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Reducing the transmission of sexually transmitted infections

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Robert Irwin, BA (Hons), MSc, RN.

Senior Charge Nurse, HIV and Sexual Health Team, Kennet and North Wiltshire Primary Care Trust, Chippenham, Wiltshire

This is a two-part series comprising: - May 2003: Reducing the transmission of STIs; - June 2003: Treatments and screening for STIs and problems for health-care staff

The number of new diagnoses of acute sexually transmitted infections in UK genitourinary medicine clinics has risen sharply since 1991 (PHLS, 2002). In a recent survey of 11 161 people aged 16 to 44 conducted in the UK, 10.8% of men and 12.6% of women reported having had a sexually transmitted infection at some time (Fenton et al, 2001). Sexually transmitted infections have important implications for both individual and public health as they can be associated with preventable infertility, serious obstetric and neonatal morbidity, anogenital malignancies, the transmission of HIV and psychosexual distress.

In the UK genitourinary medicine (GUM) clinics provide specialist services for the diagnosis and treatment of STIs. Although GUM clinics are used by a wide spectrum of the population and are relatively efficient at attracting those at greater risk of acquiring a sexually transmitted infection, only a minority of people reporting risk factors for STI acquisition attend such clinics (Johnson et al, 1996). Indeed, data from a survey reported by Fenton et al (2001), reveals that only 76% of men and 57% of women who reported ever being diagnosed with an STI had been to a GUM clinic.

Recently, the Department of Health issued the first national strategy for sexual health and HIV in England (DoH, 2001; 2002). The strategy contains targets to reduce newly acquired HIV and gonorrhoea infections, proposals for expanding chlamydia screening for targeted risk groups and a model of sexual health services delivered by every primary care trust, giving nurses and other primary care staff a broader role in the control of STIs.

Strategies for controlling STIs

Sexual behaviour, and therefore sexual health, is not only a function of individual and social factors, but also structural and environmental factors. This is reflected in Adler’s (1997) four requirements for an ‘agenda for success’ with regard to sexual health. These are:

- Clear, easily available sex education for young people before they start to have sexual relationships

- Health education initiatives for specific groups among whom the prevalence of STIs is disproportionately high

- Government interdepartmental initiatives that recognise that poor sexual health is driven by poverty and social alienation

- An expanded and adequately resourced infrastructure of open access services for the diagnosis and treatment of sexually transmitted infections.

The evidence base for STI/HIV prevention is still dispersed and unsystematic (DoH, 2001), and what constitutes acceptable and effective interventions for STI prevention still needs to be agreed. A standard mathematical model used to describe the ‘reproductive rate’ of sexually transmitted infections is outlined in Box 1. According to this model the basic reproductive rate of an STI (Ro) is a function of the efficiency of transmission (b), the average rate of acquiring new sexual partners (c), and the average duration of infectiousness (D), (Catchpole, 1996). Consequently, Catchpole (2001) suggests that sexually transmitted infections can be prevented and controlled by interventions that:

- Reduce the risk of transmission in a sexual encounter (b)

- Reduce the rate of sexual partner change (c)

- Reduce the period of infectiousness in individuals (D).

Interventions designed to reduce the risk of transmission during a sexual encounter

Three health-promotion interventions are commonly used. They are health education, condom promotion and vaccination.

Health education

Health education denotes a number of interrelated activities - from generating awareness of sexually transmitted infections and encouraging behaviour change (primary prevention), to discussing screening with patients who report risk factors for STI acquisition (secondary prevention). Much of the information about sexually transmitted infections is concerned with what the infections are and the likely symptoms/problems they may cause. Patients are often unaware, however, that:

- Many infections do not cause any initial symptoms (particularly in women), therefore the absence of symptoms does not necessarily equate to the absence of infection. For example, up to 80% of women and 50% of men with genital chlamydial infections do not experience any initial symptoms (Horner and Caul, 1999). For those patients who do have symptoms related to an STI, the cessation of symptoms without treatment does not mean that the infection has gone away. Symptoms that may indicate the presence of an STI are listed in Box 2

- Many bacterial and viral STIs may be acquired through oral sex (Edwards and Carne, 1998a; 1998b), including gonorrhoea, syphilis, Chlamydia trachomatis, human papillomavirus (HPV) (genital wart virus), herpes simplex virus, hepatitis B and HIV (DoH, 2000)

- Co-infection with other STIs can increase the risk of HIV transmission (Fleming and Wasserheit, 1999).

