Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Malaria -- Effective insecticide-repellent synergy against mosquito vectors

18.07.2007
The mosquitoes responsible for malaria transmission to humans belong to the Anopheles genus. One of the best known and most extensively studied is Anopheles gambiae, Africa’s principal malaria vector.

The protection recommended by the World Health Organization for people at risk from this devastating disease is the use of mosquito nets impregnated with pyrethroids, of low toxicity for mammals and highly active against mosquitoes. Unfortunately, excessive and inappropriate use of this family of insecticide, particularly by spraying, has induced a disturbing rise in the number of resistant individuals in the Anopheles populations. The mosquito nets treated with pyrethroids can therefore lose their effectiveness. It is therefore essential to devise new control strategies against these malaria vectors that are resistant to these insecticides.

IRD researchers and their partners (1) obtained encouraging results by combining a non-pyrethroid insecticide, propoxur, and a repellent, N,N-diethyl toluamide (DEET). They based their investigations on previous work which had revealed a strong synergy between the two components. A combination of the two had proved to be much more effective than the straightforward addition of their respective properties. Mosquito nets soaked with this mixture had a lethal power and irritant effect that inhibited the mosquitoes from biting. Moreover, the mosquitoes are hit by a powerful paralysing action, known as the “knockdown” effect (3), on contact with the mixture. The mortality rates determined were satisfactory, in that they equalled those obtained by using deltamethrin, a commonly-used synthetic pyrethroid, highly effective against mosquitoes.

The researchers tested two mixtures composed of a non-pyrethroid insecticide of the organophosphate family, combined with either a standard repellent, DEET, or with a new-generation synthetic repellent. Both of these mixtures show a strong synergy in the resulting lethal and paralysing effects on the mosquitoes. However, only the association between the insecticide and the standard repellent produced a synergistic effect that inhibited the mosquito from taking its blood feed. A synergistic effect was also observed with regard to the treatment’s residual efficacy which is several months longer than that of either agent applied alone. The advantage of the synergistic property of these combinations is enhanced by the fact that it significantly reduced the necessary effective doses against the mosquitoes (about 6 times that of the insecticide applied alone), to attain an efficacy equivalent to that of deltamethrin.

The nets treated with the two mixtures in the laboratory were subsequently tested in field trials, in the rice-growing area 40 km North of Bobo-Dioulasso, in Burkina Faso. This area has the specificity of harbouring two different forms of Anopheles gambiae. The first appears in May and June in the rice-fields. It shows no resistance to pyrethroids. The second emerges in September and October in puddles left by monsoon rains. These do show resistance to these insecticides. As expected, the usual pyrethroid-treated nets turned out to be effective only against non-resistant mosquitoes of the first population. Conversely, the nets pre-soaked with non-pyrethroid–repellent combinations proved excellent protection for the people of the local villages, whatever the population of mosquitoes present. Nevertheless, their residual efficacy (about 15 days) in real conditions did not match the researchers’ expectations. The team consequently envisage working in conjunction with a company able to devise a system for encapsulating the mixture to prolong the residual life of treated mosquito nets.

The efficacy of these mixtures between organophosphates and repellents therefore opens up a new pathway towards controlling pyrethroid-resistant malaria vectors. In the long term, the researchers plan to test their method on mosquitoes resistant to two other types of insecticide utilized against malaria transmission: organophosphates and carbamates.

Gregory Flechet | EurekAlert!
Further information:
http://www.ird.fr

More articles from Health and Medicine:

nachricht Biofilm discovery suggests new way to prevent dangerous infections
23.05.2017 | University of Texas at Austin

nachricht Another reason to exercise: Burning bone fat -- a key to better bone health
19.05.2017 | University of North Carolina Health Care

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

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

Im Focus: New Method of Characterizing Graphene

Scientists have developed a new method of characterizing graphene’s properties without applying disruptive electrical contacts, allowing them to investigate both the resistance and quantum capacitance of graphene and other two-dimensional materials. Researchers from the Swiss Nanoscience Institute and the University of Basel’s Department of Physics reported their findings in the journal Physical Review Applied.

Graphene consists of a single layer of carbon atoms. It is transparent, harder than diamond and stronger than steel, yet flexible, and a significantly better...

Im Focus: Strathclyde-led research develops world's highest gain high-power laser amplifier

The world's highest gain high power laser amplifier - by many orders of magnitude - has been developed in research led at the University of Strathclyde.

The researchers demonstrated the feasibility of using plasma to amplify short laser pulses of picojoule-level energy up to 100 millijoules, which is a 'gain'...

Im Focus: Can the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

3D printer inks from the woods

30.05.2017 | Life Sciences

How circadian clocks communicate with each other

30.05.2017 | Life Sciences

Graphene and quantum dots put in motion a CMOS-integrated camera that can see the invisible

30.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>