This study published in the Journal of Science showed that parasite struggled to survive in infected mosquitoes.
Wolbachia naturally infect insects from butterflies to cockroaches — but not mosquitoes. A team led by Zhiyong Xi of Michigan State University in East Lansing injected Wolbachia bacteria into thousands of embryos of the mosquito Anopheles stephensi, one female caught a lingering case and started a laboratory line of infected offspring. The mosquito mothers have passed the infection down to 34 generations of offspring, the researchers report in the May 10Science. The lineage carries less than one-third as many malaria parasites as uninfected mosquitoes do.
“It’s a very important study because they’re the first group to show that Wolbachia can establish a stable heritable infection,” says mosquito geneticist Jason L. Rasgon of Pennsylvania State University in University Park. Independent of Xi, Rasgon has been trying to coax Wolbachia bacteria into another malaria-carrying Anopheles mosquito for about eight years.
The newly infected stephensi line is still in a proof-of-principle stage, Xi says. But there’s still a long way to go before the bacteria-infected mosquitoes are even tested in the field.
Before declaring Wolbachia-infected mosquitoes ready for release, he would have to see how they would block pathogens and compete for mates in the wild.
A. stephensi is one of the major mosquito menaces in India and South Asia; some 50 to 70 mosquito species worldwide carry malaria parasites that infect people.
Struggle to Spread
BBC Science reporter James Gallagher reported that, Prof David Conway, of the London School of Hygiene & Tropical Medicine, said: “It is interesting and is the first report of Wolbachia clearly replicating, but a number of things took away the punch.”
He said the infected females produced fewer eggs than uninfected females, which meant the infection would struggle to spread in the real world.
Also he cautioned that it was in just one species, Anopheles stephensi, which carries malaria in the Middle East and South Asia. Anopheles gambiae, in Africa, is a bigger problem.