Age-old methods to fight malaria

 

Someone dies of malaria every 15 seconds, and scientists are looking at old-fashioned techniques in an effort to reduce the global death toll, writes Andrew Read

In the few minutes it takes you to read this article 20 people will die from malaria. Dr Gerry Killeen, an Irish scientist working in Tanzania, thinks that the death rate could be substantially reduced if more attention was paid to low-tech control methods that have worked in the past.

The larvae of the mosquitoes that transmit malaria live in shallow water. Before World War II, malaria control involved poisoning or draining mosquito-infested water. This larval control approach led to some spectacular successes, but it was abandoned when DDT arrived, according to Killeen. DDT was a very cheap insecticide that killed adult mosquitoes in houses and it worked - then.

Now DDT-resistant mosquitoes are widespread and Killeen believes the answer could be a return to older approaches. "We should look again at larval control," says Killeen. "There is no reason why an approach that was successful in the first half of last century should not be successful in the first half of this one."

Dr Killeen, who works at the Ifakara Health Research and Development Centre, Kilombero District, Tanzania is from Greystones, Co Wicklow; he did his PhD on the biochemistry of pig manure at University College Galway.

"When you are up to your knees in steaming viscera, the romance of it all starts to fade away," he says. He moved to the US to work on the molecular biology of mosquitoes, where he imbibed the conventional view that new drugs, genetically-modified mosquitoes and vaccines are needed to control malaria. But then he read a book about the eradication of a mosquito species from Brazil. "It completely changed my mind," he says.

The mosquito responsible for most of the malaria in Africa was accidentally released into North Eastern Brazil in the early 1930s. It rapidly spread over an area the size of the Republic, carrying malaria with it. "Tens of thousands died from malaria and others starved to death because the farmers were too sick to farm," explains Killeen.

Yet in a decade, the mosquito was eradicated. Drainage and the poisoning of larvae in every small water body was the key, he said. "It was a military-style no-nonsense campaign. They decided it just had to be done and they went and did it," says Killeen.

He believes the same approach could be used in Africa today. "It's a massive task and you can't do it from a Landcruiser. But break it into smaller tasks. In a week on foot, a trained person can visit every water body in 20 square kilometres. And one thing Africa has is lots of people."

The toxic chemicals used in Brazil in the 1930s cannot be used today, he says. But there are green alternatives. Germany uses organic pesticides to control mosquito larvae after floods in the Rhine Valley and they work, he adds.

Dr Killeen's boss, Dr Hassan Mshinda, Director of the Ifakara Centre, agrees that larval control could be of practical use in parts of Africa. "The evidence from Brazil suggests that as one strand of an integrated malaria control programme, larval control has potential, particularly in urban areas."

In cities, most mosquitoes are concentrated in small, easily accessible water bodies, says Killeen. "And by 2010, half of all people in Africa will be in urban areas." Both Dr Killeen and Dr Mshinda emphasise that larval control should be used together with bed nets and good clinical medicine, not as an alternative. But the malaria research community in non-malarious regions is taking some convincing, admits Killeen. "I've noticed that when I cross the Sahara and go North, I come across sceptics."

Fred Soper, who led the Brazilian eradication, believed nothing could be gained from further research other than the embellishment of scientific careers. The best way to learn how to eradicate mosquitoes was to get out there and try to do it. "There might be something in that," says Killeen. "You've got to learn about the local ecology and the local mosquitoes, and that can't be done from the laboratory."

Andrew Read is a research scientist at the University of Edinburgh and a British Association for the Advancement of Science Media Fellow on placement at The Irish Times