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Historical review suggests decades of treatable syphilis in Africa
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Despite a global decline in syphilis prevalence coinciding with the introduction of penicillin, rates of infection among pregnant women in sub-Saharan Africa remained unchanged for approximately 50 years, according to a systematic review of published data spanning nearly a century.
This disparity appears to have continued into recent years as well, with reports suggesting greater antenatal syphilis prevalence (ASP) in this region from 1990 to 1999 and in 2008, Chris Richard Kenyon, PhD, MPH, of the Institute of Tropical Medicine in Antwerp, Belgium, and colleagues wrote.
“Numerous papers have published descriptions of longitudinal changes in reported cases of syphilis within countries that are associated with events such as the introduction of penicillin, social disruption associated with wars or the collapse of the Soviet Union,” they wrote. “Our 11-country longitudinal case study found that although syphilis prevalence declined in all populations investigated in the post-penicillin period, it did so to varying degrees and at different times.”
Kenyon and colleagues conducted a review of studies reporting country-specific ASP data to track the variance of population syphilis rates over time. After collecting a sample of relevant studies published before 1952, they compared early rates from 11 countries with those reported after the cutoff date. ASP data distinguishing black and white populations were available for the United States and South Africa and included in the analysis. To observe more recent trends, the researchers also examined 1990 to 1999 and 2008 national ASP data collected from an Institute for Health Metrics and Evaluation database, WHO data and other published literature for these same countries. Using these findings, they implemented linear regression testing to determine any associations between ASPs, world region and various potential risk factors.
Figure 1. This image shows antenatal syphilis prevalences by country for the period 1990-1999. Darker shades of red represent higher syphilis prevalences. Syphilis prevalences range from under 0.5% to over 3%.
Source: Kenyon et al.
Click the image to enlarge.
The researchers used data from 18 pre-1952 studies and 23 post-1952 studies for the longitudinal analysis. While ASP declined among most of populations around the time of the proliferation of penicillin, ASP plateaued at approximately 6% among Zimbabweans and black South Africans until the end of the 20th century, when it fell to just over 1%. According to the researchers, ASP trends were largely similar to reports of syphilis incidence during this time period.
Bivariate risk factor analysis of the 1990 to 1999 and 2008 data revealed ASP to be negatively associated with GDP per capita, health expenditure and residence in sub-Saharan Africa. The researchers reported ASP declines between these two datasets among all regions, but noted greater prevalence within Africa compared with the other regions.
Kenyon and colleagues wrote that the higher ASP seen in Africa follows similar trends of other STDs such as HIV and herpes simplex virus-2, and could be due to a common factor driving these infections in the region. Further investigation of data linking STD incidence and connected sexual networks within high-risk populations could provide an explanation for these trends, according to the researchers.
“Although this analysis suffers from numerous limitations, if taken in conjunction with the other evidence reviewed here it generates the hypothesis that more connected sexual networks may have been partly responsible for the higher prevalences of syphilis and other STIs in high prevalence populations,” they wrote. “An improved understanding of the factors underpinning variations in syphilis rates around the world in the last 100 years could help us to better understand the current and predict the future patterning of syphilis prevalence.” – by Dave Muoio
Disclosure: The researchers report no relevant financial disclosures.
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