Trichomonas vaginalis

Lore & Background

Alfred Francois Donné (1801–1878) first described the diagnosis of trichomoniasis through microscopic observation of motile protozoa in vaginal or cervical secretions in 1836, publishing his findings in the journal Comptes rendus de l'Académie des sciences. He established the genus Trichomonas, though the species name vaginalis was added later by other authors. Eighty years later, in 1916, Hohne declared trichomoniasis as a clinical entity. The parasite exists only as a trophozoite, lacking a cyst form, though a nonmotile, round pseudocystic form with internalized flagella has been observed under unfavorable conditions. It measures approximately 9 × 7 μm, slightly larger than a white blood cell, and has five flagella—four anterior and one posterior—along with a barb-like axostyle. The organism's survival time in urine, semen, or water samples varies and is often shorter than 24 hours.

Reader's Guide

Trichomonas vaginalis remains a significant public health concern as the most prevalent non-viral sexually transmitted disease, with about 156 million new cases reported worldwide in 2020. Infection rates in men and women are similar, but women are usually symptomatic while men are usually asymptomatic. The parasite is transmitted primarily through vaginal intercourse. Treatment consists of metronidazole or tinidazole, with the CDC recommending a single 2-gram dose as first-line therapy. Recent studies have shed light on the parasite's evolution, genomic complexity, and pathogenesis, including its ability to adhere to vaginal epithelial cells and secrete extracellular vesicles that disrupt immune function. Despite relatively low rates of resistance, it remains a rising public concern, and there is no vaccine. Prevention relies on consistent condom use and screening in sexually active individuals. The parasite is associated with complications such as preterm delivery, low birth weight, increased HIV susceptibility, and cervical cancer.

Did You Know?

• Trichomonas vaginalis is an anaerobic protozoan that lacks mitochondria but contains hydrogenosomes for energy production.
• Strawberry cervix occurs in about 5% of infected women.
• Neutrophils can kill the parasite, though the primary mechanism is not definitively trogocytosis in standard parasitology references.