Then came the golden days of DDT, a highly effective insecticide first used as a delousing agent at the end of World War II. During the 1950s and 1960s, indoor residual spraying with DDT was the centerpiece of global malaria eradication efforts. DDT’s months-long ability to kill or deter adult female mosquitoes resting on treated walls after feeding led to further declines in malaria in India, Sri Lanka, the former Soviet Union, and other countries. By 1966, campaigns using DDT spraying, elimination of mosquito breeding sites, and mass treatment had freed more than 500 million people (roughly one-third of the population previously living in malarious areas) from the threat of disease (Shiff, 2002). Unfortunately, eradication was not sustained due to high program costs, community resistance to repeated house spraying, and the emergence of resistance to DDT. By the late 1960s, the hope of eradicating malaria through vector control was finally abandoned (Guerin et al., 2002). In many countries, the pendulum then swung to overreliance on chloroquine, a widely available antimalarial drug.
Sub-Saharan Africa was always a special case. With the exception of a few pilot programs, no sustained malaria control efforts were ever mounted there (Greenwood and Mutabingwa, 2002). The biggest obstacle was the widespread distribution of Anopheles gambiae, a long-lived and aggressive malaria vector. The entomological inoculation rate (EIR) (which measures the frequency with which a human is bitten by an infectious mosquito) rarely exceeds five per year in Asia or South America. In contrast, EIRs of over 1,000 have been recorded in several parts of sub-Saharan Africa (Greenwood and Mutabingwa, 2002).
Today, the global burden of malaria is concentrated in sub-Saharan Africa where stable, endemic disease is linked to poverty and highly efficient vectors. The insecticide-treated bednet (ITN)—first shown in The Gambia to reduce overall childhood mortality by 60 percent when combined with malaria chemoprophylaxis (Alonso et al., 1991)—is the vector control tool with the greatest promise for Africa. At the Africa Summit on Roll Back Malaria in Abuja, Nigeria in 2000, leaders from 44 African countries set a target of 60 percent ITN coverage of pregnant women and infants in Africa by 2005, an ambitious goal requiring roughly 160 million ITNs at an estimated cost of US$1.12 billion (Nahlen et al., 2003). Sadly, the goal is still far from being met. At the same time, insecticide resistance (involving pyrethroids and DDT) is a growing problem in Africa, along with environmental change brought by agriculture and other types of development that foster mosquito breeding. International sponsors also have withdrawn support for DDT due to environmental concerns.
With respect to malaria’s human reservoir, the overriding challenge facing Africa is the development of drug resistance by Plasmodium falciparum to cheap and effective treatments (chloroquine and sulfadoxine-