Thursday, April 21, 2016

Your dream of a world without mosquitoes is one step closer to coming true


Destroying the mosquito population may soon become more than just a dream for the bug-averse.
The plan could become reality in the Florida Keys, where Intrexon Corporation’s Oxitec Ltd. XON, +2.99%  has proposed letting genetically-engineered mosquitoes free in a bid to cut down on the Aedes aegypti strain, which transmits the Zika virus, among other mosquito-borne diseases.

If allowed, it would be the first time something like this is tried with mosquitoes in the U.S., and is aimed not at the recent surge in the Zika virus in Latin America but rather at dengue fever, another mosquito-borne disease that flared up in the U.S. in 2009 after decades of inactivity.
Oxitec calls its mosquitoes “self-limiting”: the male mosquitoes are genetically bred so when they mate with female mosquitoes, the offspring die. The male mosquitoes die off, too, so within six to eight weeks, the mosquitoes and their progeny are gone.

Mosquitoes seem like a prime candidate for eradication. Beneath their merely pesky appearance lies a disease-spreading agent, responsible for transmitting Zika virus and dengue but also chikungunya, West Nile virus, yellow fever and malaria.

Read more: What exactly is the Zika virus, and why should you care?
 

But could getting rid of the pests have other consequences? A preliminary finding by the Food and Drug Administration’s Center for Veterinary Medicine suggested Oxitec’s experiment would have “no significant impact” on the environment, though it noted findings “may change on further review.”
A 2010 article in science journal Nature found that in a world without mosquitoes, “Life would continue as before—or even (be) better.”

Oxitec’s trial is just that: a short-term experiment. With approval, it could last up to 22 months in a designated trial site. The company has been able to achieve mosquito population control in six to nine months in trials in other countries (including the Cayman Islands, Panama and Brazil), said Derric Nimmo, Ph.D., the company’s product development manager.

After that, without additional releases, the mosquito population would recover.

Still, opposition remains: there are local, vocal objections, and nearly 10,000 people have signed an online petition opposing the trial. Sponsored by the nonprofit Center for Food Safety, it compares the experiment with “the plot to a new Jurassic Park” and says it is “simply too risky for our environment and public health and is fraught with many unanswered questions.”

Oxitec has been working since before 2009 on this trial, which it has run past the Food and Drug Administration, the Centers for Disease Control and Prevention and the Environmental Protection Agency, said Oxitec’s Nimmo.

The FDA’s preliminary findings are currently open for a comment period. Then it could be three months to a year before the agency delivers its final assessment, Nimmo said, adding “but don’t hold me to that.”

In any case, large-scale “self-limiting” mosquito control is still years away, Nimmo said, though it’s possible the company could get emergency permissions if a U.S. Zika outbreak occurs.
See: Is it time to just wipe out mosquitoes?
 
Zika is expected to travel to the U.S., though there haven’t been any locally-spread cases yet. Causing symptoms such as fever, rash, muscle pain and headaches, the disease has also been connected to a paralyzing autoimmune disease, birth defects in pregnant women’s children and, most recently, a brain disease much like multiple sclerosis, the New York Post reported.

Officials at the Centers for Disease Control and Prevention said last week that the disease’s effects are “scarier than we initially thought.” Aedes aegypti is present in about 30 states, the CDC’s principal deputy director said, more than double the initial number of 12 states. The Obama administration has requested billions of dollars to fight the disease.

To be sure, there may be no perfect way of getting to a mosquito-free world.
Genetic modification plans are expensive and effective only for a limited time, Jeff Powell, a Yale University biology professor and mosquito expert told MarketWatch in an interview earlier this year.

The method also only keeps the population down when constantly used.

Powell is researching a method he believes is more sustainable: working with mosquitoes’ naturally-occurring genetic variation to change their disease-transmission abilities. The idea, though compelling, could take several years at least to get off the ground, Powell said.

But Nimmo said Oxitec’s technology wouldn’t cost any more than the $1.1 million the Keys spends on Aedes aegypti control already, “and we would be able to get greater than 90% control.”

The cost also ensures that so-called self-limiting mosquitoes would only be justified in areas severely threatened by mosquito-borne disease outbreaks, with some examples including Texas, Hawaii and Puerto Rico.

It’s also only intended for Aedes aegypti.

As for the other types of mosquitoes, might we suggest aloe vera?

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Wednesday, January 20, 2016

Florida, Illinois report travel-related Zika cases

Travel-related cases of a mosquito-borne illness running rampant in Latin America have reached Florida and Illinois, officials in those states said Tuesday. Cases of Zika virus— which health officials in Brazil believe is causing babies to be born with abnormally small heads— have also been reported in Hawaii and Texas. All of the U.S. cases thus far have involved people who traveled to Latin America.

