Background
Gambian children display high rates of Group A Streptococcus (StrepA) pyoderma, with a large diversity of emm genotypes indicating widespread circulation. The epidemiology of non-invasive StrepA (and Groups C and G streptococci) infection and carriage is poorly understood. We are conducting a longitudinal household cohort study in The Gambia to investigate prevalence, incidence and transmission of StrepA.
Methods
415 individuals (median age 16 years, 47.2% male) from 43 households have been enrolled in Sukuta, an urban area of The Gambia. Participants are visited monthly undergoing pharyngeal, normal skin and wound swabbing (in cases of pyoderma). Swabs are cultured for the presence of StrepA, C and G. Demographic and clinical data are collected at each visit. Newly culture-positive participants are swabbed weekly until negative on two occasions. Additional, unscheduled swabs are collected for new symptomatic pharyngitis and pyoderma.
Results
Within the first 5 months, incidences of StrepA, StrepC and StrepG pharyngeal carriage were 29, 14 and 48 cases per 100 person years respectively, while StrepA skin carriage incidence was 8 per 100 person years. 45 StrepA-positive pyoderma and 7 StrepA pharyngitis cases occurred. Monthly StrepG pharyngeal carriage prevalence was higher than for StrepA (2.8-8.1% vs 1.5-2.3%). Data on the duration and seasonality of carriage and associations between carriage/infection and relevant risk factors will also be presented.
Conclusions
We have found high rates of StrepA, C and G carriage and infection within households in The Gambia indicating that streptococcal carriage that may drive infection and genotype diversity.