Monday, July 19, 2010
In a lab, scientists are not building a better mouse-trap, but a better mosquito.
mosquito's transmit malaria, which affects approximately 250 million people worldwide, and kills around one million per year. And the battle to eliminate the disease, caused by the Plasmodium
parasite, is a costly one. The parasite can rapidly become resistant to the drugs used against it, and that has been the main way to combat the terrible disease.
But, scientists at University at Arizona have decided to go a different route – by creating a genetically modified mosquito (GMM) that is completely immune to the parasite. The experiment was conducted on one particular mosquito species, Anopheles stephensi
, but the researchers say that it could work with all other species that spread the parasite, such as Anopheles gambiae
, in Africa.
While the mosquito would be physically fine, I am sad to say that it will still bite, just not transmit the parasite during the blood-meal.
The previous development of a GMM generated 97 per cent resistance to the malarial parasite, but in science, that is not enough. I mean sure, most of the parasite would be eliminated, but what about that three per cent? With thousands of parasites, the odds (however good) are always stacked against.
According to the lead entomologist on the project, Michael Riehle, anything less than complete immunity would be a waste. He told the Globe and Mail that, "if even one parasite makes it through, it will produce thousands of parasites ... and that mosquito can transmit malaria."
In the diagram above, you can see how the parasite infects the mosquito, how it is transmitted to humans where it causes malaria, and what type of vaccines could be used in each specific stage of the parasite's life cycle. So, how do Dr. Riehle and his team create a mosquito immune to the parasite? It's simple – by using genetics.
The researchers inject a piece of code into mosquito eggs, and it inserts itself directly into the mosquito's genome and turns the production of a signaling molecule, known as Akt, on. The overproduction of Akt affects many aspects of the mosquito life cycle, including larval development, immune system and lifespan.
Originally, the researchers believed that this would cause the mosquito to die before the parasite had matured, but there was an interesting side effect. All the parasites were completely killed off within the mosquito.
However, the precise mechanism of action is still a mystery, according to Dr. Riehle.
"It might be affecting immunity. Or it might just be making it a more hostile environment for the parasite to pass through. We just don't know at this point."
This is only the first step to create a long-term solution against malaria, but it is a promising one. Still, there are many steps that the scientists and researchers need to do now in order to make sure that the mosquito's maintain their immunity to the parasite.
And then, the scientists would have to give the genetically modified animals a competitive advantage in the wild in order to make sure that they out compete the wild mosquito's, such as any animal without the code would die off.
There are many more difficulties in completing this venture, but it's a start.