Defining the geographical range of the Plasmodium knowlesi reservoir.

Catherine L Moyes,Nicholas M Anstey,Kirsten A Duda,Chris J Drakeley,J Kevin Baird,Zhi Huang,Andrew J Henry,Qijun Chen,Paul N Newton,Samir Bhatt,Simon I Hay,Michael Huffman,Zinta Zommers,Peter W Gething,Balbir Singh,Nick Golding,Iqbal R F Elyazar

doi:10.1371/journal.pntd.0002780

Abstract

BackgroundThe simian malaria parasite, Plasmodium knowlesi, can cause severe and fatal disease in humans yet it is rarely included in routine public health reporting systems for malaria and its geographical range is largely unknown. Because malaria caused by P. knowlesi is a truly neglected tropical disease, there are substantial obstacles to defining the geographical extent and risk of this disease. Information is required on the occurrence of human cases in different locations, on which non-human primates host this parasite and on which vectors are able to transmit it to humans. We undertook a systematic review and ranked the existing evidence, at a subnational spatial scale, to investigate the potential geographical range of the parasite reservoir capable of infecting humans.Methodology/Principal FindingsAfter reviewing the published literature we identified potential host and vector species and ranked these based on how informative they are for the presence of an infectious parasite reservoir, based on current evidence. We collated spatial data on parasite occurrence and the ranges of the identified host and vector species. The ranked spatial data allowed us to assign an evidence score to 475 subnational areas in 19 countries and we present the results on a map of the Southeast and South Asia region.Conclusions/SignificanceWe have ranked subnational areas within the potential disease range according to evidence for presence of a disease risk to humans, providing geographical evidence to support decisions on prevention, management and prophylaxis. This work also highlights the unknown risk status of large parts of the region. Within this unknown category, our map identifies which areas have most evidence for the potential to support an infectious reservoir and are therefore a priority for further investigation. Furthermore we identify geographical areas where further investigation of putative host and vector species would be highly informative for the region-wide assessment.

Highlights

The Plasmodium knowlesi parasite, found in wild monkey populations, is a serious public health concern yet almost nothing is known about its geographical extent
Costly P. knowlesi-specific molecular diagnostic techniques are only used to confirm diagnosis by microscopy in one area, Malaysian Borneo, whereas human cases have been reported from Brunei [7,8], Cambodia [9], Indonesia
Plasmodium knowlesi is a malaria parasite found in monkeys which can infect humans via mosquito bites

Summary

Introduction

The Plasmodium knowlesi parasite, found in wild monkey populations, is a serious public health concern yet almost nothing is known about its geographical extent. It is known to cause severe and fatal disease in humans [1,2,3,4] and is the most common cause of clinical malaria in high transmission regions of Malaysia [5,6] where it is three times more likely to cause severe malaria than P. falciparum [4]. The simian malaria parasite, Plasmodium knowlesi, can cause severe and fatal disease in humans yet it is rarely included in routine public health reporting systems for malaria and its geographical range is largely unknown. We undertook a systematic review and ranked the existing evidence, at a subnational spatial scale, to investigate the potential geographical range of the parasite reservoir capable of infecting humans

Methods

Results

Discussion

Conclusion