World Health Organisation backs use of DDT against malaria

The World Health Organisation (WHO) has endorsed the use of banned insecticide DDT in a new approach to controlling malaria in West Africa. Stephan Tohon, WHO’s focal point on malaria in West Africa, told a malaria evaluation meeting in the Burkina Faso capital Ouagadougou that the organisation no longer recommended the use of mosquito nets. Instead he cited the positive results of southern African countries with indoor house spraying using the partially banned insecticide DDT.

The endorsement of DDT (Dichloro-Diphenyl-Trichloroethane) will be particularly controversial. The pesticide was used in World War II to control malaria with apparent great success. DDT is toxic and kills by opening sodium ion channels in insect neurons, causing the neuron to fire spontaneously. The Swiss chemist Paul Müller won the Nobel Prize for medicine in 1948 for demonstrating DDT killed the Colorado potato beetle, a pest that was ravaging the potato crops in the developed world.

DDT contributed to the final eradication of malaria in Europe and North America and WHO’s program to combat malaria worldwide was based on the success of the drug. DDT was less successful in the tropics. Because farmers used it as a crop spray, insect populations began to develop resistance. It all began to unravel for DDT in 1962 when Rachel Carson published the hugely influential “Silent Spring” which showed the chemical resulted in reproductive problems and death in humans. The US eventually banned DDT in 1972.

With the failure of DDT, experts focussed their attentions on bednets impregnated with other insecticides. However the Stockholm Convention of 2001 which outlawed a dozen persistent organic pollutants left the door open for continued use of DDT as a vector control. Vector control works by reducing the levels of transmission and its method varies widely depending on local conditions.

Arata Kochi, head of the WHO's antimalarial campaign, is leading the charge to bring back DDT. In November 2006 he called on environmental groups to support the change. “We are asking these environmental groups to join the fight to save the lives of babies in Africa," Kochi said. "This is our call to them." Kochi is supported a group called Africa Fighting Malaria, who say that while there may be lab studies showing DDT could potentially cause cancer, no large studies show an actual increase in cancer in people.

While the jury remains out on DDT, there is no denying that malaria is one of the world’s greatest health problems. Approximately 40 percent of the world’s population, mostly in the poorest countries, are at risk of contracting malaria. Its intensity depends on local factors such as rainfall patterns, proximity of mosquito breeding sites and mosquito species. Every year, an astonishing 500 million people (one person in every twelve) become seriously ill with one of the four different types of the disease.

Malaria has serious economic impacts in Africa, slowing growth and development as well as perpetuating a vicious cycle of poverty. It mainly afflicts the poor who tend to live in malaria-prone rural areas in poorly-constructed houses with few barriers against mosquitoes. Malaria disease affects sub-Saharan Africa harder than anywhere else in the world and kills about 800,000 children younger than 5 each year. The disease also contributes greatly to anaemia among children, a major cause of poor growth and development. Malaria infection during pregnancy is associated with severe anaemia and other illness in the mother and contributes to low birth weight among newborn infants.

The cause of malaria is a parasite called Plasmodium, transmitted through bites from infected mosquitoes. In the human body, the parasites multiply in the liver, and infect red blood cells. Symptoms include fever, headache, and vomiting, usually about 10 to 15 days after the mosquito bite. If untreated, Malaria can kill by disrupting the blood supply to vital organs. The parasites have developed resistance to a number of malaria medicines and the field of malaria control has historically been dogged by problems with resistance. Each time scientists find a way to fight the parasite, the parasite finds a way to fight back. WHO says resistance can be limited if DDT is used carefully, and only where it's likely to be effective.