Dr. Brian Greenwood of the London School of Hygiene and Tropical Medicine discusses the prospects for success in the campaign to eradicate malaria with AllAfrica's Cindy Shiner. Greenwood, who has long studied the disease, recently won the prestigious Hideyo Noguchi Africa Prize by the Japanese Foreign Ministry for his research on the prevention of malaria, pneumonia and meningitis in African children.
You have said that it was indefensible to attempt to eliminate malaria in countries with neighbors that have ineffective healthcare systems and intense transmission of the disease. Can you elaborate?
I was thinking in particular of The Gambia, which has been doing very well with its malaria control program, and where it would not be impossible for them to be thinking about elimination in the next five to 10 years or so. But to do that when the country is completely surrounded by Senegal without Senegal also taking major efforts to control malaria would not be a sensible thing to do.
There are many other examples of that in Africa, particularly where you have landlocked countries surrounded by different countries. So this has to be a sub-regional or regional effort if it is going to work.
That’s already happening. The idea [is] that you start where the transmission is very low and then move progressively forward, then at least you don’t have the enemy behind you, you just have the enemy in front. That may be easier than if you’re completely surrounded with people coming into your country from all sides.
Others believe that the opposite approach would work better – to target the less severely affected countries first.
You’ve got to start somewhere first. But it certainly makes sense to start where you don’t have malaria behind you. For example, in West Africa we have had some very preliminary discussions where you might start in Mauritania, Senegal, Gambia and Guinea-Bissau, where you have deserts to the north and the Atlantic Ocean to the west. Then you would have just two sides from which you might get migration back into the country, and you try to push forward from there.
At one time there was a suggestion that Rwanda might be one of the first countries to go for elimination. But I don’t think that would be sensible. You’re much better off starting on the edges.
But if Senegal and Gambia and Mauritania did manage to achieve control in the next 10 years, would it really be possible to stop people with malaria from coming in from other West African countries, and would you be starting the whole thing off again? I don’t know what the answer is to that and we probably won’t find out until people try. Lots and lots of people go through formal border posts where it would be possible to check them. But the majority just go across the border.
How would you characterize the debate over malaria eradication or reduction?
I think it’s changed a little bit. We have come quite a long way in the past year in finding out what is really possible and what is not. I think everybody would say eradication has to be the long-term goal. Some don’t think that eradication is biologically possible, whatever resources we have. Others, including me, think it is possible to eradicate human malaria parasites but I wouldn’t want to give any time scale.
But that isn’t terribly useful. The real decision is what we’re going to do in the next five to 10 years. And there’s a pretty good consensus that for that period we may be able to eliminate malaria in some countries on the edges of the main transmission areas and achieve much better control in areas where transmission is very high. Those should be parallel processes and I think nearly everybody would buy into that now.
Where there is some discussion is where the balance of resources should be. You could say it’s better to eliminate malaria from Vanuatu and two or three countries in southern Africa and not bother too much about what’s happening in Democratic Republic of Congo and Nigeria and I think that would be very wrong. So it’s really just getting that balance as to how much of the resources should we put into elimination in areas where that’s possible. I wouldn’t want to see 50 percent of resources going to achieving elimination in those low-risk, small population countries at the expense of big ones.
The School of Tropical Medicine and Hygiene says many of the most important barriers to effective prevention and treatment of malaria can only be overcome using research that cuts across traditional scientific boundaries. Do you have examples?
I think insecticide-treated bednets is a good example and that’s probably the most powerful tool that we have at the moment. It has really involved a lot of disciplines. Chemists, entomologists, clinicians, social scientists, economists - all of those have been involved in research in getting insecticide-treated bednets used.
That is the strength of organizations such as the London School of Tropical Medicine. We do have people in each of those disciplines working together and we do have a malaria center which tries to bring people from the different disciplines to work together. I think it’s the same with TB or HIV. We’re not going to get on top of these diseases unless we use people with different skills.
Some argue that efforts have not been great enough to find new drugs and insecticides. Do you think enough is being done?
I think it’s difficult to say what is enough but certainly a great deal more is being done than what was being done say 10 years ago. I’m on the scientific panel for the Medicines for Malaria venture and I think that really has been very, very successful in bringing people together. They have got quite a large portfolio of new drugs in various stages of development and they have really managed to engage academia and pharmaceutical companies in that.
The situation is very much more encouraging than it was a few years ago. I think there will be some new antimalarials but there’s always a lot of drop-out so you have to have five or so going at the beginning of the development process to get one that can be used.
Why is it so difficult to find a vaccine for malaria?
It is a very complicated parasite. It’s got many more genes than a simple virus or bacteria. And it has evolved ways of evading the immune system so even people who have been infected with malaria throughout their life do not become immune. They stop dying from it but they still have parasites in their blood. That’s completely different from a simple virus like measles, where if you just have measles once or you have a measles vaccine you’re immune then for the rest of your life.
It is a really tough job for us to devise an artificial way for [providing immunity]. It’s the same for all the really big parasites with multiple antigens.
Might the parasite have some sort of animal reservoir.
There are four main species of human malaria and as far as we know there is no animal reservoir for those. Most people believe [if we get] all those four parasites out of humans, then that will be the end. We will have achieved eradication. But there is one, a fifth parasite, which lives in monkeys mainly, and there have recently been more human cases reported in Malaysia. So for that particular parasite there is an animal reservoir and you probably wouldn’t be able to get rid of that one unless you also got rid of it from the monkeys.
How strong and prevalent is it?
There have been only a few hundred people infected and they get infected when they go into the forest and come into contact with mosquitoes that have bitten monkeys, but it’s not a major public health issue.
What is the latest cutting-edge research that could potentially make a big impact on malaria?
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I don’t think anybody thinks there is a magic bullet. It may be a little like cancer treatment. There’s not just one wonderful drug that cured all cancers. I think most people would agree that advances in different areas probably will be effective in the end. We probably do need vaccines, some way of controlling the mosquitoes, drugs, effective treatment… I think there is progress in all of those areas.
If we did have a vaccine that was as effective as a measles vaccine then that probably would be the main tool and we might be able to stop doing other things like using bednets or spraying houses. But I think most people think we are a couple of decades away from having a vaccine that is so effective that we wouldn’t need to use other control measures as well.
There have been a lot of pushes on malaria before. Do you think it will be different this time and if so why?
Yes, I think it will. I think people have learned from the mistakes from last time. The last global eradication program was too ambitious and set too high a standard and too high a goal. When that failed everybody just sort of threw up their hands. I think this time people are being more realistic in terms of what we might be able to achieve and saying we might be able to eradicate malaria in the next 50 years but in the next 10 years we can stop transmission in 15 countries. The community can be judged on meeting certain objectives along the way.
We don’t have a lot more tools. They’re very much the same as we used in the 1960s – spraying, drugs - but I think one big difference is there has been a large expansion in the number of scientists and control people who have been properly trained in malaria-endemic countries. It’s still not enough. The [old] eradication program was very much run from Europe and the United States. I think we have a much more integrated malaria community now.
