Malaria map reveals challenges and opportunities
by Paul Chinook, TropIKA.net:
Researchers working on the Malaria Atlas Project(MAP) have published a paper describing their creation of a world map that shows the proportion of the population with parasites in their blood for the most severe type of malaria. It is over 40 years since an "endemicity" map of this kind was published.
The MAP researchers believe that, "In an international policy environment where the malaria control community has been challenged to rethink the plausibility of malaria elimination, malaria cartography will become an increasingly important tool for planning, implementing, and measuring the impact of malaria interventions worldwide".
The MAP project has so far focused on the form of malaria caused by the parasite Plasmodium falciparum. In 2008 the researchers constructed a map (1) that divides the world into three levels of risk for P. falciparum malaria: no risk, unstable transmission risk (occasional outbreaks), and stable transmission risk (endemic areas where the disease is always present). They have now developed a method to generate continuous maps of P. falciparum endemicity within the area of stable malaria risk. Using this method - and drawing on data from nearly 8,000 surveys of parasite rates completed since 1985 - the MAP team has produced a P. falciparum endemicity map for 2007.
The new map shows that high levels of P. falciparum malaria endemicity are common in Africa. Uniformly low endemic levels are found in the Americas. Low endemicity is also widespread in Central and South East Asia, but pockets of intermediate and (very rarely) high transmission remain.
The researchers say their map demonstrates that, "There are therefore significant opportunities for malaria control in Africa and for malaria elimination elsewhere."
While clearly dependent on the accuracy of the data on which it is based, the map provides an important new resource that clearly indicates areas where malaria control can be improved (for example, Africa) and other areas where malaria elimination may be technically possible. MAP intends to produce annual updates of the global P. falciparum endemicity map and this will help to monitor the progress being made towards international malaria control and elimination targets.
The Malaria Atlas Project
MAP was founded in 2005 to provide on a global scale the spatial medical intelligence that is needed for the effective planning of malaria control. The MAP team has assembled a unique spatial database on linked information based on medical intelligence, satellite-derived climate data to constrain the limits of malaria transmission and the largest ever archive of community-based estimates of parasite prevalence. The team has collated 13,621 parasite rate surveys (P. falciparum. 13,304; P.vivax. 4,613) from an aggregated sample of 2,892,214 slides in 84 countries. These data have been assembled and analysed by a group of geographers, statisticians, epidemiologists, biologists and public health specialists.
The initial focus of MAP has been centred on P. falciparum, due to its global epidemiological significance and its better prospects for elimination and control. Work begins in 2009 to map the extent and burden of the so far neglected P. vivax parasite.
Reference
Guerra CA, Gikandi PW, Tatem AJ, Noor AM, Smith DL, Hay SI, Snow RW.
The Limits and Intensity of Plasmodium falciparum Transmission: Implications for Malaria Control and Elimination Worldwide
PLoS Med. 2008 Feb;5(2):e38.
PMID: 18303939
Available from: https://www.ncbi.nlm.nih.gov/pubmed/18303939