Model-based evaluation of single-round mass treatment of sexually transmitted diseases for HIV control in a rural African population

Objectives: To compare the impact of single-round mass treatment of sexuall y transmitted diseases (STD), sustained syndromic treatment and their combi nation on the incidence of HIV in rural Africa. Methods: We studied the effects of STD interventions by stochastic simulati on using the model STDSIM. Parameters were fitted using data from a trial o f improved STD treatment services in Mwanza, Tanzania. Effectiveness was as sessed by comparing the prevalences of gonorrhoea, chlamydia, syphilis and chancroid, and the incidence of HIV, in the general adult population in sim ulations with and without intervention. Results: Single-round mass treatment was projected to achieve an immediate, substantial reduction in STD prevalences, which would return to baseline l evels over 5-10 years. The effect on syphilis was somewhat larger if partic ipants cured of latent syphilis were not immediately susceptible to re-infe ction. At 80% coverage, the model projected a reduction in cumulative HIV i ncidence over 2 years of 36%. A similar impact was achieved if treatment of syphilis was excluded from the intervention or confined to those in the in fectious stages. In comparison with sustained syndromic treatment, single-r ound mass treatment had a greater short-term impact on HIV (36 versus 30% o ver 2 years), but a smaller long-term impact (24 versus 62% over 10 years). Mass treatment combined with improved treatment services led to a rapid an d sustained fall in HIV incidence (57% over 2 years; 70% over 10 years). Conclusions: In populations in which STD control can reduce HIV incidence, mass treatment may, in the short run, have an impact comparable to sustaine d syndromic treatment. Mass treatment combined with sustained syndromic tre atment may be particularly effective. (C) 2000 Lippincott Williams & Wilkin s.