Mapping Soil-Transmitted Helminth Parasite Infection in Rwanda: Estimating Endemicity and Identifying At-Risk Populations

Abstract

Soil-transmitted helminth (STH) infections are globally distributed intestinal parasite infections caused by Ascaris lumbricoides, Trichuris trichiura, and hookworms (Ancylostoma duodenale and Necator americanus). STH infection constitutes a major public health threat, with heavy burdens observed in many of the world’s tropical and subtropical regions. Mass drug administration and sanitation improvements can drastically reduce STH prevalence and associated morbidity. However, identifying targeted areas in need of treatment is hampered by a lack of knowledge on geographical and population-level risk factors. In this study, we applied Bayesian geostatistical modelling to data from a national school-based STH infection survey in Rwanda to (1) identify ecological and population-level risk factors and (2) provide comprehensive precision maps of infection burdens. Our results indicated that STH infections were heterogeneously distributed across the country and showed signatures of spatial clustering, though the magnitude of clustering varied among parasites. The highest rates of endemic clustering were attributed to A. lumbricoides infection. Concordant infection patterns among the three parasite groups highlighted populations currently most at-risk of morbidity. Population-dense areas in the Western and North-Western regions of Rwanda represent areas that have continued to exhibit high STH burden across two surveys and are likely in need of targeted interventions. Our maps support the need for an updated evaluation of STH endemicity in western Rwanda to evaluate progress in MDA efforts and identify communities that need further local interventions to further reduce morbidity caused by STH infections.

Robust geographical determinants of infection prevalence and a contrasting latitudinal diversity gradient for haemosporidian parasites in Western Palearctic birds

“…But regardless of the underlying mechanism, our findings contribute to mounting evidence that NDVI is a key epidemiological component of vector‐borne parasite transmission. NDVI is commonly found to positively correlate with infection rates for parasites of human and animal health importance (Brooker, Clements, & Bundy, 2006; Fecchio et al., 2020; Ferraguti et al., 2016; Naranjo‐Lucena et al., 2018; Ruberanziza et al., 2019; Schlüter et al., 2016), and this ubiquitous association has consequences for assessing landscape impacts on disease transmission.…”

Parasite associations predict infection risk: incorporating co-infections in predictive models for neglected tropical diseases

“…We used data from a survey designed to detect helminth infection prevalence in Rwandan schoolchildren. A national prevalence mapping effort was designed by considering groups of administrative mapping units [37]. Schools were chosen to ensure sample sizes in each unit were representative of the population sizes in their respective geographical areas.…”

“…Two variables, NDWI and LST, were removed during this process. Because spatial autocorrelation is a common feature of helminth risk [11,17,21] and has been demonstrated for STH risk in Rwanda [37], we accounted for spatial effects by including Gaussian process spatial regression splines in the linear predictor of each regularized regression.…”

Mapping Schistosoma mansoni endemicity in Rwanda: a critical assessment of geographical disparities arising from circulating cathodic antigen versus Kato-Katz diagnostics

“…Rwanda sustained widespread public health disruption as a result of political and social unrest throughout the 1990’s [33]. Health workforce training and public health outcomes have since improved, however, infectious disease monitoring and control still present major challenges [34–36]. Previous surveys suggest that Schistosoma mansoni is highly endemic and hence a parasite of high public health importance in Rwanda [34, 37].…”