Longitudinal surveillance of group A streptococcal pharyngitis and impetigo in remote Western Australian school children informs acute rheumatic fever prevention

The prevalence of impetigo and pharyngitis - which are both superficial group A streptococcus (GAS) infections that precede acute rheumatic fever - is poorly defined. Guidelines recommend the early diagnosis of both infections to prevent ARF; however, screening to enable the concurrent detection of these infections in high-risk populations has rarely been performed. In this observational cohort study, children attending one of two schools in the remote Kimberley region of Western Australia were assessed for signs and symptoms of impetigo and pharyngitis at repeated screening visits (conducted up to three times per year), and weekly assessments were performed in response to self-reported symptoms. Throat and skin swabs and dried blood spots were collected at screens. Swabs underwent standard microbiological culture and whole genome sequencing was conducted on confirmed GAS isolates. Dried blood spots were assessed for anti-streptococcal antibody titres. A higher-than-anticipated rate of pharyngitis (29.5%), GAS-positive pharyngitis (6.3%) and GAS carriage (9%) was detected, but GAS-positive impetigo was lower (2.6%) compared with previous studies in the Kimberley. Aboriginal and Torres Strait Islander children experienced more GAS infections than did children of other ethnicities, whereas anti-streptococcal antibody titres did not differ according to ethnicity. This study provides evidence to support the need for increased investment and resourcing of ARF primary prevention in the Kimberley, due to high rates of GAS infection.