|Sexually Transmitted Diseases (STD) Prevention: New Challenges, New Approaches (AIDSCAP/FHI - USAID, 1996, 47 p.)|
by David Mabey
An STD prevention poster attracts a crowd in Mwanza, Tanzania. (Andy Hutchison/EU)
Fifteen years into the AIDS epidemic, only one randomized controlled trial of an intervention to reduce HIV transmission had been published: a study showing that the expensive antiviral drug zidovudine reduces the rate of virus transmission from mother to child. Good news though it is, this result is of little relevance to the developing world.
A study from the Mwanza Region of Tanzania, published in The Lancet in August 1995, has at last offered hope to everyone struggling to slow the spread of HIV/AIDS in developing countries. A team of investigators from the London School of Hygiene and Tropical Medicine, the Tanzania National Institute for Medical Research and the African Medical and Research Foundation (AMREF) worked together with the Tanzania Ministry of Health to see whether improved treatment of other sexually transmitted diseases (STDs), given at rural health centers and dispensaries, could reduce the incidence of new HIV infections.
Our hypothesis was that diseases such as syphilis and chancroid, which damage the skin and cause ulcers in the genital regions, and gonorrhea and chlamydial infection, which cause inflammation of the genital tract, were likely to increase the rate of transmission of HIV through heterosexual contact and that treating these diseases would reduce HIV transmission.
At the beginning of the study, medical assistants and nurses in six rural health centers were trained in syndromic management of STDs. This approach does not require laboratory facilities but depends on giving treatment for all the likely causes of syndromes, such as genital ulcers or discharges, the first time a patient is seen. During one week of classroom training and two weeks of practical training, health center staff were also encouraged to counsel their patients, offer them condoms and ask them to refer sexual partners for treatment.
Through a delivery system established for the study, the six health centers received the least expensive effective drugs for treating the major STD syndromes. For example, trimethoprim-sulfamethoxazole was the first drug of choice, along with penicillin, for treating genital ulcer disease. Health workers trained as supervisors visited each health center every eight weeks to monitor drug supplies and patient records, provide refresher training, and ensure adherence to the syndromic management guidelines.
A cohort of 1,000 adults in the communities served by the six health centers was interviewed and tested for HIV at the beginning of the study and two years after the intervention was introduced. The number of new cases of HIV infection occurring in this cohort was compared with that in another cohort selected from communities served by health centers where improved STD treatment had not been instituted. Pairs of study and comparison communities were matched based on STD attendance at the clinics and on location. An earlier survey had shown that HIV prevalence was higher along the main roads and the shores of Lake Victoria than in the more remote villages.
During the two years, 11,632 cases of STDs were treated at the six intervention health centers. About half of them were in women.
Overall, this simple intervention reduced the number of new HIV infections occurring over the two years of the study by 42 percent. This result was highly significant statistically. Fewer new infections occurred in the intervention community in each of the six pairs of communities (Figure 1). HIV incidence was reduced in both sexes and in all age groups, but particularly in those usually found to have the highest incidence in Africa - women aged 15 to 24 (Figure 2).
Results of a survey of study and comparison cohort members before and after the intervention suggest that these reductions in HIV incidence were the result of improved STD treatment rather than changes in sexual behavior. The survey found little change in reported sexual behavior during the two years and no differences between the study and comparison communities.
For the first time, a randomized controlled study among the general population has shown that it is possible to slow the spread of HIV in Africa, and at an affordable cost. Preliminary back-of-the-envelope calculations suggest that the cost was approximately U.S.$300 per HIV infection averted, or $13 to $20 per healthy life year saved, which compares favorably with the cost of other health interventions such as childhood immunization. Moreover, since the cheapest effective drugs were used and treatment was given through existing health facilities, it should be possible to introduce and sustain such an intervention in any developing country with a functioning health service.
This is not to say that health education and condom promotion should be forgotten, nor to deny that the social and economic determinants of the HIV epidemic (such as poverty, migrant labor, urbanization and gender inequality) should be addressed. But in the short to medium term, the results of the study should provide a message of hope for those dedicated to controlling this devastating epidemic.
1. Hayes R., P. Mosha, A. Nicoli, et al. 1995. A community trial of the impact of improved STD treatment in rural Tanzania: 1. Design. AIDS 9:919-26.
2. Grosskurth, J., F. Mosha, J. Todd, et al. 1995. A community trial of the impact of improved STD treatment in rural Tanzania: 2. Baseline survey results. AIDS 9:927-34.
3. Grosskurth, H., F. Mosha, J. Todd, et al. 1995. Impact of improved treatment of sexually transmitted diseases on HIV infection in rural Tanzania: randomised controlled trial. The Lancet 346:530-36.
David Mabey, FRCP, a professor of communicable diseases at the London School of Hygiene and Tropical Medicine, was one of the investigators who conducted the study in Mwanza.
Figure 1. Rates of new HIV infections over two years in six paired communities
Figure 2. Rates of new HIV infections by sex, age and intervention status