Treponema pallidum (Syphilis)

Syphilis is a sexually transmitted disease caused by primary infection by the spirochete Treponema pallidum. It is still a common sexually transmitted disease in many areas of the world despite the availability of effective treatments and widespread public education programs regarding safe sexual practices.

Pathogenic treponemes are rapidly destroyed by heat, cold, and drying, and so they are usually spread by direct contact. Sexual transmission is the usual mode of infection, and this occurs through skin lesions or mucous membranes coming in contact with an open lesion. Transmission can also occur through parenteral exposure through contaminated needles or blood, but this is rare. Serological screening and the use of stored blood components has virtually eliminated the possibility of transfusion-associated syphilis.

The disease progresses through several stages if left untreated. The first stage, or primary stage, is characterized by the appearance of a lesion called a “chancre” which develops between 10 and 90 days following the initial infection. The chancre is a painless, solitary lesion with raised, well-defined borders, and is an endothelial thickening composed of an aggregate of lymphocytes, plasma cells and macrophages. These usually occur on the external genitalia, but in women, may also occur in the vagina or cervix. The chancre may last for 1 to 6 weeks, after which it heals spontaneously.

If syphilis is not diagnosed during the primary stage, 25% of cases progress to the secondary stage, in which systemic dissemination of the organism occurs. The secondary stage occurs about 1 to 2 months after the disappearance of the chancre, but in some cases, the primary lesion may still be present. Symptoms of the secondary stage include generalized lymphadenopathy, malaise, fever, pharyngitis, and a rash on the skin and mucous membranes.

The secondary stage may last from 1 week up to 8 weeks, and spontaneous healing occurs as in the primary stage. The latent stage follows the disappearance of the secondary stage, and is characterized by a complete lack of symptoms. Patients are noninfectious during the latent stage, with the exception of pregnant women who can pass the disease onto the fetus.

Approximately 33% of untreated patients develop the tertiary stage. This stage can occur anytime after the secondary stage, from months to years; typically, the tertiary stage occurs between 10 and 30 years after resolution of the secondary stage. Tertiary syphilis has three main clinical manifestations: gummatous syphilis, cardiovascular disease and neurosyphilis.

Gummas are localized areas of granulomatous inflammation found mostly on bones, skin or subcutaneous tissue, and represent the host response to infection.
The lesions can reach up to 10cm in diameter and contain lymphocytes, plasma cells and perivascular inflammation.
Cardiovascular disease associated with tertiary syphilis usually involves the descending aorta and symptoms arise due to the destruction of elastic tissue in the arterial walls. Aortic aneurysm, thickening of the valve leaflets or narrowing of the ostia are all typical cardiovascular complications of tertiary syphilis.

Neurosyphilis is the most common manifestation of tertiary syphilis, but it can occur anytime after the primary stage, and can be present throughout all stages of the disease. If it occurs during the first 2 years following the initial infection, neurosyphilis usually takes the form of acute meningitis. Later manifestations of neurosyphilis include destruction of the lower spinal cord and chronic progressive dementia. These later manifestations take at least 10 years to occur and are very rare due to early detection and treatment of the disease with penicillin.

Congenital syphilis occurs when a woman who has early syphilis or early latent syphilis transits treponemes to her fetus. The fetus is usually affected during the second or third trimester of pregnancy and fetal or perinatal death occurs in around 40% of cases. Affected liveborn infants usually do not exhibit symptoms during the first few weeks of life. Symptoms in 60 to 90 % of affected infants then develop thereafter, and include a variety of manifestations: rhinitis; a typical skin rash that is prominent around the mouth, the palms of the hands and soles of the feet; generalized lymphadenopathy; hepatospenomegaly; jaundice; anemia;
painful limbs; bone abnormalities; and neurosyphilis.

Laboratory diagnosis of syphilis may be performed by the direct detection of spirochetes, nontreponemal serological tests and treponemal serological tests.

Sample Volume : 10 µl
Controls/ Calibrators : 3 controls
Incubation : 20’+ 20’