Don't ignore trichomoniasis

If you haven't heard of this infection before, don't worry. It is the 'stepchild' of sexually transmitted infection - one that is hard enough to pronounce, let alone find information about why it is important to avoid.

Around 120 million women worldwide are diagnosed with trichomoniasis each year. It affects men and women but is diagnosed more frequently in women. In the UK in 2003, 6,152 women were diagnosed, compared to 283 cases in men, with the incidence staying fairly constant year on year. It is most prevalent in people aged 20-45.

Left untreated, it usually causes no symptoms in most cases ? especially in males - but it can cause vaginitis in some women and non-gonococcal urethritis in men.

If trichomoniasis is so common and causes significant risks to women's health, one would expect to find more interest in its prevention. There are several reasons why this STI has been ignored. First, its symptoms - primarily discharge and irritation of the vagina and urethra - have been seen as troubling but are not considered as serious as other STIs. And second, the most common treatment - a drug called metronidazole - is highly effective and has not been threatened by the development of resistant organisms that have caused problems in treating other STIs.

The causes
The organisms that cause trichomoniasis are protozoan (the simplest, single-cell organism in the animal kingdom) called trichomonads, the most common being Trichomonas vaginalis. This parasite resides primarily in the genitourinary tract, where it finds the warmth and moisture needed to grow and multiply.

Trichomoniasis is the least common of three types of vaginitis. The other two are bacterial vaginosis (BV), which is an overgrowth of normal bacteria, and vulvovaginal candidiasis, more commonly known as yeast infection. Trichomoniasis makes up only about five per cent of vaginal infections.

Complications
As with BV, recent research has clearly shown that trichomoniasis can be associated with pre-term delivery complications. Research also links trichomoniasis with an increased risk of HIV transmission (HIV is the virus that leads to AIDS). Although more study is needed, experts estimate that women infected with this STI are two to four times more likely to contract HIV than uninfected women. The reason for this increased risk is that vaginitis increases a response from the immune system, producing more of the cells that HIV targets for infection. Trichomonads can also harbour infective bacteria such as those causing chlamydia and gonorrhoea.