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Enumerators and village officials on the way to collect samples and conduct household interviews.

Geostatistical surveys

Data isn’t just a tool for planning—it’s the cornerstone of effective strategies aimed at eliminating parasitic diseases.

Accurate and up-to-date data is crucial for driving progress toward parasitic disease elimination. Yet, significant data gaps still exist across sub-Saharan Africa.

Closing these gaps is essential. It ensures treatment strategies are based on the most reliable information, allowing ministries of health to target interventions and speed-up progress towards elimination.

The success of elimination programs depends on having precise, current data. That’s why Unlimit Health partners with ministries of health to conduct impact assessments—empowering these programs with the insights they need to reach the right people, at the right time, and make real progress toward their goals.

Why impact assessments

Impact assessments are crucial for tracking disease prevalence of diseases like schistosomiasis (SCH) and identifying “hotspots” where the disease is consistently widespread. The results of these assessments help ministries of health (MoHs) decide which sub-IUs need treatment, how often they should receive it, and ensure alignment with the WHO guideline on control and elimination of human schistosomiasis (2022) and the  WHO SCH and STH M&E Framework  (2024).

These assessments are for understanding the disease’s current spread through advanced epidemiological methods and tests. They offer a cutting-edge, cost-effective solution to close critical data gaps and ensure treatment is targeted where it is most needed, optimising resources and improving outcomes.

However, conducting impact assessments in low resource settings presents a challenge: maximising data quality while minimising survey costs. The cost and burden of surveys can rise significantly as the number of sites increases, particularly in large countries – the more sites sampled = the higher the survey cost. Balancing the need for comprehensive data with available resources is key to maintaining both accuracy and cost-efficiency.

The value of geostatistical surveys

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To enhance the effectiveness and cost-efficiency of impact assessments, our country partners are increasingly turning to geostatistical methods. This approach offers a smart solution for site selection, ensuring that surveys remain both cost-effective and statistically sound.

Unlike traditional methods, the geostatistical method uses a grid pattern to select sites. This helps to achieve an even geographical distribution and requiring fewer sites to survey, making it more efficient. When the ministry of health focuses on disease elimination, this method is especially valuable in pinpointing persistent “hotspots” – areas with high, ongoing prevalence, thereby enabling better targeted interventions.

Where we have used this approach

Countries such as Côte d’Ivoire, Democratic Republic of Congo (DRC), Ethiopia, Madagascar and Zanzibar have partnered with us to conduct impact assessments using the geostatistical methodology. This approach had been instrumental in addressing significant data gaps to small areas (e.g. sub-IU level), helping to ensure that future interventions are based on the most accurate and up-to-date information.

By applying the geostatistical methodology, we can calculate the probability that a small area exceeds a certain threshold – such as the10% prevalence rate for SCH treatment decisions, according to WHO guidelines – This allows for precision targeting of interventions.

While we’ve successfully conducted surveys in several countries, large data gaps still remain across sub-Saharan Africa. As emphasised in the  WHO 2021-2030 NTD Roadmap, data plays a critical role in driving targeted interventions.

Closing these data gaps ensures that treatment strategies are informed by the most accurate and reliable data, enabling ministries of health to reach the most hard-to-reach populations and ultimately achieve elimination goals.