Chlamydia trachomatis and sexually transmitted disease

Chlamydial organisms are small bacteria that need to be inside cells to multiply. There are three species, Chlamydia trachomatis, C psittaci, and C pneumoniae. Serotypes A, B, and C of C trachomatis are the cause of the blinding disease trachoma. Serotypes D to K are sexually transmitted and, world wide, are an important cause of morbidity in both men and women. In men chlamydial infection causes up to half of all acute non-gonococcal urethritis and at least one third of acute epididymitis.1 In women such infection causes up to half of all mucopurulent or follicular cervicitis, and in developed countries up to 60% of pelvic inflammatory disease,1 a condition associated with a substantial risk of subsequent infertility and ectopic pregnancy. C trachomatis infection may also trigger reactive arthritis in men and women.2 Transmission of the organisms to newborn infants from mothers, usually during birth, may lead to neonatal conjunctivitis and pneumonia.epididymitis.

Progress in understanding the pathogenesis of genital chlamydial infections has come with the recognition that some persistent or recurrent disease (including chronic non-gonococcal urethritis and ectopic pregnancy and infertility associated with pelvic inflammatory disease) may be due to a delayed hypersensitivity response to C trachomatis.3 So how widespread is this infection in Britain? Unfortunately, the information we have is based on a few prevalence studies in general practice and in gynaecology and antenatal clinics*RF 4-6*; in these, 7-12% of women in the childbearing years have been found to be infected. The number of men attending genitourinary medicine clinics in England with a new attack of non-specific genital infection (about half of which may be caused by C trachomatis) showed a sustained rise throughout the late 1970s and early 1980s, then declined slightly, and more recently stabilised. In 1991 there were about 72000 cases.7 While gonococcal infections have continued to decline, chlamydial infections remain a blight7.

Why should this be? The answers seem fairly clear. Firstly, genital chlamydial infections - at least in women - are usually asymptomatic and thus easily become widespread. Secondly, strategies for detection and screening have been haphazard, so that the identification of infected people, with or without symptoms, has been incomplete. Thirdly, until recently the methods used for routine diagnosis were insensitive.8 Fourthly, contact tracing has taken a back seat since the emergence of HIV and AIDS. One consequence is a lot of individual anguish and big demands on health resources. My own conservative estimate is that genital and associated chlamydial infections and their sequelae cost Britain at least pounds sterling 50m a year for diagnosis and management. An even more depressing picture has been painted for the United States9.

Thinking positively, however, we should emphasise that chlamydial infections are treatable. In Sweden a programme of widespread screening was started in the early 1980s, and assiduous contact tracing and treatment have been effective in vastly reducing the incidence and prevalence of genital chlamydial infections in the population - to the point where in 1991 they were almost negligible.10 A small increase in infection in the 15-19 year age group in 1992 (T Ripa, personal communication) should dispel any complacency, however, and the results of subsequent monitoring will be awaited with considerable interest. The small size of the Swedish population and their attitudes to sexual health may well have made the problem easier to deal with, but there seems no inherent reason why similar results should not be achieved in Britain. What we first need to do is to define more precisely the prevalence of genital chlamydial infections in different populations. This does not require the use of new, highly sensitive diagnostic methods. Relatively insensitive, cheap, but nevertheless specific detection procedures can be used if their performance features are known accurately enough. Furthermore, urine samples may facilitate detection of urogenital chlamydial infections in population based prevalence studies.11 Once the overall prevalence has been defined accurately enough to provide a dependable baseline for future reference then more sensitive diagnostic tests can be applied on an individual basis in the context of a well designed and evaluated programme of screening, treatment, and contact tracing. The newer, more sensitive tests are not cheap - these include polymerase or ligase chain reactions8.

The alternative to this approach is to give antibiotics to women in perceived high risk groups5 without testing for chlamydial infection - an approach recognised generally as poor medicine and carrying the risk of undertreatment and the emergence of organisms resistant to antibiotics.

Vaccination may eventually be feasible,12 but preliminary results suggest that effective protection will be difficult to achieve. The Swedish experience suggests that vaccination may be indicated only as an adjunct to case finding, diagnosis, and treatment in the highest risk groups.

The targets in the Health of the Nation include a reduction in sexually transmitted infections, with gonococcal disease being used as a marker; the aim is to reduce its incidence by 20% by 1995.13 This may be achievable with little effort, since the disease is already declining - but a similar decline in the incidence of genital chlamydial infections will surely not be achieved unless there is adequate financial support for the active programme I have outlined. Steps should be taken now. In the long term they will pay for themselves.