Antigen Detection Assays Trichomonas vaginalis
Trichomonas vaginalis is an anaerobic, flagellated protozoan parasite and the most common curable STD. The World Health Organization (WHO) estimates that 170-190 million cases of infection are acquired annually worldwide and are increasing each year. As a result, T. vaginalis is receiving more attention, prompting an increased demand for both diagnosis of trichomoniasis and screening for asymptomatic infections.
T. VAGINALIS LIFE CYCLE
Trichomonas vaginalis is a single cell flagellum parasite that lives in the female vagina and the male urethra. Infections are transmitted directly when the organism moves from one host to another, usually during sexual contact. It has long been recognized as a common cause of vaginitis, known as trichomoniasis. Infection of the female genital tract can also result in cervicitis, urethritis, and adverse pregnancy outcomes including premature rupture of membranes and low birth weight babies. Though it was once virtually ignored, T. vaginalis infection in men is now recognized as an important cause of nongonococcal urethritis and is associated with prostatitis and male infertility. In addition, trichomoniasis is a risk factor for sexual transmission of HIV. It has been demonstrate to play a critical role in amplifying HIV transmission by lowering the barrier of access to lymphocytes and macrophages.
Trophozoite in vaginal and prostatic secretions and urine
Multiplies by longitudinal binary fission
Trophozoite in vagina or orifice of urethra
= infective stage = diagnostic stage
Source: Center for Disease Control
Diagnosis Approximately 70% of women with T. vaginalis do not exhibit symptoms and consequently diagnosis based on clinical symptoms alone is unreliable. The most commonly used method of diagnosis is direct microscopic observation (wet mount) of vaginal secretions and although both rapid and inexpensive, the sensitivity of this technique is generally very low (50 to 70%). Newer methods, such as rapid antigen testing and transcription-mediated amplification, have demonstrated greater sensitivity, often detecting 3-5 times more T. vaginalis infections than wet-mount microscopy. There is also a move towards self-testing as existing commercial antigen-detection assays are easy to use and provide reliable results in approximately 10 minutes. Screening of asymptomatic women with HIV infection for T. vaginalis is recommended because of the adverse events associated with asymptomatic trichomoniasis and HIV infection. Screening should also be considered for persons receiving care in high-prevalence settings (e.g., STD clinics and correctional facilities) and for asymptomatic persons at high risk for infection.
Sexually Transmitted Diseases (STDs)- Reagents for Assay Development 25
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