Adult gonorrhea, chlamydia and syphilis prevalence, incidence, treatment and syndromic case reporting in South Africa: Estimates using the Spectrum-STI model, 1990-2017

Abstract

Objectives: To estimate trends in prevalence and incidence of syphilis, gonorrhea and chlamydia in adult men and women in South Africa.

Methods: The Spectrum-STI tool estimated trends in prevalence and incidence of active syphilis, gonorrhea and chlamydia, fitting South African prevalence data. Results were used, alongside programmatic surveillance data, to estimate trends in incident gonorrhea cases resistant to first-line treatment, and the reporting gap of symptomatic male gonorrhea and chlamydia cases treated but not reported as cases of urethritis syndrome.

Results: In 2017 adult (15-49 years) the estimated female and male prevalences for syphilis were 0.50% (95% CI: 0.32-0.80%) and 0.97% (0.19-2.28%), for gonorrhea 6.6% (3.8-10.8%) and 3.5% (1.7-6.1%), and for chlamydia 14.7% (9.9-21%) and 6.0% (3.8-10.4%), respectively. Between 1990 and 2017 the estimated prevalence of syphilis declined steadily in women and men, probably in part reflecting improved treatment coverage. For gonorrhea and chlamydia, estimated prevalence and incidence showed no consistent time trend in either women or men. Despite growing annual numbers of gonorrhea cases - reflecting population growth - the estimated number of first line treatment-resistant gonorrhea cases did not increase between 2008 and 2017, owing to changes in first-line antimicrobial treatment regimens for gonorrhea in 2008 and 2014/5. Case reporting completeness among treated male urethritis syndrome episodes was estimated at 10-28% in 2017.

Conclusion: South Africa continues to suffer a high STI burden. Improvements in access and quality of maternal, STI and HIV health care services likely contributed to the decline in syphilis prevalence. The lack of any decline in gonorrhea and chlamydia prevalence highlights the need to enhance STI services beyond clinic-based syndromic case management, to reinvigorate primary STI and HIV prevention and, especially for women, to screen for asymptomatic infections.

Fig 1. Estimated trends in active syphilis in South African adults, 15–49 years.

(a) prevalence in women; (b) prevalence in men; (c) incidence in women and men. Prevalence data shown have been adjusted for diagnostic test performance and under sampling of high-risk populations, as described in the methods and detailed in S1 File. Solid lines are the best estimate; dotted lines are 95% Confidence Intervals. Blood donor data are shown, but these were not used in the default scenario, they were only used in the sensitivity analysis.

Fig 2

Estimated trends in gonorrhea in South African adults, 15–49 years: (a) prevalence in women; (b) prevalence in men; (c) incidence in women and men. Prevalence data shown have been adjusted for diagnostic test performance, urban/rural location, and under sampling of high-risk populations, as described in the methods and detailed in S1 File. Solid lines are best estimates; dotted lines are 95% Confidence Intervals. ANC = antenatal care clinic attendees, FP = family planning clinic attendees; PHC = Primary health clinic attendees.

Fig 3

Estimated trends in chlamydia in South African adults, 15–49 years: (a) prevalence in women; (b) prevalence in men; (c) incidence in women and men. Prevalence data shown have been adjusted for diagnostic test performance, urban/rural location, and under sampling of high-risk populations, as described in the methods and detailed in S1 File. Solid lines are best estimates; dotted lines are 95% Confidence Intervals. ANC = antenatal care clinic attendees, FP = family planning clinic attendees; PHC = Primary health clinic attendees.

Fig 4

Spectrum estimates of antibiotic resistant gonorrhea, South Africa: (a) Proportion of gonorrhea cases among men presenting to PHCs with male urethritis syndrome in national sentinel surveillance; (b) estimated annual incident gonorrhea cases resistant and susceptible to the 3 first-line antibiotic treatments shown in Fig 4A. • Ciprofloxacin: Resistance data shown includes intermediate resistance (Minimum Inhibitory Concentration (MIC) = 0.12–0.50 μg/mL, and full resistance (MIC of ≥1 μg/mL) ([68]. • Azithromycin: Resistance as estimated and shown is defined as Intermediate resistance, i.e. MIC = 0.50 μg/mL [69]; • Cefixime: Resistance as estimated and shown is defined as MIC = 0.25 μg/mL [69]. Annual surveillance in Gauteng province did not detect any consistent, progressive and sustained increase by year in MIC₅₀ (minimum antimicrobial concentration needed to inhibit 50% of isolates) & MIC₉₀ (minimum antimicrobial concentration needed to inhibit 90% of isolates). • Ceftriaxone: Resistance, defined as MIC = 0.25 μg/mL (EUCAST 2018; version 8.0), was detected in 2/324 (0.6%) of cases surveyed in 2009, but in 0% of cases in 2008 and 2010–2017 (number of cases ranged from 128 to 338); and no significant increase in the MIC over time was detected. • In 2017 ciprofloxacin resistance was not tested by NICD; cefixime (CXM), ceftriaxone were tested and no resistance detected to the extended-spectrum cephalosporins. The prevalence of intermediate resistance to azithromycin was 1.8%. Sources: National Institute of Communicable Diseases [4,5,41,42].