) Report "Sexually Transmitted Diseases Treatment Guidelines, 2010" Mortality and Morbidity Weekly Report 59 (December, 2010): RR12, 1-114.