Posts Tagged ‘mosquito’

by David Nield

Scientists are genetically modifying mosquitoes in a high-security lab – and they’re hoping the insects will help wipe out some of the mosquito-borne diseases that continue to plague communities worldwide.

It’s known as a gene drive: where mosquitoes modified to be incapable of passing on a particular virus are used to replace the existing population of insects over several generations, with the modified genes being passed on to all their offspring.

The idea has attracted controversy because it messes with the fundamentals of nature, but it’s now under consideration by the World Health Organisation (WHO). This particular testing has entered a new phase, NPR reports, with a large-scale release of genetically modified mozzies inside a facility in Terni, Italy.

“This will really be a breakthrough experiment,” entomologist Ruth Mueller, who runs the lab, told Rob Stein at NPR. “It’s a historic moment. It’s very exciting.”

Using the ‘molecular scissor’ editing technique CRISPR, a gene known as “doublesex” in the bugs has been altered. The gene transforms female mosquitoes, taking away their biting ability and making them infertile.

At the moment, the bugs are being released in cages designed to replicate their natural environments, with hot and humid air, and places to shelter. Artificial lights are used to simulate sunrise and sunset.

The idea is to see if the mosquitoes with CRISPR-edited genetic code can wipe out the unmodified insects inside the cages. It follows on from previous proof-of-concept studies that we’ve seen before.

Ultimately these mosquitoes could be released in areas hit by malaria, bringing the local mozzie population crashing down and saving human lives. The disease is responsible for more than 400,000 deaths every year – mostly young children.

Reducing those figures sounds like a great idea, so why the controversy? Well, many scientists are urging caution when it comes to altering genetic code at this fundamental level – we just don’t know what impact these genetically edited mosquitoes will have on the world around them.

For that reason the lab has been designed to minimise any chance that the specially engineered mosquitoes could escape. The testing has also been specifically located in Italy, where this mosquito species – Anopheles gambiae – wouldn’t be able to survive outside in the natural climate.

“This is a technology where we don’t know where it’s going to end,” Nnimmo Bassey, director of the Health of Mother Earth Foundation in Nigeria, told NPR. “We need to stop this right where it is. They’re trying to use Africa as a big laboratory to test risky technologies.”

Some experts think adding genetically modified mosquitoes to natural ecosystems could harm other plants and animals that depend on them. There are a lot of unknowns.

The team behind the new experiments counters the critique by saying they’re working slowly and methodically – and that the potential side effects are outweighed by the benefits of eradicating malaria.

At the moment scientists are targeting just one species of mosquito out of hundreds, and several more years of research and consultation are planned before genetically edited mozzies would ever be released.

“There’s going to be concerns with any technology,” one of the research team, Tony Nolan from Imperial College London in the UK, told NPR.

“But I don’t think you should throw out a technology without having done your best to understand what its potential is to be transformative for medicine. And, were it to work, this would be transformative.”

https://www.sciencealert.com/scientists-take-first-step-in-controversial-mosquito-gene-drive-experiment

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by Jennifer Kay

Mosquitoes are a year-round downside to living in subtropical Miami, but millions of bacteria-infected mosquitoes flying in a suburban neighborhood are being hailed as an innovation that may kill off more bugs that spread Zika and other viruses.

Miami-Dade County Mosquito Control and Habitat Management Division is releasing non-biting male mosquitoes infected with teh naturally occurring Wolbachia bacteria to mate with wild female mosquitoes.

The bacteria are not harmful to humans but will prevent any offspring produced when the lab-bred mosquitoes mate with wild female mosquitoes from surviving to adulthood. This drives down the population of Aedes aegypti mosquitoes that thrive in suburban and urban environments and can spread Zika, dengue fever and chikungunya.

During a six-month field trial approved by the U.S. Environmental Protection Agency, over half a billion of the mosquitoes bred by Kentucky-based MosquitoMate will be released in a suburban neighborhood split by long, narrow canals near the University of Miami, said South Miami Mayor Philip Stoddard.

Miami-Dade County is testing MosquitoMate’s insects as a potential mosquito-control method about 10 miles southwest of Miami’s hip Wynwood neighborhood, where health officials confirmed the first local Zika infections spread by mosquitoes on the U.S. mainland in July 2016.

Stoddard, a zoology professor at Florida International University, said he volunteered his city for the trial, wanting to keep the outdoor cafes in his city from becoming another ground zero for a mosquito-borne virus outbreak.

“All those diseases are still a concern,” he said. “They’re still in the Caribbean and could move to the mainland to cause problems.”

By the end of 2016, Florida health officials had confirmed 1,456 Zika infections in the state, including 285 cases spread by mosquitoes in Miami-Dade County. Just two local Zika infections were reported in Florida last year, including one Miami-Dade case.

If MosquitoMate’s bugs perform well in South Miami, Wolbachia could be added to regular mosquito control operations as a long-term preventative strategy, said Bill Petrie, Miami-Dade County’s mosquito control chief.

“It’s not a silver bullet,” he said. “You’d want to integrate it into your existing methods.”

