Control of Sexually Transmitted Infections (STIs)

More than 300 million new cases of curable sexually transmitted infections (STI) occur each year, with a global distribution that closely mirrors that of HIV. Each new infection not only increases HIV transmission risk but also carries the potential of other serious complications including fetal loss, stillbirths, infertility, ectopic pregnancy and severe congenital infections. Syphilis alone, when present during pregnancy, results in fetal loss in a third of cases, and half the surviving infants suffer congenital disability.

There are a few large-scale interventions that demonstrate the potential impact of STI control on HIV transmission. Thailand reduced the incidence of curable STIs by more than 80 percent in less than five years through a comprehensive effort that included both improved STI treatment and targeted promotion of condom use in commercial sex establishments (100 percent condom policy). During this period, HIV prevalence, which had been increasing rapidly, began to fall. Through sustained application of these interventions, Thailand stabilized HIV transmission early and averted a far more extensive epidemic. There is also evidence that more limited STI interventions can have an impact on HIV transmission. In rural Mwanza, Tanzania, improving the case management of STI through the syndromic approach in clinics reduced the incidence of new HIV infection by 40 percent. In nearby Rakai, Uganda, on the other hand, mass antibiotic treatment of the sexually active population at nine-month intervals resulted in neither reduction of most curable STIs nor of HIV transmission.

Experience in STI control programming teaches us that reducing high rates of STIs requires a comprehensive strategy for both prevention and treatment. Such a strategy includes such well-known aspects of STI control programs as ensuring effective diagnosis and treatment, encouraging treatment adherence and partner treatment, and avoiding re-infection. It is equally important, however, to pay attention to who uses existing clinical services and who does not–even the most technologically advanced services will have little impact on STI prevalence if access to those services is poor. One of the most important challenges in STI control is orienting effective services to reach the people who are most frequently exposed to infection and have the most frequent opportunity to pass infection on to others.

Strategies can be formulated that address the many facets of STI transmission dynamics and STI treatment priorities found in communities. Among the components of STI control that have been effectively used together to reduce prevalence are:

• Communication strategies to promote services, improve symptom awareness and STI treatment seeking behavior as well as condom promotion and adequate condom supplies.

• Efficient and effective management of STI in clinics accessible to the majority of the population–with particular attention to making services acceptable to adolescents and young adults. The goal is to maximize the proportion of such encounters that are effectively managed ("no missed opportunities") while avoiding costly over-treatment in settings where STI prevalence is low. The appropriate balance between the sensitivity of approaches to identify infection and avoidance of over-treatment remains a central issue in STI control and must be determined by local priorities.

• Targeting interventions to population groups with the greatest risk of acquiring and transmitting STI. Outreach and peer education among high transmission networks is the foundation of targeted interventions. Preventive and curative services for individuals in these networks go hand-in-hand. Effective STI treatment reduces rates of complications as well as efficiency of HIV transmission. Individuals are more receptive to condom use and other prevention messages when they are delivered along with quality, non-judgmental curative services ("prevention-care synergy").

• Improving STI management in important informal sector outlets (e.g., pharmacies where many people, especially male bridging groups, seek treatment).

• Screening or presumptive treatment of the most important core and bridging groups as short-term measures to reduce STI prevalence.

• Selective implementation of more focused disease control measures designed to rapidly reduce the prevalence of specific STIs and/or their complications. Such control targets might include the elimination of congenital syphilis, enhanced control of genital ulcer disease, or the elimination of infectious adult syphilis or chancroid.

• Improving the reliability and relevance of surveillance and evaluation data including laboratory data to guide control efforts and measure progress.

• Addressing structural changes to modify underlying conditions that facilitate STI transmission. Examples include provision for family housing for migrant workers to reduce demand for commercial sex, and promotion of 'safe house' rules in brothels where the pressure to use condoms comes from the management rather than the individual sex worker.

STI case management remains an important, but not the sole, component of STI control. The syndrome approach endorsed by WHO/UNAIDS has become the standard of care in many countries for management of the most common STI syndromes. By directing treatment against the common causes of easily identified syndromes, primary health care workers can achieve high rates of cure without the delay and cost involved with laboratory workups. Syndrome algorithms also serve to reduce treatment failures and re-infection by stressing the importance of treatment adherence, condom use and partner treatment. Syndrome management is most effective and cost-effective for syndromes such as urethral discharge and genital ulcer disease. Present approaches to managing vaginal discharge syndromes in women are less accurate and better combinations of syndromic and laboratory diagnosis and screening are needed. For now, more sensitive and costly approaches can be adapted for populations in which prevalence and exposure are relatively high, while in lower risk populations, treatment of the more common vaginal pathogens may be more cost-effective. As simpler, more affordable and accurate diagnostics become available, STI case management guideline recommending combinations of syndrome and laboratory diagnostic methods will become feasible under field conditions.

Resources

1. Alder M, Foster S, Grosskurth H, Richens J, Slavin H. Sexual Health and Health Care: Sexually Transmitted Infections — Guidelines for Prevention and Treatment. Health and Population Occasional Paper. Department for International Development, London. 1996.
2. Control of Sexually Transmitted Diseases: a handbook for the design and management of programs. AIDSCAP/Family Health International, 1996.
3. Dallabetta G, Gerbase A, Holmes K. Syndromic Approach to STD Management. Sex Transm Inf 1998:74 (Suppl 1): S1-S11.
4. UNAIDS. Female Sex Work HIV Prevention Projects: Lesson learnt from Papua, New Guinea, India and Bangladesh. UNAIDS Case Study, Geneva. 2000.
5. UNAIDS/98.2. Relationships of HIV and STD Declines in Thailand to Behavioural Change: A synthesis of existing studies. UNAIDS Best Practice Collection, 1998.
6. Vuylsteke B, Jana S. Reducing HIV Risk in Sex Workers, Their Clients, and Their Partners. In HIV/AIDS Prevention and Care in Resource-Constrained Settings: A Handbook for the Design and Management of Programs. Family Health International/IMPACT. (Forthcoming)
7. WHO/GPA/TCO/PMT/95.18/H. STD Case Management. A training manual, 1995.
8. UNAIDS/WHO. Sexually transmitted diseases: policies and principles for prevention and care. UNAIDS Best Practice Collection. 1999.
9. UNAIDS/WHO. Consultation on STD interventions for preventing HIV: What is the evidence? UNAIDS Best Practice Collection 2000.
10. WHO/HIV-AIDS/2001.01. Guidelines for the Management of Sexually Transmitted Infections. World Health Organization, Geneva. 2001.
11. Evaluating Sexually Transmitted Infection Control Programs. In Evaluating Programs for HIV/AIDS Prevention and Care in Developing Countries: A Handbook for Program Managers and Decision Makers. Family Health International. In press (available September 2001).
12. WHO/CHS/HIS/99.2. UNAIDS/WHO Working Groups on Global HIV/AIDS/STI Surveillance. Guidelines for Sexually Transmitted Infections Surveillance., 1999.
13. Van Dyck E, Meheus AZ, Piot P. Laboratory Diagnosis of Sexually Transmitted Diseases. World Health Organization, Geneva. 1999.