Seasonal and Spatial Dynamics of the Primary Vector of Plasmodium knowlesi within a Major Transmission Focus in Sabah, Malaysia.

Meng L Wong,Loke T Khaw,Wan-Yusoff Wan-Sulaiman,Indra Vythilingam,Heather M Ferguson,Kimberly Fornace,Tock H Chua,Chris Drakeley,Cherng S Leong,Timothy William

doi:10.1371/journal.pntd.0004135

Abstract

BackgroundThe simian malaria parasite Plasmodium knowlesi is emerging as a public health problem in Southeast Asia, particularly in Malaysian Borneo where it now accounts for the greatest burden of malaria cases and deaths. Control is hindered by limited understanding of the ecology of potential vector species.Methodology/Principal FindingsWe conducted a one year longitudinal study of P. knowlesi vectors in three sites within an endemic area of Sabah, Malaysia. All mosquitoes were captured using human landing catch. Anopheles mosquitoes were dissected to determine, oocyst, sporozoites and parous rate. Anopheles balabacensis is confirmed as the primary vector of. P. knowlesi (using nested PCR) in Sabah for the first time. Vector densities were significantly higher and more seasonally variable in the village than forest or small scale farming site. However An. balabacensis survival and P. knowlesi infection rates were highest in forest and small scale farm sites. Anopheles balabacensis mostly bites humans outdoors in the early evening between 1800 to 2000hrs.Conclusions/SignificanceThis study indicates transmission is unlikely to be prevented by bednets. This combined with its high vectorial capacity poses a threat to malaria elimination programmes within the region.

Highlights

Significant progress has been made fighting malaria in the last decade, decreasing the incidence of cases and mortality by 30% and 47% respectively on a global scale [1] and reducing cases by 76% in Asia Pacific countries [2]
Plasmodium knowlesi has been reported from all countries in Southeast Asia with the exception of Lao PDR and Timor Leste
We conducted a longitudinal study in Kudat district, Sabah, to determine and characterize the vectors of P. knowlesi within this transmission foci

Summary

Introduction

Significant progress has been made fighting malaria in the last decade, decreasing the incidence of cases and mortality by 30% and 47% respectively on a global scale [1] and reducing cases by 76% in Asia Pacific countries [2]. In the Malaysian state of Sabah, this parasite is responsible for the greatest number of malaria cases with 815 and 996 cases reported respectively in 2012 and 2013 [20]. This growing burden of P. knowlesi presents a notable obstacle to malaria elimination in Malaysia where historically, most transmission has been due to human-specific parasite species [17]. The simian malaria parasite Plasmodium knowlesi is emerging as a public health problem in Southeast Asia, in Malaysian Borneo where it accounts for the greatest burden of malaria cases and deaths. Control is hindered by limited understanding of the ecology of potential vector species.

Methods

Results

Discussion

Conclusion