Spatio-temporal analysis of association between incidence of malaria and environmental predictors of malaria transmission in Nigeria

Oluyemi A Okunlola,Oyetunde T Oyeyemi

doi:10.1038/s41598-019-53814-x

Oluyemi A Okunlola, Oyetunde T Oyeyemi

Open Access

https://doi.org/10.1038/s41598-019-53814-x

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Abstract

Malaria still poses a significant threat in Nigeria despite the various efforts to abate its transmission. Certain environmental factors have been implicated to increase the risk of malaria in Nigeria and other affected countries. The study aimed to evaluate the spatial and temporal association between the incidence of malaria and some environmental risk factors in Nigeria. The study used malaria incidence and environmental risk factors data emanating from 2015 Nigeria Malaria Indicator Survey accessed from the Demographic and Health Survey database. A total of 333 and 326 clusters throughout the country were used for malaria incidence study and environmental variables respectively. The spatial autocorrelation of malaria incidence and hotspot analysis was determined by the Moran’s diagram and local Moran’s I index, respectively. The relationships between the malaria incidence and the ecological predictors of transmission were analysed in all the six geopolitical zones of Nigeria from 2000–2015 using ordinary least square (OLS), spatial lag model (SLM), and spatial error model (SEM). Annual rainfall, precipitation and proximity to water showed significant positive relationship with the incidence rate of malaria in the OLS model (P < 0.01), whereas aridity was negatively related to malaria incidence (P < 0.001) in the same model. The rate of incidence of malaria increased significantly with increase in temperature, aridity, rainfall and proximity to water in the SEM whereas only temperature and proximity to water have significant positive effect on malaria incidence in the SLM. The modelling of the ecological predictors of malaria transmission and spatial maps provided in this study could aid in developing framework to mitigate malaria and identify its hotspots for urgent intervention in the endemic regions.

Highlights

Malaria is a major public health concern and has continued to be one of the major focus of Sustainable Development Goals[1]
It is proposed that certain environmental factors significantly influence the incidence rate of malaria in Nigeria in space and time
The incidence of malaria was higher in the Northern than in the Southern region of Nigeria

Summary

Introduction

Malaria is a major public health concern and has continued to be one of the major focus of Sustainable Development Goals[1]. A number of environmental and ecological factors are known to influence transmission of malaria. Chief among these are rainfall and temperature. Despite the burden of malaria in Nigeria, the use of spatial statistics to examine interrelationship between incidence of malaria and prevailing environmental factors are still relatively understudied. This method is very useful in identifying disease hotspots within a specific region for possible intervention. Studies in East and West African countries have supported the observations on malaria hotspots persistence following overall reduction in malaria transmission[13,14]. It is expected that the models will identify malaria transmission clusters in Nigeria for necessary interventions

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