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Abstract
Background Little information is available on the epidemiology of syphilis in West Africa, where this infection is routinely screened in antenatal clinics to prevent congenital infection. In order to inform control programmes, the burden of active syphilis was estimated among pregnant women and adults in Burkina Faso.
Methods This study enrolled 2136 pregnant women from 98 healthcare facilities and 1679 consenting women and men from the general population of Ouagadougou, the capital city. After a face-to-face interview on demographic characteristics, blood samples were collected and tested for syphilis. Active syphilis was defined by a dually positive result on rapid plasma reagin and Treponema pallidum haemagglutination antibody tests.
Results The overall seroprevalence of active syphilis was 1.7% (95% CI 1.3 to 2.2), with similar rates between women (1.2%, 95% CI 0.7 to 2.3) and men (1.8%, 95% CI 1.0 to 3.0) in Ouagadougou, and a trend for higher prevalence among pregnant women from semi-urban areas (2.2%, 95% CI 1.0 to 4.5) compared with rural areas (1.7%, 95% CI 1.2 to 2.4, p=0.06). The prevalence tended to be higher among women aged 20–24 years (2.6%, 95% CI 1.3 to 7.6) and men aged 30–34 years (3.9%, 95% CI 0.8 to 11.0) than at other ages. However, age, marital status, location and education were not associated with syphilis.
Conclusion The low prevalence of syphilis among pregnant women and the adult general population is very encouraging but should not challenge the amount of resources dedicated to sexually transmitted infection and HIV prevention.
- Burkina Faso
- prevalence
- rural
- seroepidemiology
- seroprevalence
- syphilis
- urban
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Syphilis remains a major cause of reproductive morbidity and poor pregnancy outcomes in sub-Saharan Africa, which justified a routine serological screening during antenatal consultations. In addition, syphilis infection substantially increases the sexual transmission of HIV.1
The prevalence of syphilis among pregnant women varies widely throughout Africa, from 17.4% in Cameroon, 8.4% in South Africa to 6.7% in the Central African Republic.2 In Burkina Faso, the syphilis prevalence among pregnant women was 0.24% between 1995 and 1998.3 In the general population, only three cases of syphilis have been detected among a random sample of 2364 adults in 2000.4
In order to document syphilis prevalence in Burkina Faso, we conducted a cross-sectional study among the general population in the capital city and among pregnant women in four geographically distant provinces of Burkina Faso.
Methods
Study among pregnant women
A serosurvey was conducted between May and July 2003 among pregnant women attending all antenatal clinics (n=98) from Boulgou, Poni, Seno and Yatenga provinces.5
Study in the general population in Ouagadougou, capital city
We used a two-stage clustered sample design, in the first stage we randomly selected 59 of 713 administrative areas, and in the second stage we randomly selected 20 households in each area. All adults aged 15–49 years present in the selected households were invited to participate in the study. After informed consent, individuals were interviewed to collect data on demographic factors, medical backgrounds and behaviours related to the risk of HIV/sexually transmitted infections (STI).
Common procedures for the two studies
Active serological syphilis was diagnosed by a positive rapid plasma regain (RPR) test (any titre), confirmed by the Treponema pallidum haemaglutination assay test (TPHA; at dilution below 1:80) (Newmarket Laboratories Ltd, Germany). Prevalences are reported with 95% CI computed using Poisson distribution because of small proportions. All analyses (estimation, CI) adjusted for the Ouagadougou clustered design. In particular, we specified individual weight, secondary sampling units and primary sampling unit.6 A p value less than 0.05 was considered significant.
Ethical considerations
The Ministry of Health of Burkina Faso approved the study. Participants with active syphilis and their partners were treated based on the National STD Treatment Guidelines. Because HIV test results were unlinked, women and men who wished to know their HIV status were referred to a nearby facility for free voluntary counselling and testing.
