What’s the News: Biochemists at the University of Arizona have found a promising new way to fight disease-carrying mosquitoes. In their research project, published in the journal PNAS, the scientists blocked mosquitoes’ ability to digest blood, making blood-sucking deadly to the winged pests. This technique could someday be used alongside other strategies to battle mosquitoes, like repellents and traps.

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As the number of bacteria in mosquitoes’ guts (x axis) went up,
the malaria parasite levels dropped faster than a cartoon anvil.

What’s the News: We know the bacteria living in our guts are important to our health—but the bacteria in mosquitoes’ guts could be too. Researchers have discovered a species of mosquito gut bacteria that destroys the malaria parasite, keeping the disease from spreading to humans. This explains why some Anopheles mosquitoes (the only genus that transmits malaria) don’t spread it, and it spurs the imagination towards possible ways of tamping down the disease.

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What’s the News: Forget masking our scent or making us taste bad—sensory overload might be our most potent tool in repelling mosquitoes. And we might someday have a repellent for the job: Scientists have just discovered a molecule that zaps all of a mosquito’s odor receptors at once, overwhelming it. The molecule’s not ready to be deployed yet, but early tests indicate it could be thousands of times more effective than DEET.

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What’s the News: When mosquitoes finish a piping-hot meal of blood, they have more than your average postprandial snooze, biologists have found: they go into heat shock, producing proteins most organisms only make when something is terribly wrong.

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Selfish genes could help destroy mosquitoes’ ability to carry malaria.

What’s the News: Many scientists have played with the idea of creating a genetically modified mosquito that won’t transmit malaria, which kills about 850,000 people a year, and releasing it into the wild. But in the face of the millions of mosquitoes out there that do ferry malaria around, how would the trait spread fast enough to make a difference?

Now, scientists have developed a way to cause a “selfish” gene to spread to more than half of a mosquito population over just a few generations, suggesting a method to quickly and broadly disrupt genes required for carrying malaria.

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Swarms of genetically modified mosquitoes? This isn’t science fiction: The Malaysian government announced earlier this week that it unleashed 6,000 genetically modified (GM) skeeters into a forest as part of a plan to fight dengue fever, a potentially fatal affliction that can affect up to 100 million people each year.

The news appears to have caught the Malaysian media and public by surprise; many recent news stories reported that the study had been postponed after intense protests. As recently as 17 January, the Consumers’ Association of Penang and Sahabat Alam Malaysia, two groups opposing the use of GM insects, called on the National Biosafety Board to revoke its approval for the study. Scientists, too, were under the impression that the work had yet to begin, says medical entomologist Bart Knols of the University of Amsterdam. A 24 January blog post by Mark Benedict, a consultant at the Centers for Disease Control and Prevention in Atlanta who monitors the field closely, mentioned that the Malaysian study was “planned.” [ScienceNOW]

The study itself included the release of 12,000 male mosquitoes in total: 6,000 unaltered and 6,000 GM Aedes aegypti mosquitoes. The goal was to track how well the two types survived and how far they spread. U.K. biotech firm Oxitec created the modified mosquitoes, which don’t produce viable offspring. Researchers hope that if these altered males mate with wild females, it will bring the overall mosquito population down. The strategy has been tried once before in the Grand Cayman Islands, and results from that experiment are due to be published soon.

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Researchers from the Imperial College London have a new strategy to combat malaria. The species of mosquito responsible for the spread of malaria in Africa, Anopheles gambiae, only mates once during its life. Putting a stop to their one shot at reproduction should slow down malaria transmission. Anopheles males deploy a glob of proteins and fluids known as a “mating plug” that is essential for ensuring sperm is correctly retained in the female’s sperm storage organ, from where she can fertilise eggs over the course of her lifetime [BBC News]. Without a mating plug, the sperm is not stored and the mosquitoes can’t reproduce. Simply put, the researchers want to prevent male mosquitoes from plugging in the wild.

