Malaria is a major scourge on health in many parts of the world, particularly in Sub-Saharan Africa where over 90% of declared cases have been recorded. Mosquito nets impregnated with insecticides are considered as a good prevention and control weapon against the mosquito vectors, in particular in areas where malaria is strongly endemic.
The only insecticides currently recommended by WHO (1) are pyrethroids whose rapid action causes a “knock-down (KD)” (2) effect and high mortality when mosquitoes come into contact with it, at much smaller doses than those which are toxic for humans and other mammals. Resistance is, however, emerging among many vector species, including Anopheles gambiae in tropical Africa. IRD scientists from the research unit “Vector population characterization and control” therefore investigated a new strategy. This involves combining as a mixture, in the same mosquito net, two insecticides with distinct action mechanisms, a pyrethroid (bifenthrin) and a carbamate (carbosulfan) (3). The results of a recent trial conducted in the Bouaké region of the Ivory Coast show that use of doubly impregnated mosquito nets are effective in terms of mortality and blood-feeding inhibition among adult A. gambiae and Culex resistant to one or other of the insecticides. The positive interaction, or synergy, which sets in between the pyrethroid and the carbamate gives such combined impregnation a clear advantage. The process requires doses far below those usually applied in single impregnation. It consequently reduces the cost and toxicity of the treatment, thus ensuring the safety of users, especially of children.
The synergy between the pyrethroid and the carbamate underwent prior investigation in laboratory experiments on adult A. gambiae susceptible to these two classes of insecticide. The strongest synergy of action was observed in the proportion of 6.25 mg/m2 of carbamate (in other words 1/50th of the recommended dose) to 25 mg/m2 of pyrethroid (1/2 the recommended dose). That ratio was subsequently repeated in the Ivory Coast field trial. This mixture led to a mosquito mortality rate of 80%, about twice the expected rate assuming absence of any interaction between the two insecticides (41%). However, if the carbamate proportion was stepped up, there was a corresponding loss in the speed of action and the KD effect of the pyrethroid. This antagonism, strongest when the minimum effective dose of pyrethroid was combined with the maximum recommended dose of carbamate, was attributable to carbamate’s irritant and repellent action which keeps the mosquitoes away and precludes sufficiently long tarsal contact with the pyrethroid for it to work.
Marie Guillaume | alfa
Kakao in Monokultur verträgt Trockenheit besser als Kakao in Mischsystemen
18.09.2017 | Georg-August-Universität Göttingen
Ultrasound sensors make forage harvesters more reliable
28.08.2017 | Fraunhofer-Institut für Zerstörungsfreie Prüfverfahren IZFP
At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.
Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
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25.09.2017 | Physics and Astronomy