The long struggle to treat and prevent malaria is still under way, but a few key discoveries have marked the way forward, outlined by a leading expert in tropical medicine.
Top 5 breakthroughs against malaria, how long they took to enter mainstream treatment, what impact they had.
Seasonal malaria chemoprophylaxis (SMC) and work on developing a malaria vaccine are bringing new hope in the battle against the disease that claims over 600,000 lives every year. What other discoveries have had a major impact on the prevention and control of malaria?
Dr. Brian Greenwood, Professor of Clinical Tropical Medicine at the London School of Hygiene and Tropical Medicine, tells Thomson Reuters Foundation his top five breakthroughs in the global fight against malaria.
Quinine, European discovery 1620-30s, time to large-scale use ~100 years
“Quinine had a major impact on mortality from malaria when used for treatment and facilitated colonisation of the tropics when used for prophylaxis. However, it was expensive and not widely available to populations of endemic areas,” Greenwood said.
Quinine was the first effective treatment against malaria caused by Plasmodium falciparum. The drug, made from the bark of the cinchona tree, was discovered when Spanish conquistadors landed in Peru in 1532. Jesuit missionaries were aware of its potential from a very early stage. According to the online Catholic Encyclopaedia they had “learned the healing power of the bark from natives during the years 1620-1630.” The priests became the primary traders of the bark.
Chloroquine, discovered 1934, 12 years to come to market
“Chloroquine was much cheaper than quinine and used widely in endemic populations, saving millions of lives until resistance emerged,” Greenwood said.
Hans Andersag discovered chloroquine in 1934 at Bayer laboratories in Germany. It was ignored for a decade because it was considered too toxic for human use. After a series of lapses and confusion during the war, chloroquine was finally recognized and established as an effective and safe antimalarial in 1946 by British and U.S. scientists.
Dichlorodiphenyltrichloroethane (DDT), discovered 1874, large-scale use began after World War Two.
In 1874, German chemistry student Othmer Zeidler synthesized DDT for his thesis, but its insecticidal property was not discovered until 65 years later by Paul Müller in Switzerland. Armed forces first used the new insecticide to control louse-borne typhus during World War Two. It then proved effective against malaria-carrying mosquitoes and was used for malaria control.
Insecticide-treated nets (ITNs), developed 1970s, took a decade to realise full potential
“Treated nets reduce clinical attacks of malaria (not mortality) by about 50 percent. Their widespread use has played an important part in the recent reduction in mortality from malaria in Africa of about 30 percent,” Greenwood said.
Nets have been used for hundreds of years, but in 1897 Ronald Ross, the first Briton to win the Nobel Prize, discovered malarial parasites in mosquitoes in India and suggested that nets might provide protection. Less than a decade later, nets were first used widely by Col. William Gorgas during construction of the Panama Canal to curb the malaria epidemic that jeopardized the Canal’s future. Insecticide-treated nets, which cut malaria by a further 50 percent, were tested in The Gambia by the Medical Research Council in 1984.
Artemesinin, discovered 1972, 30 years to come to market.
“Artemesinin saved the day after chloroquine resistance emerged, and reversed an increasing mortality from malaria,” Greenwood said.
Chinese scientist Tu Youyou discovered artemesinin in the leaves of Artemisia annua (annual wormwood). It was found to clear malaria parasites from patients' bodies faster than any other drug. However, the Chinese government restricted access to the purified drug and the plant from which it was extracted. News of the discovery reached scientists outside China when results were published in the Chinese Medical Journal in 1979. In 2002, artemesinin-based drugs were added to the WHO's Essential Medicines list.
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