Anopheles gambiae is the only known species of mosquito to use a mating plug. (However, mating plugs are found in other animals where they prevent multiple males from reproducing with a female. Plug checking mice in research laboratories is a right of passage for many graduate students.) In their research, written up in the journal PLoS Biology, scientists were able to alter the mosquitoes’ genes so that they could no longer form a plug, and thus were unable to reproduce. If this process could be developed for use in the field, perhaps in a spray form like an insecticide, it could “effectively induce sterility in female mosquitoes in the wild,” [study author Flaminia] Catteruccia wrote, offering potential as “one more weapon in the arsenal against malaria” [Reuters]. The WHO is optimistic that their increased funding efforts will produce more technologies similar to this one and that, hopefully, one of them will prove effective.

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Amidst concerns over the safety of DEET, scientists are on the lookout for a new mosquito repellent. Now they may have found a way to keep biting insects at bay–by blocking their olfactory sense, according to a paper published in Nature.

Mosquitoes sense the presence of humans and animals by detecting the carbon dioxide we exhale with each breath. Researchers have found two compounds, 2,3-butanedione and 1-hexanol, that could keep the biters at bay by blocking the insects’ ability to detect this gas. Using these compounds could be advantageous because the amount of chemical required is relatively small…. Further, the chemicals themselves are not complicated to manufacture and are available through conventional sources. “From both perspectives, this adds up to a viable tool in tackling the problems like that of malaria in Africa” [Scientific American], says study coauthor Anandasankar Ray. Considering the number of diseases spread by insects such as mosquitoes–for example, 250 million people contract malaria each year–there’s a lot more at stake here than a few itchy bug bites.

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Mosquitoes that have made their way to the Galapagos Islands via tourist planes and boats are threatening the rare native species endemic to the region, according to a study published in the journal Proceedings of the Royal Society B.

Culex quinquefasciatus, known as the southern house mosquito, can carry diseases dangerous to wildlife, such as avian pox and West Nile virus. Not only have the insects hopped a ride onto the islands, but they’ve also bred with native species once they reach the shore, the study found. That means they pose an ongoing threat to the Galapagos’ rare species and delicate ecosystem, which inspired Darwin’s theory of evolution after he observed the island’s unique array of wildlife. “You only need a single infectious mosquito to initiate a disease cycle,” [co-author Simon] Goodman…[T]he Galapagos “have globally important biodiversity — endemic species found nowhere else in the world,” said Goodman [Telegraph].

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Powerful bug repellant DEET may do more than keep mosquitoes and other biting critters at bay–it might cause neurological damage in mammals, according to a study published in BioMed Central Biology.

Developed in 1946 by the U.S. Army, DEET has been used by the public for more than half a century to repel bugs like mosquitoes, along with the diseases they can carry. The new study, however, shows that DEET—aka N,N-diethyl-meta-toluamide—may be harmful for a variety of animal cells. In lab tests, it caused damage to mosquitoes, cockroach nerves, mouse muscles, and enzymes purified from fruit flies and humans. Applications of DEET slowed or halted the actions of the enzyme acetylcholinesterase. This enzyme hangs out between nerve and muscle cells, breaking down a messenger molecule after it has passed information from one cell to another. If this messenger isn’t properly recycled, it can build up and lead to paralysis [Science News].

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The mighty tortoises that roam the Galapagos Islands may not have many predators, but a new study suggests that the giant reptiles could run into serious problems due to the diminutive black salt marsh mosquito. Researchers genetically analyzed the mosquito, and found that it was not introduced recently by humans but instead arrived about 200,000 years ago. Since then the insect has evolved so much it is practically a distinct species from the mainland variety. For one thing, the insect has adapted to be able to feast on the blood of lizards, tortoises and other reptiles and not solely on mammals, as it does on the mainland [The New York Times].

