A new evidence-based global distribution map of Plasmodium vivax malaria, published August 3 in the open-access journal PLoS Neglected Tropical Diseases, is used to estimate that 2.85 billion people lived at risk of infection with this parasite in 2009. The map, created as part of the Malaria Atlas Project (MAP), a multinational research collaboration funded mainly by the Wellcome Trust, reviews a host of information that challenges the dogma that P. vivax transmission is absent through large swathes of Africa and uses novel methods - including new global maps of the protective Duffy negativity blood condition - to estimate global populations at risk.
The study concludes that of the almost 3 billion people exposed to some risk of P. vivax transmission in 2009, 91% of them live in Central and South East Asia. Importantly, more than half of those exposed to this risk live in areas where P. vivax malaria transmission is extremely low or unstable and where prospects of sustained control and elimination are relatively good.
The authors used the most recent obtainable P. vivax case-reporting data for all malaria-endemic countries in efforts to classify risk into three classes: malaria free, unstable, and stable. Risk areas were further refined using temperature and aridity data based upon their relationship with parasite and vector bionomics. Medical intelligence was used to modify risk in specific areas where transmission was reported as absent (e.g., large urban areas and malaria-free islands). The human population at risk under each level of transmission was then derived by combining the categorical risk map with a high-resolution population surface adjusted to 2009 and a global map of Duffy negativity prevalence. Duffy negativity is the absence of the Duffy blood-group antigen in red blood cells, which translates into partial protection against infection with P. vivax. A high Duffy negativity prevalence in a population indicates increased protection against P. vivax infection, and vice versa.
"This study represents the first step in our efforts to provide the malaria control and research community with an evidence-based cartography of P. vivax malaria," says co-author Dr. Simon Hay of the University of Oxford. "We can now focus on trying to model the endemicity of the disease to provide more detailed global burden estimates, although this is complicated by the unusual biology of P. vivax".
Co-author Dr Carlos Guerra adds: "New evidence shows that P. vivax malaria is not as benign as was thought, and yet, as our study shows, remains the most widespread form of human malaria. Understanding where transmission of this parasite occurs at the global scale is fundamental in planning strategies for the control of this debilitating, and often lethal, disease".
Further information about the Malaria Atlas Project can be found at www.map.ox.ac.uk.
FINANCIAL DISCLOSURE: SIH is funded by a Senior Research Fellowship from the Wellcome Trust (#079091), which also supports CAG, PWG, and CWK. REH is funded by a Biomedical Resources Grant (#085406) from the Wellcome Trust to SIH. RWS is funded by a Wellcome Trust Principal Research Fellowship (#079080), which also supports APP and WHT. TPVB is funded by a grant from the Belgian Fond National pour la Recherche Scientifique and the Fondation Wiener-Anspach. AJT is supported by a grant from the Bill and Melinda Gates Foundation (#49446). BHM is funded by a grant from the University of Oxford - Li Ka Shing Foundation Global Health Programme. IRFE is funded by grants from the University of Oxford - Li Ka Shing Foundation Global Health Programme, the United States Navy, and the Oxford Tropical Network. JKB is funded by a grant from the Wellcome Trust (#B9RJIXO) and by the South East Asia Infectious Disease Research Network. This work forms part of the output of the Malaria Atlas Project (MAP, www.map.ox.ac.uk), principally funded by the Wellcome Trust, United Kingdom. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
COMPETING INTERESTS: The authors have declared that no competing interests exist.
PLEASE ADD THIS LINK TO THE PUBLISHED ARTICLE IN ONLINE VERSIONS OF YOUR REPORT: http://dx.plos.org/10.1371/journal.pntd.0000774 (link will go live upon embargo lift)
CITATION: Guerra CA, Howes RE, Patil AP, Gething PW, Van Boeckel TP, et al. (2010) The International Limits and Population at Risk of Plasmodium vivax Transmission in 2009. PLoS Negl Trop Dis 4(8): e774. doi:10.1371/journal.pntd.0000774
CONTACT:
Press Office Contacts
Pete Wilton
Press Officer, Mathematical, Physical and Life Sciences and Spin-outs
University of Oxford
+44 (0)1865 283877
pete.wilton@admin.ox.ac.uk
Craig Brierley
Senior Media Officer, The Wellcome Trust, U.K.
+44 (0)20 7611 7329
c.brierley@wellcome.ac.uk
Juliette Mutheu
Public Relations Officer
Malaria Atlas Project, KEMRI-Wellcome Trust Programme, Nairobi
+254 (0)20 2720163; 2715160
jmutheu@nairobi.kemri-wellcome.org
Author contacts for commentary
Dr Simon Hay: simon.hay@zoo.ox.ac.uk (+44 (0)1865 271243)
Dr Carlos Guerra: carlos.guerraloaiza@zoo.ox.ac.uk (+593 94 267 944)
Suggested impartial contacts for commentary
Dr Ric Price
Menzies School of Health Research
rnp@menzies.edu.au
Prof. Ivo Mueller
Papua New Guinea Institute of Medical Research
ivomueller@fastmail.fm
Dr Peter Zimmerman
The Center for Global Health & Diseases
paz@case.edu
Disclaimer
This press release refers to an upcoming article in PLoS Neglected Tropical Diseases. The release is provided by the article authors and the Malaria Atlas Project. Any opinions expressed in these releases or articles are the personal views of the journal staff and/or article contributors, and do not necessarily represent the views or policies of PLoS. PLoS expressly disclaims any and all warranties and liability in connection with the information found in the releases and articles and your use of such information.
About PLoS Neglected Tropical Diseases
PLoS Neglected Tropical Diseases (http://www.plosntds.org/) is a peer-reviewed, open-access journal devoted to the pathology, epidemiology, prevention, treatment, and control of the neglected tropical diseases, as well as public policy relevant to this group of diseases. All works published in PLoS Neglected Tropical Diseases are open access, which means that everything is immediately and freely available subject only to the condition that the original authorship and source are properly attributed. The Public Library of Science uses the Creative Commons Attribution License, and copyright is retained by the authors.
About the Public Library of Science
The Public Library of Science (PLoS) is a non-profit organization of scientists and physicians committed to making the world's scientific and medical literature a freely available public resource. For more information, visit http://www.plos.org.
Journal
PLoS Neglected Tropical Diseases