 |
|
Earlier bites by uninfected mosquitoes boost West Nile deaths in lab mice
November 16, 2007GALVESTON, Texas - There's one more reason to try to avoid being bitten by mosquitoes, scientists have discovered: bites from mosquitoes that aren't infected by the West Nile virus may make the disease worse in people who acquire it later from West Nile-infected mosquitoes.
Researchers from the University of Texas Medical Branch at Galveston (UTMB) announced their discovery in a paper published online by the journal PLoS ONE. In the paper, they describe experiments showing that lab mice on which mosquitoes have previously fed are far more likely to die from West Nile infection than are mice unexposed to such mosquito bites.
The effect is induced by mosquito saliva, according to UTMB professor Stephen Higgs, one of the paper's senior authors.
"This virus is transmitted from mosquitoes in saliva, and we'd already demonstrated that mosquito saliva has an effect on the vertebrate immune system that makes West Nile infection worse," Higgs said. "What this new work shows is that the saliva delivered by even earlier feedings can also alter the course of the infection. This is important, because in natural situations in many parts of the world - Southeast Texas, for example - animals and some people are being exposed to mosquito feeding almost continuously."
In their experiments, researchers exposed sedated mice to feeding by between 15 and 20 Aedes aegypti mosquitoes for an hour once a week. Scientists then allowed a single West Nile virus-infected mosquito to feed once on each of these mice and also on each of a control group of mice that were previously unbitten by mosquitoes.
The results were striking: 68 percent of mice exposed to two weekly mosquito feedings died of West Nile virus, and those exposed to four weekly mosquito feedings suffered a 91 percent mortality rate. By contrast, the virus killed only 27 percent of the mice previously unexposed to saliva from mosquitoes that were free of West Nile infection. Analyses of responses of the mouse immune systems also showed a strong contrast between the previously exposed and unexposed mice.
"When we examined the immune reactions, one that stood out was an increase in the immune signaling molecule interleukin-10," said Brad Schneider, the paper's lead author and a UTMB alumnus who is now a postdoctoral fellow at the Institut Pasteur in Paris. "This host response to the saliva of the mosquito causes a shift in the immune response at the site where the virus first contacts the host, and the virus takes advantage of this shift."
The UTMB researchers were surprised to find that mosquito bites seemed to have a detrimental effect with West Nile virus, because multiple earlier bites from other uninfected arthropods can actually protect against the parasites and bacteria carried by them. "Previous work has clearly indicated that pre-exposure to the bites of uninfected sand flies has a protective effect for mice against cutaneous leishmaniasis," said Dr. Lynn Soong, the paper's other senior author and an immunologist who works on the sand fly-transmitted protozoan parasite infection, dubbed "Baghdad boil" by American troops in the Middle East.
"Since this goes against the work we've seen with both bacteria and parasites, we definitely didn't expect this result," Schneider said. "But when we stood back and looked at it, it made sense. For a parasite or bacterium, the influx of immune cells brought in by this inflammatory response would be negative, but with the West Nile virus, you're just giving it more susceptible cells to infect."
Both Higgs and Schneider emphasized that the mouse experiments offered no definitive answers to the question of human responses to West Nile. "This is a mouse model, but that's the best we've got at the moment," Higgs said. "The thing is, it suggests that there may be yet another reason to avoid mosquitoes, to tidy up your yard and wear mosquito repellant."
University of Texas Medical Branch at Galveston
"This virus is transmitted from mosquitoes in saliva, and we'd already demonstrated that mosquito saliva has an effect on the vertebrate immune system that makes West Nile infection worse," Higgs said. "What this new work shows is that the saliva delivered by even earlier feedings can also alter the course of the infection. This is important, because in natural situations in many parts of the world - Southeast Texas, for example - animals and some people are being exposed to mosquito feeding almost continuously."
In their experiments, researchers exposed sedated mice to feeding by between 15 and 20 Aedes aegypti mosquitoes for an hour once a week. Scientists then allowed a single West Nile virus-infected mosquito to feed once on each of these mice and also on each of a control group of mice that were previously unbitten by mosquitoes.
The results were striking: 68 percent of mice exposed to two weekly mosquito feedings died of West Nile virus, and those exposed to four weekly mosquito feedings suffered a 91 percent mortality rate. By contrast, the virus killed only 27 percent of the mice previously unexposed to saliva from mosquitoes that were free of West Nile infection. Analyses of responses of the mouse immune systems also showed a strong contrast between the previously exposed and unexposed mice.
"When we examined the immune reactions, one that stood out was an increase in the immune signaling molecule interleukin-10," said Brad Schneider, the paper's lead author and a UTMB alumnus who is now a postdoctoral fellow at the Institut Pasteur in Paris. "This host response to the saliva of the mosquito causes a shift in the immune response at the site where the virus first contacts the host, and the virus takes advantage of this shift."
