Recall the saying “there are a thousand ways to skin a cat”?
Researchers are rephrasing it in regard to the mosquito. Fifty years ago, we thought that the war against malaria was pretty much won.
We had quinine and chloroquine, which were effective against the parasite that causes the disease. And we had invented the molecule dichlorodiphenyltrichloroethane, DDT for short, an effective insecticide that killed mosquitoes that carry the malaria parasite within themselves.
Alas, with their very fast generation time and mutation abilities, the parasites became resistant to the drugs and the mosquitoes, resistant to DDT.
By the turn of the century, malaria has come back with a vengeance, killing a million people each year, most of them children and debilitating hundreds of millions more.
The classical format
And the WHO, under the leadership of Mrs. Gro Harlem Brundtland, started the worldwide Rollback Malaria programme. Programmes of this kind still stick to the ‘classical’ format — namely, a better drug, an effective vaccine, safer yet sure-fire insecticides, public health measures and so forth.
The tools of molecular biology and genetic engineering have been put to use as well. One biologist has tried to generate a collection of ‘sterile’ female mosquitoes in the lab.
The idea is to let them loose, have them mate with the males and produce — nothing. In a few months, the idea goes, it will be the end of mosquitoes in the area.
And since there is no ‘vehicle’ to carry them, the malaria parasite too will have disappeared. You ‘shoot the messenger’ for success!
Alas, this idea has not taken off; on one hand is the scale of the effort and on the other is the ever-present mutation of the mosquito genome.
Enter Bill Gates. After making billions and billions of dollars, doing perhaps the noblest thing ever, not only has the Bill and Melinda Gates Foundation been supporting research towards the elimination of HIV-AIDS through drugs, vaccines and public health measures, but has also turned its attention on malaria, safe water, energy, the environment and other desperate problems that need solutions.
The Foundation is not ‘classical’; it poses ‘Grand Challenges’ and offers grants to researchers around the world to think up ideas that can meet and win over these challenges. And fight against malaria is among the top. Many remarkably new ideas have come about, two of which are discussed here. Both are ideas that existed elsewhere but apply to the context of malaria.
One is the idea of Dr. Brian Foy of Colorado State University. He notes that it takes the malaria parasite almost two weeks to mature inside the mosquito’s body — from the time a mosquito bites an infected person to the time it bites the next person and thus transmits the parasite to the latter.
Carriage time
It is this carriage time between ‘blood meals’ that Dr. Foy wants to focus on. “If only we could make one of those blood meals toxic to the mosquito, you would basically kill it before it could transmit the parasite”, he argues.
In order to do so, Dr. Foy borrowed the idea and the molecule from another debilitating disease, river blindness, caused by a parasitic worm carried by the tsetse fly.
The drug ivermectin is effective in knocking out some vital life processes in the parasite, killing it and thus winning over the disease. Indeed, thanks to the generosity of the Carter Foundation (established by the former U.S. President), river blindness in Africa is pretty much eradicated, thanks to a sustained campaign of free distribution of the drug to all people in the vulnerable regions of Africa.
Foy realized that ivermectin is just as deadly to the mosquito as it is to the river blindness parasite.
His idea is thus to give ivermectin to people, who then pass it along with their blood to the mosquito that bites them. The drug kills the mosquito that is infected with the malaria parasite, and thus stops the transmission of the disease.
Double benefit
Field trials of the idea, done in Senegal in West Africa show that mosquitoes die in about a week after ivermectin was given in an anti-river blindness campaign. The people who were given the drug thus had the double benefit — against river blindness and malaria. Larger campaigns are planned to check its wider effectiveness.
An even more remarkable, almost bizarre, borrow from another field comes from the astrophysicist Jordin Kare, who once fabricated ‘Mocking bird’, an extremely small (75 kg) reusable launch vehicle. He has developed what he calls a photonic mosquito fence.
He puts up a small shelf mounted on a lamp-post or wall, equipped with a cheap camera and a light bulb. The cameras are connected to a central computer.
When the camera detects any movement, the computer checks to see if it matches with the frequency of wing beating of a mosquito (unique numbers for male and females), and a laser beam is activated, zapping the mosquito to ashes!
Former U.S. President Ronald Reagan wanted “Star Wars” laser burners to knock off Soviet missiles. Dr. Kare’s is a ‘micro” and “softer” version, and against the lowly but deadly mosquito. Different strokes for different folks.
© 2009 The Hindu