Prevalence of group A streptococcal carriage in school children from Cape Town: A cross-sectional study and systematic review

Background. Asymptomatic children can be a major reservoir of pharyngeal group A streptococcus (GAS). The role of GAS carriage causing subsequent infections resulting in the manifestation of clinical symptoms, or being associated with transmission to uninfected individuals, is not entirely clear. Furthermore, data on GAS carriage from countries in Africa remain scant with only a few studies reporting carriage. Objectives. We performed a cross-sectional study to determine the prevalence of asymptomatic pharyngeal carriage of group A streptococci in school children in Cape Town. We considered our results in the context of a meta-analysis of data of GAS carriage in Africa. Methods. We conducted a school-based cross-sectional study from 2009 to 2011 in two Cape Town peri-urban communities, enrolling 950 healthy learners. Pharyngeal swabs were obtained from learners and processed at the National Health Laboratory Service (NHLS) microbiology laboratory at Groote Schuur Hospital, Cape Town. Thereafter, we conducted a systematic review through a comprehensive literature search among several sources. Prevalence estimates with 95% confidence intervals (CIs) were determined using a random-effects meta-analysis model. Results. GAS was isolated from 31 participants corresponding to a carrier rate of 3% (95% CI 2% - 4%). Combining our results with 18 other studies revealed a pooled prevalence of 9% (95% CI 6% - 11%). Regional pooled rates were similar across southern, eastern and northern Africa, of between 9% (95% CI 6% - 11%) and 11% (95% CI 4% - 21%) while countries within Central Africa had a pooled estimate of 7% (95% CI 5% - 9%). Western Africa had the lowest pooled estimate of 2% (95% CI 1% - 2%). Conclusion. There was a relatively low rate of carriage of GAS in asymptomatic school children residing in South Africa. Pooled prevalence rates revealed regional differences across the African continent as regards the rate of GAS carriage, with the western and northern African regions having rates of GAS carriage that were lower and higher respectively than those of East, Central and southern African countries, which demonstrated similar rates of carriage.