Trichomoniasis is a sexually transmitted infection caused by the protozoan Trichomonas vaginalis.
Trichomoniasis is a sexually transmitted infection (STI), which can affect both men and women. It classically causes vaginal discharge in women and urethral discharge in men, which is associated with soreness (due to vulvovaginitis or urethritis) and/or dysuria.
Trichomoniasis is the most common non-viral sexually transmitted infections worldwide.
Worldwide, trichomoniasis is extremely common but in the UK it is a relatively rare diagnosis with only an estimated 6000 cases/year. In the UK, 90% of cases occur in women due to the higher rate of spontaneous clearance in men.
Trichomoniasis is caused by infection with the protozoan Trichomonas vaginalis.
T. vaginalis is a flagellated Protozoa (single-celled eukaryote) that is able to infect squamous cells of the urogenital epithelium. It most commonly infects areas of the vagina and urethra. Other sites of infection include the cervix, bladder, Bartholin glands, and prostate.
Humans are the only known reservoir for T. vaginalis and it is almost always sexually transmitted. The Protozoa can be transmitted between women and men, women and women, but rarely between two men. Co-infection with other conditions is common (e.g. rates of co-infection with bacterial vaginosis range from 20-80%).
Trichomoniasis classically causes a malodorous, frothy green-yellow discharge.
Patients with suspected trichomoniasis should be referred to a genitourinary medicine (GUM) clinic.
Women should undergo a formal assessment with speculum examination. Around 5-15% will have a normal examination. Swabs are taken from the lateral walls of the vagina for pH testing and a high vaginal swab is taken from the posterior fornix for gram staining, microscopy and culture. Alternatively, a self-taken low vaginal swab can be used for gram stain, microscopy and culture.
Vaginal pH is usually completed as part of the diagnostic work-up. An elevation in vaginal pH >4.5 is supportive of the diagnosis of trichomoniasis, but can also be seeing bacterial vaginosis (BV).
In men, a urethral swab or first void urine sample can be taken for gram stain, microscopy and culture.
Patients being investigated for trichomoniasis should be offered STI screening to include chlamydia, gonorrhoea, syphilis and HIV. This can be organised through a sexual health or GUM clinic.
Diagnosis of trichomoniasis involves identification of the protozoan from a vaginal (women) or urethral (men) sample. There are several tests that can be used to identify the organism:
Co-infection with other conditions (e.g. BV or candidiasis) is common. Important to differentiate between candidiasis, trichomoniasis and BV, which also present with increasing vaginal discharge.
Oral metronidazole is the treatment of choice in symptomatic patients.
The only reliable curative treatment of trichomoniasis is the use of 5-nitroimidazole drugs (e.g. metronidazole/tinidazole). Use of metronidazole or tinidazole has a cure rate up to 95%.
Patients need contact tracing of any recent sexual contacts. This is usually orchestrated via a GUM clinic. Any sexual partner(s) within four weeks of presentations will require empirical treatment.
Patients with trichomoniasis should be advised to engage in sexual abstinence for one week after both themselves and any partner has completed treatment.
Both men and women are at risk of complications associated with trichomoniasis.
For more information see NICE CKS guidelines or British Association for Sexual Health and HIV (BASHH) guidelines.
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