Using genetically modified fungi to infect mosquitoes that harbour malaria parasites could be an effective way to control the spread of malaria, researchers said.
Scientists from Britain and the United States inserted the genes of human antibodies or scorpion toxins into a fungus called Metarhizium anisopliae that infects mosquitoes. They found that certain of these combinations were able to stop the development of malaria-causing parasites in the mosquitoes.
Writing in the journal Science, the researchers said the approach could become an environmentally friendly way of fighting malaria, and might also be used to control other insect- or bug-borne diseases such as dengue fever or Lyme disease.
"Though applied here to combat malaria, our transgenic fungal approach is very flexible and allows design and delivery of gene products targeted to almost any disease-carrying arthropod," said Raymond St. Leger, a professor of entomology at the University of Maryland, who led the study.
240 million malaria cases each year
Infection by malaria-causing parasites results in around 240 million cases of the disease around the world every year and kills more than 850,000 people, many of them children, according to the World Health Organisation.
Most malaria cases are in sub-Saharan Africa, but the disease affects people in more than 100 countries worldwide.
Treating mosquito nets and houses with insecticides is one of the major prevention strategies, but mosquitoes can develop resistance to insecticides, making them ineffective.
'No permanent fix'
"Mosquitoes have an incredible ability to evolve and adapt, so there may be no permanent fix," said St. Leger.
But he added that the results of this study suggest that spraying malaria-transmitting mosquitoes with the genetically-modified fungus could dramatically reduce transmission of the disease to humans and provide an effective biopesticide for some decades.
St. Leger and a team from the Johns Hopkins School of Public Health in the United States and Britain's University of Westminster created their transgenic fungus by starting with Metarhizium anisopliae and then inserting genes into it for a human antibody or a scorpion toxin.
Both the antibody and the toxin specifically target the malaria-causing parasite, P. falciparum, they explained.
The team then compared three groups of mosquitoes that had all been heavily infected with malaria parasites and found that, compared to the other treatments, spraying mosquitoes with the transgenic fungus significantly reduced parasite development.
The malaria parasite was found in the salivary glands of 25% of the mosquitoes sprayed with the transgenic fungus, compared to 87% of those sprayed with an unmodified strain of the fungus, and to 94% of those that were not sprayed at all.
"Now that we've demonstrated the effectiveness of this approach ... our principal aim is to get this technology into field-testing in Africa as soon as possible," St. Leger said. - (Kate Kelland/Reuters Health, February 2011)