Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Malaria: synergy of insecticide mixture applied to mosquito nets against resistant Anopheles

13.11.2003


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.


This control strategy, based on the use of double-impregnated mosquito nets and the positive interaction between two insecticides of different classes, could be implemented as an effective barrier against A. gambiae, the major malaria vector in Sub-Saharan Africa. The results obtained in the Ivory Coast against resistant mosquitoes also offer the prospect of extending the approach to other harmful insects, such as Culex quinquefasciatus, the main nuisance insect in urban areas. Research work continues, calling on such techniques as electrophysiological methods to unravel the physiological mechanisms brought into play on activation of the pyrethroid-carbamate synergy effect. A better understanding of these interactions should provide a basis for more efficient control strategies, more selective towards nuisance insects and vectors of human diseases.

Marie Guillaume | alfa
Further information:
http://www.ird.fr/fr/actualites/fiches/2003/fiche183.htm

More articles from Agricultural and Forestry Science:

nachricht New 3-D model predicts best planting practices for farmers
26.06.2017 | Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign

nachricht Fighting a destructive crop disease with mathematics
21.06.2017 | University of Cambridge

All articles from Agricultural and Forestry Science >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

Im Focus: On the way to a biological alternative

A bacterial enzyme enables reactions that open up alternatives to key industrial chemical processes

The research team of Prof. Dr. Oliver Einsle at the University of Freiburg's Institute of Biochemistry has long been exploring the functioning of nitrogenase....

Im Focus: The 1 trillion tonne iceberg

Larsen C Ice Shelf rift finally breaks through

A one trillion tonne iceberg - one of the biggest ever recorded -- has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice,...

Im Focus: Laser-cooled ions contribute to better understanding of friction

Physics supports biology: Researchers from PTB have developed a model system to investigate friction phenomena with atomic precision

Friction: what you want from car brakes, otherwise rather a nuisance. In any case, it is useful to know as precisely as possible how friction phenomena arise –...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

The technology with a feel for feelings

12.07.2017 | Event News

Leipzig HTP-Forum discusses "hydrothermal processes" as a key technology for a biobased economy

12.07.2017 | Event News

 
Latest News

Researchers create new technique for manipulating polarization of terahertz radiation

20.07.2017 | Information Technology

High-tech sensing illuminates concrete stress testing

20.07.2017 | Materials Sciences

First direct observation and measurement of ultra-fast moving vortices in superconductors

20.07.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>