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Good News in Malaria Control… Now What?

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  • 1 Malaria Control Program, PATH, Ferney-Voltaire, France

In this issue of the American Journal of Tropical Medicine and Hygiene, Immo Kleinschmidt and colleagues1 describe remarkable malaria control progress and benefits on the island of Bioko in Equatorial Guinea over the last 4 years. Using a pre-program time period as their comparison, they show that between 2004–2008 with high household coverage of twice-yearly indoor residual spraying (IRS), the introduction of artemisinin combination treatment (ACTs), the use of intermittent preventive treatment in pregnant women (IPTp), and the somewhat more recent introduction of very high coverage with long-lasting insecticide treated mosquito nets (LLINs), they had remarkable impact on malaria infection, disease, and mortality in the population.

Although they present their findings fully in their article, some merit repeating. First, their efforts achieved 4 years of very good coverage: spraying IRS every 6 months in typically > 80% of households; achieving 73% LLIN use (not just ownership) in households through house-to-house distribution with instruction and education all provided at no cost to the people; widespread training of doctors and nurses, routine use of diagnostics and free first-line treatment of children < 15 years of age and pregnant women with ACTs (artesunate + sulfadoxine-pyrimethamine) for their malaria infections; and expansion of their IPTp program (but for this intervention, only reaching 19% of women with the recommended 2 dose regimen). Overall, their prevention with IRS + LLINs reached more than 80% of the population by 2005 and 95% by 2008!

The consequences were no less remarkable. In somewhat simplified terms, their high intervention coverage reduced Anophelene mosquito abundance by > 90% and reduced sporozoite rates in the remaining mosquitoes by > 90%. Infection prevalence in 2- to 5-year-old children was down ~57% to 18%; fever rates in the previous 4 weeks were down ~56% to 6.3%; ACT treatment needs decreased by ~62%; anemia rates (Hb < 8 gm/dL) in 2 to 5 year olds were down ~87% to just 2%. This progress appears to have contributed substantially to a reduction in all-cause under-five mortality from 152 → 55 deaths per 1,000 live births (down ~64%); and the drop occurred rapidly and timed directly with the intervention scale-up.

These are findings from a program effort, albeit well monitored and supported with national contributions and much external support from experts and donors. And, the authors must rely on before-scale-up and after-scale-up comparisons. As a consequence, the authors document as well as possible the other potential contributions to improved child survival. The improved economy in Equatorial Guinea caused by the oil industry is explored and the slightly lower rainfall during the 2005–2008 program years is examined in their analysis. They looked for other substantial improvements in disease control efforts (e.g., immunization coverage, other maternal or child health interventions) and found no dramatic scale-up of these programs during this interval to account for their findings.

In summary, scaled up malaria control with currently available interventions works; it reduces vector populations and their transmission potential, lowers infection rates, illness rates, anemia rates, and saves lives. This is consistent with the controlled trials for some of the interventions25 and with the small but growing number of reports from other programs.68 And, perhaps remarkable but not so surprising in retrospect, these benefits appear to accrue almost immediately upon introducing the interventions at high coverage.

Fantastic!… now what? That is a critical question for Bioko Island, for Equitorial Guinea, and for the many malaria-endemic countries, particularly in sub-Saharan Africa.

For Bioko Island, by achieving scale-up to > 80% coverage with multiple interventions, the recently developed Roll Back Malaria Global Malaria Action Plan (RBM-GMAP)9 would suggest that they have moved to the phase of “sustained control” and have the potential to head toward “elimination.” For sub-Saharan Africa, this is not a well-worn path and there is still much to be learned. At least three important opportunities lie ahead: 1) learning about the next-step interventions to gain further reduction in malaria transmission; 2) learning about the systems to sustain high coverage and the systems required to eliminate and then keep out malaria; and 3) learning about the partnerships for financing, providing expertise, and doing the daily work to sustain control and then eliminate malaria. Perhaps Bioko Island can be a leader and teacher for these uncharted next steps.

