Shrinking the malaria map

Over the last 150 years, the 'malaria map'—or geographic limits of endemic malaria—has been progressively shrinking. Progress continues and we have many reasons to be optimistic. The first paper in The Lancet Series on Malaria Elimination is written by Professor Richard Feachem and Ms Allison Phillips of the Global Health Group, University of California, San Francisco, CA, USA, and their colleagues including the Minister of Health from Ethiopia.

"The UCSF Global Health Group (GHG) and the Malaria Elimination Group (MEG) are proud to join with The Lancet to launch this synthesis of the best information and research available on malaria elimination today," said Professor Feachem, Director of the GHG and Chair of the MEG. "We hope that this Series raises awareness of the great progress that has been made in elimination, illuminates the many challenges that remain, and mobilises the malaria community and malaria-endemic countries to continue shrinking the malaria map."

Elimination refers to a state in which interventions have interrupted endemic transmission and the risk of re-establishment is minimised. This state requires continual commitment to maintain it. The alternative state is controlled low-endemic malaria, where countries have reduced the malaria threat so that it is no longer a major public health burden, but where transmission would occur even in the absence of imported cases.

During the first half of the 20th century, 178 countries had endemic malaria. From 1945 onwards, 79 have eliminated malaria. These include the UK (1952), USA (1952), Australia (1970) and most recently Morocco (2005) and Turkmenistan (2010). However, 99 countries still have endemic malaria, and of these 32 are moving from controlled low-endemic malaria to elimination while the other 67 are controlling malaria.

Steady progress has been made towards shrinking the malaria map over the last 150 years. This has taken place in the southern hemisphere from south to north, and in the northern hemisphere from north to south. All of the 32 malaria-eliminating countries are on the outer margins of the malaria map. These 32 countries span all geographies, sizes, and income levels and include Argentina, China, Iraq, Mexico, Malaysia, North Korea, South Africa, and Turkey. More than 2 billion people live in these 32 nations.

The 66 countries continuing to control malaria are all at or not far from the equator, and include most countries in sub-Saharan Africa, India, much of southeast Asia and some of South America.

The authors say: "Countries deciding to switch from controlled low-endemic malaria to elimination need to do so based on comprehensive understanding of technical, operational, financial, and socioeconomic feasibility. Countries should avoid moving towards elimination based on national aspirations not backed by evidence."

The paper highlights that the war on malaria is dealing with two main malaria parasite species—Plasmodium falciparum and Plasmodium vivax—which have unique characteristics. Scientific knowledge and available drugs are much more advanced for P. falciparum then they are for P. vivax. 25 of the malaria-eliminating countries are solely or mainly fighting a battle against P. vivax malaria. This was also the case with almost all the countries that successfully eliminated in the past.*

To battle P. vivax malaria, there are a number of urgent needs: improved diagnostic tests and a robust point-of-care method for screening for deficiency in glucose-6-phosphate dehydrogenase. Some 5—20% of the population have this deficiency in P. vivax endemic areas, and it puts them at risk of haemolysis when taking primaquine, the only available drug for raical cure P. vivax (haemolysis is the breaking open of red blood cells and can lead to anaemia, jaundice and death). Additional drugs are needed for radical treatment of P. vivax, particularly for a special dormant phase unique to this species (termed a hypnozoite stage) in which the parasite lays dormant in the liver of the host for up to several years.

While malaria elimination likely has benefits such as improved tourism and investment, a strengthened surveillance system, and national pride, malaria elimination should be viewed as a regional and global public good that brings systemic benefits that reach far beyond just one country.

Several concerns have been raised about attempting to eliminate malaria. Will enhanced activity increase resistance in both parasites and the mosquitoes? Will elimination efforts divert vital funds away from high-burden countries still in the control phase? And what if elimination efforts fail—will this make malaria rebound in those nations to higher levels than before? However, the authors highlight that while elimination may have the above risks, maintaining controlled low-endemic malaria also poses similar risks.

The paper also shows that no country can realistically act alone in this war on malaria (even if it is an island). Malaria does not respect borders and multi-country elimination efforts can be an effective strategy. Many countries are starting to understand this and are joining forces. For example in Southern Africa, the Elimination 8 (E8) is an initiative with a long-term plan to eliminate malaria from the four countries on the margin of the malaria map (Botswana, Namibia, South Africa, Swaziland) in collaboration with their northern neighbours (Angola, Mozambique, Zambia, Zimbabwe) who will subsequently eliminate.

The authors say that an essential factor in determining elimination feasibility is development of a user-friendly feasibility assessment tool that can be applied by all countries embarking on, or contemplating, malaria elimination. They conclude: "Eliminating countries must receive appropriate support and recognition for their efforts, and the historical trend since the middle of the 20th century in shrinking the malaria map must continue."

Professor Richard Feachem, Director, Global Health Group, University of California, San Francisco, CA, USA. T) +415 624 9444 E) feachemr@globalhealth.ucsf.edu

Ms Allison Phillips, Global Health Group, University of California, San Francisco, CA, USA. T) +1 415 490 7925 E) PhillipsAA@globalhealth.ucsf.edu

Alternative contact: Kristen Bole, UCSF Public Affairs. T) +1 415-476-2743 E) KBole@pubaff.ucsf.edu

For full Series paper 1, see: http://press.thelancet.com/malelim1.pdf

NOTE: THE ABOVE LINK IS FOR JOURNALISTS ONLY. IF YOU WISH YOU CAN PROVIDE A LINK TO THE DEDICATED SERIES PAGE ON THE LANCET.COM, WHERE ALL USERS CAN DOWNLOAD PAPERS FOR FREE ONCE THEY HAVE REGISTERED (ALSO FREE). THE LINK TO USE IS BELOW (NOTE THIS WILL GO LIVE WHEN EMBARGO LIFTS): http://www.thelancet.com/malaria-elimination

Note to editors: * The great majority of successful malaria eliminators are outside Africa. Outside Africa, P. vivax either co-exists with P. falciparum or is the predominant species (see Figure 3, Paper 1). During intensive control measures, P. falciparum declines more rapidly than P. vivax because P. falciparum lacks a dormant liver stage. Thus the endgame for nearly all malaria eliminators has been a fight against P. vivax. This will continue to be the case almost everywhere outside Africa.

If you would like some background information about malaria and how it is transmitted, the Series authors direct you to chapter 5 of the book "A Prospectus on Malaria Elimination". Link as below:

http://www.thelancet.com/malariabackground.pdf