A recent report issued by the British Medical Association recommends that ‘the provision of risk-reduction counselling (for example guidance on safer sex and routes of transmission) should be a standard part of STI clinical care’ (BMA, 2002). The concept of ‘safer sex’ provides the focus of much patient-related information, although notions of what constitutes ‘risk’ in terms of sexual activities may vary between professionals (Holder et al, 1997). It is the Department of Health’s intention to set clear standards for sexual health information and STI/HIV prevention at all levels of service provision (DoH, 2001). In clinical practice information about STI/HIV prevention needs to be tailored to the needs of the individual. The provision of information alone is seldom enough by itself to effect sustained behaviour change, although health education interventions in which factual information about STI transmission and prevention is presented alongside skill development and motivation building can achieve short-term increases in reported condom use (Shepherd et al, 2001). It is important for practitioners to recognise that most sexual behaviour is motivated behaviour. Green (1996) notes that ‘there are many reasons why people conduct their sex lives in the way that they do, but these can be summarised as two basic reasons: because they like it that way, or because they do not feel that they have any alternative’.

In a recent review of trials of interventions in STI/HIV prevention only two methodologically rigorous studies reporting successful interventions were identified, making the question ‘what makes a successful intervention?’ very difficult to answer adequately (Stephenson et al, 2000). One of these studies was a randomised controlled trial of risk reduction counselling carried out in five STD clinics in the USA (Kamb et al, 1998). The results of this study do seem to indicate that brief counselling interventions using personalised risk-reduction plans can increase condom use and prevent new STIs. More recently, the findings of a study by Imrie et al (2001), suggest that the cognitive-behavioural intervention under investigation may have led to an increased, albeit transient, risk of acquiring a new sexual infection. Consequently, Imrie et al (2001) conclude that: ‘Even carefully formulated interventions should not be assumed to bring benefit. It is important to evaluate their effects in randomised trials using clinical end-points whenever possible.’

Promoting the use of condoms

Using condoms consistently has been shown to reduce (although not eliminate the risk completely) the transmission of HIV and certain other STIs such as gonorrhoea. The BMA recently recommended that health professionals should ‘continually encourage the use of condoms’ (BMA, 2002). The use of condoms as a barrier to STI acquisition/transmission is limited by three aspects. These are as follows:

- Method failure: the theoretical failure rate of the device, excluding that attributable to user failure)

- User failure: the incorrect use of condoms

- Limitations of condoms: as a condom covers only a certain area of the genitalia skin-to-skin transmission of some conditions such as HPV infection may still be possible.

Encouraging the use of condoms is the focus of much practical health promotion, with attention given to increasing the availability of condoms as well as teaching patients how to use condoms correctly.

Although the benefits of condom use to individuals exposed to HIV and certain other STIs may be substantial, the large-scale promotion of condom use may have certain limitations as a strategy for STI control. Richens et al (2000) suggest three ways in which a large increase in condom use might fail to affect STI transmission:

- Interventions designed to promote the use of condoms may appeal more strongly to those people who are ‘risk-aversive individuals who contribute little to epidemic transmission’ (Richens et al, 2000)

- Rises in the transmission of STI may occur as a result of condom failure

- Increased condom use may be accompanied by what Richens et al (2000) term a ‘risk compensation mechanism’. This occurs when an increase in the use of condoms is accompanied by a decision to switch from inherently safer strategies, such as having few sexual partners to riskier strategies such as changing partners frequently or partner concurrency (that is, having more than one sexual relationship during the same period of time).

A comparison of data from the National Survey of Sexual Attitudes (NATSAL) conducted in 1990-1991 and recently again in 1999-2001, revealed that, although the level of reported condom use had risen, the benefits of greater condom use were off-set by increases in reported numbers of partners (Johnson et al, 2001). Combining data on condom use and numbers of sexual partners, Johnson et al (2001) found that ‘overall the proportion of the population who reported two or more partners in the past year and did not use condoms consistently, had increased between surveys’.

This has a number of implications for the role of practitioners as health promoters. Simply promoting the use of condoms without discussion of other risk factors for STI transmission may be counterproductive. It is also important to be aware that, once people have a relatively accurate perception of risk, future changes in sexual behaviour are unlikely in those who have no desire for change (Richens et al, 2000).

