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Indoor Residual Spraying Bill Brieger | 24 Apr 2010 06:48 am

For the love of a pesticide???

Some people love their spouse, some people love their new car, and apparently some people love DDT.

Love is not a particularly rational emotion, even more so when it comes to inanimate objects like cars and pesticides. Those who love DDT have now even equated stopping its use with population control in Africa.  One wonders where these same people stood when real ‘population control’ or genocide was happening in Rwanda and Darfur (to name a few of the more obvious human atrocities). Somehow one doubts banning of DDT can be equated with Darfur.

Long before DDT was banned, the malaria eradication efforts of the 1950s-60s were grinding to a halt in many African countries for the basic reasons that health systems could not support sustained efforts and donors were tiring of funding the project. There is also the not so simple matter of insects developing resistance when only one pesticide is being used.

who-ddt.jpgOne key lesson of the earlier eradication project was that relying on a single intervention technology was not enough to control, much less eradicate, a complicated disease like malaria.

Now that we have several proven tools (long lasting insecticide treated nets, artemisinin-based combination therapy, rapid diagnostic tests, intermittent preventive treatment AND indoor residual spray) in addition to new tools on the horizon (e.g. vaccines), we can apply those in combinations that best suit the epidemiological situation in each country and region of a country.

Yes, spraying was included above, and is an integral component of current malaria control and elimination efforts because it can now be targeted, as with the other interventions, in the most effective places such as areas that have more seasonal and unstable transmission and thus, where annual spraying can be effective. Yes, DDT is included in the WHO approved list of chemicals for indoor use, but for countries that want choice, there are a dozen alternatives.

Why annual spraying? DDT may be cheap, but the spraying operation is not. Nor is it convenient to the people whose homes are sprayed. Spraying more than once a year would be more time and cost consuming than present funding and community tolerance could support. Very high year-round malaria transmission settings are not so amenable to IRS as they would require more frequent spraying.  WHO recommends the following for appropriate IRS use in epidemiologically appropriate areas:

Achieving [the highest possible] level of coverage and timing spraying correctly – in a short period of time before the onset of the transmission season – are crucial to realize the full potential of IRS. IRS is indicated only in those settings where it can be implemented effectively, which calls for a high and sustained level of political commitment.

Approved use of any pesticide for public health comes with the following caution: “When implementing IRS, it is critical to ensure that adequate regulatory control is in place to prevent unauthorized and un-recommended use of public health pesticides in agriculture, and thus contamination of agricultural products. Pesticide contamination can have serious ramifications for trade and commerce for countries exporting agricultural products.”

Those who love DDT may not find these concerns expressed about the object of their affection very comforting. But then love is fickle. Maybe next year these same people will fall in love with BPA.

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