The relationships of scabies and skin infection, with acute rheumatic fever and rheumatic heart disease: a protocol for a national cohort study in New Zealand

Introduction: Recent studies report data showing an association of scabies with acute rheumatic fever (ARF) and rheumatic heart disease (RHD). However, no study to date has explored the temporal sequence of the relationships between scabies and bacterial skin infection with ARF and RHD. We aim to investigate these relationships using temporal separation of exposures and outcomes using record-linkage data. Materials and methods: We will create a national cohort of children aged one to ten years, with the cohort commencing from 1 January 2016, and being followed until the end of 2024. De-identified data will be collected from hospital discharge records (national minimum dataset (NMDS)), dispensing records, and mortality records and linked using a unique identifier. Children who were dispensed medications or had hospital discharge codes for scabies will be considered “exposed” and those with a hospital diagnosis of ARF or RHD during follow-up will be considered having the outcome of interest. Hospitalisation due to skin infections shall be treated as a potential mediator. Sociodemographic variables will also be collected from the same sources to control for confounding. Discussion: Spatial analysis will be carried out to determine the high prevalence regions for scabies, skin infections, ARF, and RHD in New Zealand. Survival analysis using Cox-proportional hazards model will be employed to determine hazards ratio (HRs) linked to scabies, skin infection, and scabies plus skin infection, adjusted for potentially confounding variables. Conclusions: Since scabies is reversible and treatable, if we find evidence supporting an association with ARF and/or RHD, then improvements in the diagnosis and treatment of scabies to subsequently lessen childhood morbidity and mortality become a healthcare delivery and public health priority.