In Illinois, two pregnant women who traveled to the affected area have contracted the virus, and doctors are reportedly monitoring their health and pregnancies.
“There is virtually no risk to Illinois residents since you cannot contract Zika virus from another person, but only through the bite of an infected mosquito,” Illinois Department of Public Health director Nirav D. Shah, M.D., J.D., said in a news release. “But since this is a time of year when people travel to warmer climates and countries where Zika virus is found, we are urging residents, especially pregnant women, to take preventive measures when traveling in affected countries and check health travel advisories.”

The Florida Department of Health has confirmed three Zika cases. Two of those people live in Miami-Dade County and traveled to Colombia in December, and the third infected person lives in Hillsborough County and traveled to Venezuela in December, according to the Washington Post. None of the residents are pregnant women.

An individual can contract Zika when an infected mosquito bites them. There’s no vaccine nor antiviral treatment for the virus.

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Thursday, April 30, 2015

Irresistible to mosquitoes? It might be your body odor

Aedes aegypti
Are you a favorite target of mosquitoes each summer? It may have to do with your genes. For a recent study involving twins suggests that our DNA plays a big role in just how attractive we are to these tiny, pesky — and sometimes dangerous — insects.

Scientists have long observed that about 20 percent of people are particularly attractive to mosquitoes.

Just what makes those people mosquito magnets has been a puzzle, however. Diet has been a leading contender, but research findings linking various types of foods to mosquito attractiveness are inconsistent — with one possible exception. A 2010 study found that people who drink beer appear to be more likely to get bitten than those who abstain.

As for certain foods being “natural” mosquito repellants, well, there’s no good evidence for that, either. One old wives’ tale — that eating garlic cuts down on being bitten — didn’t hold up under scientific scrutiny. And taking vitamin B has been shown to be ineffective as well.
Body odor, however, has been linked to mosquito attractiveness, and it’s known that a person’s particular body odor is controlled, at least in part, by genetic factors. So the authors of the current study, which was published online last week in the journal PLOS ONE, decided to investigate whether those two factors combined could mean that genetics underlies our attractiveness — or unattractiveness — to mosquitoes.

Study design

For this pilot study, researchers at London School of Hygiene and Tropical Medicine conducted a series of experiments involving 18 identical and 19 non-identical (fraternal) twins.
Identical and fraternal twins are used to test heritability factors because the genetic code from identical twins is nearly the same while that from fraternal twins is not. (Fraternal twin share the same amount of genetic material as any pair of siblings.)

During one of the experiments, each woman from a twin pair was asked to place a hand on a branch of a Y-shaped tube. Dengue mosquitoes (Aedes aegypti) were then released into the third branch of the tube to see which twin they would fly to (and how quickly) — in other words, to see which twin they were most attracted to. Other forms of the experiments were also conducted. In one, for example, each woman was tested against a tube of “clean air.”

This study explores whether or not mosquitoes are attracted equally to twins.
An analysis of all the data revealed that the mosquitoes were equally attracted to identical twins, but not to fraternal ones.

In fact, the level of heritability involved in being attractive (or not) to mosquitoes observed in this study turned out to be very similar to the heredity levels for height and IQ.

Caveats and implications

Of course, this was a small, pilot study. When studies involve this few participants (only 74), the results can’t be considered conclusive.

But if the findings do hold up after further research, they may have important — indeed, lifesaving — implications, say the study’s authors.

“Now that we know that your level of attractiveness to mosquitoes is controlled genetically, the next stage is to identify the genes that are involved,” explains James Logan, a co-author of the study and a professor of medical entomology at the London School of Hygiene and Tropical Medicine, in a video released by his institution. “That might allow us to determine how much at risk a certain population is in a developing country, and that would have implications for controlling diseases like malaria or dengue.”

Malaria, dengue and yellow fever — just three of the many diseases transmitted by mosquitoes — kill several million people globally each year, according to the World Health Organization.
“The other thing we might be able to do,” added Logan, is to “develop a drug — a pill that you might take when you go on holiday — that would cause your body to produce natural repellants and would minimize the need to actually put repellants on your skin.”

Those Brits have to go on holiday to encounter mosquitoes?

You can read the study in full on the PLOS ONE website. The video in which Logan explains his study (and in which two twins demostrate the experiment) is also available online.

Thursday, June 26, 2014

The 'raiders' have landed

           
 
 
 
 
 
 
Posted: Wednesday, June 25, 2014 11:04 am
               
Joe and Patty Harmon set up a mosquito net in their backyard to prevent the annoying creatures from interfering with daily outdoor activities. The Harmons love the outdoors too much to give it up, so now they are prepared.
 
“This time we are determined to have it – to be a mosquito refuge,” Patty Harmon said. With mosquitoes coming out more often than not, Kansans should be prepared for the worst, as there are now two mosquito-borne diseases to look out for – West Nile virus and chikungunya.
“It’s hard to tell if we have more (mosquitoes) than we ever had,” said Julia Hulsey, director of the Reno County Health Department.

