A mosquito is smaller than a paperclip, but it can potentially take down a human with just a bite. Recently, a scientist has found a strain of bacteria that, if ingested by a mosquito, may kill it as well as prevent it from passing on two serious diseases, malaria and dengue. Although this research is still in its infancy, it could someday be used to end the threat of malaria.
The bite of an infected mosquito can transmit either malaria or dengue fever. Mosquitoes are home to a parasite from the genus Plasmodium that can pass on malaria, which causes symptoms such as fevers, vomiting and headaches. A mosquito-borne virus called the dengue virus causes dengue fever. The symptoms of dengue are joint and muscle pain, skin rashes and headaches. Combined, there were about 319 million cases of these diseases in 2010 alone.
So far, scientists have focused on decreasing mosquito populations as the most effective way to fight these illnesses, since there are no vaccines and few effective treatments. Current control methods include spraying with DDT and using bed nets.
George Dimopoulos, a microbiologist and immunologist at the Bloomberg School of Public Health, is interested in a different area of research. Dimopoulos and his fellow researchers believe that if they can interrupt the interaction between the mosquito and the parasite or virus, the mosquito would be unable to pass on the disease to a human.
The researchers found that if they fed antibiotics to a mosquito, the mosquito could be infected with more pathogens than mosquitoes not fed antibiotics. This implies that the bacteria in the mosquitoes’ guts are acting against these organisms.
“This finding prompted us to go out in the field and start studying,” Dimopoulos said.
He decided to see if any bacteria naturally found in the mosquito gut could block transmission of the malaria parasite or dengue virus.
The researchers flew around the world to catch mosquitoes, from Panama to Zambia to Puerto Rico. They used a human-landing catch, which means that a human being was used as bait, and when a mosquito landed on him, it was snatched up before it could bite. This way, they were able to catch the mosquitoes that actually feed on humans.
Once they had their mosquitoes, the scientists dissected their guts and identified the bacteria living inside. The researchers fed these bacteria to mosquitoes and then infected them with malaria and dengue. Several different strains of bacteria inhibited the malaria parasite and dengue virus. However, one strain, Chromobacterium, stood out. Chromobacterium not only prevents mosquitoes from getting malaria and dengue, but it also shortens the life spans of the mosquitoes in which it resides.
Although Dimopoulos believes that they are at least ten years away from turning his research into a viable way to control malaria, he has a plan for how it could be utilized. Scientists in Israel have come up with a device called a honey trap, basically a bird feeder for mosquitoes. It can be loaded with Chromobacterium-laced nectar that mosquitoes will snack on. Once the mosquitoes are infected with Chromobacterium, the idea is that they either won’t live long enough to infect anyone, or the bacteria will prevent them from passing on the parasite. The scientists also isolated the chemical that makes this bacterium so effective, and they hope to use it to develop a treatment for malaria and dengue.
Dimopoulos acknowledges some criticisms of his work. He has not yet done enough research to know if mosquitoes will become resistant to Chromobacterium over time. Also, introducing Chromobacterium to the environment would expose humans to it, and no one yet knows the extent of this safety concern. Despite these obstacles, investors are intrigued by Dimopoulos’s discoveries.
“There are already some entrepreneurs that are knocking at our door,” Dimopoulos said.
His long-term goal is to use not just one but a combination of different bacteria to combat malaria and dengue. These bacteria would be utilized in conjunction with other vector-control methods, since malaria cannot be eradicated by just one strategy.
“It’s like a war: You have to have all types of weapons to win it,” Dimopoulos said.
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