mosquitoes

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Irrigation leads to better crops and more malaria | 

An irrigation canal in the northwestern Indian state of Gujarat.

Andres Baeza

An irrigation canal in the northwestern Indian state of Gujarat.

Mosquitoes and plants thrive where there is water. Farmers in arid regions who use irrigation systems to collect water also construct a mosquito breeding ground.

New research shows that irrigation systems malaria prone areas can cause an increase in local malaria risk that lasts for more than a decade. Even when health authorities mount a response to kill off mosquitoes using insecticides, the problem of malaria is still worse than before the open water.

“In these dry, fragile ecosystems, where increase in water availability from rainfall is the limiting factor for malaria transmission, irrigation infrastructure can drastically alter mosquito population abundance to levels above the threshold needed to maintain malaria transmission,” said lead author and University of Michigan graduate student Andres Baeza.

Baeza and her team studied cases of malaria in northwest India. Infrequent and inconsistent rain makes for more challenging farming and is why farmers employ various irrigation methods to ensure crop health. The study looked at the effects of a large irrigation project that will provide enough water to cover more than 47 million acres.
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Taking a closer look at whether anti-malaria programs really work | 

Malaria and the mosquitoes that carry it met a formidable foe in the form of nets laced with deadly pesticides a decade ago. Hanging a net above the bed so that it drapes around the people inside provided protection from mosquito bites while not making it hotter in tropical locations nor harming the people that use them.

Programs flourished that distributed and/or sold the bed nets. People used them and progress towards ending malaria seemed on track.

Ten years later malaria is still around and the mosquitoes are showing signs of resistance to the insecticide used in the bed nets. Journalist Amy Costello, host of the podcast Tiny Spark, recently traveled to Malawi to see what was actually happening in the fight against malaria. She sees mosquitoes that are surviving the only pesticide used in bed nets to kill them and families using bed nets with giant holes.

The story was carried by Public Radio International’s The World earlier this week. It’s the first in a series of stories called Tracking Charity. Like she does with the malaria piece, Amy will travel around the world to see if aid projects are delivering on their promises.

“To my mind, the most important barometer of aid effectiveness is how it impacts the people it is trying to help. That is why I will put the recipients of aid at the forefront of every story I report,” explains Costello in introducing the series.

“I am interested in knowing if programs work for them. I want to find out what happens to people who live at the end of dirt roads when charitable projects don’t pan out as promised.”

In this week’s podcast, I spoke with with Amy about the project (our producer re-recorded my questions to improve audio quality). We discuss her previous investigations into TOMS shoes and medical volunteers following the Haitian earthquake. Costello explains why she is driven to take a tougher look at the business of doing good and the resistance she receives from people in and out of the charity sector.

And don’t miss a podcast! Subscribe on iTunes.

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Should my bacteria worry about genetically modified mosquitoes? | 

Flickr, Gustavo

I hate to admit it, but I kind of like the idea of genetically altering mosquitoes — or the bacteria they carry around — to fight disease.

I’m enough of a geek to think this is cool stuff and, frankly, I am not that fond of mosquitoes. But then I start to worry about how this could impact my own bacteria … Tom Paulson the microbiome.

I’ll explain that shortly, but first it needs to be said that this once-novel idea of producing GM skeeters is no longer so novel.

Turns out, lots of labs are now working on some variation of genetic modification in mosquitoes aimed at undermining the bug’s ability to spread disease whether it be malaria, dengue or some other ‘vector-borne’ illness. I seem to read a story about genetically modified mosquitoes every other week. The Gates Foundation funds a number of these projects.

So the media may still think this approach is new, wacky and weird. But it isn’t really. I can’t seem to find a comprehensive list of all the US-based projects for genetically modifying insects, but here’s an old but good overview by the Pew Charitable Trust and a more recent European Union report listing thousands of such projects or proposed projects.

Perhaps the best story of late on GM skeeters is by Michael Specter, in the New Yorker — about Oxitec‘s GM mosquito factory in Brazil. (Non-subscribers have to pay to read it, but it’s well worth the price).

Another such project was reported recently by scientists at Johns Hopkins University (my alma mater), in which a common bacterium found in the guts of these bugs was altered to secrete proteins toxic to the malaria parasite. They report that these toxins harm neither humans or mosquitoes.

I haven’t read their paper so I can’t tell how they tested the human toxicity. Chances are, it was a fairly quick test that looked at immediate harm to human cells or something like that. The problem here is that, when it comes to testing human harm, these quick toxicity tests may be almost meaningless. Continue reading

Nets protect against malaria, scientists say (but you already knew that) | 

Global health number crunchers, led by Seattle’s Institute for Health Metrics and Evaluation, have determined after an exhaustive survey of medical and demographic records in 22 sub-Saharan African countries that treated bed nets do protect against malaria.

