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Declining Prevalence Rates of Syphilis Among Police Officers in Guinea-Bissau, West Africa, 1990–2010

Lindman, Jacob Lopatko*; Månsson, Fredrik; Biague, Antonio; Da Silva, Zacarias José; Andersson, Sören§; Norrgren, Hans

doi: 10.1097/OLQ.0000000000000012

We analyzed prevalence rates of syphilis (positive Treponema pallidum hemagglutinin antigen/T. pallidum particle antigen and venereal disease research laboratory test) among police officers in Guinea-Bissau from 1990 to 2010 and found a significant decline from 4.5% to 0.4% (P = 0.0065). Our results are in line with other recent reports from West Africa. More research is needed to identify the reasons for this decline.

A study of police officers in Guinea-Bissau found a significant declining syphilis prevalence trend in 1990 to 2010.

From the *Department of Clinical Sciences Lund, Division of Infection Medicine, Lund University, Lund, Sweden; †Department of Clinical Sciences, Infectious Diseases Research Unit, Lund University, Malmö, Sweden; ‡National Public Health Laboratory, Bissau, Guinea-Bissau, West Africa; §Department of Clinical Microbiology, Örebro University, Örebro, Sweden; and ¶Department of Clinical Sciences Lund, Division of Infection Medicine, Lund University, Lund, Sweden

The authors want to thank Babetida N’Buna, Aquilina Sambu, Eusebio Ieme, Isabel da Costa, Jaqueline Barreto, and Ana Monteiro Watche at the Health Station of the Segunda esquadra and Cidia Camara, Carla Pereira, Julieta Pinto Delgado, Leonvengilda Fernandes Mendes, Ana Monteiro, and Ansu Biai at National Public Health Laboratory in Bissau.

Supported by the Department for Research Cooperation (SAREC) at the Swedish International Development Agency.

No conflict of interest exists.

Correspondence: Jacob Lopatko Lindman, Department of Clinical Sciences Lund, Division of Infection Medicine, Lund University, Ystad hospital Ystad, Lund, Sweden. E-mail:

Authors contributions: Antonio Biague was medically and organizationally responsible for the clinical sites. Zacharias José Da Silva was responsible for analyses of HIV and syphilis serology at the laboratory. Sören Andersson developed the HIV and syphilis testing algorithm. Fredrik Månsson and Hans Norrgren coordinated the laboratory and clinical work. Jacob Lopatko Lindman, Fredrik Månsson, and Hans Norrgren were responsible for analysis of data and writing the manuscript.

Received for publication March 24, 2013, and accepted June 7, 2013.

Syphilis is an important sexually transmitted infection (STI) that may cause various symptoms including genital ulcers, systemic disease, and congenital syphilis as well as enhancing the transmission of HIV.1,2 In Guinea-Bissau, studies have reported prevalence rates of active syphilis ranging from 1.0% to 3.9%3,4 and serological evidence of previous syphilis infection ranging from 11.3% to 12.1%5,6 in diverse risk groups such as pregnant women, female urogenital patients, military personnel, and police officers. Recent studies in some high-prevalence countries in West Africa have indicated declines in syphilis prevalence. A study in The Gambia concluded that the prevalence of syphilis among genitourinary patients had declined significantly over the period 1994 to 2007.7 A review of several small studies in Burkina Faso has also provided evidence of a declining syphilis prevalence trend.8 The most recent study on syphilis in Guinea-Bissau3 showed a prevalence of 1.0%, which corresponds well with the declining trend of syphilis reported from The Gambia7 and the findings in Burkina Faso.8 The aims of this study were to explore whether the evidence of a decreasing syphilis prevalence reported from Guinea-Bissau and other countries in West Africa could be seen in our cohort of police officers and to identify risk factors for syphilis toward which preventive measures might be targeted.

For this study, we used syphilis serology results at the time of inclusion into a cohort of police officers. All persons with a regular employment in the Guinea-Bissau police force have been invited to participate in the study, which has been voluntary with less than 2% refusal to participate. For this study, inclusion started in January 1990 and ended on December 31, 2010. As a result of the civil war in 1998 to 1999, no tests were performed from June 1998 until the end of 2002. Information of demographic information, sexual risk behavior, and symptoms related to STIs was obtained via a questionnaire. All current episodes of urethral discharge or genital ulcer disease (GUD) were verified clinically. Blood samples for HIV and Treponema pallidum serology were collected at inclusion. Individuals with serological signs of syphilis infection as well as participants with GUD received treatment free of charge. Syphilis testing was performed at the National Public Health Laboratory, Bissau. Sera were screened for T. pallidum antibodies with T. pallidum hemagglutinin antigen (TPHA; Fujirebio, Japan). In year 2000, the TPHA test was replaced by T. pallidum particle antigen (TPPA; Fujirebio) by the manufacturer. All seroreactive samples of TPHA/TPPA were further analyzed with a venereal disease research laboratory test (VDRL; Sypal, Diagast, Lille Cedex, France). Laboratory testing was carried out according to the directions of the manufacturers, and all tests were run against positive and negative controls. Only those participants positive by both TPHA/TPPA and VDRL were considered as having active syphilis. Individuals with positive TPHA/TPPA test result were defined as having serological evidence of previous syphilis infection. The present study was approved by the Ethics Research Committee at the Karolinska Institute, Stockholm, Sweden, and the Ministry of Health in Guinea-Bissau.

