Eradicating disease

Oct. 17, 2011, 10:13 a.m.


David Dickson


Mother and child under malaria bednet, Ghana

Insecticide-treated bednets and artemisinin-based drugs have put malaria eradication within reach.

Flickr/World Bank Photo Collection

Focussing on the steps needed to eradicate malaria, not just control it, can broaden and stimulate support for health research agendas.

Next week in Seattle, United States, the latest malaria forum organised by the Bill & Melinda Gates Foundation will focus on strategies for tackling the disease, particularly in Africa. It includes three sessions on elimination and eradication, and its title — 'Malaria Forum on Optimism and Urgency' — captures much current thinking on the topic.

The meeting follows one held in London last week, at which the Carter Center, the foundation set up by former US president Jimmy Carter, reported it has helped to reduce the number of sufferers from guinea worm disease from 3.5 million in Africa and Asia in the 1980s, to fewer than 2,000 today. It is on target to eliminate the disease by 2015.

Success in the fight against malaria [1, 2] and guinea worm disease have spurred those dealing with other infectious diseases to explore how to move from treatment and control to eliminating them from large regions of the world, if not eradicating them entirely.

There has been scepticism about this suggested paradigm shift. Some point to the enormous logistical challenges, particularly for diseases that are difficult to diagnose, or whose prevalence is poorly understood.

Others point to the negative impact of losing the public's trust if well-publicised targets are missed. And there is a concern that such campaigns may use resources that would be better spent on other control measures.

But aiming for elimination or eradication can highlight the financial commitments required to make a wider impact where treatment and prevention strategies have been relatively successful on a small or regional scale, such as with malaria. And it can also stimulate the extra scientific efforts that are just as necessary.

Obstacles to eradication

When the idea of eradicating malaria was first raised by the Gates Foundation at its 2007 forum on the disease in Seattle, not everyone felt it was a sensible target. "There was an underlying sense that this was seriously disconnected from reality," said one participant in a debate held at the 7th European Congress on Tropical Medicine and International Health in Barcelona, Spain, last week.

Some remember earlier efforts to eradicate the disease after the Second World War, primarily through the widespread use of DDT, and treatment with drugs such as chloroquine. Despite some local successes, the disease returned as a major health threat in the 1980s and 1990s after the mosquito vector developed resistance to DDT.

The obstacles to disease eradication are not always scientific. For example, the WHO's efforts to eradicate another disease, polio, have been hampered by suspicion in northern Nigeria about using vaccines produced in the developed world. The disease is now spreading again in several West African countries.

Both setbacks have led to the criticism that eradication campaigns can be politically motivated but scientifically unjustified.

Science fuels success

There is also a danger that the successes of these campaigns can be overshadowed by their failures. It is sometimes forgotten, for example, that the DDT-based malaria campaigns led to its elimination in many countries, particularly in East Asia.

Similarly, the WHO's polio campaign may not have achieved its target of eradication. But it is 99 per cent of the way there. In India, one of the most difficult countries in which to make progress, no new cases have been reported in the past nine months. As another participant in Barcelona put it: "If India can do it, why can't Africa?"

And there is, of course, the success of the smallpox eradication programme, with the last known case reported in Somalia in 1977.

All this suggests that pursuing the elimination and eradication of certain diseases can be highly effective — however ambitious, and despite potential setbacks. The challenge is to ensure that any such strategy is based on robust scientific evidence, and that the technical tools (such as vaccines) required are available or can be readily developed.

Applying political pressure

Work on malaria suggests that focusing on the science and technology required to eliminate a disease, rather than just control it, can pay off — and that such approaches could be applied to other diseases. For example, programmes can place greater emphasis on research into transmission pathways, not just the treatment of patients.

Such a target can also increase pressure to generate epidemiological data to demonstrate the effectiveness of elimination campaigns and compare control strategies. Policymakers can then decide, for example, whether to start elimination programmes in locations where a disease is most or least prevalent.

In the case of malaria, it is now clear that tools developed by the scientific community over the past decade — such as insecticide-impregnated bednets and artemisinin-based drugs — have put global eradication within our grasp.

Two challenges remain. The first is to use scientific evidence of feasibility to leverage the massive financial resources — and the political commitments behind them — that are required to achieve this goal. It is not a task that can, or should, be left to the Gates Foundation alone.

The second is to use the progress achieved with malaria to generate demand for research on the range of tools needed to eliminate other challenging diseases.

Not every eradication campaign will succeed in reaching its goal. But that does not undermine the value of efforts that may take us further in controlling a disease than we would have done otherwise.

David Dickson
Editor, SciDev.Net


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