Delegates at the meeting in Southampton yesterday were given bleak warnings about the rise in drug-resistant strains of the potentially lethal blood parasite transmitted by mosquito bites.
Adrian Hill, a malaria researcher at the Institute of Molecular Medicine at Oxford University, said: 'There is a danger that no matter what (drugs) you give to people travelling to dangerous parts of the world, you can't guarantee they won't get malaria.'
The threat is not only to short- term visitors to Africa, South America and Asia. Two million children in those continents die each year from malaria. According to Dr Hill, this figure could easily rise to 10 million a year as drug-resistant strains spread.
Studies in Thailand by scientists funded by the Wellcome Trust demonstrated that drugs were losing the battle against the main malaria parasite, Plasmodium falciparum. The trust said that the researchers had found clear evidence that quinine, which has been used for 500 years, was becoming ineffective.
'It is predicted that within five years many malaria cases in parts of Thailand and adjacent countries will be untreatable with any currently available drug,' the trust said. Scientists also reported a 'dramatic upsurge' in drug-resistant strains of the parasite in Kenya. Drug-resistant malaria was now widespread throughout sub- Sahara Africa, and the situation was equally grave in Central and South America. Bridget Ogilvie, the trust's director, said: 'It's a very worrying prospect.' She said that companies were reluctant to spend the huge amounts of money necessary to develop new drugs and vaccines, particularly if the disease was prevalent in countries that could not afford to pay for the drugs.
Attempts to produce a working malaria vaccine have proved unsuccessful. The results of the biggest trial of a prototype, on tens of thousands of volunteers in South America, have yet to be evaluated.
Dr Hill said another line of vaccine research was to investigate the 10 human genes that conferred some degree of resistance against malaria.
One such gene, which is linked with a 40 per cent reduction in a child's risk of severe malaria, appears to help the human immune system to recognise and attack the malaria parasite.
Other parasites are also becoming increasingly resistant to drugs, researchers told the conference. Nematode worms, which infect one in five of the population and cause serious disorders such as elephantiasis and river blindness, can produce strains resistant to the anthelmintic drugs used to treat infection.