In the absence of affordable treatments or an effective vaccine, prevention is currently the only realistic option for HIV control in developing countries. Sexually-transmitted infections (STIs) are thought to enhance the risk of HIV infection through sexual contact. What is the best way to control STIs and hence reduce the spread of HIV?

The World Health Organisation promotes syndromic treatment of STIs in areas lacking reliable diagnostic services. But is this the most successful approach? Researchers from Erasmus University in the Netherlands and the London School of Hygiene and Tropical Medicine investigated whether mass STI treatment of a population is a more effective strategy for HIV prevention.

Studies strongly suggest that STIs enhance the sexual transmission of HIV by increasing both the susceptibility of HIV-negative individuals and the infectiousness of people with HIV, but the magnitude of this enhancement is unknown.

Syndromic management involves treating people who have signs and symptoms of STIs without laboratory diagnosis, using drugs targeting a range of diseases. A trial in Mwanza, Tanzania showed that this approach can reduce HIV incidence by an estimated 38 percent over two years. Successful syndromic treatment of STIs relies on the recognition of symptoms. Infected individuals must seek treatment and complete their drug therapy. However, STIs are often symptom-free. Even patients who have symptoms may fail to recognise them or to access effective treatment. Also, sexual partners of STI patients rarely receive treatment in developing countries. Mass STI treatment has been suggested as an alternative to overcome these limitations.

This study uses data from the Mwanza trial to assess the likely impact of mass STI treatment in a rural population in which STIs play an important role in HIV spread. A computer simulation is used to predict the short- and long-term effects, on STIs and HIV, of a single round of mass treatment in comparison to syndromic treatment.

The projections indicate that:

• Single-round mass treatment may substantially reduce the prevalence of gonorrhoea, chlamydia and chancroid.
• Over the short term, the impact of mass treatment on prevalences of these STIs and on the incidence of HIV may be comparable to that of sustained syndromic treatment.
• If it is not repeated regularly, however, the impact of mass treatment is only temporary and in the longer run much smaller than that of sustained syndromic treatment.
• The impact of mass treatment on syphilis is complex and requires further investigation.

The researchers conclude that:

• The effectiveness of mass treatment compared to syndromic management depends on the relative contribution to HIV transmission of commonly symptom-free curable STIs such as gonorrhoea and chlamydia, and symptomatic curable STIs such as chancroid.
• Although the many variables make firm predictions difficult, these simulations suggest that single-round mass STI treatment may be as effective as syndromic treatment in a rural African setting, but only in the short-term.
• Mass treatment followed by sustained syndromic treatment would be particularly effective, both in the short- and long-term.

Source(s):
‘Model-based evaluation of single-round mass treatment of sexually transmitted diseases for HIV control in a rural African population’ by E. L. Korenromp et al., AIDS 14 (2000)

Funded by: Commission of the European Communities

id21 Research Highlight: 15 June 2001

Further Information:
Eline Korenromp
Centre for Decision Sciences in Tropical Disease Control (CDTDC)
Department of Public Health
Faculty of Medicine and Health Sciences
Erasmus University Rotterdam
PO Box 1738
3000 DR Rotterdam
The Netherlands

Tel: +31 10 408 7714/7985
Fax: +31 10 408 9449/9455
Contact the contributor: korenromp@mgz.fgg.eur.nl

Erasmus University, Rotterdam

Richard Hayes
Infectious Disease Epidemiology Unit
London School of Hygiene & Tropical Medicine
Keppel Street
London WC1E 7HT
UK

Tel: +44 (0)20 7927 2243
Fax: +44 (0)20 7637 4314
Contact the contributor: Richard.Hayes@lshtm.ac.uk

London School of Hygiene and Tropical Medicine, UK

Other related links:
Search the UNAIDS site for epidemiological data and other information.

The CDC National Prevention Information Network holds a wealth of HIV-related resources.

The WHO's Department of HIV/AIDS also provides lots of relevant information.