Recent advances in the diagnosis of Trichomonas vaginalis infections

Trichomonas vaginalis is an anaerobic protist and the causative agent of trichomoniasis, cervicitis, and urethritis, a widespread sexually transmitted infection of the urogenital tract of humans, causing symptoms particularly in women where the parasite feeds on vaginal epithelial cells. It infects approximately one fourth billion people worldwide. The causative parasite is a flagellated parasitic protozoan, typically pyriform but occasionally amoeboid in shape, extracellular to genitourinary track epithelium with a primarily anaerobic lifestyle. Vaginitis symptoms include yellow vaginal discharge, malodor, pruritus, and dysuria. The infection may result in a phenomenon referred to as “strawberry cervix,” which describes a small, bright red punctate lesions caused by tiny hemorrhages on the surface of the cervix. Whole-genome sequencing of T. vaginalis has revealed its size unusually large, at about 160 megabase which is approximately sixfold larger than was originally estimated and which represents one of the largest genomes among the parasites. Genome is organized into six chromosomes consisting of up to 60,000 genes. The repetitive gene sequences are the basis to use for molecular tests. Trichomoniasis diagnosis is usually done with a physical examination by expert physician and an array of the laboratory test. The laboratory diagnosis is done either with wet-mount preparations, which permit the microscopic visualization of the motile trichomonad, or with Papanicolaou (pap) smears test in which the pear- or tear-shaped organisms resemble degenerate squamous epithelial cells. The Aptima T. vaginalis assay test kit is an FDA-approved assay that can detect T. vaginalis from asymptomatic or symptomatic patients. It has a sensitivity of 95.3%–100% and specificity of 95.2%–100%. However, the antigen detection test lacks sensitivity, particularly in males, while NAATs, though highly sensitive and specific, nonetheless require sophisticated laboratory equipment and skilled personnel, and are relatively costly. Though, laboratory-based detection of infection can be used on the samples already being collected for other infection screening such as chlamydia/gonorrhea. Therefore, development of highly sensitive laboratory detection method, particularly molecular methods such as PCR, or novel recent CRISPR/Cas9, is an important alternative for screening of trichomoniasis in high-risk population group to bring down the trichomoniasis cases.