Scientists come up with "unique" mosquitoes to fight malaria

US scientists at Johns Hopkins University in Baltimore, Maryland have created a genetically engineered strain of malaria-resistant mosquito that is able to survive better than disease-carrying insects, a unique solution to one of the world's deadliest diseases that has claimed millions of lives.

Scientists believe that such a mosquito, which carries a gene that prevents it being infected by the malaria parasite, could replace malaria-laden mosquitoes and eventually prevent humans being infected with the disease.

In cage experiments, the scientists, led by Dr Mauro Marrelli, allowed equal numbers of GM and ordinary "wild" mosquitoes to feed on malaria-infected mice.

When the insects were fed on malaria-infected mice, the resistant mosquitoes had a higher survival rate than the non-resistant ones, says the report published in Tuesday's issue of Proceedings of the National Academy of Sciences.

As the resistant and nonresistant mosquitoes reproduced, more of the transgenic mosquitoes survived and after nine generations the 70% of the insects belonged to the malaria-resistant strain, triggering the possibility of replacing regular mosquitoes that carry the disease with resistant ones that don't spread disease.

In laboratory work the researchers found that besides having the higher survival rate the genetically-altered mosquitoes comparatively laid more eggs. However, when both groups of insects were fed non-infected blood they competed equally well.

Claiming the unique findings, the scientists wrote in the journal, "To our knowledge, no-one has previously reported a demonstration that transgenic mosquitoes can exhibit a fitness advantage over non-transgenics."

However, they warned the research only shows a human malaria-resistant mosquito is practical, but needs more testing.

"This was proof of principle," Jason Rasgon of the department of molecular microbiology and immunology at Johns Hopkins University said in a telephone interview. "The next step would be to work in a system more epidemiologically relevant" but still in the lab.

Genetically modified mosquitoes that interfered with development of the malaria parasite would inhibit the organism to become re-established after it had been uprooted from a target area, scientists said.

Calling the recent findings less significancant, William C. Black IV, a professor of entomology at Colorado State University, said instead of P. falciparum, which causes malaria in humans the work was done with Plasmodium berghei, which infects mice.

Although, P. berghei is often used in laboratory work as it is easy to manipulate, but many of its properties are specific to that of parasite and it is not always a good model for the human form, Black said. If the researchers can repeat the work using the human type of malaria then there is a chance of taking it into the field, he added.

"On the other hand, finding a gene that confers resistance and is stable for a long period of time is significant," said Black, who was not part of the research team.

Malaria, spread by the single-celled parasite Plasmodium, engulfs an estimated 700,000 to 2.7 million lives each year around the world, 75 percent of them African children, according to the federal Centers for Disease Control and Prevention. The disease is endemic in parts of Asia, Africa, and central and South America. In sub-Saharan Africa, a child dies of malaria every 30 seconds.