HEALTH: Control vs elimination - the great malaria debate
Bed nets are a first step
LONDON, 1 November 2010 (IRIN) - In 2007, Bill and Melinda Gates committed their foundation to eradicating malaria. It was, said Richard Feachem
, director of the Global Health Group, part of the University of California, San Francisco, “a shock to the system for the malaria community, because for a couple of decades the ‘E’ words, eradication and elimination, were not used in polite company”.
That reticence was due to the very public failure of elimination campaigns, but the debate has been re-opened with the publication by the medical journal, The Lancet
, of a special series on the subject.
The study sets out the real progress that has been made, assesses the chances for countries that might feel ready to try to eliminate all transmission within their borders, weighs up potential costs and benefits of elimination over control, and establishes research priorities for the tools that can make elimination possible.
The overall message is that malaria can be eliminated – indeed, has been wiped out in many places – but moving from control to elimination might not necessarily save money, or be quick or simple.
In 1945, the world malaria map was pretty much red all over, endemic almost everywhere except in the far north – Norway, Sweden, Iceland and Greenland, and in the Swiss alps. Now, 65 years later, the whole of Europe and North America is malaria free, as are Russia, Australia and some southerly parts of Latin America, as well as some islands, such as Mauritius.
The push to eliminate malaria is now going on along the borders of the world’s malaria zone, in North Africa and the Middle East, Central Asia, China and Central America. Morocco was certified malaria-free earlier this year; Turkmenistan just last week. Meanwhile, countries in Latin America and southern Africa are working to shrink the malaria zone in the south.
These are countries that have already achieved a high degree of malaria control, through vector control, the use of bed-nets, and effective diagnosis and treatment. Huge social and economic benefits have been realized. Children do not miss school; adults are no longer too debilitated to work.
Bruno Moonen, of the Clinton Health Access Initiative, says the decision to move from control to elimination is not as easy or as obvious as one might imagine. “When infection gets below 1 percent of the population, you have to make a choice. And you may choose to say, ‘We have almost no deaths and very few cases, and we can handle that’.”
He makes the point that elimination is much harder than control: all malaria cases have to be fully treated, including mild cases that might not normally have presented at a clinic. Then the sick person’s family and neighbours have to be screened, looking for people who have no symptoms but are carrying the parasite. Then they have to be treated with an aggressive drug regimen, even though they are not ill.
This is complicated by the fact that in most countries that could try to eliminate malaria, the predominant strain of the parasite is Plasmodium Vivax, which can lie dormant in the liver for years. Detection techniques for the dormant form are not totally effective, and the only drug available to eliminate them from the system – Primaquine – can cause a potentially fatal reaction in some people. Giving low doses over two weeks is safer, but raises compliance problems in healthy people who can see no obvious reason why they should be taking drugs at all. The Lancet identifies better tests for P Vivax and better drugs against the dormant form of the parasite as key research priorities.
And all this time control measures cannot be relaxed. As one of The Lancet contributors, Oliver Sabot, put it: “The moment you take your eye off the ball, malaria is going to come roaring back.” Even when a country is malaria-free, there still has to be surveillance to catch imported cases. Geoffrey Targett, of the London School of Tropical Medicine, said the UK still sees about 1,500 imported cases of malaria a year.
Sabot’s studies of Zanzibar, Mauritius, Swaziland and two areas of China indicate that elimination would probably be more expensive than low level control in most cases. Only Zanzibar showed a clear cost benefit, because its current control programme is already very expensive. His conclusion: “Someone considering elimination should not consider cost savings as one of the benefits.”
There may of course be other, less tangible benefits. Tourists may prefer to visit malaria-free Mauritius, for instance, rather than nearby Madagascar. There would also be a huge sense of accomplishment in being able to say a country had conquered the disease.
So is there a risk of governments embarking on elimination as a prestige project, without thinking through the implications? Feachem thinks there is, telling IRIN: “There are a number of malaria-endemic countries that have begun to speak about elimination in a way which is almost certainly premature… In our view they should do a feasibility study and be influenced by the mass of evidence, and for some of these ‘premature eliminators’, if they did such a study, they might retreat and say, ‘Not yet,’ not just because of their own situation but also because of their neighbours’.”
Even so, in the long term Feachem believes malaria can be conquered. “My guess,” he says, “would be 2050 or 2060. That would be a reasonable guess for complete eradication.”