PREVALENCE AND INCIDENCE OF SYPHILIS AND ITS ASSOCIATION WITH HIV-1 INFECTION IN A POPULATION-BASED STUDY IN THE KAGERA REGION OF TANZANIA

Population-based prevalence and incidence studies on HIV-1 infection w ere started in the Kagera region of Tanzania in 1987. The prevalence a nd incidence of infection with Treponema pallidum was studied to enabl e development of better strategies for STD control. Serological diagno sis of a past or treated infection with Troponema pallidum was made by seropositivity only to TPHA testing while active syphilis has diagnos ed by seropositivity to both VDRL and TPHA tests. Seroconversion was m easured in 1989 by finding TPHA serologically positive individuals dur ing the follow-up period among the initially seronegative study popula tion of 1987. The overall prevalence of active syphilis in the total s ample of adults in the region was found to be 5.9% while that of past syphilis was 13.5%. The association between the prevalence of HIV-1 in fection and syphilis of both types was found to be highly significant. However, the association between one pre-existing infection and seroc onversion in the other was present but not statistically significant. The overall incidence of syphilis based on seroconversion in a cohort of adults in the region was found to be 11.6 per 1000 person-years at risk. In view of these findings, syphilis is a significant health prob lem in the region with a high level of transmission and efforts should be made to control it. Intervention studies should use these base-lin e data and monitor changes in syphilis incidence which may indicate ch anges in sexual behaviour. Such indicators could also be useful for ev aluating the impact of interventions directed at reducing the transmis sion of HIV, syphilis and other STDs in the region.