Elsevier

The Lancet

Volume 376, Issue 9752, 6–12 November 2010, Pages 1592-1603
The Lancet

Series
Operational strategies to achieve and maintain malaria elimination

https://doi.org/10.1016/S0140-6736(10)61269-XGet rights and content

Summary

Present elimination strategies are based on recommendations derived during the Global Malaria Eradication Program of the 1960s. However, many countries considering elimination nowadays have high intrinsic transmission potential and, without the support of a regional campaign, have to deal with the constant threat of imported cases of the disease, emphasising the need to revisit the strategies on which contemporary elimination programmes are based. To eliminate malaria, programmes need to concentrate on identification and elimination of foci of infections through both passive and active methods of case detection. This approach needs appropriate treatment of both clinical cases and asymptomatic infections, combined with targeted vector control. Draining of infectious pools entirely will not be sufficient since they could be replenished by imported malaria. Elimination will thus additionally need identification and treatment of incoming infections before they lead to transmission, or, more realistically, embarking on regional initiatives to dry up importation at its source.

Introduction

The Roll Back Malaria strategy of Scaling Up for Impact through universal coverage with effective interventions,1 supported by an increase in malaria funding,2 has achieved low rates of malaria transmission in some areas and consequently a much reduced disease burden.3, 4 Some countries, including several with historically medium-to-high transmission, are nearing a state of controlled low-endemic malaria,5 and policy makers have a decision to make: accept low rates of malaria transmission with a strategy of consolidation of control6 or redirect activities with the aim to eliminate malaria.

During the Global Malaria Eradication Program (GMEP), WHO Expert Committee reports described specific activities of an elimination programme through its defined phases, and provided advice based on years of experience from field campaigns.7, 8, 9, 10 Since the 1970s, when WHO shifted the short-term strategic aim to control11 and relegated eradication to a long-term goal, there has been little scientific inquiry into or strategic thought about the theory, goals, and best approaches for national elimination. At the same time, many countries considering elimination nowadays have higher intrinsic transmission potential than do those that eliminated malaria during the GMEP and have to plan to maintain elimination despite continual importation of infections. Accordingly, the decision to move from controlled low-endemic malaria to elimination needs politicians, policy makers, and programme managers to have an informed understanding of the operational requirements for a contemporary elimination strategy so that they can set realistic goals and timelines that are relevant to malaria epidemiology nowadays.

The decision to convert a malaria programme that has successfully achieved a high level of control, such that malaria is no longer a major public health problem, into an elimination programme is complex12, 13 and should take into account technical, operational, and financial feasibility.14 There is a broad consensus about the strategies that are needed to achieve controlled low-endemic malaria, which are based on universal coverage with prevention and treatment measures—all of which have a strong evidence base from empirical trials, observational studies, and routine monitoring and evaluation.1, 3, 15, 16, 17, 18 However, elimination cannot be achieved by doing more of the same; transition from sustaining control to elimination demands additional activities. In the third paper in this Series, we review the activities needed to achieve and maintain malaria elimination in areas that have already reduced transmission to very low rates by identification of the essential operational changes that have to accompany a switch in focus from burden reduction to interruption of transmission. In doing so, several important knowledge gaps are identified that, in some cases, makes it challenging to provide evidence-based guidance about how to eliminate malaria.

Key messages

  • The most important operational difference between a control and an elimination programme is the concentration of activities to identify and attack foci of clinical and asymptomatic infections that perpetuate transmission

  • Detection and curing of the high proportion of infections needed to interrupt transmission requires a robust surveillance system that combines passive and active case detection methods with rapid response, with radical treatment and targeted vector control

  • Most malaria-endemic countries considering elimination should aim to prevent importation of infections through proactive case detection at the border, screening of high-risk migrants, and implementation of cross-border and regional initiatives that can reduce transmission at the source of migration

  • Because elimination has a known quantitative goal to end endemic transmission and reduce the number of locally acquired cases to less than a specific threshold, monitoring systems incorporating extremely sensitive laboratory techniques such as PCR, genotyping, and serology have to be put in place to track progress

  • Malaria elimination cannot be business as usual, but needs a systemic and new programmatic approach supported by political and financial commitment, ideally throughout an entire region of nations

Section snippets

Differences between control and elimination

The programmatic focus of a country seeking to control malaria as a public health problem involves the effective treatment of clinical malaria that is detected through passive surveillance integrated into the public health infrastructure and prevention of disease through high coverage with vector control measures. The main determinant of an elimination campaign is that, by contrast with a programme designed to maintain controlled low-endemic malaria, it seeks to interrupt endemic transmission

Methods and strategies to interrupt local transmission

Halting endemic transmission and draining the reservoir needs reduction of Rc, the basic reproduction number under control, to less than 1.22 To drain the reservoir within a reasonable timeframe, mathematical models suggest that Rc should be less than 0·5.23 Although reductions to such a rate might be possible on average throughout a country through the same scale-up of vector control activities that are necessary to achieve low parasite prevalence, foci will remain in which such reductions are

Reduction of the importation of infections

Even for countries that have long eliminated malaria, some importation is inevitable. In the USA, for example, 1298 cases were reported in 2008.92 However, intrinsic transmission potential is sufficiently low that only occasional cases of local transmission result from these importations. If comprehensive health-care systems and disease-reporting mechanisms exist, passive case detection can be sufficient to avoid resurgence from imported cases if the intrinsic transmission potential is low. In

Measurement of progress

One of the differences emphasised by the WHO Expert Committee between eradication and control programmes was that the administrative standard of progress for control was measurement of accomplishments, whereas for eradication it would change to measurement of what remains to be accomplished.9 Because elimination has a known quantitative goal of ending endemic transmission and reducing the number of locally acquired cases below a specific threshold,5, 13 monitoring systems are essential to track

Conclusions

Politicians and policy makers need to understand that malaria elimination should not take a business-as-usual approach. The most notable change will involve the evolution of a surveillance system linked to rapid response, robust epidemiological data, and sustained vigilance over a long time. Most countries aiming for elimination do not yet have the surveillance systems required for an elimination effort and will need to invest substantially to improve disease notification and analysis.104

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