Over the past decade, malaria has jumped on the first place from the third place in the number of deaths per year (after pneumonia and tuberculosis) among infectious diseases. From 1.5 million to 3 million people annually die from malaria (15 times more than from AIDS.) At the same time, only 65 dollars are spent on treatment and research in the world per one death from malaria, while it makes $ 3,400 per one death from AIDS. It is especially striking, because 2.4 billion people reside in the areas where malaria is spread, which makes 40% of the world. The reason is that 90% of malaria cases are recorded in Africa, and 70% of the rest occur in India, Brazil, Sri Lanka, Vietnam, Colombia and the Solomon Islands, i.e. the countries of the “third” world (Kinkela, 2011).
DDT is the best-known organochloride insecticide to fight malaria vectors. Although this compound was synthesized in 1874, its insecticidal properties were discovered only in 1939 by Swiss chemist Paul Muller, awarded with the Nobel Prize for the discovery a decade later. Throughout 1960’s, the number of negative consequences of the misuse of DDT increased, which eventually led to the prohibition of DDT in many countries by 1970’s.
Until that time, the widespread use of DDT had already led to the emergence of mosquito populations resistant to DDT in many areas. Besides, it has been scientifically proven that the toxin accumulates in the fat tissues of animals and humans, and has an especially deleterious effect on the reproduction function of birds (accumulating in the egg shell). Under normal conditions, DDT can be preserved in soil for up to 12 years, while under anaerobic conditions it can be dissolved by certain types of soil microorganisms in 2-4 weeks. The speed of decomposition is strongly dependent on temperature: the higher temperature is, the faster the decomposition is (Kinkela, 2011).
DDT is characterized by resistance to concentrated acids and by poor solubility in water (according to some data, the solubility of DDT is estimated by several units of nanograms per liter), but good solubility in lipids. A characterizing feature is also the presence of benzene rings in the structures of the molecules of organochloride pesticides, which contribute to the extremely high stability of these substances. Being an extremely persistent compound, DDT is able to migrate in the biosphere for a long time staying in the same condition. For example, during the intensive use of DDT in the past (the half decay period may be about 20 years), the biosphere received several million tons of this toxin (Kinkela, 2011).
However, the WHO currently recommends going back to the residual insecticide spraying, and not only in the areas of epidemies, but also in the areas characterized by high and constant malaria transmission rates, including the whole Africa region. Along with this, it is offered to use some alternative types of insecticides for the areas, where the mosquitoes have become resistant to DDT, in order to control the DDT resistance evolution.
It should be marked that such policy makes some sense. For instance, due to DDT, not a single person died from malaria in India in 1965, while in 1948, the disease killed 3 million people. According to the National Academy of Sciences of the US estimates, on a whole, DDT managed to save 500 million lives during the whole period of its application until the prohibition. Nowadays, program data show that timely and correct application of indoor residual spraying with DDT can reduce the rates of malaria transmission by 90% (WHO Position Statement, 2007).
Generally, the WHO actively promoted indoor residual spraying for malaria until the early 1980’s, when due to the increased DDT-related concern regarding health and environment, the organization stopped promoting it and had to focus on other methods of prevention instead. Extensive researches and testings carried out later have demonstrated that well-managed program for DDT indoor residual spraying can be considered safe for both wildlife and people (WHO Position Statement, 2007).
Indoor residual spraying represents itself the application of long-acting insecticides on roofs and walls of living houses, as well as shelters for domestic animals, in order to kill malaria-carrying mosquitoes which land on these surfaces. Thus, indoor residual spraying contributes much for quick reduction of the number of infections caused by malaria-carrying mosquitoes. There are clear evidences obtained that indoor residual spraying is also as cost effective as other measures of malaria prevention programs. With proper use, DDT is not producing any kind of health risks. Besides, DDT can now be called the best of the dozen insecticides which are approved by the WHO as safe for spraying inside homes (WHO Position Statement, 2007).
One of the leading figures in the global fight against malaria, the U.S. Senator Tom Coburn once compared DDT indoor spraying with providing a huge mosquito net over an entire household for twenty-four-hour protection (Kinkela, 2011). We can support his ideas by admitting that nowadays, with WHO’s unequivocal leadership in this area, we are able to abandon the “junk science and myths” which have been a clear aid and comfort zone for the real enemy, not DDT, but malaria-carrying mosquitoes annually threatening the lives of more than 300 million children on the Earth.
Of course, not to say that scientists are in place to address this problem. For example, earlier this year, former developers of the American missile defense system “Star Wars” laser created a special installation, shoot down mosquitoes. Of course, the murder does not occur, the mosquito only deprived of its wings, so theoretically it could reach the man on foot and still infect its malaria (Kinkela, 2011).
At the same time, scientists do not stay on the same level in addressing this problem. For example, earlier this year, former developers of the American missile defense system “Star Wars”, created special laser equipment shooting down mosquitoes. It is noticeable that this machine does not kill the insects; it just damages the wings of the mosquitoes, so purely theoretically they could reach a man on foot and still infect him with malaria (Kinkela, 2011).
A group of entomologists from Arizona University led by Professor Michael Riele offered an even more radical method. With the help of genetic engineering, they created a mutant which prevented the reproduction of plasmodia – parasitic protozoa that cause malaria. If the experiment is found to be successful, the next step is the introduction of these mutants in their “enemy camp”, so that they gradually multiplied and replaced the usual ones, thus ending with a dangerous disease (Kinkela, 2011).
Many researchers argue that malaria prevention may be more cost effective than treating the disease in the long run, but the capital cost is required in many hard-to-reach areas where the poorest people in the world live.
Kinkela, D. (2011). DDT and the American Century: Global Health, Environmental Politics, and the Pesticide That Changed the World. The University of North Carolina Press.
WHO Position Statement. (2007). The use of DDT in malaria vector control. Retrieved from http://www.who.int/malaria/publications/atoz/who_htm_gmp_2007/en/index.html