Trichomonas vaginalis (TV) is a motile, flagellated protozoan (Figure 14.1) which colonises the lower genital tract of males and females.

Epidemiology

Globally, T. vaginalis is the single most prevalent non‐viral sexually transmitted infection (STI). The WHO estimated that more than 270 million cases occurred in 2008, greater than the combined total for chlamydia and gonorrhoea [1]. However, T. vaginalis diagnosis is relatively rare in the United Kingdom, with around 9500 cases reported each year, compared with over 200 000 cases of chlamydia [2,3].

Clinical features

T. vaginalis has an incubation period of 4–28 days [4], and up to 50% of infected women are asymptomatic. Symptoms vary and are mainly secondary to the vulvovaginitis. The discharge is classically frothy, offensive smelling, and purulent (Figure 14.2). Infection of the urethra and paraurethral glands is common. Dysuria may be a feature.

One of the classic clinical signs is the ‘strawberry cervix’ due to punctate haemorrhagic lesions on the ectocervix. However, this is seen in only about 2% of women [5].

Diagnosis

The simplest and most commonly used diagnostic test for T. vaginalis is microscopy of a wet mount preparation of vaginal fluid in saline. This demonstrates the motile flagellated protozoa and should be performed as soon as possible after the sample is taken, as the organisms become less motile over time. Wet mount microscopy has a sensitivity of 60–70% compared with culture in women [6–8], so ideally vaginal samples should be sent for culture. Nucleic acid amplification tests (NAATs) offer the highest sensitivity for the detection of T. vaginalis. Polymerase chain reaction testing has shown increased accuracy in comparison to both microscopy and culture ranging from sensitivities of 88%–97% and specificities of 98%–99%, depending on the specimen and reference standard (APTIMA TV, Genprobe). They should be the test of choice where resources allow and are becoming the current ‘gold standard’ [5

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