Serological markers for treponemal infection in children in rural Kilimanjaro, Tanzania: evidence of syphilis or non-venereal treponematoses?

Objective: To determine the seroprevalence of treponemal infection and possible risk factors among children aged 0-14 in the general population of a rural Tanzanian village.

Methods: The survey was conducted as a part of a cross section study of a total village population on HIV and sexually transmitted disease. Among 1708 registered children aged 0-14, the 553 first attending were tested for treponemal infection with both rapid plasma reagin test (RPR) and Treponema pallidum Haemagglutination test (TPHA). These children belonged to a household cohort--also including their parents, siblings, and other household members--with 1339 members; 1224 (91.4% participated in the survey and 82.1% of these were tested for treponemal infection.

Results: The overall prevalence for the TPHA test was 6.4% among girls and 1.1% among boys (odds ratio, OR = 6.5; 95% confidence interval, CI: 1.9-22.3). The sex difference was most pronounced in the age group 10-14; 11.1% among girls versus 1.0% among boys (OR = 12.8; CI: 1.6-101.9). Among the 20 children who were TPHA positive, we found two cases of active, congenital syphilis. There was a lack of association between positive serology in children and positive serology in their parents.

Conclusion: The highly significant predominance of girls testing positive for TPHA, and the concomitant lack of association between parents' and children's serostatus might point to sexual transmission as being the most common route of transmission of treponemal infection in girls during childhood in this village. The sources of infection for the seropositive girls are possibly found outside the family.