The long road to victory over humanity's old enemy malaria
Steve Connor is the Science Editor of The Independent. He has won many awards for his journalism, including five-times winner of the prestigious British science writers’ award; the David Perlman Award of the American Geophysical Union; twice commended as specialist journalist of the year in the UK Press Awards; UK health journalist of the year and a special merit award of the European School of Oncology for his investigative journalism. He has a degree in zoology from the University of Oxford and has a special interest in genetics and medical science, human evolution and origins, climate change and the environment.
Thursday 10 November 2011
The first global campaign to eradicate malaria was launched in 1955 by the World Health Organisation, but it had to be abandoned 20 years later with a less ambitious target of malaria control – such were the difficulties of wiping out this pernicious parasitical disease.
Malaria is caused by a blood parasite that has proved too complicated for conventional eradication programmes based on measures such as better sanitation, drugs and vaccines. A further complication is that the parasite is transmitted by mosquitoes.
There are four types of human malaria, but the one caused by the parasite Plasmodium falciparum is the most deadly. It is transmitted exclusively through the bite of Anopheles mosquitoes, which come in 20 different species, although the most dangerous are those that bite at night, according to the WHO.
Because Anopheles need standing water to breed, many eradication programmes in temperate regions of the world have worked by relatively simple measures aimed at eliminating the breeding sites – such as the draining of water-logged land.
Malaria transmission is most intense in tropical regions where mosquitoes have longer lifespans. This, along with the strong human-biting habit of African mosquitoes, is the main reason why 85 per cent of the 781,000 malaria deaths worldwide occur in sub-Saharan Africa, the WHO said.
About half the world's population are at risk of malaria and in 2010 there were 225 million cases. Most of the deaths, however, occur in African children under five – malaria is responsible for one in five deaths among African infants. Controlling mosquitoes is still the most effective method of limiting the transmission of malaria. One of the most effective methods at preventing the spread of the disease within a community is using bed nets impregnated with insecticide spray.
Drugs against malaria have also been effective, but they are expensive and suffer from the problem of drug resistance. Drugs that were effective in the past, such as chloroquine and sulphadoxine-pyrimethamine, are less effective due to the evolution of resistant malaria strains. The most recent anti-malaria drug, artemisinin, is used in combination with other drugs to minimise the development of resistance, but there are already reports of resistant strains of malaria developing against it.
This is one of the reasons why there has been renewed focus on the development of vaccines, despite the fact that there are no effective ones in use against any parasitical disease. The most promising candidate vaccine, known as RTS,S/AS01 and manufactured by GlaxoSmithKline, has shown limited success in the first results of clinical trials involving young African children. However, there is now real hope that a "second generation" vaccine based on the latest discovery by British scientists may produce a novel vaccine that could indeed eradicate malaria completely, a dream for more than half a century.
Heroes of the study
The lead scientists behind the study were Gavin Wright and Julian Rayner, from the Sanger Institute near Cambridge, – but the breakthrough was a global effort. Harvard University scientists carried out genetics studies and others in Senegal provided malaria parasites samples. A team in Oxford worked on the uses of vaccine development.
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