Health: The bug that strikes before you know it

It's the most common sexually transmitted disease in Europe. Yet despite being curable, chlamydia is making many women infertile. Cherrill Hicks reports on a time-bomb

She's in her twenties or early thirties, a typical young professional: she'd like babies sometime, but not right now. She is, she thinks, well informed about health. She hasn't slept around, exactly - just sown a few wild oats. But she's been lucky - she's never had a sexually transmitted disease. Never picked up anything nasty ... Or has she?

As a sexually active young woman, she stands a one in 10 chance of having caught, without realising, the most common sexually transmitted disease in Europe. In most people, it is symptomless. Caught early, it is easily cured. But untreated, it can cause pelvic infection, painful sex, ectopic pregnancy and infertility. She's probably never heard of it: it's called chlamydia.

"Chlamydia is the silent disease," says Peter Greenhouse, consultant in sexual health at Ipswich Hospital. "Most people think that with a 'dose' of a sexually transmitted disease, you get some pain or discharge. But if you have this infection, you probably won't know it. Chlamydia is completely curable, yet it's causing large numbers of women to lose their fertility. The tragedy is that nothing's been done about it."

Chlamydia trachomatis is a specialised bacterium that is transmitted through sexual intercourse (although, less commonly, it can infect the eyes). The bug can only survive in the most delicate of membranes: in men it inhabits the urethra (the tube by which urine is excreted from the bladder), and in women, the urethra and the cervix, or neck of the womb.

In most women (and men), it causes no symptoms. "Some women may get irregular bleeding between periods or after intercourse, or heavier periods," says Greenhouse. "Or a slightly heavier discharge from the vagina. But these signs are often very minimal, easily confused with other conditions and likely to be missed. This means women may acquire the infection from a sexual partner and know nothing for months, even years. Most women who get it never find out. Only 40,000 cases a year are identified, but the real number of cases is likely to run into hundreds of thousands. Male partners go undiagnosed too."

In many women, fortunately, the bug travels no further than the cervix where it seems to cause few problems. But in just under half of all cases, chlamydia travels upwards into the womb and fallopian tubes, a development that can take anything from a few weeks to several years. Spread of the infection can be triggered by menstruation, because this is when the mucous plug which guards the cervix comes away, exposing the womb to infection. "Spread is sometimes accompanied by severe pelvic pain, which makes sex painful and can ruin a relationship," says Greenhouse.

Disturbingly, there is a high risk of the infection spreading if a woman with chlamydia has an abortion, or is fitted with an intra-uterine coil, because in both cases, the womb is exposed to infection. And repeated exposure to chlamydia is also thought to make the bug more aggressive: a woman whose regular partner is unknowingly infected may get it only mildly at first, but as the relationship continues, it is very likely to spread.

Once chlamydia has taken hold, the consequences can be devastating. The bug attacks the fallopian tubes, the place where egg and sperm meet to fertilise.

"The infection destroys the hairs [called cilia] which waft the egg down the tube towards the womb," says Greenhouse. "This is why chlamydia is a chief cause of ectopic pregnancy [one which develops outside the womb, normally in the fallopian tube]." Ectopic pregnancy can cause serious bleeding and is the leading cause of death in mothers-to-be in the first three months of pregnancy. Partly, it is thought, because of the rise in cases of chlamydia, the number of ectopic pregnancies has doubled in the past decade and is now increasing by almost 5 per cent yearly.

Chlamydia also results in inflammation of the tubes, called salpingitis. A severe infection can cause the ends to swell up, causing permanent blockage and infertility. In men, the consequences are normally less serious. It is the main cause of non-specific urethritis (NSU), or inflammation of the urethra; less commonly it can cause infection of the testicles, giving rise to pain and sterility.

So chlamydia is an infertility time-bomb: picked up in the teens or early twenties, it may lurk unrecognised for years, only to be discovered when a woman wants a baby - and finds she is infertile. "Chlamydia is the single largest reason for tubal infertility which in itself is responsible for about one third of all infertility," says Greenhouse. "It is also thought to cause a significant amount of what we call unexplained fertility. In such cases the tube may look normal and open but the lining is damaged and non-functioning."

Given the damage and misery it can cause, estimates of those with chlamydia are frightening. Because it often goes undiagnosed, there are no definite figures, but research has found that between 5 and 15 per cent of young, sexually active women are infected, with the highest rates among teenagers.

The good news is that if diagnosed correctly and caught early enough, chlamydia is easily treated with antibiotics and there have been big improvements in diagnosis. Until recently, the only test available, which involved taking a swab from the cervix, was thought to miss 40 per cent of cases of infection; but new tests, widely used in Sweden and the US, which can identify the bacteria's genetic material, are being developed which have a 90 per cent accuracy rate. They can identify minute quantities of the infection, although they are more expensive and not yet widely available.

Specialists in sexual health say too little has been done to tackle the problem of chlamydia, even though its effects have been recognised for years. "We have a modern health service in Britain to rival any in Europe, but when it comes to chlamydia we might as well be Latvia," says Professor Alan Templeton, chair of the study group on the disease, set up by the Royal College of Obstetricians and Gynaecologists.

Mr Greenhouse agrees: "Chlamydia was discovered in the early part of the century and we've known for 20 years that it is a major cause of pelvic inflammatory disease and infertility."

In Sweden, where screening programmes together with improvements in treatment and a major educational campaign were established in the Seventies, rates of tubal inflammation have fallen dramatically. "By 1980, enough was known about chlamydia from the Swedish experience and that of other countries to start a campaign in Britain," says Greenhouse. "Medical opinion thought it was the next big thing to attack - but it never happened."

This was partly, he says, because a new disease - HIV and Aids - "got in the way". Professor Templeton agrees. "Until recently the Department of Health were not entirely convinced of the cause," he says. "HIV took greater priority in terms of funds, research and campaigning."

The lack of public education, and the emphasis on Aids has meant that few people have even heard of chlamydia, he says. "If you ask a woman of 25 what gonorrhoea is, she will tell you. If you ask her about chlamydia, she has no idea."

In addition, the stigma that still surrounds sexually transmitted disease means many women are reluctant to consult a doctor or clinic, even if they do suspect they have an infection. STDs are associated with promiscuity, and for someone in a stable relationship there is an automatic presumption of infidelity, although Mr Greenhouse points out that since you can be infected for years without knowing, there is a good chance it predates any current relationship.

Things are beginning to change, albeit slowly. Professor Templeton's study group has recommended a major campaign of public education around chlamydia, as well as improvements in the treatment of women with pelvic pain. A government working party on the topic is currently considering whether screening programmes should be introduced for particularly high- risk groups - sexually active teenagers, women having an abortion or a coil fitted, and those who change partners frequently. Whether other women will be offered screening is still under discussion: the sticking point, of course, will be cost.

Britain was pioneering IVF at the same time as the anti-chlamydia campaign began in Sweden, Mr Greenhouse points out. "How much better women's health would be served if a small fraction of the resources committed to infertility treatment had instead been devoted to its prevention"n