Syphilis is one of the oldest diseases that's been considered an epidemic and been known to afflict mankind since 1492, the year Christopher Columbus discovered the New World. It was one of the most common infections before the discovery of antibiotics, recorded to have afflicted up to 10% of the Western World's adult populations. However, it was one of the first bacterial infections that successfully responded to antibiotics for syphilis treatment. But until today the debate with regards to what constitutes optimal treatment still remains.

The controversy revolves around the failure to grow in vitro culture of treponema pallidum in both vitro on routine culture media or in tissue culture. So far the only successful laboratory culture for Treponema pallidum rests in laboratory animals. This failure complicates clinical correlation of signs and symptoms to the presence or absence of replicating spirochetes. This also makes performing simple in vitro antimicrobial susceptibility tests difficult, forcing clinicians to rely solely on insubstantial serological tests in diagnosing syphilis also on measuring the efficacy of syphilis treatment.

Microbiology of the bacterium causing Syphilis

A thin, tightly coiled spirochete, a pallidum subspecies of the bacterium treponema pallidum cause the syphilis infection. This bacterium cannot grow on standard culture media because it is microaerophilic. It is related to the other spirochete genera; Borrelia and Leptospira which are also highly infectious to man, and is a member of the Spirochaeticea family. The T. pallidum subspecies pertenue, the bacterium causing yaws; the T. carateum, the bacterium causing pinta; and the T. pallidum subspecies endemicum, the bacterium associated with endemic or non-venereal syphilis are the other pathogenic treponemes that stand as a threat to mankind.

Epidemiology of Syphilis

Syphilis can be spread through the birth placenta (congenital syphilis) from mother to her baby, close contact with active sores and lesions of an infected person through kissing, direct contact or transfusion of fresh human blood. But the most common cases of transmission is by way of sexual contact. In the early stage of infection, a person with syphilis is more infectious through the existence of chancres, mucous patches around the mouth, or condyloma latum (wart-like lesions on the skin around the genitals and anus), also at the 4th year of the syphilis latency stage. A healthy person with a strong immune response even if he/she has latent syphilis is in essence not liable to spread infection, although he/she is prone to reinfection.

Syphilis is a global disease and the rate of infection is rising especially in young adults. The World Health Organization's (WHO) is alarmed with the rate with which this disease is spreading where infections occurring predominantly in persons between the ages of 15 and 40 years. It is also saddening to note the yearly reports of about 1 million infants born each year with congenital syphilis.

Before the discovery of penicillin, syphilis had inflicted about 10% of the urban population in the US. By 1950s recorded incidence of infection were at low levels and were almost wiped out by the year 2000. Towards the end of the year 1999, U.S. Surgeon General David Satcher, of the Center for Disease Control and Prevention's (CDC) announced a National Plan to Eliminate Syphilis.

However, it seems everything they had planned remained a plan because by 2000 there is an annual increase in the rate of infection with primary syphilis and secondary syphilis in the U.S alone. This increase was prevalent in men because of the increase in incidences of sex between men, although by 2004-2008 syphilis cases in women also increased. The noted prevalence is highest in the urban areas, of the South Eastern U.S. states, among African Americans, and in less educated persons in the lower income bracket.

Clinical manifestations of syphilis

Clinical manifestations or symptoms and signs of syphilis has been consistent and well documented for over 100 years; and are conventionally categorized into five stages.

5 clinical stages of syphilis

  • Incubation stage
  • Primary stage - occurs 3 to 90 days (a median of 3 weeks) after infection, characterized by a single, painless chancre or ulcer that develops at the site of contact. 
  • Secondary stage - 6 weeks (range 2 to 16 weeks) after inoculation, occurs when the immune response is overwhelmed by a large load of the spirochete bacterium.
  • Latent stage; early latent and late latent - months to years post-infection, with no outward indicative manifestations despite the presence of the bacterium in the body.
  • Late or tertiary syphilis; neurosyphilis, cardiovascular syphilis and gummatous syphilis - 10 to 25 years after the initial infection, an autoimmune response to recurrent exposure to antibiotics.