2.5.5 Trichomoniasis

“Trich”.

Epidemiologic data is limited because the infection is in most countries not a reportable STI and may be underdiagnosed. Around 3% of women of reproductive age in the United States are infected, with an estimated rate of asymptomatic cases as high as 50%. The WHO estimates that there are 180 million new infections acquired worldwide annually.

Trichomoniasis is a sexually transmitted infection (STI) caused by the protozoan parasite Trichomonas vaginalis and may cause urogenital symptoms. Asymptomatic carriers or infections with mild and unspecific symptoms are frequent.

The incubation time is usually 1-2 weeks, but up to half of infected females have no symptoms and can be asymptomatic carriers for years. Most symptomatic females have vaginal discharge with an offensive odour. The classic symptom is a yellow-green, frothy discharge, which is present in less than 10% of symptomatic females. Other symptoms include pruritus vulvae and vaginal burning sensation. There can also be dysuria and pain or bleeding during sexual intercourse. The cervix may have a punctate or strawberry-like appearance.

T. vaginalis is present in 30-70% of the male partners of infected females, but most infected males have no symptoms. If there are symptoms, they are usually a result of urethritis (urethral discharge, meatal irritation, and dysuria). Symptoms in males may disappear within a few weeks without treatment.

However, infected and asymptomatic males can continue to infect female sexual partners. Up to 10% of the cases of non-gonococcal urethritis in males are caused by T. vaginalis.

In women, a vaginal or cervical smear can be investigated by direct microscopy. In men a urethral swab and in women a high vaginal or cervical swab can be sent to the laboratory for culture of the organism. Nucleic acid amplification test and tests detecting Trichomonas antigens in urethral or cervical smears are also available. It is harder to detect T. vaginalis in men and false negative results are common. Therefore, it is usually recommended that male sexual partners of infected females receive empiric treatment (without microbiological confirmation). Trichomoniasis increases the risk of HIV- transmission, so HIV testing and screening for other STIs should be undertaken as well.

Barrier contraception (condoms) do not fully protect from Trichomonas, since this parasite can infect areas that are not covered by a condom.

First-line treatment consists of metronidazole p.o. 400–500 mg × 2–3 for 5-7 days. A single dose of metronidazole 2 g p.o. has also been used but might be less effective. The alternative is tinidazole as a 2 g single dose p.o. It is important also to treat the sexual partner of the patient. Sexual activity should not take place until the symptoms have cleared.