Background:
Group A Streptococcus (GAS) has significant global burden, though little is known about its acquisition and transmission in high-burden settings, including Africa. We describe the design of a primary school-based study, aiming to characterise GAS transmission dynamics within primary school-aged children's classrooms, households and environment in The Gambia.
Methods:
iSpySchool is an ongoing prospective cohort study of 6-12 year-old children in The Gambia, exploring immunological responses to GAS infection. At enrolment, participants provide samples including oropharyngeal (OPS) and skin (NSS) swabs. We will nest a transmission study within iSpySchool, with a sub-set of classes undergoing fortnightly OPS/NSS for the 2025-2026 academic year. Following a culture positive GAS event, there will be additional testing of classmates (D7), index-case household members (D0, D7 and D14), and the classroom environment. All samples will receive downstream quantitative PCR and, where positive, direct emm-typing, to establish bacterial load and identify transmission events in culture negative but PCR positive infection/carriage. Cultured isolates will undergo WGS. Our transmission study with a high testing frequency aims to establish infection/carriage incidence, emm-linked transmission, and classroom/household secondary attack rate according to bacterial load.
Results:
To date, 138 iSpySchool participants have been recruited. At enrolment, 1.4% (2/138) had pharyngitis, none isolating GAS, and 8.0% (11/138) had pyoderma, with 82% (9/11) isolating GAS. Asymptomatic carriage was 3.6% (5/138) for OPS and 1.4% (2/138) for NSS.
Conclusion:
The integrated design of our nested study aims to improve understanding of GAS transmission in Africa, to inform future public health interventions and vaccine policy.