Malaria’s ground zero
As new waves of malaria threaten the globe, worried scientists want to conduct a mass inoculation in a Cambodian region where new vaccines always seem to stop being effective, reports Robin McKie ,of The Observer.
AS malaria continues to pose a mounting, and deadly, threat around the globe, worried scientists want to conduct a mass inoculation in an area of Cambodia where new vaccines have very quickly lost their effectiveness in the past. The town of Pailin is under the scrutiny of world health experts as a result.
PAILIN is a small settlement nestling in tropical rainforest near Cambodia’s border with Thailand. It is an unassuming town that lies at the centre of one of the country’s main logging areas. It was here, in the late 1970s, that the Khmer Rouge set up one of its main strongholds and ruled Cambodia with a ferocity that caused at least 2 million deaths. It is a grim legacy.
But Pailin has another unwanted claim to fame, one also associated with widespread death. The town lies at the heart of a region that has seen successive waves of resistance to malaria drugs arise in local people and then spread across the globe. The resulting death tolls can be measured in millions of lives, scientists say.
Just why malarial drug resistance has arisen here is not clear. Nevertheless scientists are emphatic: the region has seen the creation of several mutations in malaria parasites that have allowed them to shrug off medicines that once protected humans. Even worse, they have discovered a new wave of malarial drug resistance has recently appeared in this tiny area and has already begun to move into Myanmar and towards India and Bangladesh.
The prospect has so alarmed scientists and politicians that the issue will be raised as an emergency topic at the heads of Commonwealth meeting in London this week. There are 19 Commonwealth member states in Africa, the continent most vulnerable to malaria. According to World Health Organisation statistics about 90% of all malaria deaths occur in Africa. Hence the concern.
‘‘The problem is that we are pussyfooting around,’’ said Prof Sir Nicholas White, of the Mahidol Oxford Tropical Medicine Research Unit.
‘‘The World Health Organisation has failed us. We need very firm direct action and at present we are not getting that.’’
Resistance to major malaria drugs first appeared in the late 1950s when chloroquine, then a highly successful treatment for the disease, began to lose its efficacy. Crucially, this resistance first appeared in Pailin on the CambodianThai border and then spread to Africa by the early 1980s. Several million deaths were added to toll of lives lost to the disease as a result.
A new set of drugs known as pyrimethamines were then developed and used to treat malaria. But once more resistance to the drugs appeared and again it first manifested itself around Pailin before spreading westwards. Again the death toll soared.
Then, at beginning of this century, a new set of malarial medicines was developed. Known as artemisinins, they were discovered in 1972 by Tu Youyou, a Chinese scientist who was awarded the 2015 Nobel prize in medicine for her work. Administered with a sloweracting second drug, artemisinins have become the medicine of choice for dealing with malaria across the globe, leading to deaths and case numbers declining globally.
But scientists have recently discovered once more that resistance to key malarial drugs has evolved — and in exactly the same place as before: the farms and village that surround Pailin.
Just why this tiny region of Southeast Asia has proved to be such a fertile zone for the emergence of deadly resistance to malarial medicine is not clear, a point stressed by Dominic Kwiatkowski, director of the centre for genomics and global health at Oxford University.
‘‘We would love to know the answer, but it is not obvious,’’ Kwiatkowski said.
‘‘One idea is that resistance keeps arising here for historical reasons. Maybe it has something to do with the way that malarial medicines are administered here. But how exactly?’’
In fact, the theory is just one of a great many other suggestions put forward to explain why this resistance is appearing here first. The local strain of malaria parasites may have some special properties, or the ecology of the region may have features that boost the rise of resistance.
‘‘The crucial point is that we need to do something about it and once we have, we need to monitor the situation very, very carefully,’’ Kwiatkowski said.
One factor that recently became clear is that malarial drug resistance appeared very quickly in the region. Writing in Lancet Infectious Diseases in February, researchers from the Wellcome Sanger Institute and collaborators reported resistance to combination therapies that included artemisinins arose almost as soon as the treatment was introduced as a firstline malarial drug. However, this loss of efficacy was not spotted for several years.
The implications of this failure were stressed by Ben Rolfe, head of the Asia Pacific Leaders Malaria Alliance.
‘‘On our watch, drugresistant strains have spread almost unnoticed,’’ he told the BMJ recently. ‘‘As a result, we now risk a global resurgence of the disease.’’
The question facing scientists — and heads of state and health leaders — is straightforward: what can be done? White, who is scheduled to speak at the Commonwealth Heads of Government meeting, is emphatic.
‘‘We have a window of opportunity but it is closing rapidly.’’
What is needed is a campaign to use current drugs, while they still have some efficacy, not only on people who already have malaria but on those who have been infected but who have not shown symptoms yet.
‘‘These individuals carry small numbers of parasites and although they don’t get ill they are sources of new infections,’’ White said.
‘‘Mosquitoes bite them, take their blood and spread it to others. They are the source of new infections.’’
The plan, proposed by White and other scientists, is that everyone in a village should be treated with antimalarial drugs. In addition, it is proposed a third antimalarial drug be added to the combination therapy currently used.
‘‘It is called mass drug administration. It is very controversial but it works — if it is done as part of a concerted strategy. If you do it badly you will only make the problem of resistance worse. So this has to be done right. But if we don’t do it then malaria will become uncontrollable,’’ White said.
WHO officials say the dangers posed by the new malaria superbug are exaggerated and better prevention efforts, monitoring and treatments will limit its spread from the Mekong region. Others are not so sure. ‘‘We are currently on a cliff edge,’’ a spokesman for the Ready to Beat Malaria campaign said.
‘‘We can continue to battle the disease or risk an acute and deadly resurgence.’’
White concurs.
‘‘We running out of time and unless we act rapidly, people will suffer and the people who will suffer most will be the children of Africa.’’ — Guardian News and Media