Background
Syphilis is a sexually transmitted infection (STI) caused by the spirochete
Treponema pallidum, and it continues to be a main public health problem worldwide [
1]. It spreads primarily through sexual contact and vertical transmission and can rarely be spread through blood transfusion. Syphilis can be successfully controlled by effective public health measures due to the availability of a sound diagnostic test and effective and economical treatment options [
2]. However, if syphilis is left untreated, it can lead to devastating fetal outcomes [
3].
Pregnant women are sexually active and are at risk of STI, including syphilis [
4]. Globally, 36 million people are infected with syphilis, out of which 2 million are pregnant women. More than half of infected women transmit the infection to their babies resulting in adverse pregnancy outcomes including early fetal death, stillbirth, preterm birth, low birth weight, neonatal death, and congenital infection in infants [
5].
Syphilis remained a major cause of reproductive morbidity and poor pregnancy outcomes in developing countries [
4]. In sub-Saharan Africa, syphilis sero-prevalence ranges from 4 to 15%, and can cause adverse outcomes in 50–80% of pregnancies [
6]. Ethiopia is among the top three sub-Saharan countries with the highest numbers of adverse pregnancy outcomes attributed to syphilis [
7]. Furthermore, studies have demonstrated that 21% children born from seropositive mothers in Ethiopia developed signs of syphilis. Besides, stillbirth and abortion rates of syphilis diagnosed women were almost double relative to the general population [
8].
Previously established systematic review and meta-analysis conducted on the prevalence of syphilis among pregnant women in Ethiopia includes only five studies with smaller sample size and did not report syphilis prevalence based on the diagnostic test modality. Besides, it failed to demonstrate syphilis-HIV co-infection and predictors of syphilis sero-positivity [
9]. Thus, in the absence of concrete and inclusive evidence in STI endemic settings including HIV and syphilis, this systematic review and meta-analysis was conducted to determine the updated pooled prevalence of syphilis among pregnant women in Ethiopia. Moreover, syphilis sero-reactivity associated factors and syphilis-HIV co-infection was also determined in this study to guide public health intervention and control measures.
Discussion
Syphilis is one of the easily preventable and treatable sexually transmitted infections but continued to exert a high burden worldwide especially in sub-Saharan Africa where resources are scarce. Therefore, prevention and control of syphilis among pregnant women using appropriate intervention measures is crucial for the emergence of syphilis free generation. For that, determining the actual burden of syphilis infection and antenatal care (ANC) follow-up screening plays a great role in early diagnosing and treatment of syphilis, and prevention of its vertical transmission. This study aimed to determine the updated pooled prevalence and factors associated to syphilis positivity, and the pooled syphilis-HIV co-infection among pregnant women in Ethiopia.
This meta-analysis showed that the overall pooled prevalence of syphilis among pregnant women in Ethiopia was 2.32% (95% CI, 1.68–2.97). The pooled prevalence was two times higher than the recent nationwide HIV/syphilis sentinel reports among ANC attendees in Ethiopia (1.1%) [
33]. The variation in syphilis prevalence between this meta-analysis and the sentinel survey might be due to the rough estimate nature of the sentinel report that might underrepresent the actual burden of the diseases. Contrastingly, previous meta-analysis reported higher prevalence of syphilis among pregnant women in Ethiopia, 3.67% [
9] relative to this study. This might be because of the previous meta-analysis includes studies with higher syphilis prevalence conducted in the pre-antiretroviral therapy availability. However, given the known synergy between HIV and syphilis [
11], we have excluded studies conducted prior to HIV antiretroviral availability in this meta-analysis. Besides, the diseases dynamics may change overtime and impact the observed prevalence [
34]. Partly, it may be due to the difference in the number of included studies (5 studies in earlier meta-analysis and 13 articles in this study), indicating the sample size may impact the prevalence.
On the other hand, the pooled prevalence in this meta-analysis was comparable with the report from a countrywide surveillance of HIV/syphilis prevalence among pregnant women attending ANC in Tanzania (2.5%) [
35]. The similarity in syphilis prevalence in Ethiopia and Tanzania might be partly due to the WHO’s increased focus and prioritization of antenatal syphilis (in conjunction with HIV and hepatitis B virus) screening for better intervention measures. Besides, combination rapid HIV/syphilis tests are now used to a greater degree in ANC which may also result in increased syphilis testing/diagnoses in different countries of the world to indicate the actual picture of the diseases in various settings.
As shown in subgroup analysis, this study indicated relatively higher prevalence of syphilis using treponemal diagnostic test modality 2.53% (95% CI, 1.92–3.14%) compared to the non-treponemal test 1.90% (95% CI, 0.40–3.40%). This could be due to reactivity to a treponemal test implies infection but it does not determine whether the infection is recent or remote or whether it has been treated or not [
32]. Thus, it suggests that treponemal tests stay positive for decades after treatment and may not always indicate active infection. On the other hand, non-treponemal tests have a high false-positive rate and are difficult to interpret on their own [
32]. Therefore, considering the difficulty of syphilis diagnosis, the results have to be interpreted with care.
Regional analysis showed a higher and lower prevalence of syphilis in SNNP (4.06%) and in Oromia (1.46%) respectively. Higher syphilis prevalence in SNNP might be attributed to the risky socio-cultural practices such as polygamy is more practiced in SNNP [
36] relative to other regions of Ethiopia. Partly, it might be due to the difference in the number of studies included in each category.
In addition, pooled estimate of syphilis-HIV co-infection was also assessed. Consequently, the overall pooled prevalence was 0.80% (95% CI, 0.60–1.01%). A comparable result (0.73%) was obtained from Republic of Congo [
37]. While a study in Tanzania reported lower (0.3%) prevalence [
35], another study from Rwanda indicated higher (1.2%) prevalence [
38] of syphilis-HIV co-infection relative to the findings of this study. The difference in prevalence of syphilis-HIV co-infection might be attributed to the variation in level of implementation and integration of STI prevention and control measures in different countries.
Besides, the association between pregnant women with and without previous history of multiple sexual partner and syphilis sero-positivity was measured in this study. Accordingly, pregnant women with previous history of multiple sexual partners were 2.98 times more likely to get syphilis infection compared to women without such partner. This was consistent with previously established evidences [
39‐
42] and could be attributed to the fact that people with multiple sexual partner has higher risk of getting STI including syphilis. This study also showed that pregnant women with previous history of STI were 4.88 times at higher risk of developing syphilis relative to pregnant women without such history. This is in line with the findings from Malawi [
43] and China [
44]; this could be partly due to lack of behavioral change and other prevention interventions that resulted in maintaining risky behaviors among women who had history of previous STI.
On the other hand, this meta-analysis also demonstrated that married women had 63% lower risk of developing syphilis compared to those who are not cohabiting (single, widowed, divorced). This was comparable with earlier studies conducted in rural Tanzania [
45] and three sub-Saharan countries [
46]. This might be due to the tendency of non-cohabiting women to practice high-risk sexual behaviors like having multiple sexual partners. Partly, this could be because of women in ANC are sexually active age groups, suggesting that if they are non-cohabiting they may have high-risk sexual behaviors.
Limitations
Given the difficulty of syphilis diagnosis, most of the included studies used treponemal diagnostic test alone which may impact the prevalence report. Some regions in the country were not represented in this study due to lack of established original studies in the area. Furthermore, all included studies were facility based. Thus, interpretation of findings has to be with due consideration of these limitations.
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