Biomed Analysis: To control or eradicate malaria?
Some scientists worry that renewed enthusiasm for malaria eradication could distract from vital control efforts, says Priya Shetty.
Lately, malaria scientists have once again begun talking about eradication. It is not a word they use lightly. The last attempt, in the 1950s, failed miserably. Millions of people died because, far from disappearing, the disease came back stronger than ever.
Since then, the global health community has focused on reducing the number of cases and severity of the disease and lowering death tolls.
But ridding the world of this disease, which kills more than a million people every year, was a hot topic at the fifth Multilateral Initiative on Malaria (MIM) meeting earlier this month (November) in Nairobi, Kenya.
Several high-profile international groups, most notably the Gates Foundation, are pushing elimination and eradication. At first glance, these are unquestionably positive goals.
Yet some researchers fear that health infrastructure in regions like Africa is ill-equipped to roll out eradication tools, and are nervous that the shift will divert funds from much-neededbasic control measures.
Same goal, different approach
The last attempt to eradicate malaria focused on vector control — through large-scale insecticide spraying in malaria-endemic areas — alongside treatment with chloroquine.
Within a decade, new generations of drug-resistant parasites and insecticide-resistant mosquitoes emerged. Scientists were powerless to stop the resurgence.
Now, groups such as the Malaria Elimination Group and the Malaria Eradication Agenda (malERA) are setting about things differently.
A major change, according to Pedro Alonso of malERA, is that scientists now realise eradication cannot be achieved with vector-control alone. A wider array of tools, including drugs and vaccines, is needed. Research into the best options will be crucial said Alonso, who is based at the University of Barcelona, Spain.
Vaccines: A new hope
A workable malaria vaccine — long-heralded but ever elusive — seems finally to be within reach. GlaxoSmithKline Biologicals' RTS,S vaccine is the most promising malaria vaccine yet, having just become the first ever vaccine to enter phase three trials.
Understandably, expectations for this pre-erythrocytic vaccine (one that attacks the parasite before it invades red bloodcells) are high. But phase two trials have suggested it would only be 50 per cent effective, which means that research into other vaccines must continue.
Of course for eradication, the ideal malaria vaccine would go one step further and block disease transmission. Such vaccines work by triggering antibody production in an infected person against the sexual stage of the parasite. When a mosquito bites that person and sucks up parasites, it takes in antibodies that stop the parasite replicating, thereby stopping transmission.
But there is no transmission-blocking vaccine even close to being available. And this type of vaccine does not treat the disease or rid people of parasites, so it has little immediate benefit to sufferers. To be rolled out, researchers and communities will need to have already fixed their sights on eradication — and be convinced of its long-term benefits.
Distraction from control?
Many researchers do seem to be moving towards eradication. The Nairobi MIM meeting dedicated a whole day (one-fifth of the conference) to it. And there was a definite buzz surrounding the RTS,S vaccine.
But would this enthusiasm exist if Melinda Gates had not made her impassioned speech on eradication in 2007? Few researchers can afford to ignore the funding giant that is the Gates Foundation.
Even those who are grateful for the foundation's philanthropy privately admit to occasional unease about its ability to set global research agendas through the sheer amount of funding it provides.
And the direction such funds set does concern some researchers. At the MIM conference, Rose Leke from the Biotechnology Center in Yaounde, Cameroon, admitted to worries that the focus on eradication might divert funds from vital yet mundane control efforts, such as increasing bednet use or public awareness.
Other delegates expressed concern that not enough money would go into drug discovery. New antimalarials are needed, particularly given the threat of drug-resistance against artemisinin combination therapies (ACTs), the most effective malaria drugs available.
Be bold and believe?
So far at least, malaria control seems to be taken seriously. For example, the WHO adopted mass distribution of bednets as a basic standard in 2007. And the number of bednets in Africa has jumped from around ten million to 170 million in the past four years.
Even eradication advocate Alonso cautions against the hype surrounding progress towards elimination and eradication. Scientists and policymakers must be realistic about what is and is not possible if they are not to lose the public's trust.
Indeed, more than one researcher seemed startled when, at the MIM conference opening, Beth Mugo, Kenya's minister of public health and sanitation, ambitiously declared the country was aiming to be malaria-free by 2017 (see Kenya hopeful it can eliminate malaria).
Eradication may never be possible. But, with more support for malaria than ever, we should at least take the idea seriously. If eradication is integrated with robust control efforts the end might be in sight for malaria. The time is right to drive some streams of research and development in that direction.
Otherwise all we are doing is putting a small sticking plaster on one of the biggest global health challenges of our time.