The prevalence and incidence of active syphilis in women in Morocco, 1995-2016: Model-based estimation and implications for STI surveillance

<div><p>Background</p><p>Evolving health priorities and resource constraints mean that countries require data on trends in sexually transmitted infections (STI) burden, to inform program planning and resource allocation. We applied the Spectrum STI estimation tool to estimate the prevalence and incidence of active syphilis in adult women in Morocco over 1995 to 2016. The results from the analysis are being used to inform Morocco’s national HIV/STI strategy, target setting and program evaluation.</p><p>Methods</p><p>Syphilis prevalence levels and trends were fitted through logistic regression to data from surveys in antenatal clinics, women attending family planning clinics and other general adult populations, as available post-1995. Prevalence data were adjusted for diagnostic test performance, and for the contribution of higher-risk populations not sampled in surveys. Incidence was inferred from prevalence by adjusting for the average duration of infection with active syphilis.</p><p>Results</p><p>In 2016, active syphilis prevalence was estimated to be 0.56% in women 15 to 49 years of age (95% confidence interval, CI: 0.3%-1.0%), and around 21,675 (10,612–37,198) new syphilis infections have occurred. The analysis shows a steady decline in prevalence from 1995, when the prevalence was estimated to be 1.8% (1.0–3.5%). The decline was consistent with decreasing prevalences observed in TB patients, fishermen and prisoners followed over 2000–2012 through sentinel surveillance, and with a decline since 2003 in national HIV incidence estimated earlier through independent modelling.</p><p>Conclusions</p><p>Periodic population-based surveys allowed Morocco to estimate syphilis prevalence and incidence trends. This first-ever undertaking engaged and focused national stakeholders, and confirmed the still considerable syphilis burden. The latest survey was done in 2012 and so the trends are relatively uncertain after 2012. From 2017 Morocco plans to implement a system to record data from routine antenatal programmatic screening, which should help update and re-calibrate next trend estimations.</p></div

Time trends in (a) HIV incidence, prevalence and mortality and (b) condom usage, in Morocco.

<p>Epidemiological estimates and condom usage assumptions from the Spectrum Goals model. HIV incidence rates shown are the hazard/density, within the uninfected population. Abbreviations: MSM = Men who have sex with men; F = women; M = men.</p

Spectrum-estimated prevalence and incidence rate (per 100,000 person-years) of active syphilis in 2016 in women 15–49 years, Morocco.

<p>Spectrum-estimated prevalence and incidence rate (per 100,000 person-years) of active syphilis in 2016 in women 15–49 years, Morocco.</p

Prevalence data used, and adjustments for diagnostic test performance, and missing high-risk populations, in the Spectrum-STI estimation of syphilis prevalence and trend for adult (15–49 years) women in Morocco.

<p>Prevalence data used, and adjustments for diagnostic test performance, and missing high-risk populations, in the Spectrum-STI estimation of syphilis prevalence and trend for adult (15–49 years) women in Morocco.</p

Prevalence of RPR positivity, sentinel surveillance in Morocco.

<p>Data shown are for RPR positivity regardless of TPHA status. For some of these years and population groups, TPHA was also measured, but the dual combined RPR/TPHA status was not recorded. Since there were more data points for RPR than for TPHA, the current figure shows the RPR results. For sample sizes, numbers testing positive and corresponding TPHA positivity results, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0181498#pone.0181498.s003" target="_blank">S2 Table</a>.</p

Spectrum-estimated national syphilis prevalence, women 15–49 years, Morocco.

<p>Data are shown after adjustments for diagnostic test performance, and missing high-risk populations, as described in the Methods. Dashed green lines are 95% Confidence Intervals around the estimate.</p