Introduction
Substantial progress in reducing the morbidity and mortality caused by malaria worldwide has encouraged the Global Malaria Action Plan to outline a long-term vision for malaria eradication through shorter-term efforts to eliminate the disease1 (throughout, we define eradication and elimination as outlined in the first report in this Series2). 32 of the 99 countries in which malaria is endemic have declared a national policy for malaria elimination or are pursuing spatially progressive elimination within their borders.2
Elimination of malaria would be feasible if the technical, operational, and financial challenges to the permanent interruption of transmission could be overcome.3 Elimination is technically feasible if malaria interventions can be deployed at a sufficiently high coverage to interrupt local malaria transmission and be maintained for a duration sufficient to eliminate the local reservoir of parasites.4, 5 Since elimination should be considered a one-way transition from malaria-endemic to non-endemic status, technical feasibility also requires an assessment of the probability of malaria being re-established.6 Technical assessments frame the scale of the operational challenge, itself further defined in terms of the human capital, national infrastructure, and political commitment needed by nations to reach their elimination goals. Definition of overall elimination feasibility requires the simultaneous consideration of technical and operational constraints.
Recent authoritative reviews have provided expert opinion on the feasibility of malaria elimination by region (eg, Schapira and colleagues7). We undertook a complementary approach based on the current understanding of the global spatial epidemiology of malaria and the application of mathematical transmission models to define the technical difficulty of elimination of the disease. Spatial data for indicators related to the operational feasibility of malaria elimination were assembled and, in combination, we attempted to define quantitatively which countries are currently the most and the least feasible candidates for malaria elimination. We undertook technical feasibility analyses for Plasmodium falciparum only because the theoretical modelling framework8, 9, 10 and global cartography11, 12 for this species are sufficiently well developed. Since the same is not true for Plasmodium vivax,13 we restricted the analysis for this species to operational feasibility. Our approach focused on available indices and did not attempt to predict future changes to technical or operational feasibility. Nor did we consider the costs of elimination, which are addressed in a separate paper in this Series.14 Rather, we present a framework to show combinations of technical and operational constraints to elimination in the 99 malaria-endemic countries in an attempt to provide an objective and contemporary relative ranking between nations, rather than an absolute assessment of feasibility. Our approach represents one of many for the construction of composite indices, and since uncertainties are inherent in the datasets used, our results are not definitive statements on feasibility, but a provisional attempt to provide an indication of the challenges faced by each nation relative to others. Although our primary focus was on the relative feasibility of elimination between countries, the results are relevant to the full range of control, including the relative feasibility of effective national scale-up of interventions for those countries not considering elimination.
Key messages
- •
Substantial spatial data and an established modelling framework enable evidence-based, species-specific assessments of the feasibility of malaria elimination for policy makers
- •
The approach presented aims to identify rate-limiting steps to feasibility of malaria elimination and thus provides the opportunity to objectively assess the relative merits of national malaria intervention plans
- •
Results for relative elimination feasibility vary between countries when technical or operational aspects of feasibility are considered, highlighting different challenges faced by nations
- •
Elimination of Plasmodium falciparum from the Americas is most feasible, with a less than 50% reduction in 2007 transmission levels needed continent-wide
- •
Elimination of P falciparum from African countries is least feasible, with much of west and central Africa needing a more than 90% reduction in 2007 transmission levels to achieve elimination
- •
Substantial developments in modelling and mapping are needed for estimation of the technical feasibility of eliminating Plasmodium vivax (and Plasmodium malariae, Plasmodium ovale, and Plasmodium knowlesi)
- •
These relative rankings are an objective and easily updated guide; they should be augmented by detailed country-level feasibility assessments before an elimination campaign is started