Checkout some of our archived posts below!
Published August 09, 2011| Reuters
Releasing genetically modified, spermless male mosquitoes into the wild could in future help to prevent malaria transmission and reduce the chances of large outbreaks of the killer disease, British scientists said on Monday.
Researchers from Imperial College London sterilized male mosquitoes by genetically modifying them to neutralize a gene required for sperm production.
In a study to see how these mosquitoes would fare when trying to get a mate, they found that female mosquitoes cannot tell if the males they mate with are fertile, or spermless and therefore unable to fertilize the females’ eggs.
The researchers said findings suggest that in future it might be possible to control the size of the malaria-carrying mosquito population by introducing a genetic change that makes males sterile. Female mosquitoes would then unknowingly mate with the modified males and fail to produce any offspring.
Malaria is a mosquito-borne disease that affects up to 300 million people and kills nearly 800,000 every year. Its threat is greatest in Africa, where the World Health Organization says a child dies of malaria about every 45 seconds.
Public health experts are working toward the eventual global eradication of malaria, but progress is slow and there is a constant need for better and cheaper ways to get there.
“In the fight against malaria, many hope that the ability to genetically control the mosquito vector will one day be a key part of our armory,” said Flaminia Catteruccia from Imperial’s life sciences department, who led the study.
But she added that for these currently theoretical control ideas to work in practice, scientists have to establish whether the insects would continue to mate as normal, unaware that their sexual mechanisms had been tampered with.
After mating for the first and only time in her life, the female mosquito goes through certain physiological changes, then eats a meal of blood, and lays a batch of eggs.
In this research, Catteruccia’s team found that this behavior pattern was the same whether or not the mating had produced fertilized eggs that could hatch into mosquito larvae.
Using Anopheles gambiae mosquitoes, the species primarily responsible for malaria spread in Africa, the team created spermless males by injecting ordinary mosquito eggs with a protein that disrupts the development of their testes and prevents them from producing sperm as adults.
Crucially, this did not interfere with any other sexual function or behavior in either the female or the male, they explained in their study, published in the journal Proceedings of the National Academy of Sciences.
The scientists said they were also encouraged to find that after mating with a spermless male, the female made no attempt to find another mate, and so effectively missed out on the opportunity to reproduce and pass on her genes.
This was contrary to what they had expected based on studies of other species such as fruit flies, where females tend to mate with more than one male to ensure their eggs are fertilized.
Another group of British scientists said last year they had created genetically sterile Aedes aegypti mosquitoes which early field trials suggested could be used to halt the rapid spread of another infectious disease, dengue fever.
By Amy Wimmer Schwarb
ST. AUGUSTINE, Fla | Fri Jul 15, 2011 4:48pm EDT
(Reuters) – James David’s job of controlling mosquitoes in a part of Florida that Spanish explorers once dubbed “Los Mosquitos” is often futile.
But this year, the fight “feels like a sort of hand-to-hand combat,” said David, the mosquito control and coastal services director for St. Lucie County in southeast Florida.
In the past two years, David’s local government has cut 42 percent of mosquito control funding and a quarter of his staff. This year, the state slashed its contribution to local mosquito control by half.
Just weeks ago, with a line-item veto, Republican Governor Rick Scott closed a university mosquito lab that David had relied on for pesticide research.
All this comes as most local mosquito control officials agree the mosquito situation is the worst they have seen since 1998, when El Nino caused rampant rains and the pesky insects that come with them, said Shelly Redovan, executive director of the Florida Mosquito Control Association.
“It’s a bad mosquito year,” Redovan said. “And when you’ve also got reduced funding, it’s going to be tough.”
Florida’s depressed property values and high foreclosure rates have left the state with fewer tax dollars to spend, and nearly every facet of public life has been touched as lawmakers try to pay the state’s bills.
Yet effective management of mosquitoes has been so closely linked to the state’s prosperity that mosquito control officials fear they are victims of their own success.
“We should never, ever forget from where we’ve come,” said Angela Weeks-Samanie, an environmental specialist with the Florida Department of Agriculture and Consumer Services, which administers the state mosquito control funds.
“In the blink of an eye, we could go back to where we were when Florida was uninhabitable.”
SLEEPING ON THE BEACH
Mosquitoes have been part of the state’s recorded history since the arrival of the first European settlers. The Spanish, French and English all recounted tales of sleeping on the beach, covered in sand, to escape them.
When Florida was being considered for statehood, U.S. congressmen debated whether mosquitoes would prevent it from ever being a suitable place to live.
Mosquito-spread Yellow Fever broke out in the 1870s and 1880s in pockets throughout Florida — including Jacksonville, Tampa, Key West and the Panhandle — and led to the formation of the State Board of Health in 1889.
More recently, the insects have been common perpetrators in disease outbreaks, such as in the early 2000s, when West Nile virus was spreading in Florida, and in 2010, with dengue fever in the Florida Keys.
This year, the mosquitoes seem to be hitting coastal areas hardest. Lee County, which includes Fort Myers in southwest Florida, set a record in May for the number of mosquito complaints.
One day that month, the county received 457 calls from citizens.
Meanwhile, the Orlando area farther inland is seeing mosquito numbers that are similar to last year’s.
The most likely reason: This year’s troublemakers appear to be floodwater mosquitoes, which thrive in different conditions than the species that lay eggs in standing water.
“Floodwater mosquitoes lay their eggs above the high-tide line, where it’s dry,” said Roxanne Connelly, president of the state Mosquito Control Association and an associate professor of entomology at the University of Florida.
Several months of dry conditions followed by heavy rainfall created ideal conditions for this species, she said.
“Then, sometime later, when you get a high tide or some other influence, they all hatch at the same time,” she said. “They become adults at the same time. And they’re all looking for blood at the same time.”
In one three-acre salt marsh in St. Lucie County, David found mosquito larvae packed so tightly that 1 million were squeezed into an area the size of a pickup truck bed.
Spraying with heavy equipment was ineffective because winds were strong. The pesticide he chose didn’t work, so he changed chemicals twice.
“We were sending out hand crews over and over again at dusk and dawn, trying to spray by hand,” David said. “We’d treat it; it would look like we got a great knockdown. And then, three hours later, it would be just as bad it was before.”
(Editing by Colleen Jenkins and Peter Bohan)
Florida Mosquito Control