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 Researchers discover a new link to fight billion-dollar threat to soybean production
14.02.2017 | University of Missouri-Columbia

nachricht Important to maintain a diversity of habitats in the sea
14.02.2017 | University of Gothenburg

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: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Positrons as a new tool for lithium ion battery research: Holes in the electrode

22.02.2017 | Power and Electrical Engineering

New insights into the information processing of motor neurons

22.02.2017 | Life Sciences

Healthy Hiking in Smart Socks

22.02.2017 | Innovative Products

VideoLinks
B2B-VideoLinks
More VideoLinks >>>