Tracing the Itch: A Spatiotemporal Analysis of Scabies Rates and Its Risk Factors Using the Global Burden of Disease 2021 Data.

Background and objectives: Scabies is a neglected disease believed to be more prevalent in resource-poor nations. Published data describing global trends in scabies incidence and prevalence rates and factors associated with global regional differences are limited. Identifying regions with scabies prevalence rates over 10% and implementing mass-drug administration is recommended. We aimed to identify global high-risk areas to facilitate region-specific targeted interventions.

Methods: Data on scabies incidence and prevalence in 204 countries and regions from 1990 to 2021 were extracted from the Global Burden of Disease database. Temporal trends in age-standardised rates were estimated using Joinpoint regression. Local indicators of spatial association were used to determine contiguous areas of high prevalence. The association of socio-demographic and economic factors with scabies was determined using locally weighted scatterplot smoothing and log-normal regression models.

Results: Global prevalence of scabies in 2021 was 2.71% (95% confidence interval [CI]: 2.41% to 3.04%). Age-standardised rates of scabies have marginally declined globally from 1990 to 2021 with an Average Annual Percentage Change (AAPC) of -0.10 (95% CI: -0.05 to -0.14) for incidence and -0.09 (95% CI: -0.05 to -0.14) for prevalence. Spatial clustering of high scabies prevalence was present in tropical Latin America, Southeast Asia, and the Pacific Islands. Rates have shown an increasing trend over time in high-income regions such as Australasia and parts of Europe. Scabies rates have increased over time in high-middle and high sociodemographic index regions. There is a significant positive association between warmer latitudes with increasing urbanisation and scabies prevalence.

Conclusion: Owing to the exploratory nature of the GBD data, our findings are hypothesis generating, rather than confirmatory. Scabies prevalence remains high in several global regions. Progress to reduce scabies prevalence is slow with existing programmes. Scabies control policies should be further prioritised to accelerate progress in reducing the prevalence of this important tropical disease.