Glow In The Dark GM Mosquitoes Prevent Spread Of Malaria

Featured Article
Main Category: Tropical Diseases
Also Included In: Infectious Diseases / Bacteria / Viruses;  Blood / Hematology;  Veterinary
Article Date: 20 Mar 2007 - 6:00 PDT

email to a friend   printer friendly   view / write opinions   rate article

US scientists have genetically engineered mosquitoes with eyes that glow in the dark and do not carry malaria that have a better survival rate than their wild counterparts.

The study is published in this week's early online edition of the journal Proceedings of the National Academy of Sciences.

The scientists, led by Dr Mauro Marrelli from Johns Hopkins University in Baltimore, Maryland, suggest that the transgenic malaria-resistant mosquito could one day be introduced into the wild where it would outbreed natural mosquitoes and reduce the spread of malaria.

Malaria is an infectious disease caused by a single-celled protozoan parasite called Plasmodium of which there are ten species that infect humans. The parasite needs two hosts to complete its life-cycle: female Anopholes mosquitoes, and the bloodstream of a vertebrate where it invades and damages red blood cells.

Female mosquitoes feed on blood to get the extra protein they need during their egg-laying phase, and thereby transmit Plasmodium from infected vertebrates to non-infected vertebrates.

Dr Marrelli and colleagues had already shown in previous experiments that transgenic anopheline mosquitoes would not pick up the Plasmodium (in this case, they used the species P. berghei) when fed on infected mice.

However, this was the first study where they were able to show that the transgenic mosquitoes had a twofold survival advantage over their nontransgenic siblings. They were more fertile and also enjoyed lower mortality. Again, they demonstrated this using mice as the vertebrate host.

In fact the transgenic mosquitoes eventually replaced non-transgenic ones when fed on infected mice, but when fed on non-infected mice the two mosquito populations remained the same.

In order to identify the transgenic mosquitoes, the researchers inserted an extra gene that made their eyes glow a different colour.

The transgenic mosquitoes were made by activating the SM1 peptide gene in the lumen of their midgut, where the Plasmodium parasite lives during its mosquito -host phase.

Dr Marrelli and his team concluded that "when feeding on Plasmodium-infected blood, transgenic malaria-resistant mosquitoes have a selective advantage over nontransgenic mosquitoes".

They suggest this offers opportunities for "devising malaria control strategies by means of genetic modification of mosquitoes".

Malaria infects over 300 million people worldwide and kills up to 3 million people every year; mostly small children in sub-Saharan Africa.

There is no vaccine and the only current medical way to provide immunity is preventive treatment that is too expensive for many people living in poor communities.

There is a vicious cycle of poverty that prevents poor communities being able to pay for treatment, coupled with endemic malaria that depresses economies in the communities most affected.

Symptoms of malaria infection include feeling light headed, being short of breath and tachycardic, rather like having anemia. Infected people also get general symptoms like fever, nausea, chills, flu-like aches and pains. In very serious cases the result can be coma and death.

"Transgenic malaria-resistant mosquitoes have a fitness advantage when feeding on Plasmodium-infected blood."
Mauro T. Marrelli, Chaoyang Li, Jason L. Rasgon, and Marcelo Jacobs-Lorena.
PNAS, published March 19, 2007, 10.1073/pnas.0609809104

Click here for Abstract.

Click here for Malaria Foundation International.

Written by: Catharine Paddock
Writer: Medical News Today
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today