Elsevier

The Lancet

Volume 376, Issue 9752, 6–12 November 2010, Pages 1566-1578
The Lancet

Series
Shrinking the malaria map: progress and prospects

https://doi.org/10.1016/S0140-6736(10)61270-6Get rights and content

Summary

In the past 150 years, roughly half of the countries in the world eliminated malaria. Nowadays, there are 99 endemic countries—67 are controlling malaria and 32 are pursuing an elimination strategy. This four-part Series presents evidence about the technical, operational, and financial dimensions of malaria elimination. The first paper in this Series reviews definitions of elimination and the state that precedes it: controlled low-endemic malaria. Feasibility assessments are described as a crucial step for a country transitioning from controlled low-endemic malaria to elimination. Characteristics of the 32 malaria-eliminating countries are presented, and contrasted with countries that pursued elimination in the past. Challenges and risks of elimination are presented, including Plasmodium vivax, resistance in the parasite and mosquito populations, and potential resurgence if investment and vigilance decrease. The benefits of elimination are outlined, specifically elimination as a regional and global public good. Priorities for the next decade are described.

Introduction

A three-part strategy to eradicate malaria has been developed1, 2, 3, 4 and is now widely endorsed:5, 6, 7, 8, 9, 10 (1) aggressive control in highly endemic countries, to achieve low transmission and mortality in countries that have the highest burden of disease and death; (2) progressive elimination of malaria from the endemic margins, to shrink the malaria map; and (3) research into vaccines and improved drugs, diagnostics, insecticides, and other interventions, and into delivery methods that reach all at-risk populations.

Much effort and investment has rightly been devoted to part one of this strategy, aggressive control in highly endemic countries, and has resulted in a massive scale-up of effective interventions11, 12, 13 and substantial reductions in mortality and morbidity from malaria in some endemic countries.13, 14, 15, 16, 17, 18 Investment and activity in part three of the strategy, research into new interventions and delivery methods, have increased in the past decade, and a research agenda for malaria eradication has been developed.6 By contrast, part two of the strategy, shrinking the malaria map, has received less attention, which has resulted in a deficit of evidence-based knowledge and guidance. This four-part Series about malaria elimination begins to fill this gap.19, 20, 21, 22

Section snippets

Historical summary

Efforts to control and eliminate malaria on a large scale date back to the late 19th century, with the discovery of the plasmodium parasite and its transmission by anopheline mosquitoes. During the first half of the 20th century, when 178 countries had endemic malaria, little progress was made, partly because efforts were disrupted by World Wars 1 and 2. However, from 1945 to 2010, 79 countries eliminated malaria.23, 24 Despite exponential population growth in malaria-endemic areas during the

Definition of elimination

The terms elimination, eradication, and control are often used loosely, which results in misunderstanding.43 The word eradication has previously been used to describe what we now call elimination,44 but is used only to mean the “permanent reduction to zero of the worldwide incidence of infection caused by a specific agent as a result of deliberate efforts. Interventions are no longer needed.”45 Generally, cessation of malaria transmission in a defined geographic area, such as an island or an

Elimination

Figure 1 shows a world map with countries categorised by their epidemiological status: 109 countries are malaria free, 67 are controlling endemic malaria, and 32 are malaria-eliminating countries. There are, necessarily, discretionary judgments to be made with respect to marginal countries that could be categorised as either controlling or eliminating malaria. We have been conservative when making these judgments. For example, Madagascar and Haiti have both adopted elimination goals,50, 51 but

Characteristics of malaria-eliminating countries

Malaria-eliminating countries share three important characteristics. First, most of them lie at the margins of malaria-endemic regions (figure 1). For example, Algeria, China, and Mexico are situated at the most northern margins of endemic malaria transmission, and Argentina, South Africa, and Vanuatu are situated at the most southern margins of endemic malaria transmission. Second, malaria-eliminating countries already have substantial malaria-free areas. Third, transmission in

Comparison of past and present malaria-eliminating countries

Countries that have successfully eliminated malaria tend to be wealthier than those that are seeking to eliminate. This finding raises two important questions. When they were in the process of eliminating malaria, were the countries that have achieved elimination wealthier than the countries that are currently trying to eliminate? And, at the time, did they have stronger health-care systems than malaria-eliminating countries do at present?

We reviewed the economic situation in the 32 present

Achieving elimination

A conducive environment, including political, social, financial, operational, and technical factors, is imperative for successful elimination. As history has taught us, a universal approach is ineffective, and each country or region pursuing elimination should thoroughly assess their situation and develop a strategy for elimination and prevention of reintroduction. The second paper19 in this Series outlines the details of technical considerations, the third paper20 presents operational

Challenges of elimination

The specific challenges in elimination of malaria vary substantially between countries and regions and, although common agendas exist, some countries and regions need unique solutions. The long-term research agenda, as defined by MalERA,6 will enable the development of new generations of diagnostics, drugs, vaccines, and insecticides during the next decades. For the 32 malaria-eliminating countries, most of these new interventions will come too late to assist their elimination efforts, although

Risks of elimination

Risks of malaria elimination exist both globally and nationally. Globally, concern focuses mainly on issues of finance and resistance. Some are concerned that too much emphasis on or investment into elimination will take funds away from the important and life-saving goal to reduce malaria morbidity and mortality in high-burden countries.10, 76 We agree fully that shifting investments from part one of the three-part strategy, aggressive control in highly endemic countries, to part two, shrinking

Benefits of elimination

Although the benefits of controlling malaria are well documented and understood,86 the benefits of eliminating malaria are understood to a lesser extent, are difficult to quantify, and need further research. Many differences between the benefits of elimination and controlled low-endemic malaria will be negligible. Development of a standardised set of indicators to help a country measure and monitor the benefits of elimination will help to gain and sustain political commitment and community

Future strategies

When planning the elimination agenda for the next decade, the first point to emphasise is that efforts directed at shrinking the malaria map should in no way detract from control in highly endemic countries or the development of new interventions and delivery methods. However, greater attention to shrinking the malaria map is crucial for global malaria eradication.

Gaining international consensus on the circumstances under which a country can regard itself as a malaria-eliminating country, and

Conclusion

Deliberate shrinking of the malaria map started over 150 years ago and countries have continued to make remarkable progress since. As history has taught us, a decision to pursue elimination needs thoughtful consideration of the many challenges, risks, and benefits, and planning for the prevention of reintroduction. With 32 countries working towards elimination, appropriate recognition and support for their efforts is crucial. This Series seeks to initiate a process of developing evidence that

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