Modified mosquitoes may halt spread of malaria: study

Mosquitoes infected with a type of bacteria may be used to stop the spread of malaria as they show signs of resistance to the parasite that causes the disease, according to a new study published online in the U.S. journal Science.

The mosquitoes infected with the bacterium called Wolbachia, which is naturally found in up to 70 percent of insects, also have the ability to pass the bacterium to their offsprings, researchers from U.S. Michigan State University (MSU) and China's Sun Yat-Sen University reported Thursday.

"In a sense, Wolbachia acts as a vaccine of sorts for mosquitoes that could protect them from malaria parasites," said Zhiyong Xi, MSU assistant professor of microbiology and molecular genetics who leads the study. "Our study shows that in the future it's possible the entire mosquito population will lose the ability to transmit malaria to humans."

In their study, the researchers focused on Anopheles stephensi mosquitoes, the primary malaria carrier in the Middle East and South Asia, and found the key to the malaria research was identifying the correct species of Wolbachia -- wAlbB -- and then injecting it into mosquito embryos.

Out of the thousands of embryos injected by the researchers, one developed into a female that carried Wolbachia, they said. The mosquito line derived from this female has maintained Wolbachia wAlbB infection with a 100 percent infection frequency through 34 generations, at which time the study ended.

The team then introduced various ratios of Wolbachia-infected females into a noninfected mosquito population. In each case, the entire population carried the bacteria in eight generations or less.

"Wolbachia-based malaria control strategy has been discussed for the last two decades," said Xi. "Our work is the first to demonstrate Wolbachia can be stably established in a key malaria vector, the mosquito species Anopheles stephensi, which opens the door to use Wolbachia for malaria control."

Xi described the Wolbachia-based strategy as a cost-effective way to fight malaria, a disease that in 2010 affected 219 million people and caused an estimated 660,000 deaths.

Once Wolbachia has been released into a mosquito population, it is quite possible that it won't need to be reapplied, making it more economical than other methods like pesticide or human vaccine. This adds special value to the feasibility of this control strategy, considering most of the malaria endemic areas are suffering from poverty, Xi said.