**8. Chancroid**

470 Current Topics in Tropical Medicine

late congenital syphilis. These adverse pregnancy outcomes can be prevented by syphilis

Initial diagnosis of syphilis is typically based on clinical presentation. *Treponema* spirochetes are Gram negative but they cannot be visualized using conventional light microscopy. Darkfield microscopy and direct fluorescent antibody test of spirochetes from lesion exudates and tissue provide definitive diagnosis of early syphilis. These tests however are not utilized in most settings. Presumptive diagnosis of syphilis relies on two types of testing for antibody in blood serum or cerebrospinal fluid. The Venereal Disease Research Laboratory (VDRL) and Rapid Plasma Reagin (RPR), Toluidine Red Unheated Serum (TRUST), and Unheated Serum Reagin (USR) tests utilize a non-treponemal antigen. The VDRL and RPR tests are the most widely used of these. VDRL and PRP testing is most sensitive in the middle stages of the disease, early syphilis and late stage disease may be missed. Detectable antibody titers are not attained until 1-4 weeks after appearance of the chancre and titers often decline to undetectable levels in latency. Non-treponemal tests are nonspecific and can give false-positive results and occasionally false negative results under conditions of antibody excess which can occur during secondary syphilis. Positive results are confirmed with a test utilizing treponemal antigens, such as the fluorescent treponemal antibody absorbed (FTA-ABS) test, treponemal enzyme immunoassay (EIA), microhemagglutination assay for *T. pallidum* antibodies (TPHA), and direct fluorescent antibody-*T. pallidum* test (DFA-TP). These tests are more sensitive than non-treponemal tests in detecting primary and tertiary syphilis. Non-treponemal test antibody titers usually correlate with disease activity and become non-reactive with time after treatment. Treponemal test antibody titers do not correlate disease activity and most (75-85%) will remain reactive for the rest of their lives. Commercially available point-of care tests for syphilis have been introduced recently although these are too expensive for most situations

Benzathine penicillin G, 2.4 million units by intramuscular injection (IM) in a single dose for adults or 50,000 units/kg IM for children, is the preferred treatment for primary, secondary, and early latent stage syphilis. Alternatively, procaine penicillin at 1.2 million units IM daily for 10 days is used. Penicillin allergic non-pregnant patients may be treated with doxycycline, 100 mg orally twice daily for 2 weeks or tetracycline, 500 mg orally four times daily for 2 weeks. Penicillin allergic pregnant patients may receive erythromycin, 500 mg orally, 4 times daily for 14 days. Late latent stage syphilis and tertiary syphilis is treated with three doses benzathine penicillin G at 1 week intervals, 2.4 million units IM each dose for adults and 50,000 units/kg for children. Alternatively, procaine penicillin at 1.2 million units IM daily for 20 days is used. Penicillin allergic non-pregnant patients with late latent stage or tertiary syphilis may be treated with doxycycline, 100 mg orally twice daily for 4 weeks or tetracycline, 500 mg orally four times daily for 4 weeks. Penicillin allergic pregnant patients may receive erythromycin, 500 mg orally 4 times daily for 4 weeks. Neurosyphilis is treated with intravenous aqueous crystalline penicillin G, 3-4 million units every 4 hours (18-24 million units per day) for 10-14 days, or with daily IM injections of procaine penicillin, plus 500 mg probenecid orally 4 times daily, both for 10-14 days. Penicillin

screening to identify and treat maternal infections prior to 24 weeks gestation.

**7.4 Diagnosis** 

in the developing world.

**7.5 Treatment** 

*Haemophilus ducreyi*, a fastidious Gram-negative facultative anaerobic coccobacillus, is the causative agent of chancroid. Chancroid is transmitted by vaginal, anal, or oral sex with an infected individual. The organism enters thru breaks in the epithelium and resides primarily in the extracellular spaces. *Haemophilus ducreyi* can resist phagocytosis and untreated lesions may take months to heal.