All statistical analyses were performed with the computer software STATA 10.1. For the analysis of trends of prevalence of TPHA/TPPA and VDRL reactivity at the time of inclusion in the study, participants were divided into 7 time strata (Tables 1 and 2). Trends in change of seroprevalence were calculated by Cochran-Armitage test for linear trend comparing the TPHA/TPPA and VDRL seroprevalence over all 7 periods, adjusted for age in 4 categories (≤24, 25–34, 35–44, ≥45) and sex. A multivariate analysis was performed on risk factors found to be significantly associated with active syphilis in the univariate analyses for both sexes jointly. Risk factors deemed important for theoretical reasons were also included in the multivariate analysis.





A total of 4792 police officers were included in the cohort in 1990 to 2010, of whom 12.9% were women. Four thousand seventy hundred eighty-eight had a recorded TPHA/TPPA test result at the time of inclusion. The marriage rate at inclusion was 74.3%. The median age at inclusion was stable over the different periods with only 2 exceptions, a lower median age for women in 1992 to 1993 and a higher median age for men in 1996 to June 1998. The total prevalence of TPHA/TPPA reactivity and active syphilis was 12.9 and 2.8%, respectively, but pronounced changes were noted over the study period (Tables 1 and 2). The prevalence of active syphilis among the police officers decreased significantly from 4.5% in 1990 to 1991 to 0.4% in 2008 to 2010 (P = 0.0065). No significant declining trend of TPHA/TPPA reactivity in 1990 to 2010 was found (P = 0.73). However, the prevalence of TPHA/TPPA reactivity in 2008 to 2010 was significantly lower compared with the other periods after age and sex adjustment (adjusted P < 0.05). Potential factors that could influence active syphilis among police officers are presented in Table 3. Sexual risk taking was in general high in the different groups. Surprisingly, contact with commercial sex workers and a self-reported history of GUD were not associated with active syphilis (data not shown). Factors found to be significantly associated with active syphilis in the multivariate analyses were age at least 45 years, HIV infection, and ethnicity. Regarding the association with HIV, when analyzing for subtype, only HIV-2 remained significantly associated with active syphilis.



We observed a significant decrease in prevalence rates of active syphilis among 4783 police officers in Guinea-Bissau between 1990 and 2010. There was no significant declining trend of TPHA/TPPA seroprevalence, but because this group includes previously treated individuals and individuals with old infection, this is not a surprising finding. A declining trend of TPHA/TPPA seroprevalence is likely to be seen in approximately 10 to 15 years time. Our findings are in line with a recent report from The Gambia that showed a declining trend of syphilis among genitourinary patients from 11.2% to 1.5% in 1994 to 2007.7 In addition, a study from Guinea-Bissau in 2006 to 2008 reported a syphilis prevalence of 1.0% in women presenting with urogenital symptoms.3 These findings together with our results and data from Burkina Faso8,9 suggest a decline of syphilis in parts of West Africa. The reasons for the declining prevalence of serological syphilis are not obvious. In Guinea-Bissau, syphilis and HIV are the only STIs where an etiologically based laboratory diagnostic service has been in place for many years. However, a screening program for STIs or antenatal screening for syphilis has never been introduced in Guinea-Bissau, so the observed decline in syphilis is most likely not a result of improved syphilis diagnosis and treatment. The increased use of antibiotics has been suggested to be one of the reasons for the declining syphilis trend in The Gambia.7 This is likely part of the explanation in Guinea-Bissau as well, where antibiotics have become more widely available in pharmacies. Increased awareness of HIV through preventive campaigns or the visible impact of the HIV epidemic could have led to sexual behavior changes, which also could play a part in the observed decline in syphilis. The association between HIV-2 and syphilis that we found has previously been reported from Guinea-Bissau10,11 and The Gambia.7 We found no association between HIV-1 and syphilis infection. This is in line with a recent study from Guinea-Bissau that found no association between syphilis infection and HIV-1, only herpes simplex virus type 2 and Mycoplasma genitalium were associated with HIV-1 infection of the 10 STIs they investigated.3 The lack of association between HIV-1 and syphilis in the police cohort is likely caused by a young epidemic of HIV-1 with relatively few cases of dual infection with HIV-1 and syphilis. Surprisingly, prevalence of active syphilis increased with age, with significantly higher prevalence rate in the age group of participants 45 years or older as compared with those younger than 25 years. Therefore, it is important to include also older age groups when designing local preventive intervention campaigns. The decreased risk of active syphilis in police officers being non-Balanta/Fula is a complex finding, which indicate different social traditions in different ethnic groups.

Findings in this study need to be interpreted in light of its limitations. We had suboptimal characterization regarding risk behavior, one example being that we did not differentiate between condom use with spouse and extramarital partners. In addition, collecting information of this sort is associated with risk of both overstating and underestimating, making the effect of bias hard to anticipate. This could be the reason why we failed to identify sexual risk behavior as a risk factor for syphilis. Lastly, this study was performed on mostly male police officers, limiting the generalizability of these findings.

To summarize, we have found a declining prevalence rate of active syphilis in police officers in Guinea-Bissau over the last 20 years. We can only speculate about the reasons behind this declining trend. It may be caused by changed sexual behavior or increased antibiotics use in the population. More studies are needed to explore the reasons behind this declining syphilis trend.

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