Syphilis is one of the most important and pervasive infections occurring in human beings. It is a sexually transmitted disease caused by an elongated, motile, flexible bacterium which is twisted spirally and scientifically known as Treponema pallidum.  Treponemes may be pathogenic and some are even found as commensals inside the mouth, intestine and genital region. Natural infection occurs only in human beings. The bacteria can easily enter through the soft parts of the skin. The disease may also be transferred from mother to child.
Different species of Treponemes causes diseases like;
           1. Venereal syphilis (T. pallidum)
           2. Endemic syphilis (T. pallidum)
           3. Yaws (T. pertenue)
           4. Pinta (T. careteum)
Treponemal infection induces three types of antibodies in the human. The first is the regain antibody which answers the Kahn test or VDRL or Wassermann tests for detection of syphilis. The second is a group antigen, which is seen in T. Palladium, and the third is a species specific polysaccharide antigen, which answers the tests for those patients infected with T. Pallidum.
Venereal syphilis is acquired mainly by sexual contact. The bacterium enters the body through small cuts or abrasions. The clinical condition starts after an incubation period of about 1 month and consists of 3 stages; primary, secondary and tertiary.
A painless, avascular, superficially enlarged chancre called as ‘hard chancre’ appears either on the genitals or mouth or nipples. This is surrounded by thick, slimy exudates rich in spirochetes (Bacteria). It heals off within 10-40 days without any treatment. After 3 months of the healing of these lesions secondary syphilis sets in.  
Secondary lesions occur due to the increased multiplication of spirochetes they circulate through blood. Some of them heal spontaneously, whereas some take about 4-5 years. Tertiary lesions contain few spirochetes and represent manifestations of delayed hypersensitivity.
In case of non-venereal syphilis, the chancres normally occur on fingers. Transplacental transmission occurs during pregnancy. The congenital infection from reaching the fetus can be prevented by treating the mother before 4 months of pregnancy.
Lab diagnosis of syphilis includes;
           1. The demonstration of spirochetes under the microscope
           2. The direct fluorescent antibody test for T. pallidum (DFA-TP).
           3. Serological tests like antibody reacting with cardiolipin antigen (standard test for syphilis), group specific antigen and specific antibodies to T. pallidum.    
    
A single dose of benzathine penicillin G is effective in the early stages. Tetracycline or erythromycin is given for penicillin allergic patients.Endemic syphilis is common among young children. The disease advances only with the development of secondary lesions with mucous patches and skin lesions.

Yaws (a tropical infection of the skin, caused by the bacteria  “T. pallidum”) is transmitted by direct contact. Primary lesions occur as extra genital papule, which enlarges and develops into ulcerating in granuloma. Hippolates pallippes (a type of flu) acts as mechanical vectors. Pinta is characterized by extra genital papule which does not ulcerate but develops into a psoriaform patch.

The only way to prevent is to avoid unsafe sexual practices. Use of antiseptics like potassium permanganate or antibiotics reduces the threat of the infection. No vaccines are available for this disease. The disease is only getting increased in the society as the values, customs and habits are changing. Concurrent infection with HIV is common, and may lead to the evolution of neurosyphilis.