Results
The seroprevalence of syphilis was 1.7% (95% CI 1.3 to 2.2) among all participants (N=3815), with a good response rate (93.5% among pregnant women and 77.2% in Ouagadougou).
A total of 64 pregnant women (3.0%) was positive for RPR; 38 were positive for TPHA, giving an active syphilis seroprevalence of 1.8% (95% CI 1.3 to 2.5), ranging from 0.6% (95% CI 0.2 to 1.9) in Boulgou province to 3.6% (95% CI 2.2 to 5.9) in Poni province (table 1). Pregnant women living in rural areas tended to be less infected (1.7% vs 2.2%) than those living in semi-urban areas (main cities of the province) (p=0.06).
Demographic variation of the syphilis prevalence in pregnant women and the general population of Burkina Faso
HIV prevalence in this population was 2.5% (95% CI 1.9 to 3.3), ranging from 1.3% (95% CI0.5 to 2.9) in Seno province to 3.6% (95% CI 2.2 to 5.7) in Boulgou province.
In Ouagadougou, active syphilis seroprevalence was 1.5% (95% CI 1.1 to 2.3). There were 32 RPR positive and 25 TPHA positive individuals. The prevalence of active syphilis tended to be higher among women aged 20–24 years (2.6%, 95% CI 1.5 to 3.7) and men aged 30–34 years (3.9%, 95% CI 0.4 to 8.2). However, age, marital status, location and education were not associated with syphilis in multivariable analysis (data not shown).
Discussion
The prevalence of syphilis among pregnant women in this study was lower than in a similar study from 1997 (2.5%, 95% CI 1.7% to 3.5%),7 but with important regional variations.
The syndromic management of STI was implemented in Burkina Faso in 1996. The widespread use of antibiotics and good access to health care may have contributed to the decline in syphilis and sexually transmitted disease prevalence,8 along with a decline in risky sexual behaviours resulting from HIV prevention programmes.
The differences in syphilis prevalence between urban (Ouagadougou) and rural areas (pregnant women) may be explained by different sexual behaviours, the urban area being more exposed to HIV prevention programmes. The development of HIV prevention initiatives towards rural areas could be pivotal to reduce syphilis further.
This low prevalence of syphilis infection should not challenge the systematic screening of this infection among pregnant women. Terris-Prestholt and colleagues9 estimated the cost effectiveness of the intervention according to different levels of syphilis prevalence varying from 2% to 15%. The cost per disability-adjusted life-year saved decreased substantially as prevalence increased. However, even at prevalence as low as 2%, antenatal syphilis screening and treatment remains cost effective (US$33 per disability-adjusted life-year saved including stillbirth).
The low prevalence of syphilis in Burkina Faso is encouraging, but should not divert the resources dedicated to STI and HIV prevention in the country to other interventions.
Key messages
Although the seroprevalence of active syphilis was as low as 2% among pregnant women in Burkina Faso, it still justifies the need for systematic screening during pregnancy.
Age, marital status, urban or rural location and education were not associated with active syphilis. Pregnant women from semi-urban areas tended to be more infected with syphilis than pregnant women from rural areas.
This survey confirms the decrease of bacterial STI in this African region over the past 15 years.
Acknowledgments
The authors would like to thank the staff from the four provinces of Burkina Faso, the staff of centre MURAZ, the Ministry of Health and the National AIDS Control Programme. They would also like to thank all the individuals who gave their time to be interviewed as part of this study.
Footnotes
Part of the contents of this manuscript was presented at the 5th International AIDS Society conference on HIV pathogenesis, treatment and prevention, Cape Town (South Africa), 19–22 July 2009.
Funding This work was supported by the United Nations Development Programme (UNDP), WHO, the United Nations Population Fund (UNFPA), and the embassies of Holland, Switzerland, Denmark and Belgium.
Competing interests None.
Patient consent Obtained.
Ethics approval This study was conducted with the approval of the Ministry of Health of Burkina Faso.
Provenance and peer review Not commissioned; externally peer reviewed.