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Should pyrethroids be banned for Indoor Residual Spraying (IRS)?

May 20, 2010 - 11:41 -- Bart G.J. Knols

Today a new forum topic was launched by Drs Derek Charlwood and Erling Pedersen from DBL in Copenhagen. They argue that pyrethroids should no longer be used for indoor residual spraying and be reserved for use on bednets. What's your opinion?

After all, they argue, its the only class of insecticides that can be used on nets at the moment. In support of the debate on this topic, let me add some questions here:


- Will it make a difference, in terms of resistance development, if pyrethroids will no longer be used for IRS and only on nets?


- Would banning of pyrethroid use in agriculture stop resistance development now that millions of treated nets have found their way into African homes?


- Is the combination of IRS and nets, both based on pyrethroids, speeding up resistance development?


- Will 'combination therapy', that is IRS based on non-pyrethroid insecticide combined with a pyrethroid-treated net be a better way forward?


- The chemical industry will not like the idea. Who should enforce the ban if it is considered worthwhile?


Your answers and views can be put directly under the forum topic (click here), and your final judgement in the poll (click here).




Ole Skovmand's picture
Submitted by Ole Skovmand on

In the seventies, the Danish Pest Infestation Laboratory by the insecticide resistance expert Dr Keiding, made a voluntary agreement with the insecticide industry in Denmark NOT to introduce pyretrhoids for IRS for fly contro to avoid pyretrhoid resistance development in house flies. In the early 80ies, I went on behalf of the laboratory to Northern Germany and Southern Denmark and collected house flies from farms on both sides of the German- Danish border. In Germany, there was no such agreement and permethrin was used for IRS; There was a consistent and high pyrehroid resistance in Germany just 30 km south of the border and further south, and a consistent low or absent pyretrhoid resistance in Denmark. When it was present, it was the kdr form that already had developed during the early DDT days and never completely regressed.
Pyretrhoids have a contact repellent effect which makes them the most sutiable for bed nets, because we do not just want to kill mosquitoes, we first of all want that they do not transfer malaria. Hence, if they take off after short contact with the net, this is the best. For wall treatment, we want them to stay on the walls untill they have picked a lethal dosage of insecticide, so that insecticide better NOT be a pyrethroid.

The ONLY way to avoid that pyrehroid resistance develop rapidly and thus destroy the most advantageous group of insecticides for bed net treatment, it is to prohibit their use in wall treatment whether this is IRS or socalled wall lining with pyrethroid treated insecticide - if a voluntary agreement cannot be made with the same result.