Duh, you say.

Flickr, 4Cheungs

You might well think it’s a no-brainer to ask if handing out hundreds of millions of insecticide-treated bed nets in sub-Saharan Africa helps to reduce malaria.

But it’s not.

To begin with, there are lots of things that can — and do — reduce the incidence of malaria deaths and illnesses. There is the practice of indoor household spraying of insecticide, which has been increased along with the massive campaign to distribute insecticide-treated nets (ITNs).

There also seems to be a routine ebb-and-flow of malaria severity in the tropics. The disease, like many things in nature, tends to alternate between severe and mild cycles. It’s not clear why.

Flickr, Aya Rosen

And there was this confusing report recently, about the unexplained decline in mosquito populations in parts of Africa. This happened even in places where nobody was spraying or using bed nets.

There’s changes in rainfall patterns and land use that affect mosquito breeding. There are changes in access to malaria drugs (which has also been increased in recent years). And there’s a chronic problem of misdiagnosis of malaria in poor communities lacking labs. Continue reading

Altered skeeter update: Infecting mosquitoes to fight dengue | 

Flickr, Gustavo

The idea of altering mosquitoes to fight disease appears to be quite contagious.

It’s almost become a news category unto itself, with at least a story every month or so involving something like:

Bacteria.

Scientists in Australia want to expand upon successful field tests indicating that infecting mosquitoes with a particular bacteria, known as Wolbachia, prevents the bugs from transmitting the dengue virus.

WHO

Dengue cases over time

Dengue, also known as dengue fever or “break-bone” fever, is exploding worldwide and so there are a number of efforts underway to stave off the epidemic, including finding a vaccine and, well, messing with mosquitoes.

Here are a number of good stories on the latest strategy aimed at fighting disease by messing with mosquitoes:

NPR:  Better you than me: Scientists sicken mosquitoes to stop dengue

WashPost: Field tests show bacterial oddball may be a dengue destroyer

Nature News: Bacterium offers way to control dengue fever

Guardian: Injecting mosquitoes with bacteria could stop dengue fever

Few of the news reports go into much detail scrutinizing the potential adverse side-effects, whether to humans, the environment or the skeeters, but that’s routine for news stories based on early stage scientific studies.

The bacterium, Wolbachia, is a common insect infector and is widely regarded as fairly benign if not downright beneficial. Still, you never know when you fool with Mother Nature — which is why we do phased scientific testing.

Another problem with any intervention is evolution, aka resistance. Bugs have a way of finding ways around things that get in their way. Still, the scientists say, if this approach can work for a decade or so we will do much to hold the dengue explosion at bay.

I’ll be writing more later about the dengue vaccine research, which is perhaps less exciting than manipulating skeeters but perhaps more feasible.

 

Scientists create spermless mosquitoes to help combat spread of malaria | 

Wikimedia Commons photo

The major buzz on the health and science news front today is coming from a report in Proceedings of the National Academy of Sciences about the laboratory creation of spermless mosquitoes.

BBC News is just one among many news agencies reporting on the scientific work of the Imperial College London, which is part of an ongoing effort to curb the spread of malaria worldwide. According to the BBC:

 

“Experts say that this is an important first step toward releasing sterile males into the wild to reduce the size of mosquito populations.”

ABC World News reported that:

“Monday’s research is just the most recent example of a number of mosquito-modifying techniques tested in the past few years in hopes of limiting the mosquito population or the bugs’ disease transmission capabilities. Continue reading

Students dissecting mosquitos, tracking down malaria | 

Students from Whitman Middle School on Thursday learned a bit more about malaria research by perfecting a very specialized, if peculiar, skill — dissecting mosquitoes to remove their salivary glands. This was the latest class of recruits for Seattle BioMed’s BioQuest program.

Here are some of the young scientists at work, beginning with 12-year-old Emma Doherty. Another 6th grader featured later in this slide show can be seen grimacing as she watched an instructional dissection (which, frankly, looks more like what I would call a dismembering) of a mosquito on a display screen.

She later turned to her microscope and began pulling into pieces the skeeters, mumbling to herself: “This is disgusting.” But she was smiling.

Seatte BioMed is home to one of the world’s largest malaria research teams. One of their primary goals is to identify an effective vaccine against malaria. BioQuest typically gears its program toward high school students. These students were given special, advanced access as finalists in Whitman’s science fair.