Identifying Plasmodium falciparum transmission patterns through parasite prevalence and entomological inoculation rate

Benjamin Amoah,Alinune N Kabaghe,Tinashe Tizifa,Willem Takken,Robert S Mccann,Henk Van Den Berg,Emanuele Giorgi,Michele Van Vugt,Themba Mzilahowa,Paula Moraga,Michael G Chipeta,Dianne J Terlouw,Peter J Diggle,Kamija S Phiri,Monicah Mburu,Steven Gowelo

doi:10.7554/elife.65682

Abstract

Monitoring malaria transmission is a critical component of efforts to achieve targets for elimination and eradication. Two commonly monitored metrics of transmission intensity are parasite prevalence (PR) and the entomological inoculation rate (EIR). Comparing the spatial and temporal variations in the PR and EIR of a given geographical region and modelling the relationship between the two metrics may provide a fuller picture of the malaria epidemiology of the region to inform control activities. Using geostatistical methods, we compare the spatial and temporal patterns of Plasmodium falciparum EIR and PR using data collected over 38 months in a rural area of Malawi. We then quantify the relationship between EIR and PR by using empirical and mechanistic statistical models. Hotspots identified through the EIR and PR partly overlapped during high transmission seasons but not during low transmission seasons. The estimated relationship showed a 1-month delayed effect of EIR on PR such that at lower levels of EIR, increases in EIR are associated with rapid rise in PR, whereas at higher levels of EIR, changes in EIR do not translate into notable changes in PR. Our study emphasises the need for integrated malaria control strategies that combine vector and human host managements monitored by both entomological and parasitaemia indices. This work was supported by Stichting Dioraphte grant number 13050800.

Highlights

National malaria control programmes, working in collaboration with global stakeholders, have achieved extensive intervention coverage over the last two decades, leading to significant reductions in morbidity and mortality due to malaria (Bhatt et al, 2015b)
P. falciparum to develop in the human host, we considered that current PfPR may depend on P. falciparum entomological inoculation rate (PfEIR)
We found that hotspots of PfEIR and hotspots of PfPR overlapped at times, but the amount of overlap varied over time

Summary

Introduction

National malaria control programmes, working in collaboration with global stakeholders, have achieved extensive intervention coverage over the last two decades, leading to significant reductions in morbidity and mortality due to malaria (Bhatt et al, 2015b). Malaria is still a leading global health problem. The previous successes and current challenges have motivated ambitious, yet feasible, global and national targets towards malaria elimination. A wide range of metrics exists for monitoring malaria parasite transmission. The strengths and limitations of each metric are related, in part, to the step of the parasite transmission cycle it measures (Tusting et al, 2014). These strengths and weaknesses, including the sensitivity of each metric, which vary across epidemiological settings and as parasite transmission declines within a given setting (The malERA Refresh Consultative Panel on Characterising the Reservoir and Measuring Transmission, 2017). Two of the most commonly monitored metrics are the prevalence of Plasmodium parasites and the entomological inoculation rate (EIR), especially in moderate to high transmission settings

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Discussion

Conclusion