Mapping Schistosomiasis and STH Risk in Angola: A Targeted Approach to Control

Background: The Need for Granular Data

Angola has been battling schistosomiasis and soil-transmitted helminth (STH) infections, two neglected tropical diseases (NTDs), with a school-based preventive chemotherapy (PC) program since 2013/2014. However, a 2021 evaluation revealed limited impact at the provincial level. This geospatial analysis aimed to provide a more detailed picture of infection risk to refine control strategies.

Methods: Combining Parasitology and Environment

Data from school-based prevalence surveys conducted in 2014 and 2021, covering thousands of schoolchildren, formed the foundation of this study. Researchers integrated this parasitological data with environmental and climatic information – including temperature, precipitation, elevation, vegetation, and proximity to water – to create predictive risk maps. Sophisticated statistical models, incorporating spatial autocorrelation where necessary, were used to analyze the data and generate these maps.

Results: Shifting Sands of Infection

The resulting maps revealed a dynamic landscape of infection risk. In Huambo province, small high-risk schistosomiasis areas persisted in the north and south, while a central STH hotspot remained relatively stable over time. Uige province experienced a decrease in southwestern schistosomiasis hotspots, but an overall increase in predicted risk elsewhere. Worryingly, high-risk STH zones expanded throughout Uige. Zaire province saw the emergence of co-endemic hotspots, with increasing risk for both schistosomiasis and STHs.

Conclusion: Refining Control Strategies Through Targeted Action

These risk maps provide crucial insights into the geographical distribution of schistosomiasis and STH infections in Angola. By pinpointing high-risk areas within each province, this analysis empowers decision-makers to optimize control efforts. Specifically, the expanding STH risk in Uige and the co-endemic hotspots in Zaire highlight the need for targeted interventions and potentially broader community-based surveys.

This granular approach to understanding infection risk is vital for enhancing the effectiveness of preventive chemotherapy programs and moving towards the WHO's goal of eliminating these NTDs as a public health problem. The findings underscore the importance of moving beyond province-level assessments and embracing more nuanced, location-specific strategies for combatting these persistent infections.