STD Treatment to Prevent HIV Infection: Implications of Recent Community-Level Studies

July 1998

Evidence from two major community-level, randomized trials has begun to clarify conditions under which STD treatment is likely to be most successful in reducing HIV transmission. The trials were conducted to examine the potential impact of STD treatment on HIV prevention. While both were community-level, randomized, controlled trials, there were differences in the design and the conditions under which the trials were carried out.

The first trial, conducted in Mwanza, a rural area of Tanzania, demonstrated a decrease of about 40% in new, heterosexually transmitted HIV infections in communities with continuous access to improved treatment of symptomatic STDs, as compared to communities with minimal STD services, where incidence remained about the same (Grosskurth et al., 1995). However, in the second trial, conducted in Rakai, Uganda, a reduction in HIV transmission was not demonstrated when the STD control approach was community-wide mass treatment administered to everyone every 10 months in the absence of ongoing access to improved STD services (Wawer, 1998).

What were some of the important differences in the two interventions?

• In Rakai, the intervention was STD mass treatment carried out in all households, regardless of symptom status, as compared to Mwanza where the intervention was the treatment of symptomatic STDs provided through improved clinic-based services.
• In Rakai, mass treatment was offered intermittently every 10 months, whereas in Mwanza, treatment was available on a continuous basis.
• In Mwanza, STD treatment was only for symptomatic STDs, whereas the mass treatment approach in Rakai treated both symptomatic and asymptomatic STDs.
• In Rakai, there was no referral for partners since it was presumed that partners were reached during mass treatment; in Mwanza, patients referred partners to clinics, although less than 30% actually presented for treatment.

What were some of the key differences in the two communities when they were studied?

• Rakai was at a much later stage of the HIV epidemic than Mwanza. Mwanza was experiencing a relatively early HIV epidemic, with community HIV prevalence of about 4%, whereas Rakai represented one of the world's most mature epidemics, with a community HIV prevalence of approximately 16%.
• Rakai had relatively low prevalence of curable STDs, and Mwanza's prevalence was slightly higher.

What do these differences mean for HIV prevention?

While additional research is needed, results of these two studies provide some direction for how STD prevention efforts can be best targeted as a tool to prevent HIV transmission. Toward this end, communities should consider the following:

• Continuous access to improved STD services is likely to have greater impact on HIV transmission than an intermittent mass treatment approach to STD control.
• In later stages of the HIV epidemic, the contribution of curable STDs to increasing HIV transmission may decline.
• Treating symptomatic STDs may be more important in reducing HIV transmission than treating asymptomatic STDs. However, treatment of asymptomatic STDs is critical to reducing rates of other STDs and their serious complications.
• STD treatment is especially critical in populations with substantial rates of curable STDs and early or growing HIV epidemics.

References:

Grosskurth H et al. 1995. "Impact of improved treatment of sexually transmitted diseases on HIV infection in rural Tanzania: randomized controlled trial." In: The Lancet, 346:530-36.

Kassler W et al. STD control for HIV prevention in the US: Is there likely to be an impact? [Abstract No. 33238]. In: Conference Supplement of the 12th World AIDS Conference. Geneva, Switzerland, June 28-July 3, 1998.

Wawer, MJ. The Rakai randomized, community-based trial of STD control for AIDS prevention: no effect on HIV incidence despite reductions in STDs [Abstract no. 12473]. In: Conference Supplement of the 12th World AIDS Conference. Geneva, Switzerland, June 28-July 3, 1998.