 |
|
Groundbreaking research shows DEET's not sweet to mosquitoes
August 19, 2008Spray yourself with a DEET-based insect repellent and the mosquitoes will leave you alone. But why? They flee because of their intense dislike for the smell of the chemical repellent and not because DEET jams their sense of smell, report researchers at the University of California, Davis.
Their groundbreaking findings will be published Monday, Aug. 18, in the Proceedings of the National Academy of Sciences (PNAS).
"We found that mosquitoes can smell DEET and they stay away from it," said noted chemical ecologist Walter Leal, professor of entomology at UC Davis. "DEET doesn't mask the smell of the host or jam the insect's senses. Mosquitoes don't like it because it smells bad to them."
DEET, the common name for N,N-diethyl-3-methylbenzamide, is the most common active ingredient in insect repellents. Developed by scientists at the U.S. Department of Agriculture and patented by the U.S. Army in 1946, DEET is considered the "gold standard" of insect repellents. Worldwide, more than 200 million people use DEET to ward off vectorborne diseases.
But DEET's mode of action or how it works has puzzled scientists for more than 50 years. Scientists long surmised that DEET masks the smell of the host, or jams or corrupts the insect's senses, interfering with its ability to locate a host. Mosquitoes and other blood-feeding insects find their hosts by body heat, skin odors, carbon dioxide (breath), or visual stimuli. Females need a blood meal to develop their eggs.
Leal said previous findings of other scientists showed a "false positive" resulting from the experimental design.
Entomologist Jim Miller of Michigan State University praised the UC Davis researchers' work as correcting "long-standing erroneous dogma."
"For decades we were told that DEET warded off mosquito bites because it blocked insect response to lactic acid from the host -- the key stimulus for blood-feeding," Miller said. "Dr. Leal and co-workers escaped the key stimulus over-simplification to show that mosquito responses -- like our own -- result from a balancing of various positive and negative factors, all impinging on a tiny brain more capable than most people think of sophisticated decision-making."
Miller added that the UC Davis research shows that recent work on DEET mode-of-action, published in the journal Science, apparently was "flat-out wrong."
"One of the great attributes of science is that, over time, it is self-correcting," he said.
Mosquitoes detect DEET and other smells with their antennae. Leal and researcher Zain Syed discovered the exact neurons on the antennae that detect DEET (N,N-diethyl-3-methylbenzamide). These neurons are located beside other neurons that sense a chemical, 1-octen-3-ol, known to attract mosquitoes.
"I was so delighted when I first encountered the neuron that detects DEET, a synthetic compound," said Syed. "I couldn't believe my eyes because it goes against conventional wisdom. So I repeated the experiment over and over until we discussed the findings in the lab."
The UC Davis investigators set up odorless sugar-feeding stations, including some that contained DEET, and found that DEET actively repelled Culex quinquefasciatus mosquitoes, also known as Southern house mosquitoes. The mosquito transmits West Nile virus, St. Louis encephalitis, and lymphatic filariasis, a disease caused by threadlike parasitic worms.
"Despite the fact that DEET is the industry standard mosquito repellent, relatively little is known about how it actually works," said UC Davis research entomologist William Reisen. "Previous studies have suggested a 'masking' or 'binding' with host emanations. Understanding the mode of action is especially important because DEET is used as the standard against which all other tentative replacement repellents are compared."
Major Dhillon, president of the American Mosquito Control Association and district manager of the Northwest Mosquito and Vector Control District, Riverside, praised the UC Davis work as "a breakthrough."
"In the future, this new knowledge can be incorporated into developing new repellents and may be in control strategies for Culex quinquefasciatus and other mosquitoes," he said.
University of California - Davis
DEET, the common name for N,N-diethyl-3-methylbenzamide, is the most common active ingredient in insect repellents. Developed by scientists at the U.S. Department of Agriculture and patented by the U.S. Army in 1946, DEET is considered the "gold standard" of insect repellents. Worldwide, more than 200 million people use DEET to ward off vectorborne diseases.
But DEET's mode of action or how it works has puzzled scientists for more than 50 years. Scientists long surmised that DEET masks the smell of the host, or jams or corrupts the insect's senses, interfering with its ability to locate a host. Mosquitoes and other blood-feeding insects find their hosts by body heat, skin odors, carbon dioxide (breath), or visual stimuli. Females need a blood meal to develop their eggs.
Leal said previous findings of other scientists showed a "false positive" resulting from the experimental design.
Entomologist Jim Miller of Michigan State University praised the UC Davis researchers' work as correcting "long-standing erroneous dogma."
"For decades we were told that DEET warded off mosquito bites because it blocked insect response to lactic acid from the host -- the key stimulus for blood-feeding," Miller said. "Dr. Leal and co-workers escaped the key stimulus over-simplification to show that mosquito responses -- like our own -- result from a balancing of various positive and negative factors, all impinging on a tiny brain more capable than most people think of sophisticated decision-making."
Miller added that the UC Davis research shows that recent work on DEET mode-of-action, published in the journal Science, apparently was "flat-out wrong."
"One of the great attributes of science is that, over time, it is self-correcting," he said.
Mosquitoes detect DEET and other smells with their antennae. Leal and researcher Zain Syed discovered the exact neurons on the antennae that detect DEET (N,N-diethyl-3-methylbenzamide). These neurons are located beside other neurons that sense a chemical, 1-octen-3-ol, known to attract mosquitoes.
"I was so delighted when I first encountered the neuron that detects DEET, a synthetic compound," said Syed. "I couldn't believe my eyes because it goes against conventional wisdom. So I repeated the experiment over and over until we discussed the findings in the lab."
