Human exposure to zoonotic malaria vectors in village, farm and forest habitats in Sabah, Malaysian Borneo

Brown, R., Chua, T. H., Fornace, K. , Drakeley, C., Vythilingam, I. and Ferguson, H. M. (2020) Human exposure to zoonotic malaria vectors in village, farm and forest habitats in Sabah, Malaysian Borneo. PLoS Neglected Tropical Diseases, 14(9), e0008617. (doi: 10.1371/journal.pntd.0008617) (PMID:32886679) (PMCID:PMC7497982)

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The zoonotic malaria parasite, Plasmodium knowlesi, is now a substantial public health problem in Malaysian Borneo. Current understanding of P. knowlesi vector bionomics and ecology in Sabah comes from a few studies near the epicentre of human cases in one district, Kudat. These have incriminated Anopheles balabacensis as the primary vector, and suggest that human exposure to vector biting is peri-domestic as well as in forest environments. To address the limited understanding of vector ecology and human exposure risk outside of Kudat, we performed wider scale surveillance across four districts in Sabah with confirmed transmission to investigate spatial heterogeneity in vector abundance, diversity and infection rate. Entomological surveillance was carried out six months after a cross-sectional survey of P. knowlesi prevalence in humans throughout the study area; providing an opportunity to investigate associations between entomological indicators and infection. Human-landing catches were performed in peri-domestic, farm and forest sites in 11 villages (3–4 per district) and paired with estimates of human P. knowlesi exposure based on sero-prevalence. Anopheles balabacensis was present in all districts but only 6/11 villages. The mean density of An. balabacensis was relatively low, but significantly higher in farm (0.094/night) and forest (0.082/night) than peri-domestic areas (0.007/night). Only one An. balabacensis (n = 32) was infected with P. knowlesi. Plasmodium knowlesi sero-positivity in people was not associated with An. balabacensis density at the village-level however post hoc analyses indicated the study had limited power to detect a statistical association due low vector density. Wider scale sampling revealed substantial heterogeneity in vector density and distribution between villages and districts. Vector-habitat associations predicted from this larger-scale surveillance differed from those inferred from smaller-scale studies in Kudat; highlighting the importance of local ecological context. Findings highlight potential trade-offs between maximizing temporal versus spatial breadth when designing entomological surveillance; and provide baseline entomological and epidemiological data to inform future studies of entomological risk factors for human P. knowlesi infection.

Item Type:Articles
Additional Information:This work was funded by the Biotechnology and Biological Sciences Research Council Doctoral Training Programme (Grant No. 1517720; to HF and RB) and the Medical Research Council (Grant No. G1100796; to TC, KF, CD, IV and HF).
Glasgow Author(s) Enlighten ID:Fornace, Dr Kimberly and Brown, Rebecca and Ferguson, Professor Heather
Creator Roles:
Brown, R.Formal analysis, Investigation, Methodology, Writing – original draft
Ferguson, H. M.Supervision, Writing – original draft
Authors: Brown, R., Chua, T. H., Fornace, K., Drakeley, C., Vythilingam, I., and Ferguson, H. M.
College/School:College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
Journal Name:PLoS Neglected Tropical Diseases
Publisher:Public Library of Science
ISSN (Online):1935-2735
Published Online:04 September 2020
Copyright Holders:Copyright © 2020 Brown et al.
First Published:First published in PLoS Neglected Tropical Diseases 14(9): e0008617
Publisher Policy:Reproduced under a Creative Commons License
Data DOI:10.7910/DVN/3QG1HP

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
167761Defining the biomedical, environmental and social risk factors for human infection with Plasmodium knowlesiHeather FergusonMedical Research Council (MRC)G1100796/1Institute of Biodiversity, Animal Health and Comparative Medicine