Another horrific mosquito-borne disease, Zika, is now decimating South and Central America. It leads to brain-damaged babies; the World Health Organization claims it is now "spreading explosively", and will proliferate to every continent and become widely and deeply embedded in populations. There is no known cure for it and it could take decades to find one. It now joins malaria, dengue and chikungunya as another scourge spread by mosquitoes. The only solution is to exterminate the mosquitoes that spread these diseases by pesticides.
The most potent of these is DDT. The US National Academy of Sciences estimated DDT had saved 500 million lives from malaria by 1970. In India, effective spraying had virtually eliminated the disease by the 1960s, so much so that the mosquito nets which were ubiquitous in my childhood had disappeared from urban houses by the time I was at university in the late 1950s. The indoor residual spraying of DDT decreased the cases of malaria from 100 million a year in 1953 to 150,000 by 1966; deaths due to malaria, which were nearly a million a year in the 1940s, decreased to about 1,500 a year in 1966.
Then in the 1970s, largely as a result of an environmental scare promoted by Rachel Carson's book Silent Spring, US President Richard Nixon's Environmental Protection Agency under William Ruckelshaus banned DDT - against all the expert advice he had been given. Foreign aid agencies and various UN organisations began to take a jaundiced view of DDT, and the use of DDT declined. Not surprisingly, the mosquitoes hit back and endemic malaria returned to India. By 1997, UNDP's Human Development Report 2000 estimated there were about 2.6 million malaria cases.
So why did DDT fall out of favour despite its demonstrated merits? Rachel Carson in 1962 started the DDT hysteria with her claim that its use had devastating effects on bird life, particularly those higher up the food chain. It was also claimed that DDT causes hepatitis and cancer in humans. Numerous scientific studies showed these fears to be baseless. It was shown to be safe to humans - causing death only if eaten in the size of pancakes! In 1971, in defense of its use, the distinguished biologist Philip Handler, then president of the National Academy of Sciences said: "DDT is the greatest chemical that has ever been discovered". Commission after commission, expert after Nobel Prize-winning expert has given DDT a clean bill of health. (See E M Whelan, Toxic Terror, 1993, and for India, K N Mehrotra, 'Use of DDT and its Environmental Effects in India', Proceedings of the Indian National Science Academy, 1985, and for a recent survey: "Use of DDT in fighting malaria", www.appopedia.org.).
But this evidence had no effect on environmentalists, whose misanthropic views were summarized by Alexander King, co-founder of the Club of Rome, who in 1990 said, "My chief quarrel with DDT in hindsight is that it has greatly added to the population problem". Paul Ehrlich said this about India: "I came to understand the population explosion emotionally one stinking hot night in Delhi… The streets seemed alive with people. People eating, people washing, people sleeping, people visiting, arguing and screaming. People thrusting their hands through the taxi window, begging. People defecating and urinating. People clinging to buses. People herding animals. People, people, people." Whilst another has argued: "It may be unkind to keep people dying from malaria so that they could die more slowly of starvation". Whilst yet another has said: "Some day anti-malarial vaccines will probably be developed, which may even wipe out the various forms of the disease entirely, but then another difficulty will arise: important wild areas that have been protected by the dangers of malaria will be exposed to unwise development." (Cited in R Tren and R Bate, When Politics Kills: The political economy of malaria control, 2001).
These misanthropes are fortunate to live in once-malarial countries in Europe and America where DDT had done its life-saving work three decades before the ban. Following the US EPA's ban, the environmentalists succeeded in getting all developed countries to ban the chemical for all uses. Many developing countries followed suit by banning the pesticide in agriculture, and some for all uses. USAID and the WHO, who had been at the forefront of the mosquito eradication programmes based on house spraying with DDT, turned their backs on DDT. USAID has maintained that, as DDT is not registered by the EPA for use in the US, foreign assistance is not available for programmes that use DDT. Thus the WHO - whose Malaria Expert Committee had earlier ruled that DDT is safe and effective for malaria control - in 1979 began championing a strategy which ignores the causal link between decreasing numbers of houses sprayed and increasing malaria, by emphasising curative and de-emphasising preventive measures.
The decline in house spraying created DDT-resistant mosquitoes. Nevertheless, whenever DDT was vigorously used - as in Mexico - malaria rates declined despite the increased resistance of mosquitoes. Recent research has shown why. It has been found that DDT is "highly effective at repelling mosquitoes that are resistant to it". Thus DDT not only kills mosquitoes not resistant to it but also repels mosquitoes which are resistant. "If the house wall is sprayed with DDT, the mosquitoes will stop entering," says Donald Roberts, professor emeritus of tropical diseases at the Uniformed Services University of the Health Sciences. "If they don't enter, they can't touch people while they sleep. In terms of disease control, it works beautifully." ('DDT's ability to repel mosquitoes trumps resistance', Nature Medicine, 2007.)
In 2004 the Persistent Organic Pollutants (POPS) Stockholm Convention was signed by 170 countries, restricting the use of DDT to vector control, thus permitting its public health use. The WHO, which had removed its ban on DDT use for public health, was however charged to reduce and ultimately eliminate DDT. India continues to produce and use DDT for public health purposes and has rightly opposed the POPS proposed deadline of 2020 for a DDT ban.
But India no longer seems to be using DDT to kill or repel mosquitoes through house spraying, as it did in the National Malaria Programme of 1953 and then through the National Malaria Eradication Programme (NMEP) in 1958. DDT remains the cheapest and most effective means for controlling mosquitoes. The time has come to start a massive programme of DDT house spraying to kill or deter mosquitoes in a new MMA - Macchar Maro Andolan.