Researchers have found a strain of bacteria that can infect mosquitoes and make them resistant to the malaria parasite. The study, in the journal Science, showed the parasite struggled to survive in infected mosquitoes. Malaria is spread between people by the insects so it is hoped that giving mosquitoes malaria immunity could reduce human cases. Experts said this was a first, distant prospect for malaria control. Malaria is a major global disease. The World Health Organization estimates that 220 million people are infected annually and 660,000 die. The study at Michigan State University in the US looked at the Wolbachia bacterium, which commonly infects insects. It passes only from females to their offspring. In some insects the bug is exceptionally good at manipulating insects to boost the number of females for its own ends. Wolbachia kills male embryos in some butterflies and ladybirds. In other situations, it can produce males that can breed only with infected females, and even allows some female wasps to give birth without mating. Malaria-carrying Anopheles mosquitoes are not naturally plagued by Wolbachia, yet laboratory studies have shown that temporary infection made the insects immune to the malaria parasite.