I’ve written several posts debunking the myth that using DDT is banned, pointing out that is used in places like South Africa. Now Professor Bunyip has finally discovered this fact and slams Tim Blair for spreading the myth:
South Africa had stopped using DDT in 1996. Until then the total number of malaria cases was below 10,000 and there were seldom more than 30 deaths per year. But in 2000, [South Africa] saw malaria cases skyrocket to 65,000 and 458 people were killed….
Last year [after DDT's re-introduction] only 89 deaths were recorded.
Off you go, Tim, get cracking. Several thousand words, if you please, about how your sort of statistics never lie and why, in the great right-eyed scheme of things, hundreds of little black and brown lives preserved don’t make a rational objection to a favoured theory.
Oh wait, that’s not what he wrote. He actually slams me. Apparently he thinks this story contradicts some theory he thinks I hold. What he thinks that theory is, I cannot tell.
Mind you, the BBC article is rather misleading. The only insecticide ever mentioned is DDT, so this
leaves the impression that they are spraying DDT in Mozambique:
But the disease can never be fully eradicated without neighbouring countries also jacking up their malaria control programmes.
This led to the creation of the Lubombo Spatial Development Initiative, backed by the Global Fund to Fight HIV/Aids, Malaria and TB, which has led to an 83% and 67% drop in malaria cases in Swaziland and Mozambique respectively.
But actually, they are spraying Bendiocarb. The reason why the article is so misleading isn’t hard to find. The scientific authority cited is Richard Tren from the astroturf operation Africa Fighting Malaria.
To get a better idea of what happened I thought I’d consult a scientific journal. Tropical Medicine & International Health Dec 2004:
One problem in this data set was the coincidence of different explanatory variables. In the late-1980s, imported malaria and chloroquine drug resistance peaked simultaneously and a local outbreak occurred because of agricultural practice. In the 1990s, HIV infection and SP resistance emerged simultaneously and in addition DDT was replaced with pyrethroids. Finally, in 2000/01 malaria incidence fell substantially after re-introduction of DDT spraying, introduction of a new effective antimalaria drug, and implementation of large-scale vector control in Southern Mozambique … as part of the Lubombo Spatial Development Initiative (LSDI). The relative importance of each variable can only be inferred if long time series of malaria case data and explanatory variables are available, and perhaps not even then. So the problem is not a lack of possible explanations, but the abundance of highly plausible ones
Hmm, all those other factors got left out of the BBC story.
This article from the same journal on the reasons for the switch to pyrethroids is also interesting:
However, in recent years several shortcomings of RHS have been highlighted. The effectiveness of DDT was compromised by the insecticide’s irritant effect, which led to a high proportion of bloodfed mosquitoes leaving huts and not resting indoors (Sharp et al. 1990). Frequent replastering and painting over sprayed walls has also impaired effectiveness. In 1995, more than 48% of the homesteads replastered at least some of their walls, rendering the insecticide ineffective (Mnzava et al. 1998). The switch to pyrethroid insecticides, which do not smell or leave visible deposits, has reduced the prevalence of this practice, but it remains a common occurrence, with a fifth of homesteads replastering or painting before the end of the malaria season in 1997-1998 … Other households avoid RHS altogether by locking their houses during the spraying round.
So the repellent effect of DDT makes it less effective, even though Roger Bate claimed the repellent effect meant that DDT was still effective even when the mosquitoes were resistant.