The UTMB researchers were surprised to find that mosquito bites seemed to have a detrimental effect with West Nile virus, because multiple earlier bites from other uninfected arthropods can actually protect against the parasites and bacteria carried by them. "Previous work has clearly indicated that pre-exposure to the bites of uninfected sand flies has a protective effect for mice against cutaneous leishmaniasis," said Dr. Lynn Soong, the paper's other senior author and an immunologist who works on the sand fly-transmitted protozoan parasite infection, dubbed "Baghdad boil" by American troops in the Middle East.
"Since this goes against the work we've seen with both bacteria and parasites, we definitely didn't expect this result," Schneider said. "But when we stood back and looked at it, it made sense. For a parasite or bacterium, the influx of immune cells brought in by this inflammatory response would be negative, but with the West Nile virus, you're just giving it more susceptible cells to infect."
Both Higgs and Schneider emphasized that the mouse experiments offered no definitive answers to the question of human responses to West Nile. "This is a mouse model, but that's the best we've got at the moment," Higgs said. "The thing is, it suggests that there may be yet another reason to avoid mosquitoes, to tidy up your yard and wear mosquito repellant."
University of Texas Medical Branch at Galveston
Mosquitoes Current Events and Mosquitoes News RSSActive hearing process in mosquitoes
A mathematical model has explained some of the remarkable features of mosquito hearing. In particular, the male can hear the faintest beats of the female's wings and yet is not deafened by loud noises.
PATH Malaria Vaccine Initiative shares strategy for developing 'next-generation' malaria vaccines
Marking its tenth anniversary year, the PATH Malaria Vaccine Initiative (MVI) today unveiled a new strategy that sets the stage for an aggressive push targeting the long-term goal of eliminating and eradicating malaria. Malaria is one of the world's deadliest infectious diseases, killing nearly 900,000 people a year, most of them children in sub-Saharan Africa.
Media availability: The role of biomedical research in malaria eradication
Although malaria has been controlled in many local and regional populations, the permanent elimination of malaria parasites throughout the world remains an elusive goal, and the disease continues to claim nearly one million lives each year.
UC Davis researchers identify dominant chemical that attracts mosquitoes to humans
Scientists at the University of California, Davis, have identified the dominant odor naturally produced in humans and birds that attracts the blood-feeding Culex mosquitoes, which transmit West Nile virus and other life-threatening diseases.
UM School of Medicine researchers find extreme genetic variability in malaria parasite
Researchers at the University of Maryland School of Medicine Center for Vaccine Development (CVD) have charted the extreme genetic differences that occur over time in the most dangerous malaria parasite in the world.
Research ensures 50 million vaccinated against deadly brain infection
Research at the University of Liverpool has supported the vaccination of more than 50 million people against a zoonotic brain infection that affects thousands of children across Asia every year.
Scientists discover how to send insects off the scent of crops
Biotechnology and Biological Sciences Research Council (BBSRC)-funded research, published this week in Chemical Communication, describes how scientists have discovered molecules that could confuse insects' ability to detect plants by interfering with their sense of smell. This could reduce damage to crops by insect pests and contribute to food security.
UH Manoa researcher examines possible implications of daily commute and mosquito-borne diseases
University of Hawaii at Manoa assistant researcher Durrell Kapan recently published a paper, Man Bites Mosquito: Understanding the Contribution of Human Movement to Vector-Borne Disease Dynamics, in PLoS One. Published August 26, the paper highlights how daily commuting patterns in mega-cities may be a critically overlooked factor in understanding the resurgence of mosquito-borne diseases such as dengue fever, infecting 50-100 million people annually.
Decade-long US project to fight malaria builds thriving African mosquito net industry
In a decade-long initiative to protect millions of families from malaria in sub-Saharan Africa, a U.S. government-funded project helped sell 50 million bed nets in seven countries, crafted a voucher system to allow the poor to receive them for free or partial cost, and created enough incentives for private companies that they invested $88 million to expand their businesses.
New research confirms potential deadly nature of emerging new monkey malaria species in humans
Researchers in Malaysia have identified key laboratory and clinical features of an emerging new form of malaria infection.
