Indoor Residual Spraying – not a one-trick pony

Jasson Urbach and Donald Roberts claim that the malaria fight is hurt by flimsy anti-DDT research as they opine in Business Day (South Africa) on 9th May 2014. They are particularly exercised by an article on possible DDT effects on bird egg shells. Despite the controversy sparked by the article, there is no evidence that any individual country nor WHO itself is recommending removal of DDT from the arsenal of chemicals used in indoor residual spraying (IRS) to control malaria.

PMI: http://www.pmi.gov/how-we-work/technical-areas/indoor-residual-spraying

PMI: http://www.pmi.gov/how-we-work/technical-areas/indoor-residual-spraying

There is something about DDT that raises hackles among proponents and detractors. But malaria vector control planners do have choices. WHO recommends 14 insecticides for indoor residual spraying against malaria vectors as seen below in an list updated on 25 October 2013:

  1. DDT
  2. Malathion
  3. Fenitrothion
  4. Pirimiphos-methyl
  5. Pirimiphos-methyl
  6. Bendiocarb
  7. Propoxur
  8. Alpha-cypermethrin
  9. Bifenthrin
  10. Cyfluthrin
  11. Deltamethrin
  12. Deltamethrin
  13. Etofenprox
  14. Lambda-cyhalothrin

Ironically DDT tops the list.  No chemical is 100% safe, so the caveat with any of these chemicals is that, “WHO recommendations on the use of pesticides in public health are valid ONLY if linked to WHO specifications for their quality control. WHO specifications for public health pesticides are available on the Internet.

Interestingly, a bigger concern should be the potential for mosquitoes to develop resistance to any of the above mentioned insecticides.  This is why it is important to avoid putting all our eggs – soft or hard shelled – in one basket. Ideally insecticides should be rotated often to prevent resistance from developing.

Decisions to embark on IRS and choice of insecticides should be based on national and sub-national environmental and epidemiological characteristics, not emotional attachment to any particular product.

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