Vaccination

Catchpole (2001) suggests that the greatest potential for communicable disease control lies with vaccination. At present hepatitis B is the only sexually transmitted infection that may be prevented by immunisation (Salisbury and Begg, 1996), although it should also be noted that a vaccine also exists for hepatitis A, which may be transmitted through certain sexual acts such as oro-anal sex or digital-rectal contact.

Vaccination for hepatitis B should be offered to non-immune gay men, sex workers (of either sex), HIV-positive patients, injecting drug users, the sexual partners of individuals who are carriers of hepatitis B or at high risk of acquiring the infection, and the victims of sexual assault. With regard to hepatitis A vaccination and sexual transmission, the recommendation is that men who have sex with men ‘whose sexual behaviour is likely to put them at risk’ should be offered immunisation (Salisbury and Begg, 1996).

Trials of vaccines against herpes simplex virus (the cause of genital herpes) and HPV (the cause of genital warts) are also taking place (Gilson and Mindel, 2001). Catchpole (2001) observes that an effective vaccine against oncogenic types of HPV could result in important health gains in developed countries where cervical cancer is one of the most commonest causes of cancer-related death in women. Catchpole also states that proof of efficacy alone is unlikely to be enough to ensure that such vaccines are adopted as a means of controlling the spread of sexual infections. He notes that public acceptance of such vaccines, particularly if administration is required in childhood, may prove difficult.

Interventions to reduce the rate of sexual partner change

The risk of acquiring and transmitting a sexually transmitted infection or infections increases with the number of new sexual partners someone has (particularly if sex involves penetration), and this needs to be openly acknowledged in any information about safer sex and risk-reduction counselling. In carrying out individual risk assessment, screening for STIs should be discussed with patients who report partner concurrency or report having two or more sexual partners in the past year, as this is associated with an increased risk of sexually acquired infection (Johnson et al, 2001).

Boag and Barton (1993) suggest that some patients with psychosexual problems may change partners frequently in order to try to solve these problems, and consequently place themselves and their partners at increased risk of infection. The identification of patients who are experiencing psychosexual or relationship problems and providing these patients with information about sources of help for such difficulties, may also have some effect on reducing the incidence of sexually transmitted infections (O’Gorman et al, 1990).

The relationship between sexual problems and relationship difficulties is often complex and circular. Sexual anxieties, dissatisfaction or dysfunction may be factors in the ontogenesis of relationship problems, and also consequences of such difficulties. Where instability or dissatisfaction characterises a relationship, the probability of one or both partners having sex outside of that relationship increases. The diagnosis of a sexually transmitted infection in one or both partners may sometimes be a precipitant for sexual and relationship difficulties.

In clinical practice, the presentation of relationship and sexual problems often tends to be covert or indirect because of the embarrassment or shame that many people feel about admitting to such problems. Covert presentations of such difficulties may include frequent attendance with non-specific symptoms, complaints or dissatisfaction with contraceptive method (especially if a chosen method has previously been unproblematic), and requests for STI/HIV screening (Irwin, 2002). Even when the disclosure of relationship or sexual difficulties is overt, it is often done extremely tentatively and is frequently couched in euphemism.

The provision of psychosexual counselling and therapy services within the NHS varies considerably from one geographical area to another. In some areas specialist sexual dysfunction clinics or psychosexual medicine clinics may exist; however, waiting lists for such clinics tend to be lengthy, and access to some clinics is by medical referral only. In other areas, health professionals trained as psychosexual counsellors or therapists may work in genitourinary medicine clinics, family planning clinics, mental health-care teams or primary care. All patients reporting any prolonged alteration in sexual function, particularly in the absence of any general relationship problems, should always be advised to attend for medical assessment to exclude the possibility of any underlying pathology.

Box 3 lists sources of information on STIs. Outside the NHS, psychosexual therapy and couple therapy is available privately (patients should be advised to contact the British Association of Sexual and Relationship Therapists for a list of accredited therapists), and also at centres run by the charitable organisation Relate.

- Next month we will discuss sexual health interventions that can reduce the period of infectiousness in patients. We will also look at the issues of screening and partner notification, discussing some of the dilemmas that health-care staff face when working in this specialism.

 

 

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