Fight against Malaria Gets Harder as Mosquitoes Evolve

Regular readers of this journal will know that containing and combating malaria is an in-house passion. Each year, 500 million people get infected, two million or so die, and the disease kills one in five African children. A parasite that lives in mosquitoes causes the disease, entering the human blood stream when the female mosquito feeds -- it does not go from person to person directly. New studies show that Africa's most dangerous type of malaria-carrying mosquito, Anopheles gambiae, appears to have split into two genetically unique strains, on their way to becoming distinct species. That means that they are becoming harder to control.

Mara Lawniczak of Imperial College London is the lead author of a new study published in the journal Science. She told the Independent, "From our new studies, we can see that mosquitoes are evolving more quickly than we thought and that unfortunately strategies that might work against one strain of mosquito might not be effective against another." She added, "This Anopheles mosquito has always been thought of as one species and even though we knew they were diversifying and hybridising we didn't think it had got this far along the path to become two distinct species. You really cannot tell by looking at them that they are so different genetically. Yet we have to know that any efforts directed at controlling mosquitoes will work in all the different groups that transmit malaria."

While biologists have yet to declare them different species (a rather arbitrary distinction in any case), the two strains (one called "S" and the other "M") have unique genomes. Previously, biologists thought differences wold appear only in certain areas of the chromosome. This latest research shows differences across the genome. These differences will have an effect on how humans contain the mosquitoes.

For example, the "M" strain is concentrated in west and central Africa and seems better adapted to laying its eggs in rice paddies than the "S" strain, which is found all across the continent (and therefore, is thought to be the ancestral strain). This means that any strategy that works in eastern Africa away from rice paddies against strain "S" must be adapted, if it can be, to dealing with the "M" strain in western Africa near rice paddies. One recent idea has been to release sterile mosquitoes into the environment so that when "wild" mosquitoes mate with them, there is no offspring. This will not work as effectively if the various strains are not attracted to one another.

In the end, this is just a case of human technology trying to outrun the evolution of other species. The rise in the resistance of various bacteria to antibiotics is another. As humans implement strategies to combat the mosquito, the mosquito changes. That is evolution in action; creationism and intelligent design offer no such explanation for this phenomenon. Yet, American schools pretend for political reasons that evolution remains unproven.

As usual, this journal closes its occasional diatribe on malaria with an appeal to readers. For US$10, Nothing But Nets can get an anti-mosquito bed net to an African family, most of whom life on just US$1 a day. As the charity explains, "Bed nets use a simple but effective prevention approach: eliminate contact with mosquitoes, eliminate malaria." So far, neither mosquito strain can get through a net.

© Copyright 2010 by The Kensington Review, Jeff Myhre, PhD, Editor. No part of this publication may be reproduced without written consent. Produced using Ubuntu Linux.

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