The UC Davis investigators set up odorless sugar-feeding stations, including some that contained DEET, and found that DEET actively repelled Culex quinquefasciatus mosquitoes, also known as Southern house mosquitoes. The mosquito transmits West Nile virus, St. Louis encephalitis, and lymphatic filariasis, a disease caused by threadlike parasitic worms.
"Despite the fact that DEET is the industry standard mosquito repellent, relatively little is known about how it actually works," said UC Davis research entomologist William Reisen. "Previous studies have suggested a 'masking' or 'binding' with host emanations. Understanding the mode of action is especially important because DEET is used as the standard against which all other tentative replacement repellents are compared."
Major Dhillon, president of the American Mosquito Control Association and district manager of the Northwest Mosquito and Vector Control District, Riverside, praised the UC Davis work as "a breakthrough."
"In the future, this new knowledge can be incorporated into developing new repellents and may be in control strategies for Culex quinquefasciatus and other mosquitoes," he said.
University of California - Davis
Mosquitoes Current Events and Mosquitoes News RSS'Airport malaria' -- cause for concern in the US
In a global world, significant factors affect the spread of infectious diseases, including international trade, air travel and globalized food production. "Airport malaria" is a term coined by researchers to explain the more recent spread of malaria to areas such as the United States and Europe, which some scientists credit to warmer climate changes.
Smaller mosquitoes are more likey to be infected with viruses causing human diseases
An entomologist at the Illinois Natural History Survey, a division of the new UI Institute for Natural Resource Sustainability, says smaller mosquitoes are more likely to be infected with viruses that cause diseases in humans.
West Nile's North American spread described
The rapid spread of West Nile virus in North America over the past decade is likely to have long-lasting ecological consequences throughout the continent, according to an article in the November issue of BioScience.
Researchers characterize potential protein targets for malaria vaccine
Researchers from Nijmegen and Leiden have now characterized a large number of parasite proteins that may prove useful in the development of a human malaria vaccine.
Small islands given short shrift in assembling archaeological record
Small islands dwarf large ones in archaeological importance, says a University of Florida researcher, who found that people who settled the Caribbean before Christopher Columbus preferred more minute pieces of land because they relied heavily on the sea.
ESA leads the way to map boreal forest
How best to map 'boreal' or northern forest with spaceborne radar is the focus of an ESA campaign currently underway in northern Sweden.
Study: Bird diversity lessens human exposure to West Nile Virus
A study by biologists at Washington University in St. Louis shows that the more diverse a bird population is in an area, the less chance humans have of exposure to West Nile Virus (WNV).
'Deadly dozen' reports diseases worsened by climate change
Health experts from the Wildlife Conservation Society today released a report that lists 12 pathogens that could spread into new regions as a result of climate change, with potential impacts to both human and wildlife health and global economies.
Common insecticide can decimate tadpole populations
The latest findings of a University of Pittsburgh-based project to determine the environmental impact of routine pesticide use suggests that malathion--the most popular insecticide in the United States--can decimate tadpole populations by altering their food chain, according to research published in the Oct. 1 edition of Ecological Applications.
New way to make malaria medicine also first step in finding new antibiotics
University of Illinois microbiology professor William Metcalf and his collaborators have developed a way to mass-produce an antimalarial compound, potentially making the treatment of malaria less expensive.
More Mosquitoes Current Events and Mosquitoes News Articles
 | Why Mosquitoes Buzz in People's Ears: A West African Tale by Verna Aardema In this Caldecott Medal winner, Mosquito tells a story that causes a jungle disaster. "Elegance has become the Dillons' hallmark. . . . Matching the art is Aardema's uniquely onomatopoeic text . . . An impressive showpiece."--Booklist, starred review. Full... |
 | Why Mosquitoes Buzz in People's Ears (Picture Puffins) by Verna Aardema |
 | Why Mosquitoes Buzz in People's Ears by Verna Aardema |
 | Mosquitoes: A Novel by William Faulkner |
 | Hey, You!: Poems to Skyscrapers, Mosquitoes, and Other Fun Things by Paul B. Janeczko What would you say to a mailbox? What would you say to your shoe? To a sea horse? A snowflake? A bee? A mosquito? An octopus? Light? The faraway moon? What would you say to a poetry book? Give it a try: Hey, you!... |
| Mosquitoes, malaria, and man: A history of the hostilities since 1880 by Gordon A Harrison | |
 | Identification and Geographical Distribution of the Mosquitoes of North America, North of Mexico by Richard F. Darsie, Ronald A. Ward Greatly anticipated and sorely needed, this book updates the successful guide to North American mosquitoes published by the American Mosquito Control Association in 1981. It includes 12 new species that have since been added to the North American mosquito fauna, revised distribution maps of all species, and revised and completely illustrated identification keys for the adult females and fourth... |
 | The Adventures of the Three Mosquitoes: The Magic Inferno by Ralph Oppenheim Once more, The Three Mosquitoes shout out their familiar battle cry: “Let’s Go!” And the three khaki Spads take to the air, flying into terror skies, each sporting the famous Mosquito insignia. In the cockpits sat three warriors who were known wherever men flew as the greatest and most hell raising trio of aces ever to blaze their way through overwhelming odds. Always in front was Kirby,... |
 | Quick Children's Sermons 2: Why Did God Make Mosquitoes? by Group |
 | Mosquitoes of Medical Importance by Richard H. Foote, David R. Cook |
| © 2008 BrightSurf.com |