Before They Bite

June 9, 2010

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At least a million deaths occur every year due to malaria — 90 percent of them in sub-Saharan Africa — because the very efficient Anopheles gambiae mosquito ensures high transmission.

“It’s really, really hard to do anything to a mosquito to keep it from biting you,” says Dr. Marian McCord, an associate professor of textile engineering at NC State. “We need a way to injure mosquitoes without using toxic chemicals.”

How does someone in the College of Textiles get involved with mosquitoes? It started out as a proposal to the Centers for Disease Control and Prevention to find ways to increase the lifespan of the mesh nets hung over beds in many tropical countries to keep the bugs at bay overnight. The thin mesh is prone to tearing, often rendering it useless.

McCord’s proposal didn’t win funding, but it was enough to pique her interest in finding ways to stop mosquitoes. She notes that the bloodthirsty insects are becoming resistant to the insecticides often applied to nets to boost their effectiveness.

After obtaining seed funding from the University and consulting with Drs. Michael Roe and Charles Apperson in the Department of Entomology for the best way to attack mosquitoes, McCord and some biomedical engineering students went after the bugs with a vengeance.

The students anesthetized the insects and then disabled their legs or antennae, but they found that even hobbled mosquitoes were able to bite. They then tested ultra-smooth and particulate-laced surfaces for the netting to try to make it difficult for mosquitoes to land.

One of the particulates, diatomaceous earth, was found to be particularly effective. Instead of hindering landing mosquitoes, the chalky, ground-up remains of fossilized algae proved to be insecticidal, McCord says. The abrasive particles, which are safe for humans, disrupt the waxy layer that makes up a mosquito’s exoskeleton, causing the insect to dehydrate and die.

Damaging the exoskeletons could also make mosquitoes more susceptible to other infections, she says.

“If we can shorten a mosquito’s usual two-week lifespan by even a day or two,” she says, “we might be able to keep it from transmitting malaria to someone.”

McCord also is looking at stopping mosquitoes by more traditional means — for textiles researchers, at least. She’s working with German researchers on bite-proof fabrics, such as an extremely tight weave that a mosquito’s proboscis can’t fit through or nonwoven fabrics that don’t provide a straight shot at the skin.

“Hundreds of millions of people are infected by disease-carrying mosquitoes every year,” McCord says. “We’ve got to use every safe tool possible to fight these insects and the spread of disease.”