containing the invader. A malaria parasite, completing this cell red blood separates into smaller components (four round shapes lined with white walls) before bursting and infect other cells. A new vaccine is based on an antibody that retains
Kurtis J.
For thousands of years, mosquitoes have made people sick. But now, mankind may have found a way to turn the tables. In a new study, researchers report that mosquitoes giving their own infection with a bacterium that strange insects reshuffles sex life can prevent mosquitoes from transmitting malaria.
The advance is hailed by some as a milestone in medical entomology. "I'm quite jealous," says entomologist Scott O'Neill of Monash University in Australia, who has not participated. "We all tried for years and years and years." Mosquito species in question Anopheles stephensi , is a key malaria vector in South Asia and the Middle East, and the study offers the tantalizing possibility rid of entire cities such as New Delhi and Calcutta malaria, says Willem Takken of Wageningen University in the Netherlands, who was also not involved in the work. in the future, the same technique could also work for other malaria-carrying mosquitoes, such as A. gambiae , which predominates in Africa, said Takken.
scientists have long dreamed of replacing populations mosquitoes carry diseases with news that pose no threat to humans because they can not transmit the disease. in the last decade, a bacterium called Wolbachia has emerged as a promising ally in their work. These intracellular bacteria spread from mother insects to their offspring and to play some weird stuff on the sex lives of their hosts. For example, ensuring that infected men can not reproduce with uninfected females, a phenomenon called cytoplasmic incompatibility-bacteria can maximize the number of descendants infected in the next generation and sweep people in very little time.
initial idea of Scientists was to introduce genes conferring resistance to human pathogens in mosquitoes and then enlist Wolbachia to help these traits run through the population. The difficult part is to infect mosquitoes with Wolbachia first; for some reason, they seemed not lend themselves to long-term, stable infection. A landmark came in 05 Science paper in which Xi Zhiyong, then at Johns Hopkins in Baltimore, Maryland, and colleagues infected a species of mosquito called Aedes aegypti which is the main support for dengue fever, a debilitating viral disease that causes severe muscle and joint pain.
A few years later, O'Neill and others have made a surprising discovery: They do not even need to couple with Wolbachia infection resistance genes. The bacterium makes only Ae. aegypti unable to transmit the virus. Others have shown that the same is true for many other viruses and parasites.
It is not known exactly why this is; Wolbachia is a hypothesis that competition for resources with other hackers, such as dengue virus. But that has not stopped scientists from trying to make use of this phenomenon. In 2011, the O'Neill group released Wolbachia infected with Ae. aegypti mosquitoes in Australia, where they found that the infection took and spread. Currently, experiments are underway in Vietnam, where dengue is an important disease.
But dengue is not the biggest killer mosquitoes; it is malaria, which is responsible for the death of over half a million people a year and is transmitted by anopheles mosquitoes, a very different kind. They proved even more difficult to infect with Wolbachia . The quest and frustrating that not a single anopheles species is known to be naturally infected with the bacteria have led some researchers to wonder if it was possible at all, says O'Neill.
But Xi, who now heads his own group at Michigan State University in East Lansing, has done it again. In a new study published online today in Science , researchers have shown they can infect A. stephensi with Wolbachia , the infection is transmitted through at least 34 generations, and it can support entire populations in cages.
The secret? Part of it is luck, Takken said. The team worked with a strain called Wolbachia wAlbB happened to catch this mosquito. Technical skill is another factor, said entomologist Jason Rasgon of Pennsylvania State University, University Park, who was not involved in the work. Injecting mosquito eggs is "very much an art," he said, and Xi "is probably the best person in the world to do so."
The team had to inject thousands of embryos before that they have had success. Xi said part of the trick is to suck a tiny amount of cell cytoplasm of first eggs to make room for the injected bacteria and prevent cells from bursting. despite the number of horrible deaths, Anopheles mosquitoes are delicate creatures, he said.
Xi group also fed infected parasites malaria mosquitoes to test whether Wolbachia could block their life cycle within the body of the mosquito. They showed that Wolbachia infected mosquitoes will not become totally resistant to malaria, as expected. instead, the number of parasites in their saliva 14 days after exposure has decreased by about a factor of 3.4, which means that mosquitoes can still transmit the disease, although perhaps not as effective.
Another key question is whether Wolbachia infected mosquitoes can produce the same number of offspring than uninfected says Takken. If they can not, they will not be able to supplant the wild population and insects would not be flying as a program against malaria. Xi said he plans to publish another article on this issue. Studies are also needed to determine the number of infected mosquitoes should be released into the area to get fast enough results. There could be other Wolbachia strains do the job better, said Rasgon. For now, what is most important is that the researchers have succeeded in the first place, he said. It is inspired because his own group attempts to infect A. gambiae , the main vector of malaria in Africa and a goal even more difficult to infect. "It is very good for me to see that it can actually be done," he said. "We will continue to push forward."
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