Prevalence and distribution pattern of malaria and soil-transmitted helminth co-endemicity in sub-Saharan Africa, 2000-2018: A geospatial analysis

Abstract

Background: Limited understanding exists about the interactions between malaria and soil-transmitted helminths (STH), their potential geographical overlap and the factors driving it. This study characterised the geographical and co-clustered distribution patterns of malaria and STH infections among vulnerable populations in sub-Saharan Africa (SSA).

Methodology/principal findings: We obtained continuous estimates of malaria prevalence from the Malaria Atlas Project (MAP) and STH prevalence surveys from the WHO-driven Expanded Special Project for the Elimination of NTDs (ESPEN) from Jan 1, 2000, to Dec 31, 2018. Although, MAP provides datasets on the estimated prevalence of Plasmodium falciparum at 5km x 5km fine-scale resolution, we calculated the population-weighted prevalence of malaria for each implementation unit to ensure that both malaria and STH datasets were on the same spatial resolution. We incorporated survey data from 5,935 implementation units for STH prevalence and conducted the prevalence point estimates before and after 2003. We used the bivariate local indicator of spatial association (LISA analysis) to explore potential co-clustering of both diseases at the implementation unit levels among children aged 2-10 years for P. falciparum and 5-14 years for STH, living in SSA. Our analysis shows that prior to 2003, a greater number of SSA countries had a high prevalence of co-endemicity with P.falciparium and any STH species than during the period from 2003-2018. Similar prevalence and distribution patterns were observed for the co-endemicity involving P.falciparum-hookworm, P.falciparum-Ascaris lumbricoides and P.falciparum-Trichuris trichiura, before and after 2003. We also observed spatial variations in the estimates of the prevalence of P. falciparum-STH co-endemicity and identified hotspots across many countries in SSA with inter-and intra-country variations. High P. falciparum and high hookworm co-endemicity was more prevalent in West and Central Africa, whereas high P. falciparum with high A. lumbricoides and high P. falciparum with high T. trichiura co-endemicity were more predominant in Central Africa, compared to other sub-regions in SSA.

Conclusions/significance: Wide spatial heterogeneity exists in the prevalence of malaria and STH co-endemicity within the regions and within countries in SSA. The geographical overlap and spatial co-existence of malaria and STH could be exploited to achieve effective control and elimination agendas through the integration of the vertical control programmes designed for malaria and STH into a more comprehensive and sustainable community-based paradigm.

Fig 1. The prevalence of P. falciparum and any soil-transmitted helminth co-endemicity, and significant hotspots of P. falciparum and any soil-transmitted co-endemicity in sub-Saharan Africa.

The density description next to the colour-coded box refers to the prevalence of P. falciparum, whilst the column further to the right refers to density of any STH. Link to the base layer of the map: https://gadm.org/index.html.

Fig 2. The prevalence of P. falciparum and hookworm co-endemicity, and significant hotspots of P.falciparum and hookworm co-endemicity in sub-Saharan Africa.

’The density description next to the colour coded box refers to the prevalence of P. falciparum, whilst the column further to the right refers to density of hookworm. Link to the base layer of the map: https://gadm.org/index.html.

Fig 3. The prevalence of P. falciparum and Ascaris lumbricoides, and significant hotspots of P. falciparum and A.lumbricoides co-endemicity in sub-Saharan Africa.

The density description next to the colour-coded box refers, to the prevalence of P. falciparum whilst the column further to the right refers to density of A. lumbricoides. Link to the base layer of the map: https://gadm.org/index.html.

Fig 4. The prevalence of P. falciparum and T.trichiura, and significant hotspots of P,falciparum and T. trichiura co-endemicity in sub-Saharan Africa.

The density description next to the colour-coded box refers, to the prevalence of P. falciparum whilst the column further to the right refers to density of T.trichiura. Link to the base layer of the map: https://gadm.org/index.html.