Certain Bacteria Render Mosquitoes Resistant to Deadly Malaria Parasite
According to the World Health Organization, an estimated 225 million malaria cases occur worldwide annually, resulting in about 781,000 deaths. Although the disease is present in 106 countries, most cases occur in sub-Saharan Africa. Insect repellent and bed nets can help prevent transmission of the malaria parasite from mosquitoes to humans, but to control malaria one step earlier, some studies are looking to eliminate infection within the mosquito itself. Normally, when a malaria parasite infects a mosquito, it travels to the insect’s gut, where its chances for survival are slim because the mosquito’s immune system, digestive enzymes and resident bacteria create a hostile environment.
According to an article published on May 13 in the journal Science (DOI: 10.1126/science.1201618 2011), a class of naturally occurring bacteria that can strongly inhibit malaria-causing parasites in Anopheles mosquitoes has been identified. In this new study, it was found that among the various types of bacteria in the mosquito gut, Enterobacter – a type of bacteria that occurs in some but not all mosquitoes – effectively blocked infection with the malaria-causing parasite Plasmodium falciparum by 98 to 99%. The finding may have implications for efforts to control malaria. The research was partly funded by the National Institute of Allergy and Infectious Diseases (NIAID), a component of the National Institutes of Health.
By observing the interaction between the bacteria and the parasite, the study determined that Enterobacter inhibits parasite growth by producing short-lived molecules known as reactive oxygen species (ROS). Although ROS travel through body fluids in the mosquito, they do not need to be in a mosquito to inhibit parasites. Future research plans include sequencing the Enterobacter genome to better understand how it produces malaria-inhibiting ROS and studying other bacteria that reside in the mosquito gut to learn whether they have similar effects.
The authors hope to apply their findings to the field, where they would first modify Enterobacter for use in mosquitoes. The next step would be to strategically place the bacteria in the mosquitoes’ natural environment, such as in their sugar food sources or breeding sites. Although these strategies have not yet been tested in malaria prevention, sugar baits have been used successfully to expose mosquitoes to toxins.