That diversity of diet is what has researchers worried. If the black salt marsh mosquito picks up a disease like avian malaria or West Nile fever, it could quickly spread the disease to the Galapagos’s rare tortoises and marine iguanas. Says study coauthor Andrew Cunningham: “With tourism growing so rapidly the chance of a disease-carrying mosquito hitching a ride from the mainland on a plane is also increasing, since the number of flights grows in line with visitor numbers…. If a new disease arrives via this route, the fear is that Galapagos’ own mosquitoes would pick it up and spread it throughout the archipelago” [Telegraph].

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The U.S. Food and Drug Administration has approved human trials of a new malaria vaccine: it is made from a weakened form of the entire malaria-causing parasite, Plasmodium falciparum, extracted from irradiated mosquito spit. Sanaria, the company producing the vaccine, has been working with a particular stage of the P. falciparum parasite called a sporozoite. This is the stage when it leaves the mosquito’s salivary glands to enter the human bloodstream [Reuters].

To produce the vaccine, Sanaria weakens the parasite by feeding human, infected blood to mosquitoes, then [exposes] the mosquitoes to enough irradiation to cripple the parasite [New Scientist]. The mosquitoes are then killed and their saliva is extracted by hand, with each of six laboratory workers averaging a rate of 100 mosquitoes per hour. With every mosquito containing about two doses in its spit, Sanaria founder Stephen Hoffman estimates that about 1,200 doses are produced per hour.

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A mosquito‘s whiny buzz may be one of the most annoying noises to human ears, but for some mosquitoes it’s an intricate love song. A new study of the mosquito Aedes aegypti, which carries the infectious diseases dengue fever and yellow fever, has shown that when males and females mate they adjust the speed of their beating wings until their two buzzes combine to produce a harmonious tone. And this isn’t just gee-whiz science: Researchers say the finding could help in the fight against the disease-carrying insects.

The male mosquito’s buzz, or flight tone, is normally about 600 cycles per second, or 600-Hz. The female’s tone is about 400-Hz. In music, he’s roughly a D, and she’s about a G. So the male brings his tone into phase with the female’s to create a near-perfect duet. Together, the two tones create what musicians call an overtone — a third, fainter tone at 1200-Hz. Only then will the mosquitoes mate [NPR]. Researchers were surprised that the mosquitoes could detect the overtone, because they previously believed that A. aegypi males couldn’t hear frequencies above 800-Hz, and the females were thought to be completely deaf.

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To combat the persistent scourge of dengue fever, researchers have infected the virus-carrying mosquitoes with a bacterium that kills them before they’re old enough to transmit the virus to humans. Researchers say this “biopesticide” technique could cheaply and quickly reduce deaths due to dengue fever in the tropics, as the bacterium could rapidly spread through mosquito populations. Traditional [malaria-oriented] methods for controlling the spread of mosquito-borne disease, such as using bed nets and draining wetlands, are ineffective for the Aedes aegytpi mosquitoes that spread dengue fever virus because they bite during the day and thrive in urban areas [Nature News].

While the new process has only been tested in the lab thus far, researchers are very optimistic about the possibility of whittling away at the 20,000 deaths caused each year by the disease, and say it’s conceivable that transmission of the virus could be reduced to nearly zero. “We’re not trying to eliminate the population, but to let a bacterial symbiont in, and then shift the population,” said University of Queensland bacterial geneticist Scott O’Neill. “There will still be mosquitoes around, but only young ones. It’s a biological control” [Wired News].

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Firing new shots in the malaria war, a vaccine still in the testing stage is now a step closer to becoming a public health reality [Science News]. Two field trials in Kenya and Tanzania showed that the experimental drug reduced malaria infections by more than 50 percent in infants and young children; if a final set of trials proves that the vaccine is indeed safe and effective, the vaccine could be ready for use by 2011.

If the phase three trials are successful, it would be “an extraordinary scientific triumph,” said Dr. W. Ripley Ballou, deputy director for vaccines and infectious diseases for the Bill and Melinda Gates Foundation, which helped fund the research. But more importantly,” Ballou added, “it could save millions of children’s lives” [Los Angeles Times]. Malaria kills about 1 million people around the world each year, and most of the victims are children under the age of five.

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