Filed under: Domestic Policy, Education, Environment, Health Care, Junk Science, Regulation, Science/Technology, The United States | Tags: A Really Nasty Bug, Aedes aegypti mosquito, MIT Technology Review
The Zika Virus is in the news, and it is a bad one. It is carried by a mosquito, Aedes aegypti, commonly known as the yellow fever mosquito, and more recently known as the dengue mosquito that particularly affects small children. Now it is called the Zika mosquito. and seems to be associated with microcephaly in newborns. Nasty bug.
Mosquitoes like human blood, and seem to be skilled at spreading disease around. The Anopheles mosquito is responsible for malaria, which according to the World Health Organization, kills more than a million people a year — mostly children under the age of five.
As far as is known, malaria does not infect animals. The pesticide DDT has been a critically important tool in eradicating malaria in some areas of the world. Paul Herman Muller discovered the insecticidal properties of DDT in 1939, and won a Nobel Prize in Medicine, for it was an effective and affordable way to manage the public health risks carried by mosquitoes, lice, and other insects. By 1955 DDT had been used to largely eradicate malaria from Western countries, including the U.S. where it was endemic in 26 states. It helped to control typhus, yellow fever and sleeping sickness. In Sri Lanka, malaria cases dropped in 10 years from about 3 million a year to just 29 cases in 1964.
Enter Rachel Carson, whose 1962 book Silent Spring triggered the environmental movement and hysteria about pesticides. Carson had contracted cancer, and came to believe that her cancer was caused by pesticides. Rather than offering her concerns in a measured way, she took an extreme view that chemicals were causing, or would cause, cancers and harm wildlife — producing a bleak world in which “no birds sing” and “one in four” people would likely die from chemically caused cancers. The book became a Book-of the-Month Club selection, and excerpts were published in the New Yorker. Then V.P. Al Gore said in his introduction to the 1994 edition “Without this book, the environmental movement might have been long delayed or never developed at all.” A true statement.
An EPA panel had approved DDT, but EPA Director William Ruckelshaus overruled them and in 1972 the U.S. banned DDT, and most of the rest of the developed world followed suit. In 2001, the Stockholm Convention, a global treaty, banned DDT as part of a “dirty dozen” agricultural chemicals. Carson was wrong about threats to human health, but she never recommended a complete ban. Nevertheless, the damage was done, and the WHO now estimates there are between 300 and 500 million unnecessary cases of malaria a year, again, mostly young children, and mostly in Africa.
With the advent of the Zika Virus, there have been calls to release DDT from the erroneous worldwide ban, but environmentalists are devoted to their religion, not to science. Outrage that anyone should suggest such a drastic step.
Doctors have found the Zika virus in areas of the body that are protected from the immune system, such as the placenta, seminal fluid, and fetal brain tissue. It seems to be in the blood for a very limited period of time. They have found it in the tissue of infants who died from microcephaly, a rare birth defect, which results in a small head and disorder in the brain. They are learning as they go.
Stagnant water, and small amounts of water in pots, discarded hubcaps, provide the ‘ecosystem’ for the development of the virus. The Aedes aegypti mosquito has spread from sub-Saharan Africa to the Americas, Asia, the South Pacific and Australia within the last few hundred years entirely because of human activity.
“The recent development of “gene drive” technology raises theoretical possibility of winning” the war on this invasive mosquito.
Unlike an ordinary gene, which is passed on to just half of all offspring, a gene drive construct could be passed on to virtually all offspring. It can be used to spread genes that destroy female mosquito chromosomes, prevent female mosquitoes from flying, or determine whether a mosquito becomes a male.
By releasing a small number of gene-drive mosquitoes, the number of wild females could be reduced each generation until they disappear completely. Without any females to produce the next generation of eggs, the surviving males would have a very lonely last few weeks until they died out, too, along with the genetic modification that caused their disappearance.
One step at a time. But this time we’re hoping for a complete eradication of a species. The use of DDT would be helpful, but gene drive sounds like a real possibility for getting rid of the yellow fever mosquito for good.
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