More Mosquitoes Current Events and Mosquitoes News Articles
 |
Mosquitoes: A Novel by William Faulkner (Author), Frederick R. Karl (Introduction) A delightful surprise, Faulkner wrote his second novel "for the sake of writing because it was fun." Mosquitoes centers around a colorful assortment of passengers, out on a boating excursion from New Orleans. The rich and the aspiring, social butterflies and dissolute dilettantes are all easy game for Faulkner's barbed wit in this engaging high-spirited novel which offers a fascinating glimpse of Faulkner as a young artist."It approaches in the first half and reaches in the second half a brilliance that you can rightfully expect only in the writings of a few men. It is full of the fine kind of swift and lusty writing that comes from a healthy, fresh pen."--Lillian Hellman, New York Herald Tribune . |
 |
SpringStar - Mosquito Trap by SpringStar This unique mosquito trap catches only the ones that bite. Particularly effective on the Culex mosquito, the one that spreads west nile virus. The trap works by luring female mosquitoes inside using a pheromone- once inside they cannot escape. Two per average yard will reduce the population significantly. Trap can be rinsed out and reused many times during the season, more bait will be required (SpringStar mosquito refill lure, item S1519). Try it, you'll like it. |
 |
Mosquitos III by The Mosquitos On their third album, this Brazilian-flavored, New York City-based trio make it clear that they're wielding a vivid palette, curious minds and active imaginations. The opening "Moonshine" finds a slide guitar being punctuated by exuberant drums, followed by a brief, airy vocal. It ends in less than a minute and a piano enters for the second number, with Chris Root's intimate singing sounding at once but like a sunny bossa nova chanteuse and a late night continental cabaret balladeer. In less than forty minutes Mosquito manage to offer up fifteen finely chiseled slices of refreshing songcraft. Anchored by guitar or keyboards, the melodies are hook-filled without being cloying. And all the while the percussion of JuJu Stulbach dances around and through the proceedings like a giddy bird.... |
 |
Mosquito Squadron Starring: David McCallum, Suzanne Neve, Charles Gray, David Buck, David Dundas Directed By: Boris Sagal David McCallum ("The Man From U.N.C.L.E.") stars in an epic adventure that perfectly captures the explosive action and emotional torment of war. With its astonishing special effects, stark cinematography and brilliantly choreographed aerial combat sequences, Mosquito Squadron catapults the viewer into the searing heat of battle! As Allied forces struggle against the awesome might of the German Luftwaffe, an even greater threat is posed by the destructive V3 rocket nearing completion at a secret testing center. The Royal Air Force's Mosquito Squadron gears up to destroy the site, but its leader, Quint Monroe (McCallum), becomes conflicted when he discovers that the air strikemay kill hundreds of British POWsincluding the squad's former commander! |
 |
Pramex Long Lasting Insecticidal Net- Ideal for Two People by Valent BioSciences Corporation USE PRAMEX LONG LASTING INSECTICIDAL NETS when you want PROTECTION FROM BITING MOSQUITOES. Whether hiking, camping, hunting, fishing or traveling to destinations where mosquitoes are a problem, Pramex Long Lasting Insecticidal Nets are the answer. Our mosquito nets are THE ONLY NETS IN THE US THAT ARE MADE WITH OLYSET CONTROLLED RELEASE INSECTICIDE TECHNOLOGY. This unique technology automatically recharges the surface of the nets with insecticide as needed. The nets provide a physical barrier to houseflies, mosquitoes and other flying insects and REPEL MOSQUITOES on contact. FOR INTERNATIONAL TRAVELERS - The CDC recommends using treated mosquito nets when traveling to countries where mosquitoes and the serious diseases they carry can be a problem (Malaria, West Nile Virus, Dengue, etc).... |
 |
OEM Replacement Li Poly Battery for Micro Mosquito or Firefly RC Helicopters by Draganfly Innovations Inc This is an OEM (standard) replacement battery for the both the Micro Mosquito and Firefly mini RC helicopters. The single cell lithium polymer will restore flight times that may have been shorted by a worn-out battery. Note: Soldering is required for installation. Wires are pre-installed on the battery. * Voltage: 3.7 Volts LiPoly (1 cell) * Weight: 5g | 0.2 oz * Length: 32mm | 1 3/32" * Width: 20mm | 13/16" * Depth: 4.5mm | 5/32" |
 |
Mr. Mosquito by Eidos Interactive It's wrong to love Mister Mosquito. Wrong because of the repetitive gameplay, the lackluster graphics, and the awkwardness of the controls. I could also mention the repetitive dialogue, laughable AI, and interminable load times. And did I mention how short it is? But somehow none of this matters if, like I do, you fall for the charm and originality of this game. You play as a nameless mosquito whose job it is to suck the blood of the Yamada family. There are only two modes, battle and suck. To suck blood you have to first hover and wait for a target area to flash red somewhere on your victim's body, then swoop in, pierce the skin, and extract blood by twirling the right analog stick. Suck too fast or too long and you're liable to get swatted, a fate you can avoid if you keep... |
|
Mosquito Bites by Mcaa Inc /Gold Coast Mail Ctr | |
 |
Mosquito Head Net Olive Drab by TEXSPORT This Mosquito Head Net creates a barrier against bugs. The Olive Drab cotton Hat has a nylon netting and an adjustable headband that ensures a perfect fit. The elastic shoulder band keeps the netting tight with the shoulders to keep mosquitoes from sneaking in from below. Order ONLINE Now! Mosquito Head Net, Olive Drab |
 |
MQ7 - Personal Mosquito Repellent Spray by Murata Corporation MQ7 GreenScience offers an all natural, non-toxic Personal Mosquito Repellent Spray formulation that has never before achieved such levels of innovation and extraordinary performance. This product will repel and help ward off nasty mosquitoes, chiggers, no-see-ums, gnats, flies, ticks and fleas. Throughout history, cedar has been known to repel insects naturally and is probably why we are accustomed to the use of cedar wood products such as cedar lined closets, chests and hangers. All cedar oil can not be treated equally and why our MQ7 formulation is so expensive. It starts with the selection of the specie Juniperus virginania (Cupressaceae family), from which we extract the cedarwood oil. For the most part it is harvested by chainsaws as the terrain on which it grows may be steep and... |
| © 2009 BrightSurf.com |