Last month Brainiac ran a short piece on how public health workers in Brazil are releasing genetically modified mosquitoes into the wild to combat dengue fever. It’s an extreme step, brought about by necessity: In the fight against infectious diseases, mosquitoes are an elusive foe, and a new report in Nature details the surprising, even bizarre, strategies researchers use to try and track them down.
As writer Emily Sohn reports, malaria researchers in the African Sahel region, which includes Senegal and Sudan, are still baffled by a fundamental question: Where do mosquitoes go when it’s dry? The dry season in that part of the world lasts up to eight months and during that time surface water completely disappears, as do the mosquitoes. But then the rain resumes and within three days, the mosquito hordes are back.
This quick return is especially hard to figure because it takes mosquitos at least eight days to go from eggs to adulthood. The timing has led researchers to believe that mature mosquitoes may go dormant, and hide out in these African villages through the long dry season. (This is no easy feat—eight months in mosquito time is equivalent to 700 years of human time.)
If public health workers could find these hiding spots, they could snuff out the mosquitoes in their sleep—but that’s proven to be hard so far. For decades, public health workers have placed nets over suspected mosquito hiding spots, like animal burrows, barns, and tree trunks, waiting for them to emerge, but they rarely end up catching any.
One new strategy is to use German shepherds to track them back to their lairs. Tovi Lehmann, an entomologist who studies malaria at the National Institute of Health, had heard that dogs could sniff out bedbugs, and thought why not mosquitoes, too? He soaked tiny bits of string in vetiver oil, a perfume ingredient, attached the strings to the underbellies of mosquitoes, and worked with a trainer to teach German shepherds to go after them. The dogs got very good at following the scent, but so far, they’ve haven’t found any hideouts. One factor working for the mosquitoes is that it’s hot in this part of the world, and dogs can’t pant and sniff at the same time.
Researchers are considering other tracking tactics, like attaching radio transmitters to mosquitoes. They’re establishing air defenses, too, launching gigantic helium balloons hung with traps, to snag migrating mosquitoes—though it’s unclear if mosquitoes actually migrate. Malaria is serious business, of course, but there’s also something amusing about this slow boiling cat-and-mouse game. The search might seem hopeless, except for one fact, which must encourage defeated researchers: The mosquitoes have to be hiding somewhere, right?
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Leon Neyfakh is the staff writer for Ideas. Amanda Katz is the deputy Ideas editor. Stephen Heuser is the Ideas editor.
Guest blogger Simon Waxman is Managing Editor of Boston Review and has written for WBUR, Alternet, McSweeney's, Jacobin, and others.
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Guest blogger Joshua Glenn is a Boston-based writer, publisher, and freelance semiotician. He was the original Brainiac blogger, and is currently editor of the blog HiLobrow, publisher of a series of Radium Age science fiction novels, and co-author/co-editor of several books, including the story collection "Significant Objects" and the kids' field guide to life "Unbored."
Guest blogger Ruth Graham is a freelance journalist in New Hampshire, and a frequent Ideas contributor. She is a former features editor for the New York Sun, and has written for publications including Slate and the Wall Street Journal.
Joshua Rothman is a graduate student and Teaching Fellow in the Harvard English department, and an Instructor in Public Policy at the Harvard Kennedy School of Government. He teaches novels and political writing.