Each year malaria -- spread through mosquito bites -- kills about a million people, but many of the chemicals used to kill the insects become ineffective. Repeated exposure to an insecticide breeds a new generation of mosquitoes that are resistant to that particular insecticide.
"Insecticides sprayed on house walls or bed nets are some of the most successful ways of controlling malaria," said Andrew Read, professor of biology and entomology, Penn State. "But they work by killing the insects or denying them the human blood they turn into eggs. This imposes an enormous selection in favor of insecticide-resistant mosquitoes."
Read and his colleagues Matthew Thomas, professor of entomology, Penn State, and Penelope Lynch, doctoral student, Open University, UK, argue that insecticides -- chemical or biological -- that kill only older mosquitoes are a more sustainable way to fight the deadly disease.
"If we killed only older mosquitoes we could control malaria and solve the problem of resistant mosquitoes," said Read. "This could be done by changing the way we use existing insecticides, even by simply diluting them," he added.
Aging mosquitoes are easier to kill with insecticides like DDT but new generation pesticides could do it too. Read and his colleagues are working with a biopesticide that kills older mosquitoes.
"It is one of the great ironies of malaria," explained Read, whose team's findings appear today (April 7) in PLoS Biology. "Most mosquitoes do not live long enough to transmit the disease. To stop malaria, we only need to kill the old mosquitoes."
Since most mosquitoes die before they become dangerous, late-acting insecticides will not have much impact on breeding, so there is much less pressure for the mosquitoes to evolve resistance, explained Read, who is also associated with the Penn State Center for Infectious Disease Dynamics. "This means that late-life insecticides will be useful for much, much longer -- maybe forever -- than conventional insecticides," he added. "Insects usually have to pay a price for resistance, and if only a few older mosquitoes gain the benefits, evolutionary economics can stop resistance from ever spreading."
"We are working on a fungal pesticide that kills mosquitoes late in life," said Thomas. "We could spray it onto walls or onto treated materials such as bed nets, from where the mosquito would get infected by the fungal spores." The fungi take 10 to 12 days to kill the insects. This achieves the benefit of killing the old, dangerous mosquitoes, while dramatically reducing the selection for the evolution of resistance, Thomas explained.
To study the impact of late-acting insecticides on mosquito populations, the researchers constructed a mathematical model of malaria transmission using factors such as the egg laying cycle of the mosquito and the development of parasites within the insect.
Once malaria parasites infect a mosquito, they need at least 10 to 14 days -- or two to six cycles of egg production -- to mature and migrate to the insect's salivary glands. From there they can pass into humans when a mosquito bites.
Analyses of the model using data on mosquito lifespan and malaria development from hotspots in Africa and Papua New Guinea reveal that insecticides killing only mosquitoes that have completed at least four cycles of egg production reduce the number of infectious bites by about 95 percent.
Critically, the researchers also found that resistance to late-acting insecticides spreads much more slowly among mosquitoes, compared to conventional insecticides, and that in many cases, it never spreads at all.
Read says the development of biological or chemical insecticides that are more effective against older, malaria-infected mosquitoes could save the millions dollars that will have to be spent to endlessly find new insecticides to replace ones that have become ineffective.
"Insecticides that kill indiscriminately impose maximal selection for mosquitoes that render those insecticides useless. Late-life acting insecticides would avoid that fate," Read added. "Done right, a one-off investment could create a single insecticide that would solve the problem of mosquito resistance forever."
Amitabh Avasthi | EurekAlert!
Further reports about: > Entomology > Evolution-proof insecticides > Malaria > biopesticide > conventional insecticides > cycles of egg production > deadly disease > development of parasites > human blood > insecticide breeds > insecticide-resistant mosquitoes > insecticides > mosquito bites > mosquitoes
Advanced analysis of brain structure shape may track progression to Alzheimer's disease
26.10.2016 | Massachusetts General Hospital
Indian roadside refuse fires produce toxic rainbow
26.10.2016 | Duke University
Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.
This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...
Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion
Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
26.10.2016 | Power and Electrical Engineering
26.10.2016 | Awards Funding
26.10.2016 | Power and Electrical Engineering