It would not replace naled, the pesticide sprayed from airplanes during the 2016 outbreak, angering Miami residents concerned the chemicals were more dangerous than Zika. Health officials credited naled among other aggressive response efforts with stopping the outbreak.

MosquitoMate’s technology appears low-tech in the field. Infected mosquitoes are shipped weekly in cardboard tubes — similar to the ones used in paper towel rolls — from Lexington, Ky.

Each tube contains a thousand mosquitoes. In a demonstration Thursday in a city park, a cloud of mosquitoes burst from one end when a black netting cover was removed; a firm shake sent any stragglers flying out.

The trial will study how far the mosquitoes fly, how long they live in the area, and how many Aedes aegypti eggs hatch compared to untreated areas, MosquitoMate founder Stephen Dobson said.

Results from a similar trial near Key West last year are awaiting publication, he said.

Last year, the EPA approved permits for MosquitoMate to sell a related mosquito species, known as the “Asian tiger mosquito,” infected with Wolbachia as a pest control service in 20 states and Washington, D.C. Those mosquitoes also can carry viruses, but experts consider them less of a threat for triggering outbreaks than Aedes aegypti.

http://www.orlandosentinel.com/news/os-modified-mosquitoes-20180208-story.html

by Tim Spector

Everyone who has ever been camping or walking in the wild with friends can’t have failed to notice how insects seem to prefer some people’s flesh to others. Some unlucky souls are totally covered in itchy red blotches and others are miraculously spared. Sometimes only some family members are affected.

My mother has never been bitten by a mosquito (though fleas like her) while my brother and I are often the targets.

Previous observations have shown a higher mosquito preference for larger people (who produce more CO2), beer drinkers and pregnant women, and although diet was often suspected as a factor, nothing in what we eat (even garlic) stood up to scrutiny.

The authors of a new study in PLOS One claim to have found the answer. They studied the differences in attraction of skin odours to mosquitoes, specifically Aedes aegypti, in a group of brave volunteers drawn from a group of female identical and non-identical twins – part of the large national TwinsUK cohort that I set up 21 years ago. The reason for using both kinds of twin was to separate the effects of nature and nurture (or genes and environment). In humans this is the only way to get a good estimate of the contribution of genetics to the differences between people.

Our valiant twins put their hands into a specially constructed plexiglass sealed dome where the odours either attract or repel 20 female mosquitoes without being allowed to bite. Each subject was given an attractiveness score compared to the other hand at the other end of the dome. Sure enough the identical twins, who share all their genes, had consistently more similar scores compared to fraternal twins – showing a clear genetic component. This comparison estimated that 67% of the differences between people (called heritability) was down to their genes.

Repel With Smell

Why might this be? Many years ago in another twin study we showed that underarm body odour as perceived by human sniffers had a genetic basis – with huge variability in how strong smells were perceived. This showed that we have gene variations controlling both the odours we perceive and the chemical odours we produce. In this way we are similar to mosquitoes because they also have big differences in which odours and chemicals attract and repel them.

Different mosquitoes prefer different parts of our bodies to others. The species Aedes Gambiae prefers the odours of our hands and feet to other bits like groins and armpits. Some animals use their body odour to keep insects away and companies have been trying to unravel what the best chemicals are.

The twin study authors realised that the chemicals could come from glands in our skin or from the billions of microbes on the surface. They discounted the bacteria as a cause as the dogma is that bacteria can’t be influenced genetically. It turns out they were wrong.

Your Own Personal Microbes

We all have very different and unique microbial species in our mouths, guts and on our skin. We share only a small fraction of our microbial species with each other – but still have a unique microbial signature fingerprint. Until recently it was thought this variety was random or due to where we lived. But recent studies, again using UK twins, have shown the importance of genes in influencing which type of gut bacteria flourish inside us – and the same is likely to be true for our skin.

Our 100 trillion microbes outnumber our own human cells ten to one and it turns out we don’t pick them – they pick us – based on our genetic makeup. This means that, just like mosquitoes, certain microbes prefer to coexist with us and other find us rather unpleasant and settle elsewhere.

Our microbes produce many of our vitamins and chemicals in our blood, and far from being the bad guys, their diversity contributes to our health. They are also probably responsible for most of our smells and odours. Even regular hand washing can’t remove these bacteria.

The special smell many of us have between our toes comes from a bacteria called Brevibacteria linens. This is identical to the bacterial species that gives Limburger cheese its distinctive smell.

To demonstrate that bacterial species are the same wherever they grow a team of microbiologists at UCLA performed an unusual experiment. They have started making and eating cheese from human skin – and reportedly this gourmet belly-button food tastes just fine.

So, the next time you get bitten by a mosquito on the ankle – don’t blame bad luck or your cheap repellent – think of the amazing evolutionary match-making processes that hooked up your special mix of genes to a particular community of microbes that feed off your skin and produce a chemical that only certain species of mosquito find irresistible.

http://theconversation.com/chemical-attraction-why-mosquitos-zone-in-on-some-people-but-not-others-40705