Chikungunya is a new mosquito-borne virus that has spread quickly in the Caribbean since December. Chikungunya symptoms include fever, muscle and joint pain, rash and headaches, which appear within a few days to a week after a person is bitten and can last for about a week.
There have been no confirmed cases in Kansas, and all reported cases in the United States have been from travelers visiting or returning to the U.S. from affected areas, according to Aimee Rosenow, a spokeswoman for the Kansas Department of Health and Environment.

Advance Pest Control in Hutchinson said the phone calls are just coming in for mosquitoes, and they anticipate more calls this year than last, based on the rate of calls in the past week. They have a lot of repeat customers year-to-year, said Jeff Wells, mosquito technician.

Patty Harmon said she always wears bug spray. As Harmon’s grandson, Trent Biehler, who was just visiting from Olathe, emptied rainwater that was collecting from the top of the tent, Harmon said the original use for the canopy was for shade, but its newfound use would be for mosquitoes.
“I just started noticing them,” Harmon said. “We’ve set (the canopy) up so we can enjoy – have dinner, a glass of wine and good conversation.”

While visiting his grandparents, Biehler plays basketball with some neighborhood teens around 8:30 p.m., “which probably isn’t the best idea,” he said. He explained they usually run out of bug spray by the end of the night.

“Mosquitoes aren’t really a big deal for me,” Biehler said. “We just keep moving.”
There are no reported cases of West Nile virus in Kansas yet, according to Rosenow. Last year, according to the Centers for Disease Control and Prevention, 91 cases of West Nile virus were reported in Kansas, resulting in seven deaths.

Patty Harmon has to contend with mosquitoes to get her gardening work done, so she empties standing water and puts on bug spray when she is outside, but she doesn’t seem to mind the simple prevention techniques.

“We have to protect ourselves,” she said. “And I enjoy the gardening so much that it’s worth it.”
The city of Hutchinson will not be spraying, or fogging, this year. The city stopped spraying in 2009 after it was determined to be ineffective because the chemical spray had to come into immediate contact with the mosquito larvae, The News reported last year.

Surrounding areas, including Buhler, Haven and Sterling, will be spraying.
“Be aware. That’s our biggest role right now,” said Nick Baldetti, assistant director of the Reno County Health Department.

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Monday, April 14, 2014

Deadly Yellow Fever Mosquito Resurfaces In Menlo Park - CBS San Francisco

Yellow Fever Mosquito, or aedes egypti.
Yellow Fever Mosquito, or aedes egypti.

Thursday, March 27, 2014

Scripps Florida scientist awarded $2.3 million to study dengue fever and related viruses

March 27, 2014 – The outbreak of dengue fever that infected some 20 people in Florida's Martin County late last year unnerved many who feared the tropical disease had once again established a foothold in Florida. The last outbreaks occurred in 2009 and 2010 in Key West—before that, the disease hadn't struck Florida in more than 70 years.

Now, scientists from the Florida campus of The Scripps Research Institute (TSRI) have been awarded $2.3 million to study a category of viruses that cause dengue fever, West Nile, yellow fever and other diseases spread by mosquitoes and ticks. These diseases can result in flulike symptoms, extreme pain (dengue has been called "bone-break fever") and, in some cases, encephalitis.

This family of viruses, called "flavivirus," affect some 2.5 billion people worldwide and cause hundreds of thousands of deaths each year. There are no antiviral treatments and a just handful of vaccines that provide protection against only a few of these diseases.

The principal investigator for the new five-year study is TSRI Associate Professor Hyeryun Choe, who will lead the effort to understand the virus's mode of infection and how new therapies might interrupt it.

"Flavivirus uses a very clever method of infection," Choe said. "It's like using a side door to enter a house when the front door is locked."

The viruses take advantage of the process that normally occurs during programmed cell death. During programmed cell death ("apoptosis"), a lipid usually found on the inner side of the cell membranes, specifically phosphatidylserine (PS), shifts to the surface, making itself readily available to any passing cellular stranger. This is where the trouble begins.

When cells are dying from a flavivirus infection, their freshly exposed PS is grabbed by the exiting virus, and phagocytes—cells that devour invading pathogens and dead and dying cells—engulf the virus as if it were a dying cell. Once engulfed by the phagocyte, the virus quickly turns the cell's own biology on its head, forcing it to produce copies of the virus.

While some viruses (influenza A for example) do not use PS in their life cycle, the flavivirus exploits this opportunity to the hilt. Infection of cells by dengue or West Nile viruses is markedly enhanced when phagocytes express receptors that recognize and bind PS.

It appears, however, that flaviviruses use only a subset of these receptors. The high selectivity, and the potency with which some of these receptors promote flavivirus infection, suggest only a small number of receptors might be effectively targeted to treat these diseases.

"We want to understand which PS receptors contribute the most to flavivirus infections and how we might block them," Choe said. "Our studies are designed to offer insights useful in the development of new therapies."

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