Trichomonas vaginalis (TV) is a single-celled organism (protozoon) that can swim by beating five whip-like structures known as flagellae. Interestingly, TV can survive on sex toys, fingers and even lavatory seats for up to 45 minutes and, in one case, infection was thought to have been transmitted in a jacuzzi. In most cases however, infection is passed on through unprotected sex with an infected partner.

What symptoms will I notice?
TV usually causes inflammation of the vagina and cervix, producing a heavy discharge that often contains streaks of pus and blood. The discharge irritates the vulva to produce redness and soreness that may sometimes spread down the inner thighs.

Apart from this discomfort, trichomonas is not associated with long-term problems. It is often associated with other sexually transmissible infections such as gonorrhoea and chlamydia, however, which are passed on with it. As these can produce long-term problems if they remain untreated, it's important to have a full sexual health screen if TV is suspected.

How is trichomonas diagnosed?
Trichomonas vaginalis is usually diagnosed after examining fresh discharge under a microscope in a genitor-urinary medicine clinic. It can also be grown from a vaginal swab in the lab. It is sometimes recognised when examining a routine cervical smear, although telling the single-celled organism apart from pus cells is difficult.

How is trichomonas treated?
TV is usually treated with the antibiotic, metronidazole, or, if this is ineffective, tinidazole. Symptoms usually improve quickly, but it is important that your sexual partner(s) is also treated to prevent re-infection. Men can carry the infection for several weeks, although eventually it will die out. Male tests for TV are usually unhelpful so treatment will tend to be given to a man following a female partner's diagnosis.

If you're worried you have an STI or want to find out more, check out the symptoms, diagnosis and treatments for:

• Chlamydia
• Genital herpes (HSV)
• Genital warts
• Gonorrhoea
• HIV and AIDS
• Pubic lice
• Scabies
• Syphilis