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

nachricht Unusual soybean coloration sheds a light on gene silencing
20.06.2017 | University of Illinois College of Agricultural, Consumer and Environmental Sciences

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: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

Im Focus: Optoelectronic Inline Measurement – Accurate to the Nanometer

Germany counts high-precision manufacturing processes among its advantages as a location. It’s not just the aerospace and automotive industries that require almost waste-free, high-precision manufacturing to provide an efficient way of testing the shape and orientation tolerances of products. Since current inline measurement technology not yet provides the required accuracy, the Fraunhofer Institute for Laser Technology ILT is collaborating with four renowned industry partners in the INSPIRE project to develop inline sensors with a new accuracy class. Funded by the German Federal Ministry of Education and Research (BMBF), the project is scheduled to run until the end of 2019.

New Manufacturing Technologies for New Products

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

A new technique isolates neuronal activity during memory consolidation

22.06.2017 | Life Sciences

Plant inspiration could lead to flexible electronics

22.06.2017 | Materials Sciences

A rhodium-based catalyst for making organosilicon using less precious metal

22.06.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>