Mutated Mosquitoes Put Bite on Malaria, Researchers Say

May 23, 2002
Agence France-Presse

Paris - Gene engineers say they can deliver a stunning blow to malaria by modifying mosquitoes so that they no longer pass on the parasite that causes the disease.

The transgenic insects can "add a new weapon to the arsenal" of drugs and insecticides against a disease estimated to kill up to 2.7 million people a year, say a team led by Marcelo Jacobs-Lorena at Case Western Reserve University in the US state of Ohio.

The technique attacks the microscopic parasite Plasmodium at one of the key points in its complex cycle.
Mosquitoes pick up the embryonic parasite by sucking up blood, its food, from an infected human. The parasite then lodges in the mosquito's gut, where it develops into thousands of worm-like creatures called sporozoites.

These then emerge into the mosquito's saliva glands; when the insect feeds again, it spits them out, thus infecting the next person.

The Jacobs-Lorena team created a strain of mosquitoes that carry a gene that controls a peptide a short chain of amino acid that prevents the sporozoites from moving from the gut to the saliva glands, thus blocking off the transmission phase of the cycle.

Genetically modified mosquitoes that had fed on infected mice were at least 80 percent less effective at spreading the parasite than their unmodified cousins.

The amino acid gene is inserted in the "germ line" of the mosquitoes, which means that it is handed on to ensuing generations through reproduction and does not merely die out with the insects that have been modified.

That opens up the exciting prospect that mosquitoes could eventually be reduced to the level of a harmless pest rather than a vector that blights populations in tropical countries.

The research, published today in the British journal Nature, has several hurdles to overcome.
It must be tested on the human form of malaria rather than the mice type, and on strains of mosquitoes that exist in the wild rather than those that were bred in laboratories.

Also unclear is the environmental impact of releasing these genes into nature.

"This is a proof of principle and as such is a milestone in malaria research," comment Gareth Lycett and Fotis Kafatos of the European Molecular Biology Laboratory in Heidelberg, Germany.

"Molecular biologists who study mosquitoes fully appreciate the length of the road ahead...the new work is exciting, nonetheless, and represents a new era of malaria-related research."