The team on Bioko Island has established a strong evaluation system that could examine the next malaria intervention steps on the path to elimination. With rapid intervention scale up, they have likely reduced the vast majority of illness and death caused by malaria. A next step is to seek out the remaining sources of transmission. Having already reduced the vector population and the infection rate in the few remaining mosquitoes, most of the residual transmission potential is in malaria-infected people. Because of high levels of anti-malarial immunity in the population, many people continue to be infected and asymptomatic but can still transmit to mosquitoes and on to other people. Consistent with previous experience,3 a next step must be to systematically identify and treat people with infections (not just people with illness using passive or active case detection [PCD or ACD]). This could be done with full population screening for active infection (testing and treating all infected people) or mass drug administration (MDA). Indeed, some of the mathematical models examining malaria transmission suggest that this further clearance of human infection in settings with high LLIN and IRS coverage may be sufficient to eliminate transmission. 10 An additional “intervention” for testing on Bioko Island will be to establish a high quality system of identifying each new infection and investigating the infection to find its source and any possible transmission from this infection or its source; protocols for this exist 11 and could be modified to fit local situations. This aggressive case containment approach will likely be the final requirement before elimination and will be the system needed post-elimination to avoid any reintroduction of malaria. Learning how to take these steps and informing others will be an important contribution.

ACD involves systematic screening of communities for people with current or recent fever and examination of blood films collected from them. In settings with high rates of malaria immunity and much asymptomatic infection, ACD will likely miss a substantial portion of infections in the population. Active infection surveys involve screening of communities for all persons (regardless of symptoms) and testing and treating for malaria. MDA involves the use of effective malaria treatment at full treatment doses applied to entire populations to clear parasite infections; note that the use of MDA is controversial because of potential adverse drug effects, challenges to its program effectiveness depending on the efficacy and dosing requirement of the drug, and concerns about fostering drug resistance.

Between where Bioko Island is today and where it needs to be to eliminate malaria lies “sustained control” – the process of solidifying the gains made with current high intervention coverage and establishing and evolving the systems needed to maintain coverage and initiate some of the next steps noted previously. The question “is it sustainable?” has always had a pejorative connotation; yet the authors have demonstrated their ability to work for more than 4 years with multiple interventions, so “sustained control” is evidently not beyond their capacity. Identifying the systems for stable and predictable financing, expanding local capacity and responsibility (in district health teams, in communities, and in homes), and introducing the next strategies to tighten the noose around transmission will have their challenges, but will be enlightening to their neighbors and the wider RBM community.

Finally, while not described in the article, the effort in Bioko represents a remarkably successful public-private partnership. In 2002, Marathon Oil Corporation and its partners established exploration and production in the Alba Field oil and gas reserve (one of the largest in the African region), 12 and by 2003 they had launched a US$15.8 million effort to reduce malaria transmission on Bioko Island 13 to reach all of the approximate 130,000 population on the 779 sq mile (2,017 sq km) island. In 2006, the partners secured Global Fund resources to expand the work to mainland Equitorial Guinea. 14 Such partnerships are undoubtedly complex, but the incentives are compelling. Both the country and the companies get substantial revenue from the industry; the workforce and their families are healthier and reduction in illness means that they are more productive and less likely to drain the system through health costs; and the effort shows social responsibility at its best and wins business awards repeatedly. These incentives may be one of the secrets to the “sustained control” noted previously. This is not the only place where business, government, university, and non-governmental organizations have contributed to malaria control; for example, the industries in copper mines 15 and gold mines 16 have invested elsewhere in sub-Saharan Africa. This model, too, needs further exploration to see if incentive systems and partnerships can have a wider reach in malaria control.

Cementing success with sustained high coverage of existing control measures and embarking on elimination are next opportunities on Bioko Island. Not doing this would easily allow malaria to reinsert itself and reset morbidity and mortality back to where it was. Understanding the systems needed for sustained control and the next interventions on route to elimination will be important; but it may be the growth of country and local partnerships and their incentives that make or break the opportunity for continued success in malaria control on Bioko Island and elsewhere.

*

Address correspondence to Richard Steketee, Malaria Control Program, PATH Ferney-Voltaire, France. E-mail: rsteketee@path.org

Author’s address: Richard Steketee, Malaria Control Program, PATH Ferney-Voltaire, France, E-mail: rsteketee@path.org.

REFERENCES

Footnotes

ACD involves systematic screening of communities for people with current or recent fever and examination of blood films collected from them. In settings with high rates of malaria immunity and much asymptomatic infection, ACD will likely miss a substantial portion of infections in the population. Active infection surveys involve screening of communities for all persons (regardless of symptoms) and testing and treating for malaria. MDA involves the use of effective malaria treatment at full treatment doses applied to entire populations to clear parasite infections; note that the use of MDA is controversial because of potential adverse drug effects, challenges to its program effectiveness depending on the efficacy and dosing requirement of the drug, and concerns about fostering drug resistance.

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