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Can we maintain effectiveness of the tools?

May 17, 2012 - 12:30 -- Bart G.J. Knols

This week WHO reiterated the fragility of the gains the world has made over the last decade through intense deployment of vector control in the fight against malaria. Reuters published an online article on the matter titled 'Insecticide resistance threatens malaria fight'. In it, WHO Director General, Margaret Chan, warns of the seriousness of the situation in Africa and India. Apparently, in ever more places the toolbox, filled with four classes of chemicals, is gradually emptying.

WHO's global malaria programme Director Robert Newman holds the believe that 'we are ahaed of the curve', and that 'people should not throw up their hands in the air and saying that this is a catastrophy'. I wonder. Is it, or is it not?

Full-blown resistance to chemical X to me has the same outcome as stopping the use of chemical X. And we have ample historical evidence of what the net effect of that is. The ban on DDT that came in 1972 meant that many countries stopped spraying it, and saw a rapid and dramatic resurgence of malaria as a result. Thus, is it wrong to conclude that the massive spreading of pyrethroid resistance will have the same effect as stopping the use of pyrethroids and thus will have catastrophic outcomes?

Newman also argues that with proper resistance management tactics we may stay ahead of resistance. This is surprising. In February this year I attended a WHO meeting in Geneva, where Prof. Hilary Ranson explained in detail that the market for insecticides used in a programmatic manner is minimal compared to the consumer market. This means that resistance management is simply complicated if not impossible as long as consumers can buy all sorts of chemicals on the market. So what success do we expect from resistance management?

Lastly, the solution to these problems is looked for by searching new chemicals, new active ingredients, and thus new public health insecticides. With 100 million USD, donated by the Gates Foundation, the Innovative Vector Control Consortium, headquartered in Liverpool, keeps the flow in the pipeline of actives flowing. Following its first 5-yr grant (of 50 million USD), the market saw no new insecticide ready for use. Now it is hoped that by 2020 three new actives will reach the market.

1) Does this mean that during the next 8 years we will see the catastrophy that Newman refutes develop in full force?

2) And if we get three new public health insecticides on the market by 2020, how long will these 'survive' in the mainstream of malaria control before resistance emerges and we're back to square 1?

Is the world betting on the wrong horse and should we finally acknowledge that malaria vector control has to make the shift towards more durable (e.g. biological) approaches? Or is the pesticide lobby too strong for us to deal with?

Last year, the long-lasting insecticide-treated bednet industry turnover exceeded 1 billion USD. Of nets treated with pyrethroids that were shipped to countries where pyrethroid resistance is rampant. 

It certainly helps that WHO is at least acknowledging that insecticide resistance is threatening our successes in the fight against malaria, but as long as we do what we did, for sure we will get what we got...