Trichomoniasis

Definition

Pathogen and Clinical Presentation

• The pathogen is: Trichomonas vaginalis, a protozoan.
• Route of transmission: sexual — it is a sexually transmitted infection.
• Characteristic discharge: yellow-green, frothy, malodorous.
• The pH is: elevated (> 4.5).
• The classic but rare finding on the cervix: colpitis macularis (strawberry cervix).

• Trichomoniasis is a sexually transmitted infection with the unicellular, motile protozoan Trichomonas vaginalis, which lives in the lower genitourinary tract in women.

Occurrence & epidemiology

Epidemiology

• It is the most common non-viral sexually transmitted infection worldwide; nearly 156 million new infections were estimated for 2020.
• Women are affected more often than men; global prevalence in 2016 was estimated at 5.3 % in women and 0.6 % in men.

Aetiopathogenesis

Aetiology and risk factors

• Transmission is sexual; asymptomatically infected people, particularly men, can also pass on the organism over long periods.
• The infection is accompanied by an imbalance of the vaginal flora, a pro-inflammatory immune response and a raised vaginal pH.
• The infection increases the risk of transmission and acquisition of HIV and other sexually transmitted infections.

Clinical features

• A proportion of infections are asymptomatic but may become symptomatic at any time; coinfection with other sexually transmitted pathogens is common.
• Common complaints are discharge, itching, vulvar redness and swelling, dysuria and dyspareunia; a yellow-green, frothy, malodorous discharge is suggestive but rather unusual.
• In pregnancy, the infection is associated with low birth weight, preterm labour and early rupture of membranes.

Diagnosis

• Quickest method of detection: wet mount: motile, pear-shaped organisms.
• What spoils the diagnosis: cooled or dried-out specimen.
• Most reliable method of detection: nucleic acid test (PCR) from vaginal swab.
• Incidental finding possible: on Pap smear (as small grey cells).

Typical imaging findings

• Colposcopy: Abundant yellowish, thin and frothy discharge pools in the posterior fornix, running out of the os. The mucosa is reddened; pH is clearly alkaline.

• Punctate mucosal haemorrhages on the vaginal wall and cervix (strawberry cervix) are classic and visible on colposcopy in about 45 % of patients; vaginal pH is raised.
• Motile, pear-shaped, flagellated trichomonads on wet mount confirm the diagnosis; sensitivity varies widely, as the organisms can become immotile within minutes of slide preparation.
• Nucleic acid amplification tests (NAAT) are more sensitive than microscopy or culture and have largely replaced them as the reference method.

Keep learning in the app

Further reading (selection)

1. StatPearls: Trichomoniasis (NCBI Bookshelf)
2. MSD Manual Professional: Trichomoniasis
3. The Past, Present, and Future in the Diagnosis of a Neglected Sexually Transmitted Infection: Trichomoniasis (Pathogens 2024, PubMed Central)
4. DocCheck Flexikon, Trichomoniasis

Cross-references